# Why Sound Deadening Doesn't Make a Car Quieter



## Patrick Bateman (Sep 11, 2006)

Over on Facebook, people were yelling at me because I posted something that always makes people yell at me, which is that sound deadening doesn't make your car audibly quieter.

Here's a technical explanation of why this is so.

First off, we have to spend some time thinking about how sound is generated. Sound is generated when a radiator vibrates air molecules.

Here's the formula, care of Svante at diyaudio (SPL vs. Frequency vs driver movement - diyAudio)

p=Sd*Xmax*f^2*pi*rho0/(r*sqrt(2))

where p=sound pressure in Pa, Sd=eqv. piston area in m2, Xmax=max peak excursion in m, f=frequency in Hz, rho0=1.2kg/m3, r=speaker-to-mic distance in m.

The sound pressure p can be converted to sound pressure level

Lp=20*log10(p/0,00002)

So with
Sd=500 cm2
Xmax=10 mm
f=30Hz
r=1

p=0.05*0.01*30^2*3.14*1.2/(1*1.41)=1.2 Pa

Lp = 20*log10(1.2/0.00002)=95.56 dB


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## Patrick Bateman (Sep 11, 2006)

There are two fundamental takeaways in this formula:

1) If you double the displacement and keep the cone area the same, you double the SPL

2) if you double the cone area and keep the displacement the same, you double the SPL

Fundamentally, this formula is why car audio has largely moved towards subwoofers that work in small boxes: you can attain the same SPL as a larger subwoofer by using subwoofer with higher excursion.


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## Patrick Bateman (Sep 11, 2006)

If we're looking at sound transmission into the interior of an automobile, there are a couple of variables here that are important.

There's not the ONLY variables, but they're particularly important if your goal is to make the interior quieter.

The first would be to reduce the *surface area* of the panels.
The second would be to *make the panels infinitely rigid.*

Again, this goes back to the first post: the SPL that's generated by a radiator is dictated by it's surface area and by how much it moves.










One way to evaluate this in the real world, is to go and rent a car at the airport. When you take the shuttle, you may notice that these buses are _deafeningly_ loud. The reason that they're so loud is because the surface area of the interior panels are huge, there's a ton of glass, and there's nothing in the bus to keep the panels from flexing. 

IE, the panels are not rigid, and their size is huge.


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## Patrick Bateman (Sep 11, 2006)

As noted in the first post, there are two practical ways to reduce sound transmission:

1) Make the panels smaller

2) Make the panels flex less

The rigidity of a panel goes up exponentially with thickness.










This is one of the reason that dual pane glass works _exceptionally_ well. We're creating a gap between the two windows, but we're also creating a composite panel that is exceptionally rigid, because the panel is substantially thicker than a conventional window. 

For instance, my house has dual pane windows, and each pane of glass is separated by approximately 6/8". Single pane glass is just 1/8" of an inch. Dual pane windows are orders of magnitude stiffer than single pane glass. Here's some math : How to Design for Stiffness Using a Geometric Approach


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## SkizeR (Apr 19, 2011)

You already made this thread before. It was false back then, and still false now. 

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## Patrick Bateman (Sep 11, 2006)

Possibly the fundamental challenge, when trying to make a vehicle quieter using sound deadener, is that sound deadening doesn't do much to make the body panel stiffer.










IE, the application of sound deadening here, it lowers the resonant frequency of the metal, but it doesn't make the panels substantially stiffer. If you wanted to make the panels substantially stiffer, you'd want do one of two things:

1) Make the panel substantially thicker, using the same material. IE, go from sheetmetal that's 1/8" thick to 2/8" thick.

or

2) Better yet, go with some type of rigid composite.










One way to see this in the real world, is to check out some of Doug DeMuro's videos on Youtube. He has videos where he's driving carbon fiber exotics, and you can hear that these cars are _deafening._ This is because carbon fiber is light, strong and rigid, but it is also substantially thinner than steel.

For instance, 25 of 26 of the loudest cars that Car and Driver has ever measured were made of carbon fiber or fiberglass: The Loudest Cars That Car and Driver Has Ever Tested


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> You already made this thread before. It was false back then, and still false now.
> 
> Sent from my SM-G975U using Tapatalk


Cool.


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## SkizeR (Apr 19, 2011)

You're clearly talking about ONLY constrained layer damper, not noise barriers, right? Even then, lowering structure borne vibration will lower overall noise floor. How much depends on the car. Usually the cheaper the car, the bigger the difference. That said, the real gains come from decoupled noise barriers. 

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## Patrick Bateman (Sep 11, 2006)

As noted in the previous posts, possibly the easiest way to make a car quieter is to make the panels more rigid.

Arguably the ideal way to make the panels more rigid is to use a dual pane composite.

Lexus is aware of this; Toyota patented the technology in 1989:






TOYOTA MOTOR CORPORATION GLOBAL WEBSITE | 75 Years of TOYOTA | Technical Development | Body


Various materials concerning Toyota Motor Corporations' automotive business



www.toyota-global.com





Toyota has continued to patent these technologies, here's an additonal one from 2003: EP1612768B1 - Ultralight soundproof material - Google Patents

Arguably, all of these technologies work in a similar fashion as what was described in the first post: _the key to reducing sound transmission is to make the panels stiffer._


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## Patrick Bateman (Sep 11, 2006)

At this point in the discussion, someone is probably thinking _"Patrick Bateman you are an idiot, I put sound deadening in my car and it became quieter."/_

There's two reasons why this happens:

1) Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms or strengthens one's prior personal beliefs or hypotheses. It is a type of cognitive bias. In a nutshell, whenever you make a new speaker or invest $1000 in sound deadening, you have a built-in bias to expect positive results. Confirmation bias sucks; it's probably the main reason I nearly never finish a project. My reference speakers work really nice and I always evaluate my projects objectively. It's been really hard for me to come up with something that exceeds my reference speakers.









2) Due to the Fletcher Munson curves, when you apply sound deadening to your vehicle, the frequency of the panel's resonance may be lowered by the additional mass. Because we are less sensitive to low frequencies, this may cause the sound to _appear_ quieter, even though the SPL level is virtually identical.


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## SkizeR (Apr 19, 2011)

Patrick, as crazy as your ideas may be, I've always known you were a pretty damn smart guy. Its obvious. That said, I REALLY think you need to update your knowledge on sound deadening and how it works before you actually put this off as fact. The fact that you're claiming fletcher munson and mass lowering panels resonant frequency shows you actually aren't sure how a constrained layer damper actually works to reduce resonance. I'll give you a hint, it's right in its name 

This is a basic article, but covers how CLD actually works. I think you should st least understand that before making claims like this.. www.resonixsoundsolutions.com/reference-information

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## Patrick Bateman (Sep 11, 2006)

In summary: if you wanted to make a vehicle or a room quieter, you would want to make the walls smaller or make the walls stiffer. Simply adding mass to the wall (using sound deadening) only lowers the resonant frequency of the panels. The key is to increase the stiffness.


Lexus gets this; they have numerous patents which are focused on making panels stiffer, reducing sound transmission via attenuation or both. 

The Lexus patents are cited in my previous posts in this thread.

Reducing sound via attenuation is coming next...


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## SkizeR (Apr 19, 2011)

Patrick Bateman said:


> Simply adding mass to the wall (using sound deadening) only lowers the resonant frequency of the panels. ...


I see you still haven't read the link I posted, which includes measurements that not only show otherwise, but also why your information on what cld is and does is just flat out wrong. 

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## Patrick Bateman (Sep 11, 2006)

There are various materials which can attenuate sound. 










Closed cell foam attenuates sound. Open cell foam attenuates sound. Fiberglass insulation attenuates sound. Rockwool attenuates sound.

In my experiments, fiberglass insulation works really REALLY well. It is hard for me to describe how much better it works; it's not a difference of 10-20%, it's a difference of 200-400% versus closed cell foam.

IMHO, possibly the reason you don't see it a lot is because it might kill you: Fiberglass Connection to Mesothelioma | Mesothelioma.net

This is no joke; fiberglass insulation might kill you. Tread lightly.

My first house was made nearly seventy years ago, and the entire attic was filled with asbestos insulation. That attic was so quiet you could hear your heart beat. When I went into the attic, it was like I was standing on the moon. It was CRAZY.

So, yeah, different materials attenuate sound much differently and a lot of the ones that work well will probably kill you. Your mileage may vary. Right now all the cool kids are using rock wool for maximum attenuation. Go and do your research. Find out what might kill you. Be careful.

At the same time, keep in mind that many of the best materials to attenuate sound are not commonly used because there's MASSIVE legal liabilities for companies to use them, and that's probably why closed cell foam is the most common (and probably isn't the greatest.)

Again, do your research. 

With fiberglass insulation, I have generally found that you can get around 3-10dB of attenuation and it's frequency dependent. For instance, 1khz is 34cm long. If you can find space for 8.5cm of fiberglass insulation, you can achieve as much as 10dB of attenuation at 1khz.

Low frequencies are _incredibly_ long, and due to that, it's nearly impossible to attenuate those frequencies with much efficiency. 

For instance, 50Hz is 680cm long, or 6.8 meters long. 50Hz is longer than your car. Due to the very long length, it's exceptionally difficult to attenuate low frequencies passively.


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> I see you still haven't read the link I posted, which includes measurements that not only show otherwise, but also why your information on what cld is and does is just flat out wrong.
> 
> Sent from my SM-G975U using Tapatalk



The link that you posted is a measurement of how much a panel is attenuated when excited by a loudspeaker.

That's not the focus of this thread; all I care about is how to make a car quieter.

If I wanted to make a loudspeaker enclosure quieter I would build an enclosure for it. I have never argued that sound deadening doesn't reduce flex from a loudspeaker; it *definitely* does that. No argument there.

From your link:










_"The top two graphs pictured above is what’s called a waterfall graph. Waterfall graphs are much like frequency response graphs but include another domain on top of frequency vs. amplitude… which is time. Along the X-axis we have frequency in Hz., and Along the Y-axis we have amplitude in decibels. Along the Z-axis is time., In this case between 0 and 300 milliseconds. This measurement was taken by putting a speaker in a sealed enclosure, and enclosing the front of the speaker as well, with one panel being a 12” x 12” piece of 16-gauge steel. The microphone was placed at the center of the panel and 1/8” away. The initial frequency response is in the back of the Z axis, and as you move forward, it shows the decay of the response vs. time. The quicker various frequencies decay, the better the panel is damped. As you can see, when we added a 6” x 4” piece of ResoNix Square to the center of the panel, the resonance was very well damped."_


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## SkizeR (Apr 19, 2011)

Patrick Bateman said:


> The link that you posted is a measurement of how much a panel is attenuated when excited by a loudspeaker.
> 
> That's not the focus of this thread; all I care about is how to make a car quieter.
> 
> ...


You clearly didn't read the whole thing, plus I wasn't even talking about the decay graphs.. It includes measurements of peel and seal, aka mass without viscoelastic properties as well as traditional cld.look at the frequency response, especially around the 80hz resonance. Come on, you're not this stupid. 

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## Patrick Bateman (Sep 11, 2006)

Some random thoughts:

1) The trunk of a sedan and the engine bay of all vehicles might be the greatest barrier against sound transmission into the cabin of a car. I've mentioned this a million times, but my Hyundai Genesis and my old Audi had a trunk that was 100% sealed off from the cabin. No pass through for skis or anything. They're SO MUCH quieter. My Hyundai Genesis is seventy decibels at seventy miles per hour. (2015 Hyundai Genesis 5.0) A Ford Focus hatchback, with no isolation from the non-existent trunk, is three decibels louder at the same speed. (2014 Mazda 3 i Grand Touring vs. 2014 Ford Focus SE)

2) If you want a quiet vehicle, you should really think about an electric vehicle. A Tesla Model S is *eight decibels* quieter at 70mph than a Ford Focus hatchback. (Model 3 Road Noise Evaluation | Tesla)

3) Personally, I'd be really interested to see how rockwool would work for people. I haven't worked with it myself. But it's attenuation is significant. It would be particularly interesting in a sedan, where you might be able to sacrifice trunk space or legroom in exchange for sound attenuation. For instance, if you're 5'9" tall, your car probably has room for about 3" worth of rockwool up against the firewall. It might be interesting to see if that works effectively. This approach doesn't lower SPL by making the body panels stiffer, it (theoretically) reduces SPL by attenuating the sound that enters the cabin via the firewall. If you pull back the carpet in your car, you'll generally see closed cell foam behind the carpet, which is there for these reasons.


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> You clearly didn't read the whole thing, plus I wasn't even talking about the decay graphs.. It includes measurements of peel and seal, aka mass without viscoelastic properties as well as traditional cld.look at the frequency response, especially around the 80hz resonance. Come on, you're not this stupid.
> 
> Sent from my SM-G975U using Tapatalk



Yep, that's me, Patrick Bateman, stupidest member of DIY Mobile Audio. Thank you for recognizing my stupidity, I appreciate it.


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## dumdum (Feb 27, 2007)

Patrick Bateman said:


> The link that you posted is a measurement of how much a panel is attenuated when excited by a loudspeaker.
> 
> That's not the focus of this thread; all I care about is how to make a car quieter.
> 
> ...


So replace the speaker with the sound of tyres as they roll down the road and deaden the surface between the noise source and the listening position and I’d say you have a very good comparison, you are clearly ignoring the science as shown in practical demonstrations with measurements

knock your self out, but spilling bull all over the internet is a load of crap

I know from experience if I apply dynamat extreme to every panel in a car and replace the factory trim not using any other deadening product the car inside will become a quieter environment due to less transmission of external sound (from tyres etc) though the metal work of the vehicle

if I then add ccf and mass loaded vinyl it then becomes even more quiet and more like the quiet interiors of say a Lexus or a top end mercedes


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## Holmz (Jul 12, 2017)

Patrick Bateman said:


> Yep, that's me, Patrick Bateman, stupidest member of DIY Mobile Audio. Thank you for recognizing my stupidity, I appreciate it.


I think you have a lot of competition for that title.

That said, it is somewhat out of character to not study the evidence to the contrary.


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## I800C0LLECT (Jan 26, 2009)

I think this goes back to a difference in understanding and goals. I think Patrick is stating that dampener just moves the energy somewhere else....a lower octave that appears quieter to people due to Munson curve.

I think Patrick is telling us that if somebody wants to create a measurable difference at all frequencies then other techniques need to be used. I think that's where construction techniques and materials start to come into play.

At the end of the day, nobody here has done much to reduce road noise or anything that's below 200Hz. My Honda tries to use microphones and the subwoofer to combat road noise. Most people in the Honda forums disconnect that system and can't tell a difference... Probably due to Munson curve.

It's an interesting topic. How much of that road noise impacts our sub and mids? Most of the dampening we do impacts the mid-range and higher frequencies

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## dgage (Oct 1, 2013)

Patrick’s argument is predicated on the fact that all noise entering a car enters through panel resonance. This is an incomplete argument and false argument.

And comparing a Model S and Ford Focus for noise level? Tesla’s cars aren’t considered that quiet compared to true luxury vehicles. Teslas do have less drivetrain noise but if you hear a Tesla going by at speed, they really aren’t any quieter than a standard car due to the tires and road noise.


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## FlyingEagle (Sep 22, 2017)

Without data to back up the noise level in a Tesla, I can tell you that road noise is mitigated quite a bit by use of various technologies employed throughout the vehicle. I will put forward glass type and quality and technologies used in the tire interior and the composition/design of the tread/carcass.

Specifically the foam that is glued inside the tire. 

Tesla has it's own challenges using a giant chunk of aluminum/aluminium for it's frame and paneling.

Acura is using large plastic "bands" or hollow added cavity wraps on the outside of some of their SUV rims, and that is another technique at reducing the further transmission of what I assume is a certain band of frequencies that tend to be perceived as nuisance noise within the cabin, and that would excite the cabin without doubt. Also, the iwider and shorter your tire, the more noise it tends to transmit. The more you touch the road, the more it touches you.

I have driven Telsa's for work purposes and they are indeed very quiet on asphalt surfaces. Would I hazard a guess that some of what they achieve with higher end glass and tire technologies, will have a dramatic effect on not only asphalt but likely grooved concrete road surfaces, I have no doubt. Does it go hand in hand with panel construction and panel technologies? You be the judge.

This is the perception of a person, with life experience in the trade, who still has the function of his ears. No measuring machines were harmed in the making of this post.

I see 1800COLLECT's point and hopefully I haven't missed being able to follow what should be the basis for the argument of both points of view being weighed in on, here now.

Choice of wording goes a long way to tone, and being civil can help to prove a valid point. 

Good on Jason for tone. 

I will say this, if I may dgage.

To your first sentence above, this is me thinking out loud and not trying to prove or disprove anyone at this point. 

"Patrick’s argument is predicated on the fact that all noise entering a car enters through panel resonance. This is an incomplete argument and false argument. "

Does not every piece of a car attached to the road and therefore, all pieces thereby attached to those, form a chain of mechanisms through which parts of the outside world are now inducing energy into the cabin?

Do not all portions of the drive train and exhaust not have a mechanism that reduces movement and vibration into the chassis? Does not energy still now move from those mechanisms and therefore make it's way into the chassis/frame and subsequently, into the cabin.

Is there not noise already existing in the outside world, that separate of all the noise coming "in" through my questions/statements above, find it's way to excite panels and at some level, now makes it's way inside the cabin - through any and all panels but at whatever degree and regardless of noise attenuation?

I find it hard to follow the arguments being presented. Kind of like the forest for the trees. I still get that points are being proven from the direction in which they start.


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## Fish Chris 2 (Dec 18, 2019)

I'm not going to argue with anyone about what really happens with the loudness on a decibel meter after sound deadening. All I can say is, I did about 40-50% of my truck a couple months ago, and I was SO happy with the difference it made. I knew before I even started the truck and turned on the stereo. I hopped in, and closed the door, and "thud". SO solid, and no rattles ! I was SO anxious to go on and do all 4 doors... then this freaking Covid 19    
I am SO completely sold on sound deadeners in vehicles now.... and I don't care what decibel meters show, or what anyone else says. My truck just sounds / feels SO much better, and more solid with the sound deadening job only half finished !


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## I800C0LLECT (Jan 26, 2009)

Patrick isn't stating that "deadening" doesn't do anything. He's just stating that there's a difference in application and results. 

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## imickey503 (Dec 16, 2015)

the best way to solve the question is to make and model of that question and then throw unlimited funds at that question. 

And make a 100 or so. And test your theory where money is no object. 

so what's black really long and and sometimes has semen come out of it? 








that was this girl with the last name of guzzler but that's a story for another time...

that's 525 ft of pure sound silencing. 
Let's Pretend the Hull is made out of *classified* and is about *classified* inches thick
we better put some bracing inside about every *classified *feet from each other made of *classified
Lets add classified bulkheads & 24 tubes to increase stiffness and fill them up with some mass.*
let's add an additional greater than 800 feet of Mass to this by adding water all around it. 36F Seawater. 


the question is, would adding more mass or stiffness make the submarine quieter or louder? How so?


say we had a wolf and she loved the sea . she was a composite of many things, but had a brother that made of steel. which wolf would be the quieter Hunter? 


here's something to make you think. If tires are made out of rubber and they transmit noise , why is it used for sound isolation? 

how does mass of an object relate to its resonance frequency?


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## gijoe (Mar 25, 2008)

I think people are being too quick to dismiss Patrick's theory, he may end up being wrong, but let's actually look at what he's saying...

Confirmation bias is a huge problem in this hobby, and people still somehow believe they are exempt from it. You're not! This problem creeps up in sound deadening, amp selection, speaker aiming, cable selection, and just about everywhere else. If you expect to hear a difference, you will convince yourself that you do hear a difference, despite objective proof showing that no difference exists. 

Another point that should be considered, is with regard to how CLD works. Patrick is right that it lowers the resonant frequency, it doesn't eliminate it. However, lowering the frequency may lead to the perception of lower noise, which is still an improvement. 

Low frequency waves pass right through cars, CLD doesn't do anything useful for low frequencies. Even MLV doesn't stop low frequency waves, it's just not thick, or dense enough. 

So, I think Patrick has some great points that you really can't effectively block the low frequency noise that makes a car noisy to drive. You can fix high frequency resonance, and rattles, but all the work in the world is only going to make a small dent against low frequency road and tire noise. 

Even though you cannot do much at all to effectively treat low frequency noise (the biggest contribution to a noisy cabin), you can deal with some of the high frequency noise, and create an environment that can at least be perceived as being quieter. 

Regardless of whether or not low frequencies can be dealt with, fixing buzzing and rattling panels can make the cabin a more enjoyable place to listen to music.


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## I800C0LLECT (Jan 26, 2009)

Here's what I find interesting... Any W. has stated that deadening isn't worth his time with the amount of work and dedication involved vs actual results. He also seems fairly specific about doing things right. If Patrick feels the same way that's intriguing.


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## jtrosky (Jul 19, 2019)

I know that I've seen actual meter decibel readings of ambient noise levels in a car before and after sound-deadening - and the SPL meter certainly showed lower SPL levels after the deadening was done. They drove on the same road at the same speed, etc... How is that not "proof" that the car interior was quieter after the deadening was applied? An SPL meter is not very "subjective".  

Hell, just driving in a Buick compared to a Chevy can show how much of a difference using more sound-deadening can make in terms of ambient noise levels. They use the same sheet metal and the same basic car design principles - they just use more sound-deadening material to make the interior quieter.

But besides all of that, even inexpensive deadener can make the midbass in your car _so_ much better - regardless of whether or not it actually lessens the ambient noise level or not. At the end of the day, it makes your system sound better and that is all that really matters.  I was blown away by the difference sound deadener made in the midbass in my last car - completely blown away - and that was inexpensive deadener materials.


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## I800C0LLECT (Jan 26, 2009)

Well if adding Mass to a panel moves the resonance to lower frequencies then A-weighted measurements would likely be reduced. C-weighted measurements could then go upi would presume.

The energy is still present but giving different results

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## I800C0LLECT (Jan 26, 2009)

Maybe the difference here is the use of words. Treating the vehicle environment vs quieting the vehicle environment.

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## gijoe (Mar 25, 2008)

jtrosky said:


> But besides all of that, even inexpensive deadener can make the midbass in your car _so_ much better - regardless of whether or not it actually lessens the ambient noise level or not. At the end of the day, it makes your system sound better and that is all that really matters.  I was blown away by the difference sound deadener made in the midbass in my last car - completely blown away - and that was inexpensive deadener materials.



This, unfortunately can very possibly be chalked up to the confirmation bias that's been mentioned. The sound deadening hasn't improved midbass (meaning, it hasn't done anything to boost midbass frequencies), but it has likely lowered some of the higher frequency resonance that is masking some of the midbass frequencies. So, you've cleaned up the midbass response by eliminating the distortion that is being added by the higher frequency resonance, but you haven't boosted midbass at all. Obviously, reducing those resonances is good, but it's really tough to rule out confirmation bias after the amount of work that you went through to deaden your doors, and the fact that you expected an improvement. I'm not saying with 100% certainty that confirmation bias is the only thing that's lead you to the "blown away" conclusion, but I am saying that it definitely influenced your perception to some degree. How much of your effort was a real objective improvement, and how much was just a perceived improvement is the mystery.


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## jtrosky (Jul 19, 2019)

gijoe said:


> This, unfortunately can very possibly be chalked up to the confirmation bias that's been mentioned. The sound deadening hasn't improved midbass (meaning, it hasn't done anything to boost midbass frequencies), but it has likely lowered some of the higher frequency resonance that is masking some of the midbass frequencies. So, you've cleaned up the midbass response by eliminating the distortion that is being added by the higher frequency resonance, but you haven't boosted midbass at all. Obviously, reducing those resonances is good, but it's really tough to rule out confirmation bias after the amount of work that you went through to deaden your doors, and the fact that you expected an improvement. I'm not saying with 100% certainty that confirmation bias is the only thing that's lead you to the "blown away" conclusion, but I am saying that it definitely influenced your perception to some degree. How much of your effort was a real objective improvement, and how much was just a perceived improvement is the mystery.


There is NO WAY that the difference was just "confirmation bias". This was not a small improvement - it was a significant improvement that could not be chalked up to just "confirmation bias". I treated the outside door panel, the inside door panel and put CCF on top of all of it. The car basically had no sound deadening from the factory (2012 Chevy Impala). I also treated the rear deck and later the roof. I'm telling you, the difference was night and day - it was like I upgraded the door speakers - you could actually _feel_ the midbass hit harder. I don't know what exactly caused the drastic improvement - whether it was just the fact that I sealed up a lot of "air leaks" in the doors, whether it was the bulk it added, or whether it was something else - I honestly don't really know - but it was a very significant difference. Also, before the deadening, when the A/C was on, I could really feel the cold air coming out of the door handle area from the outside of the car (when I reached for the door handle to open the door). After deadening, that cold air no longer "leaked" out of that area any more. 

Are we now really trying to say that sound deadening is useless and it's all just "confirmation bias"?? There is NO WAY that I would go through all of that work again on my new car if the difference was not substantial - and I _will_ be going through all of that work on my current car when it warms up. 

I get the whole "confirmation bias" thing - but just about everyone agrees that deadening makes a substantial difference - and like I've said, I've even seen videos where they measured the ambient noise level before and after deadening - and the car was definitely quieter - unless the SPL meter also has "confirmation bias".


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## gijoe (Mar 25, 2008)

jtrosky said:


> Are we now really trying to say that sound deadening is useless and it's all just "confirmation bias"?? There is NO WAY that I would go through all of that work again on my new car if the difference was not substantial - and I _will_ be going through all of that work on my current car when it warms up.
> 
> I get the whole "confirmation bias" thing - but just about everyone agrees that deadening makes a substantial difference - and like I've said, I've even seen videos where they measured the ambient noise level before and after deadening - and the car was definitely quieter - unless the SPL meter also has "confirmation bias".


No, I'm not saying that "sound deadening is useless and it's all just "confirmation bias"" but it is worth exploring how much of the difference is due to confirmation bias, because confirmation bias absolutely contributes in this situation. 

Combine confirmation bias with our (terrible) echoic memory and it becomes really tough to validate claims like "night and day difference" without objective data that is taken in a truly scientific way (the process of obtaining this data is already vulnerable to it's own confirmation bias). I'm not saying that a difference didn't occur, but I am saying that there are some very strong factors that are contributing to our perception that need to be considered, and that these factors may contribute more significantly than any objective difference that is made by sound deadening.

Echoic memory is a *****:





Echoic memory - Wikipedia







en.wikipedia.org





I still use vibration dampening materials, but I'm also very selective about where, and how I use them, and how much effort I put into it. I recognize that pulling up carpet to lay down CLD over the floor is almost useless. The time and effort involved is significant, and in the case of the floor, the benefit is almost zero. Adding some CLD to doors since you already have to take the panel off to install new speakers makes sense, you're in there anyway, and it can only help, but pulling up carpet, adding a ton of weight with CLD, and MLV, not to mention the financial costs, probably makes much less sense when you compare the actual objective improvement. If you eliminate the portion that is confirmation bias, and eliminate the portion that is due to echoic memory, I think you'll be left with a much smaller improvement than most people realize, and I think that's Patrick's point. You can't do anything about single pane windows, and you can do very little for low frequency tire and road noise, so the objective benefits may not actually be as justifiable at the end of the day as it would seem. 

Carefully thought out sound deadening can be helpful for fixing resonance issues, but I think what Patrick is getting at, what I believe, and what Andy seems to also believe is that there is only a small real benefit, and the effort/reward ratio should be considered carefully because, most of what people are doing isn't very helpful, despite them believing it is.

The roots of this forum are in dispelling myths, and I think there is enough evidence to justify us looking into this theory. In the end, each person needs to decide how much effort they are willing to put in for a particular amount of benefit, but I do think Patrick's theory is valuable, and the true objective difference is far smaller than people think, and if they knew that then they'd spend a lot less time, money, and energy sound deadening their cars.


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## Patrick Bateman (Sep 11, 2006)

dgage said:


> Patrick’s argument is predicated on the fact that all noise entering a car enters through panel resonance. This is an incomplete argument and false argument.
> 
> And comparing a Model S and Ford Focus for noise level? Tesla’s cars aren’t considered that quiet compared to true luxury vehicles. Teslas do have less drivetrain noise but if you hear a Tesla going by at speed, they really aren’t any quieter than a standard car due to the tires and road noise.




That was something that was really frustrating about driving a Model S. Basically the drivetrain noise is virtually absent, but the road noise almost seems more offensive. 

Internal combustion engines are actually kinda nice to listen to. My Genesis is louder than a Tesla S, but I think the nature of the sound may be more offensive. With the Tesla, it feels like every little bump radiates into the cabin.

Below 30mph they're freakishly quiet though. They would be a KILLER car for someone who has a slow commute.


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## I800C0LLECT (Jan 26, 2009)

I like the submarine reference. You have two approaches to removing resonance...add mass or rigidity. A submarine uses many different techniques.

Patrick is telling us that there isn't much we can do about rigidity in context to all the panels that make up our vehicles. We know this...so what we typically do is add mass. Then we question whether it's worth the time to add material that can absorb as well. The insulation in doors is probably the best approach I've seen.

Andy W. has always said that adding mass isn't worth the time. In fact, he gave us the MS-8 and many threads and responses to help us understand the benefit of learning the environment and tuning it based on what we learned. Andy essentially stated that due to time domain, everything in our vehicle is within about 20ms and is averaged together by our brain. Werewolf used to talk about this too in reference to expanding soundstage.

I wonder what Patrick is thinking.

To get some things out of the way... Adding mass to doors is usually referenced as sound deadening. Covering holes with butyl/foil also falls under that umbrella. But it's not the same thing. That's just an attempt to separate front and back waves for your mid that's installed in the door.

Patrick hasn't stated that adding mass doesn't do anything. I think he's telling us that it's not behaving the way we think.



Sent from my Pixel 4 XL using Tapatalk


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## gijoe (Mar 25, 2008)

Patrick Bateman said:


> That was something that was really frustrating about driving a Model S. Basically the drivetrain noise is virtually absent, but the road noise almost seems more offensive.
> 
> Internal combustion engines are actually kinda nice to listen to. My Genesis is louder than a Tesla S, but I think the nature of the sound may be more offensive. With the Tesla, it feels like every little bump radiates into the cabin.
> 
> Below 30mph they're freakishly quiet though. They would be a KILLER car for someone who has a slow commute.


My VW came with something called a soudaktor, which resonates against the windshield for "fake engine noise". People hate them, and disconnect them to eliminate the fake noise. I did too, but I have a theory that VW wasn't actually trying to create a fake engine sound, they were creating a mask to hid tiny creaks and rattles. The fake sound is dull, and low, and masks the sounds that make a car feel cheaply made. I think VW was doing something with the soundaktor that is much smarter than the kids on the forums want to believe. The soundaktor makes the car more refined by helping to hide noises that the owner doesn't need to hear.


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## I800C0LLECT (Jan 26, 2009)

You're right...the soundaktor allowed the vehicle to be quiet on the outside yet still feel sporty on the inside. Pretty cool way to to create to different perspectives.

Sent from my Pixel 4 XL using Tapatalk


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## SkizeR (Apr 19, 2011)

I800C0LLECT said:


> I think this goes back to a difference in understanding and goals. I think Patrick is stating that dampener just moves the energy somewhere else....a lower octave that appears quieter to people due to Munson curve.


Except it doesn't, like, at all. Once I get home from this long drive I can go into more detail. But this isn't 1970 where panels are damped with mass. They are damped with a viscoelastic layer and a constraining layer. It literally explains how right in the link I posted, but he refuses to acknowledge it because it totally blows this idea of to smithereens

Sent from my SM-G975U using Tapatalk


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## Patrick Bateman (Sep 11, 2006)

jtrosky said:


> There is NO WAY that the difference was just "confirmation bias". This was not a small improvement - it was a significant improvement that could not be chalked up to just "confirmation bias". I treated the outside door panel, the inside door panel and put CCF on top of all of it. The car basically had no sound deadening from the factory (2012 Chevy Impala). I also treated the rear deck and later the roof. I'm telling you, the difference was night and day - it was like I upgraded the door speakers - you could actually _feel_ the midbass hit harder.



Sound deadening is _definitely_ useful if you're trying to eliminate rattling introduced by the loudspeakers themselves.

What I'm focusing on is _"how do you take a car and make it audibly quieter?"_

It's a really difficult problem because it requires *substantially* stiffening the car itself.

To keep sound from entering a cabin (or a room) we have to eliminate two things:

1) we have to eliminate any pathways that the sound can enter unimpeded. For instance, if you roll down your window by half an inch, the SPL levels inside the car can go up 10dB, because sound outside the car can enter the car unimpeded.

2) Once #1 has been satisfied, you have to prevent transmission *through* the body panels. There are only two practical ways of doing this, that I can see. The first is to keep the panels from flexing. The second is to attenuate the sound that's entered the cabin.










The Lexus patent is interesting and does something that I hadn't considered. In the Lexus patent, there are three barriers:

1) the first barrier is low density and absorbs sound

2) the second barrier is high density and absorbs sound

3) the final barrier is air tight

If I understand this right, the Lexus patent describes the following:

First, the sound enters the cabin via the firewall. For instance, the sound radiated by your engine would come in (mostly) via the firewall. One could use a single density of foam, but that is not ideal because of weight. Instead, they use two densities of foam. This provides progressively more attenuation as the sound goes further and further through the foam.










The Lexus patent specifically mentions synthetic felt, which is probably polyester. Real felt is expensive; I'm not sure if Lexus uses polyester for cost cutting. Perhaps it works as well as real felt. Somebody would have to do the research. (Lexus probably did.) Lexus mentioned in the patent that recyclability was important, and that's probably a factor here. You don't want to sell a car that can't be properly recycled.

The last barrier in the Lexus material is airtight.

It is interesting to me, because it's almost the _opposite_ of what we see in studios. Of course, in studios, they're not just trying to keep sound from _entering_ the studio, they're also trying to keep sound from _exiting_ the studio, and they're also trying to cut down on reflections at the same time.

The Lexus patent is really interesting because there's around eight different sound attenuation schemes.



EP1612768B1 - Ultralight soundproof material - Google Patents


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## Patrick Bateman (Sep 11, 2006)

My house is five hundred feet from the freeway. Due to this, it's noisy as **** when the windows are open. I have dual pane windows in the entire house. When you open a single window, it is like night and day.

This is hardly a scientific analysis, but I got out my SPL meter to see how much attenuation I get.

With the window open, I measured 37dB. Due to the pandemic, it's quieter than normal, I think on a 'normal' day that would probably be closer to 42dB or so. To put this in perspective, here are some SPL levels:










When I closed the window, the SPL level was unmeasurable on my SPL meter. I can only hazard a guess, but I'd estimate that my 3/4" dual pane windows are achieving attenuation levels of around 15dB.

Here's the crazy part : I took the glass bed off of my 3D printer, and put it where the window is, then put my SPL meter on the other side. I know this isn't even close to scientific, but I figured a pane of 2.5mm glass would provide around 6dB of attenuation. Much to my surprise, it attenuated the SPL by 1.5 decibels 

I am going to go and get my calipers and see how thick the glass on my cars are.


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## Patrick Bateman (Sep 11, 2006)

Here's some data on my windows:

1) 2011 Hyundai Genesis. I measured that the driver side window is 5.2mm thick. Car and Driver says that the Genesis is 70dBA at 70mph (2015 Hyundai Genesis 5.0). Car and Driver noted that it's quieter than the already quiet Mercedes.

2) 2018 Honda Accord. I measured that the driver side window is 4.5mm thick. Car and Driver has not published SPL data for the 2018 Accord. Motor Trend says that the 2018 Honda Accord is 69dBA at 65mph. (2018 Audi A4 Ultra Premium vs. 2018 Honda Accord 2.0T Touring: Blurred Lines - MotorTrend).

Something I noticed with the Genesis,is that there's a noticeable 'notch' in the glass, which seems to indicate that it's dual pane. Edmunds confirms that here : https://www.edmunds.com/hyundai/genesis/2009/long-term-road-test/introduction.html

Dual pane glass really seems to make a big difference; Car and Driver wrote :

_"In the case of the 2017 Audi A4 2.0T Quattro, the sound-level meter confirms its soft-spoken nature. At a steady 70 mph, the A4 puts out a mere 63 decibels. That’s less noise than you’ll get in an S-class, Audi’s own A8, and the sensory-deprivation tank also known as the Lexus LS600hL. A Rolls-Royce Phantom is quieter, but only by one decibel. Point the A4 down a highway and all you hear is a light ruffling of wind—and watch your speed, the A4 is barely louder at 100 mph. _

I wonder if the A4 is quieter than an A8 due to the combination of dual pane glass on the windows, along with a fundamentally stiff structure?

IE, you can get both the A4 and the A8 with dual pane glass, but the A4 will always be stiffer than the A8, because it's smaller. This is something that I notice with my Accord and my Genesis; the Accord just feels much "tighter" than the Genesis. And don't even get me started on my CX5, that thing feels like driving a Minivan. Hate it.


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## Holmz (Jul 12, 2017)

Fish Chris 2 said:


> I'm not going to argue with anyone about what really happens with the loudness on a decibel meter after sound deadening. ...
> ...
> I am SO completely sold on sound deadeners in vehicles now.... and I don't care what decibel meters show, or what anyone else says. My truck just sounds / feels SO much better, and more solid with the sound deadening job only half finished !


The meter number would still be useful for the rest of us to understand whether the feelings are in alignment with reality.


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## Patrick Bateman (Sep 11, 2006)

So I was thinking about how sound gets into the cabin, and it seems apparent that possibly the most important thing to prevent radiation into the cabin is that the structure must be stiff. So this isn't about *attenuating* the sound that's made it into the cabin, but just trying to achieve a structure that won't allow sound to radiate into the cabin at all.

IE, if you were driving down the road and somebody was blaring a jack hammer at 110dB right next to your car, if your car was infinitely stiff the sound wouldn't even make it into the cabin. The reason that the sound wouldn't make it into the cabin is because the sound waves (generated by that jack hammer) must cause your body panels to flex, in order for the sound to radiate into your cabin. Of course, this assumes that the cabin is 100% airtight. It is not, but that is why seals on the doors are so important to keep a car quiet.

IE, if you had a car with body panels constructed out of diamond, it would be pretty darn quiet!

There's ONE car that lets us test that hypotheis: 










The Porsche 718.

According to what I read, cutting a giant hole in the structure of your vehicle is no bueno for the rigidity of the vehicle. The measurements seem to bear this out. The Cayman (hardtop) version of the 718 is 73dBA at 70mph, as measured by Car and Driver (Audi TT RS vs. Porsche 718 Cayman S)

The convertible version of the car, the Porsche Boxster, is 84 dBA at 70 mph! (http://paws.kettering.edu/~amazzei/DataPanel/RT_2011-Porsche-Boxster-Spyder_data.pdf)

That is almost incomprehensibly loud. That is so loud, eight hours of being in a Boxster is enough to damage your hearing : Permissible Exposure Time for Noise SPL sound pressure level and duration Guidelines How long can a person endure a certain noise level before hearing damage occurs health sound level noise hearing ears impairment tinnitus damage - sengpielaudio Sengpiel Berlin

Car and Driver has always been the best source of data, to find out which cars are truly quiet, and have also been helpful in speculating WHY. For instance, the Audi A4 is remarkably quiet, quieter than many Lexuses. This seems to be due to a combination of dual pane glass and a structure that's modern and stiff. Adding weight to a vehicle isn't sufficient to make the vehicle quieter, you really want a stiff structure. This is why minivans and cargo vans and buses are noisy as hell; they may be heavy but they are NOT stiff. I drove a VW Microbus back in the day, and they're so loud, your ears ring after about an hour on the freeway. They're deafening.

It would be really useful to compare the hardtop Boxster to the ragtop Boxster to the Boxster coupe. Unfortunately, it looks like C&D has redesigned their site, and a ton of that data is G-O-N-E now. A real bummer because that data was valuable.


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## Patrick Bateman (Sep 11, 2006)

One of the reasons that I always take it with a grain of salt, when someone says "I sound deadened my car and now it's SO MUCH quieter" is that there isn't a huge difference in SPL levels between various modern cars.

IE, if you're driving a 1971 VW Microbus, that's definitely going to be a deafening experience. The vehicle was designed over half a century ago and Noise/Vibration/Harshness wasn't even a consideration.

Here in 2020, even the cheapest cars are quite refined. Here's a list of the 10 quietest cars:










These cars were measured at 90 kilometers per hour, or 56mph. I am willing to bet that it would be difficult to tell if an Audi A6 is noticeably quieter than a Toyota Prius. The SPL meter says there's a difference of 1.4dB, but that's barely audible. A lot will come down to Fletcher Munson curves. For instance, I live near a freeway, and with the windows open it's 37dBA right now, I measured that. The SPL level is noticeable but it's not maddening.

I took my SPL meter into my garage, where I have a computer with a fan that's failing. The sound of that fan is MADDENING. BZZZZZZZZZZZZZZZZZZZ all day long. It literally drives me up the wall. Every time I work out there it bugs me. I just measured it: 33 dBA.










Basically the low frequency roar of a freeway is barely audible at 33 dBA, but the 3khz whir of a fan is 10X as audible and 10X as annoying.

You've probably noticed this in your own car. For instance, the fans in my Genesis are noticeably quieter than the fans in my Accord. Higher quality fans aren't a huge expense, but they cost money and Honda knows this. There's a bean counter somewhere in Japan who specified a fan that costs one dollar less and it makes more noise. At approximately 30 decibels, the sound of a fan (at around 3khz) is annoying but the sound of the road (coming into the cabin) will be nearly inaudible.

The Fletcher Munson curves start flattening out as they get louder, and that's why road noise at freeway speeds is so irritating. 

A lot of car audio shops will tell you to just 'turn it up' to overcome road noise, but this isn't satisfying either, as SPL levels above 80 dBA can cause hearing damage. Sure, you can tolerate it for a little while, but eventually you'll want to ramp it down because it becomes unpleasant.


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## dgage (Oct 1, 2013)

I’ve stayed out of this discussion because this is layered and complex and not as simple as panels resonating. I think you were closer to it when you mentioned the Lexus patent and trying to fight sound infiltration. My thought is that sound enters mostly due to openings in the doors and vent holes and wire holes and through the area between glass and body panels. Sound also bounces around in between panels, especially wheel wheels, engine bays, and doors, which is likely the largest cause of noise infiltration.

Sound doesn’t really go through steel panels of any real thickness. And panels resonate at different frequencies so the chance of exciting panels at their certain resonances to cause noise isn’t very likely. Which leaves the areas between panels is the infiltration. Similar to Patrick’s point of the glass from his 3D printer only causing a small reduction, likely because the noise didn’t go through the glass but around. That’s not to say thicker panels or acoustic glass can’t help because they do, but the underlying infiltrations still cause the overall sound to still be loud.

Studios were mentioned and one of the main duties of sound treatments WITHIN a studio is to reduce reflections via absorption or diffraction. The following link shows how different thicknesses of different insulation’s materials have different absorption levels at different frequencies. This is also why changing the panel resonances with CLD by itself won‘t change the sound infiltration a lot, which supports my previous panel comment above. You also need to isolate panels and absorb some of the sound infiltrations.



https://www.bobgolds.com/AbsorptionCoefficients.htm



There is a lot more to this conversation than just different sizes/thicknesses of panels and glass.


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## dgage (Oct 1, 2013)

Patrick Bateman said:


> Car and Driver has always been the best source of data, to find out which cars are truly quiet, and have also been helpful in speculating WHY. For instance, the Audi A4 is remarkably quiet, quieter than many Lexuses. This seems to be due to a combination of dual pane glass and a structure that's modern and stiff. Adding weight to a vehicle isn't sufficient to make the vehicle quieter, you really want a stiff structure. This is why minivans and cargo vans and buses are noisy as hell; they may be heavy but they are NOT stiff. I drove a VW Microbus back in the day, and they're so loud, your ears ring after about an hour on the freeway. They're deafening.


The thing those quiet vehicles have in common is design and engineering for quiet. This isn’t just due to panel thickness or weight. This is due to a layered design to make doors quieter, multiple-layers of weather stripping, acoustic glass as you mentioned, panel glue between panels, etc. 

So if we were to add sound deadening and noise suppression to some of those vehicles it would make a difference in some cases. In the case of the VW bus, it might as well be a convertible as it has more in common with a convertible with all of the glass openings than a quiet car. And that VW has so many issues as noise wasn’t even remotely a design consideration, hell the engine is basically in the cabin with the people.


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## imickey503 (Dec 16, 2015)

If you made a car out of diamonds. Hmm  

I was thinking the same thing as some of the other poster. Can you just add mass to get rid of Low frequency vibrations or stiffness? Not really. Reduce? yes. Make it less audible to the human ear? yes. 

I don't want to post a long word salad, but the key to any noise reduction at lower frequency is a balance between the two. 

Electric Boat and E.A.R. both have done BILLIONS of dollars of testing to what works. That filtered down to what we use today. 

In a car body or frame, say we wanted to reduce road noise. Noise is energy. How do you get rid of that energy? 

The Toyota patents only deal with this on a specifics of STEEL/ Aluminium automotive grade steel metal frame construction vs composites. 

The reason why I pointed out the submarine is that even with all that mass? Everything being mounted on a rubber puck? The inside uses extensive amounts of Dampener material. And its even on the outside as well for 2 main reasons that should be apparent. 

The Mini cooper used to use rubber pucks for shocks. Later cars use springs and a Dampener or struts in case of McPherson based suspension. The genius is in the mounting points and how the attenuate vibration. 

There is a Balance to things. You can for example as the SPL guys do, use concrete, but road handling may be affected never mind MPG's.  

Toyota came up with the idea of using on a production car the idea of filling up the cavity's / Voids with expanding foam. Oddly enough, this has more to do with how Valves springs on your engine work. That's where a bulk of data that helped with the Toyota patents. And it got filtered down to how you can make a car quieter as it works pretty well for an engines drive train. 

If you guys ever go to an old car show, listen to the old engines and see how noisy they can be. For a time there was even a kind of motor oil that was made (and still is) that its main property outside of lubrication was to hush noise. 

I just want folks to take note that there is a LOT more to it then one metric over another. 

Also, why are you not able to hear your own heartbeat? 
the answer to that may surprise you.


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## Ge0 (Jul 23, 2007)

I'm watching this thread closely. I work in the automotive industry. I know a little about the various grades of glass and how they contribute to cabin noise. As a matter of fact, most premium German brands give you an upgrade path on your glass to reduce cabin noise. I know what you have been told in the past. But, listen to Patrick. He is on to something. 

Lowering the resonant frequency of the floor, door surfaces, and firewall by adding mass to those panels is only a small part of the equation. Don't believe me? Put two layers of Dynamat (or whatever you like) over your windshield, door glass, rear window, and panoramic sunroof. You will hear a huge difference. This will lower the resonant frequency of the noise floor but not eliminate it.

Making surfaces stiffer and raising the resonant frequency is just as important for certain applications. For example, a monstrous mid-bass driver mounted in the driver and passenger door. Do you want to lower resonant frequency within the pass band of the driver or raise it outside the pass band of the driver? Adding re-enforcement bars to my doors made a much bigger difference than weighing it down with aluminum backed goo. The sound deadening material did prevent fasteners and wires from rattling. A single layer did the trick. 3 or 4 steel bars strategically placed did the rest. 










That was my tired rant for this evening.


Ge0


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## SkizeR (Apr 19, 2011)

Ge0 said:


> Lowering the resonant frequency of the floor, door surfaces, and firewall by adding mass to those panels is only a small part of the equation. Don't believe me? Put two layers of Dynamat


For the last time, a CLD doesnt achieve its results by adding mass. It is a visco-elastic layer (the butyl) with a constraining layer (the aluminum) that puts force AGAINST resonating panels via the butyl layers shear properties while the constraining layer provides a reference. Here, read this link Reference Information & Guide – ResoNix Sound Solutions and see the graphs below. The first graph is the Peel And Seal results from 2stub's original testing. Peel and Seal is an asphalt based roofing product that has ZERO visco-elastic properties. You can see how the peak does in fact lower in frequency, but not in amplitude. This is exactly what Patrick and now geo are describing. Problem is, this is not how an ACTUAL CLD works and performs..















Moving on to real CLD products.. Here is the same test rig (i built it based off of 2stubs original test) where i tested the previous leader vs ResoNix before it was released. Red/Green is previous leader before/after application, Blue/Pink is ResoNix before/after application. You can see that there is in fact a small shift is resonant frequency, but you can see a DRASTIC decrease of resonance of the panel after application.















Waterfall graphs for good measure.. again, not tested by the same person, but same rig





























How the hell this topic is even up for debate is beyond me.


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## ErinH (Feb 14, 2007)

Let's put this in to reasonable terms:
CLD lowers the Q and the Fo (to some small degree, usually; depends on panel).
Bracing increases the Fo and Q.

If you are concerned that lowering the Q is no bueno (like a door panel with a midbass) then brace it.*
If you have a midrange enclosure and you want to damp ringing, adding CLD might make more sense since you're likely limited in space.

* I have never seen anyone provide data on CLD shifting the Fo of their panel in to a region they didn't want it to be shifted in to appreciably, but it's been a suggestion for as long as I can remember being on this forum and isn't new, like every other thing posted in this trhead, either.

CLD doesn't guarantee quieter results. A mixture of things will.

Applying peanut butter and aluminum foil to your car will also change things.
Adding lead sheeting will change things.
Running cross-bracing along sheet metal will also change things.
Changing tired will change things.
Cracking the window will change things (other than the bass ).

What does "change things" mean? It depends on which one you do, how you do it and what "things" you care about. That's where the science is. Science is not taking one generic action to resolve a generic consequence of not-understood origin.


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## Ge0 (Jul 23, 2007)

ErinH said:


> Let's put this in to reasonable terms:
> CLD lowers the Q and the Fo (to some small degree, usually; depends on panel).
> Bracing increases the Fo and Q.


This guy get's it  . Dampening is good for some applications. Stiffening and re-enforcing is good in others. Dampening is not the only solution to reducing nasty vibration that could ruin your sound system experience.

Ask yourself what do you need to accomplish before spending a huge amount of money and time. Did you ever think that you may be going bass ackwards?

You've always been taught to build sub boxes with thick ass wood and tons of internal bracing. Why? Why don't you skip the thick lumber and internal bracing and just wrap that fugger in sound deadening material instead?

How do you think OEMs can get decent bass out of an injection molded plastic sub enclosure? They use ribbing and braces in their mold. What if you could go one step further and make that plastic housing more rigid? I'll tell you. Excellent results:

































116db at less than 3% distortion down to 16Hz. A pretty satisfying bass response. Albeit the sub I was using was incredible.

Ge0


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## Ge0 (Jul 23, 2007)

User2 said:


> wow. My brain is fried.


Heh. Mine too. I think too much... I should just drink beer and play Frisbee golf instead.


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## Ge0 (Jul 23, 2007)

SkizeR said:


> Moving on to real CLD products.. Here is the same test rig (i built it based off of 2stubs original test) where i tested the previous leader vs ResoNix before it was released. Red/Green is previous leader before/after application, Blue/Pink is ResoNix before/after application. You can see that there is in fact a small shift is resonant frequency, but you can see a DRASTIC decrease of resonance of the panel after application.


With all due respect. And I do respect you SkizeR . You are talking about combating vibration / resonance WITHIN the lower pass-band of a mid-bass driver. This minimizes the effects of resonance by applying a material to dampen resonance. Here we can dump power into a driver but use dampening to absorb much of the produced energy. This is not that efficient.

What if you stiffened the panel instead to shift resonance up to 600 --> 800 Hz? This is well outside the pass-band of a typical mid-bass. Where will energy produced by this driver go now? Into the air my friend. Exactly where we want it to be .

Ge0


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## jtrosky (Jul 19, 2019)

Ge0 said:


> This guy get's it  . Dampening is good for some applications. Stiffening and re-enforcing is good in others. Dampening is not the only solution to reducing nasty vibration that could ruin your sound system experience.
> 
> Ask yourself what do you need to accomplish before spending a huge amount of money and time. Did you ever think that you may be going bass ackwards?
> 
> ...


I noticed the "Critical Mass" sub. I've been seeing some of their speakers on Ebay with crazy "Buy It Now" prices in the $15k+ range for 6.5" components (but more reasonable actual "Bid" prices). They also make 3.5" coaxials that I was considering when I bought my Illusion Audio C3CX speakers.

Are all of the Critical Mass speakers pretty good? Or are their sub the main thing for them? 

Just kind of curious - since I noticed you had one of their subs... 

Sorry for the off-topic.


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## Weigel21 (Sep 8, 2014)

I always "thought" Critical Mass was a "reasonable performer" at best, but rediculously priced. Think I remember people talking about how they don't make their own equipment, they just rebadge lower cost gear and mark it up dramatically. 

I also think that back in the day, some celebrities used Critical Mass gear and it was nothing but a marketing tactic to sell the crap as such prices.


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## tulowd (Apr 5, 2020)

Methinks there is some basic term definitions missing in a lot of good technical explanations/positions taken on here. Because they don't all fully cover the entire spectrum of sound, they can all be correct within their own context and portions of the definition.

Sound is what? .......as opposed to what it is we actually hear or perceive?
Obviously different for every person given their physiology, age etc.

Also, noise floor and dynamic range are two concepts that have not really been addressed directly here. When examining automobile design, one of the basics is to keep the natural frequency away from the range of where it induces motion / car sickness. Very low frequencies we cannot hear, but do have an effect on the passengers.

Road noise is different than vehicle noise, but both appear inside the vehicle. Harmonics and related secondary and tertiary sounds are a result of..........sound.......only a propagation thereof.

Vehicle chassis stiffness, panel stiffness, glass design, aerodynamic shape / efficiency of the vehicle, tire tread design, exhaust note, cylinder head design......the list of what influences the sounds inside a moving vehicle is virtually endless.

Given the obvious engineering that can be applied to all of these separate portions/segments would make one think it is the combination of these things that have influence. Plenty of disagreements in this thread, based on presentations / points that don't necessarily cover all bases nor acknowledge overlap between the different ideas.
They also do not fully qualify their points by showing the full scientifically required basis for making a solid argument.
This is akin to saying the measured SPL went up after adding Dynamat, so it must work in every other car like mine.
Maybe the measurement is true, but impossible to prove the postulation.

While it makes for interesting Corona isolation reading, it would appear that the wording is also loose enough to cause confusion. We also need to remember that design, engineering and prediction is not 100% accurate.
Neither is anecdotal evidence, nor even scientific measurements, if the specifics of what is being measured or designed aren't 100% clear.

Part of what makes this so much fun.

I'm currently reading Adrian Newey's autobiography "How to Build a Car". He is the most accomplished Formula 1 car designer and one of the original aerodynamicists in the field. Even with CFD and computer modelling advances as well as the wind tunnel modernizations, in a field filled with some of the most advanced technical know how on earth, the final measuring stick is still lap times.............
Think about that for a moment........the ancedotal results trump the design, theories and predictions of some of the greatest minds in technology on how to make a car go faster..........

Similar thing here, except I doubt we have any Neweys, Chapmans or Einsteins logging in......and I don't mean that disrespectfully in the least, since I'm including myself and I can barely type in complete sentences.


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## dgage (Oct 1, 2013)

2018 Rolls-Royce Phantom VIII Is The 'Most Silent' Car In The World


The eighth iteration of the Rolls-Royce Phantom was rolled out today with a red-carpet launch party and a suitably pompous press release proclaiming the car to have the “most silent” interior of anything on the road. It pretty much looks like the Rolls-Royce flagship you already know, but with a...




jalopnik.com


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## SkizeR (Apr 19, 2011)

Ge0 said:


> You are talking about combating vibration / resonance WITHIN the lower pass-band of a mid-bass driver.
> Ge0


In this case I'm also talking about lowering overall noise floor. If you lower the structure borne vibration of a car, you are lowering some of the noise floor from driving. Period. Its not a crazy amount like doing a detailed job with a noise barrier, but its still something nonetheless 

Sent from my SM-G975U using Tapatalk


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## ErinH (Feb 14, 2007)




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## gijoe (Mar 25, 2008)

Ge0 said:


> Heh. Mine too. I think too much... I should just drink beer and play Frisbee golf instead.


I'm with you Ge0, let's take a 6 pack and go throw.


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## Ge0 (Jul 23, 2007)

jtrosky said:


> I noticed the "Critical Mass" sub. I've been seeing some of their speakers on Ebay with crazy "Buy It Now" prices in the $15k+ range for 6.5" components (but more reasonable actual "Bid" prices). They also make 3.5" coaxials that I was considering when I bought my Illusion Audio C3CX speakers.
> 
> Are all of the Critical Mass speakers pretty good? Or are their sub the main thing for them?
> 
> ...


I'll answer this quick question. I don't know much about Critical Mass. My personal opinion is that their products were way over-priced for what they were. But, the same is true for many other brands mentioned in our community. I prefer to source drivers separately vs. part of an overpriced component set.

So why did I wind up using the Critical Mass LS122? Well, this was at the very beginning of the shallow mount sub revolution. Only a few options existed at the time. Most were well outside of my price range. A fellow forum member recommended trying the LS122 and happened to have one for sale. I bought the LS122 from him and also found a JL audio 13TW5. I couldn't get the JL to fit because it was a 13.5" driver. I would need to modify the vehicle too much from the stock location to make it work. The LS122 dropped right in. It did not fit my vehicles aesthetics as well (copper color in a grey and black vehicle) but sounded damn good.

It was amazing what this sub was capable of doing given it size and the tiny enclosure it was mounted in. it was not very efficient of course. But, that is nothing a 500W Zapco sub amp could not handle. I'm kind of sorry I sold it a few years ago. I have a new vehicle that could use it. I may pick another up if I can find one for a decent price. Or, I may try something new and different. Either way, I need shallow mount solutions again.

Ge0


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## Patrick Bateman (Sep 11, 2006)

tulowd said:


> I'm currently reading Adrian Newey's autobiography "How to Build a Car". He is the most accomplished Formula 1 car designer and one of the original aerodynamicists in the field. Even with CFD and computer modelling advances as well as the wind tunnel modernizations, in a field filled with some of the most advanced technical know how on earth, the final measuring stick is still lap times.............
> Think about that for a moment........the ancedotal results trump the design, theories and predictions of some of the greatest minds in technology on how to make a car go faster..........
> 
> Similar thing here, except I doubt we have any Neweys, Chapmans or Einsteins logging in......and I don't mean that disrespectfully in the least, since I'm including myself and I can barely type in complete sentences.


About 18 months ago, I learned how to do loudspeaker simulations in 3D, using a package called "Abec." Possibly the hardest piece of software I've ever learned. And learning software is basically my day job; I am paid to learn software and implement it.

So if _anyone_ should be able to pick up ABEC, it's me. And learning it was just brutal. I came close to giving up a few times.

Finally after all that work, I found that real world results were often quite different. It was a bit of a bummer, TBH.

But there's just so many damn variables to this hobby.

One of the main reasons I stopped using sound deadening was that constant directivity speakers seem to be nearly immune to interference. It's a really odd side effect of constant directivity technology. For instance, the first time that I met Earl Geddes, we were hanging out in his demo room at the Rocky Mountain Audio Fest. After about a day of hanging out, I realized that I was basically hoarse. Though it didn't _seem_ that the music was loud, I was losing my voice trying to talk over the speakers. I think what's happening here is that constant directivity speakers basically have as much output OFF axis as ON. Due to this, the speakers tend to obliterate every other sound in the room. For instance, with my Vandersteen speakers (which are conventional) if someone speaks to me in the room, I can understand them easily. With my Yamaha speakers (which are constant directivity) I can't hear anything but the speakers. You really have to shout to get your voice heard.


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## dgage (Oct 1, 2013)

Regarding your speakers, the Vandersteens vs your Yamahas, are they in the same room? My guess is no and what you’re finding is the room is different, not the speakers. I’ve heard the JBL M2 Studio Reference Monitors, which are some of the most accurate speakers on the market. In the untreated room they weren’t special AT ALL. In the treated room I heard them, they were sublime and worthy of all the marketing hype Harmon gave them. The room makes a huge difference on how a speaker sounds.


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## Holmz (Jul 12, 2017)

Patrick Bateman said:


> ... is that constant directivity speakers basically have as much output OFF axis as ON. Due to this, the speakers tend to obliterate every other sound in the room. For instance, with my Vandersteen speakers (which are conventional) if someone speaks to me in the room, I can understand them easily. With my Yamaha speakers (which are constant directivity) I can't hear anything but the speakers. You really have to shout to get your voice heard.


So what are the SPLs at the listener's position?

How much better do those Yamaha's sound compared to the Vanddersteens?


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## Ge0 (Jul 23, 2007)

dgage said:


> 2018 Rolls-Royce Phantom VIII Is The 'Most Silent' Car In The World
> 
> 
> The eighth iteration of the Rolls-Royce Phantom was rolled out today with a red-carpet launch party and a suitably pompous press release proclaiming the car to have the “most silent” interior of anything on the road. It pretty much looks like the Rolls-Royce flagship you already know, but with a...
> ...


The door glass in that vehicle weighs as much as most car doors. Also, notice the lack of a sunroof. I'll also bet it takes a crane to lower the front wind screen into place.

Ge0


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## dgage (Oct 1, 2013)

Ge0 said:


> The door glass in that vehicle weighs as much as most car doors. Also, notice the lack of a sunroof. I'll also bet it takes a crane to lower the front wind screen into place.


And they have over 300 lbs of sound deadening, panel glue, insulation between panels, etc, etc. A total focus on the engineering of sound infiltration, which includes various types of sound deadening. Not just a focus on the panels and how thick they are or the glass. It all works together as you’d expect. I tried to find a more detailed account of what they did but I guess they don’t want to share the layers upon layers of solutions they used.


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## SkizeR (Apr 19, 2011)

Speaking of a Rolls Royce.. has anyone here actually taken one apart? I have. Theres plenty of CLD. About as much as you'd expect from an average aftermarket install.


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## rton20s (Feb 14, 2011)

Patrick Bateman said:


> About 18 months ago, I learned how to do loudspeaker simulations in 3D, using a package called "Abec." Possibly the hardest piece of software I've ever learned. And learning software is basically my day job; I am paid to learn software and implement it.
> 
> So if _anyone_ should be able to pick up ABEC, it's me. And learning it was just brutal. I came close to giving up a few times.
> 
> ...





dgage said:


> Regarding your speakers, the Vandersteens vs your Yamahas, are they in the same room? My guess is no and what you’re finding is the room is different, not the speakers. I’ve heard the JBL M2 Studio Reference Monitors, which are some of the most accurate speakers on the market. In the untreated room they weren’t special AT ALL. In the treated room I heard them, they were sublime and worthy of all the marketing hype Harmon gave them. The room makes a huge difference on how a speaker sounds.


What dgage said. The first thought that came to mind was... Put the Vandersteens and Yamahas in your bathroom where the volume and reflectivity is closer to what you would have in your car. Then let us know how that A:B comparison goes.


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## rton20s (Feb 14, 2011)

dgage said:


> And they have over 300 lbs of sound deadening, panel glue, insulation between panels, etc, etc. A total focus on the engineering of sound infiltration, which includes various types of sound deadening. Not just a focus on the panels and how thick they are or the glass. It all works together as you’d expect. I tried to find a more detailed account of what they did but I guess they don’t want to share the layers upon layers of solutions they used.





SkizeR said:


> Speaking of a Rolls Royce.. has anyone here actually taken one apart? I have. Theres plenty of CLD. About as much as you'd expect from an average aftermarket install.


Exactly. Bean counters in the automotive industry aren't exactly known for letting snake oil make it into production. Much less generation after generation across just about every make and model imaginable.


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## SkizeR (Apr 19, 2011)

Another funny thing to note.. When i was looking for manufacturers of CLD when i first thought of starting ResoNix, the first US based manufacturer i came across was a huge supplier of all types of adhesives to the automotive industry. Over 5000 types to be exact. Things were going smoothly and they were able to make time for me to test some samples, talk to me on the phone about what i wanted, etc etc.. that was until the guy i was dealing with got too busy and backed up because GM put in an order for enough CLD to jam up their CLD production for 3 months... go figure


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## Ge0 (Jul 23, 2007)

SkizeR said:


> In this case I'm also talking about lowering overall noise floor. If you lower the structure borne vibration of a car, you are lowering some of the noise floor from driving. Period. Its not a crazy amount like doing a detailed job with a noise barrier, but its still something nonetheless
> 
> Sent from my SM-G975U using Tapatalk


Agreed. I won't argue with you there. However, let's go back to the original point of Patrick's thread. GLASS is your #1 contributor to cabin noise. Windshield, doors, sunroof, etc... You can dampen the **** out of your doors, floor board, and fire wall. You'll reduce road noise for sure. But wind noise is hard to overcome. Some luxury car brands combat this using thicker glass panels. Patrick was discussing the properties of double pane construction to lower noise.

Wouldn't that be great if you could skip tearing the vehicle apart to dampen surfaces / panels and get equivalent results by swapping out a wind shield? Or better yet, do both .

Ge0


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## Ge0 (Jul 23, 2007)

SkizeR said:


> Another funny thing to note.. When i was looking for manufacturers of CLD when i first thought of starting ResoNix, the first US based manufacturer i came across was a huge supplier of all types of adhesives to the automotive industry. Over 5000 types to be exact. Things were going smoothly and they were able to make time for me to test some samples, talk to me on the phone about what i wanted, etc etc.. that was until the guy i was dealing with got too busy and backed up because GM put in an order for enough CLD to jam up their CLD production for 3 months... go figure


Yep. They'll do that. GM and their main suppliers have a lot of purchasing power. Sorry you got left out. But, it appears you found a reasonable solution. 

I used to work for smaller tier automotive suppliers. I was constantly getting lock out of buying electronic components because of some surge in demand by larger suppliers. Now that I work for one of the worlds largest automotive suppliers I no longer have that problem. That is of course if my suppliers plants are not hit by an earth quake (Fukushima), or flooding (Thailand), or Covid-19 (global shut down). Now I just sit and wait to go back to work. I can plan my next audio system. But only working 2 days a week now I shouldn't buy all the gear I want. Damn mortgage and food is getting in the way .

Ge0


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## Ge0 (Jul 23, 2007)

Patrick Bateman said:


> About 18 months ago, I learned how to do loudspeaker simulations in 3D, using a package called "Abec." Possibly the hardest piece of software I've ever learned. And learning software is basically my day job; I am paid to learn software and implement it.
> 
> So if _anyone_ should be able to pick up ABEC, it's me. And learning it was just brutal. I came close to giving up a few times.
> 
> ...


Hey, I know Earl very well. He is a member of my local audio society. Brilliant guy. I've used a lot of his advice to make improvements in my car audio systems. His white papers are freely available online. You should read all you can.

Ge0


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## Ge0 (Jul 23, 2007)

SkizeR said:


> Speaking of a Rolls Royce.. has anyone here actually taken one apart? I have. Theres plenty of CLD. About as much as you'd expect from an average aftermarket install.


Nope, they wouldn't let me near it with my hammer, duct tape, and screw driver LOL! 

Seriously, we've had one in our lab before but it was off limits to anyone who was not directly related to the project. I did get to work on a Maybach S650. That's kind of close.

Ge0


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## dumdum (Feb 27, 2007)

Ge0 said:


> You can dampen the **** out of your doors, floor board, and fire wall. You'll reduce road noise for sure.
> 
> Ge0


That’s like blasphemy in this thread you do realise, I happen to agree with that statement

Damping reduces transfer of outside noise inwards, and so it does make the cabin a quieter environment by reducing the impact of noise from road vs tyres, suspension etc

Anyone who says otherwise hasn’t deadened a car and driven it before and after an install of just deadener


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## I800C0LLECT (Jan 26, 2009)

I stick to the rules that sound deadener showdown gave us years ago. The few cars I've done on my own just revealed other panels that were creating noise. So in my current car I just treated the areas surrounding the install and called it good enough. I did notice a difference without it breaking the bank or my back

Sent from my Pixel 4 XL using Tapatalk


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## Fathershelper211 (Apr 15, 2020)

Interesting article. I believe from my own experiments that results may vary.. lol I did do something really questionable. We had some sound/road noise dampening materials laying around the shop. Basically a foam piece with a tin/metallic backing on one side. Supposed to also work under the hood. I tried a piece behind my license plate. Which helps a bit. At least there is now s cushion there. I tried a piece on my trunk lid. Under the beauty trim. And I even put a piece under the rear door trim of the Tahoe. Before I ran out. That stuff did not stiffen anything. Nor does it block any sound. Lol dyno mat does add weight. It does change the vibrations and ppl who install it swear by it. Obviously they are getting results. Personally my Tahoe is more of a sound quality system. I removed the baffles from the rear vents and the rattles went away. I have a unique set up that I built to fit all the way behind the 3rd row that rounds it off. The car is a mobile broadcast station. So all the sound deadening in the world wouldn't matter. After a certain volume all you hear is music and the slight sound of your eyelids flapping.. lol sorry im not really helping here. Am I? Anyways My point is. Dude if people argue with your post and you knew it already then clearly you are just starting the same argument because your looking for an argument not a solution. We all know metal panels rattle we all know a car is like a fishbowl. We all know the challenges that environment creates. We all know our systems can be better. We all chase that dream because we are into car audio and probably anything audio. Myself I wanted my living room to have the Bass my car does so I built a isobaric box combined with a ported box and put rockford fosgate car subs with car amps powering it. Next to the couch in the corner... Its awesome btw... lol. Anyways. Good luck in life... may your audio make you happy.


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## Fathershelper211 (Apr 15, 2020)

Sorry... please note. Im talking about two different vehicles... the tahoe is one... the car is a honda


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## killadawg (Apr 29, 2018)

Not sure what I agree with here, yet I have an extremely "RIGID" car, built for racing with custom welded bracing, all solid motor and transmission mounts and all spherical stainless steel bearings, solid suspension mounts.. there is no play and no flex.. BTW a similar car without those rigidity modification is 3x quieter than mine!! so making rigid only allows more noise to travel to the interior in my instance! After sound dampening / deadening and running a fluidamper pulley, I managed to remove a moderate amount of NVH from my interior. I'm currently learning how to tune my own system, and I thought I had everything perfect (listening to my car while not running the engine or driving).. then I took it for a ride.. hahahaha well the sound went to hell because the amount of NVH is ridiculous even after 150lbs of sound deadening CLD, CCF, Tesa tape.. (nee to do the butyl rope thing on clips!!) etc.. Tire noise is ridiculous (running rallyX tires for winter, I will put quieter summers on soon). So in my case even tuning gets tricky because of the NVH change due to running the vehicle as compared to just sitting. Yet back to the topic at hand, I think *SkizeR *has the right information on this!


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## Hanatsu (Nov 9, 2010)

I've missed Bateman's threads, so much fun 


Patrick Bateman said:


> There are various materials which can attenuate sound.
> 
> Low frequencies are _incredibly_ long, and due to that, it's nearly impossible to attenuate those frequencies with much efficiency.
> 
> For instance, 50Hz is 680cm long, or 6.8 meters long. 50Hz is longer than your car. Due to the very long length, it's exceptionally difficult to attenuate low frequencies passively.


There are methods to attenuate low frequencies (even in cars) actively though... by using a second driver bandpassed selectively playing out of phase. My experiments showed that it actually works quite good to get rid of modes. Quite different to simply use EQ.

I missed your threads, always enjoyable to read through.


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## DavidRam (Nov 2, 2014)

The most effective sound deadening I have ever done in my car is divorce. Especially on the passenger side it's over 30dBs quieter, it's amazing!


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## eficalibrator (Aug 25, 2005)

killadawg said:


> Not sure what I agree with here, yet I have an extremely "RIGID" car, built for racing with custom welded bracing, *all solid motor and transmission mounts and all spherical stainless steel bearings, solid suspension mounts*.. there is no play and no flex.. BTW a similar car without those rigidity modification is 3x quieter than mine!!


You have to be kidding, right? Are you surprised that an engine, trans, and suspension with ZERO isolation brings more noise into the cabin?! Sound conducts really well through solids, which is why we put isolating layers (bushings, dampers, etc) in between them to break up the transmission path of the NVH from the factory. 

It's a completely different discussion to talk about making a normally flexible panel (like a door skin, decklid, or roof) resonate less by reinforcing it than it is to allow noises being generated by the tire/suspension/engine to get directly coupled to your listening environment.


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## killadawg (Apr 29, 2018)

eficalibrator said:


> You have to be kidding, right? Are you surprised that an engine, trans, and suspension with ZERO isolation brings more noise into the cabin?! Sound conducts really well through solids, which is why we put isolating layers (bushings, dampers, etc) in between them to break up the transmission path of the NVH from the factory.
> 
> It's a completely different discussion to talk about making a normally flexible panel (like a door skin, decklid, or roof) resonate less by reinforcing it than it is to allow noises being generated by the tire/suspension/engine to get directly coupled to your listening environment.


LOL.. No not surprised at all, I was just being devils advocate here as rigid doesn't really make things quiet, and yes I know and expected more noise, yet I didn't care at first, as this was a race car that got turned into a DD.. if I could get my invested money from this build, I would change the car out completely! squishy bushings and wobbly dampers equal ****ty response and terrible traction on the track. You can't have your cake and eat it too!! dilemma. During my isolation and car being parked it has been a great dance party system for my kids in the garage. and compared to the stock oem radio, I sounds way better even @ 75mph yet there is still the sound of my Turbo, Clutch and LSD's chattering, and suspension clanks and thuds along with tire drone. I did add mufflers to the exhaust, as those where way too loud. @ 35 -40mph it is not bad at all.


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## K-pop sucks (May 28, 2018)

The stiffer that car overall the noiser it is. Ever hear carbon fiber creak?

The noisest part of my car is the interior trim not fitting together and wind noise. The window will always be your weakest link and not worth dumping your hard earned money on deadening a car up until that point of diminishing returns. Better off spending money on skinnier tires with low rolling resistance IMO.

With that said I've went this far down the rabit hole, so I'll buy some more thinsulate and mlv to stuff in the rear and call it quits.


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## Married_Man (Sep 29, 2012)

(qualifier: I didn't make it through ALL 5 PAGES! )

Setting aside scientific theory for a moment and using common sense, it seems naive to state "sound deadening will never lower the sound level of a vehicle", and also naive to say "sound deadening will always lower the sound level of a vehicle".

Using extreme examples;

Car A has door panels made of 30ga sheet metal, car B has door panels made of brick.

Adding a single layer of sound deadening to car A door panels should measurably reduce sound levels. Adding 2 layers of sound deadening to car B door panels won't make a difference.

Wouldn't real world results vary across cars? Adding deadening to a well made, braced, stiffened vehicle may not make a measurable difference. Adding it to a junker seems like it likely would.


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## imickey503 (Dec 16, 2015)

That was Eloquent.


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## Batryoperatedboy (Jan 11, 2011)

So Patrick Bateman et al only drive nice cars. (Gross oversimplification.)


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## I800C0LLECT (Jan 26, 2009)

Batryoperatedboy said:


> So Patrick Bateman et al only drive nice cars. (Gross oversimplification.)


That's about it. Everybody go get a Lexus 

Sent from my Pixel 4 XL using Tapatalk


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## Crackfox (Apr 9, 2020)

The fact the original post contradicts itself doesnt help the argument. Adding CLD increases panel stiffness, therefore by the argument presented, does make a car quieter. Yes, welding on 1/4" steel plate will make it even quieter, but that's just silly, and we dont all have the time or money to rebuild panels out of composites. CLD might not be as good, but it still works. 

But move away for the "science" a minute, which is an incomplete assesment. Sound is something relative to the instrument measuring it. If you alter the frequency to inaudible levels, then the sound is no longer measurable and, relative to the TME is quieter. So if your ear cant hear it anymore, it is quieter. Fact. Has the sound gone, maybe not, but inaudible is perfectly fine in what we need.

The old question "if a tree falls in a field and noone is there, does it make a sound" come to mind. There are many arguments, including those that say, "what if there is a microphone and recorder there instead". Well that defeats the object of the the question. Person, TME or whatever else you want to suggest is irrelevant. If nothing is there to hear it the "sound" doesnt exist. 

Food for thought.

I'm currently mid MLV application in V my DC5/RSX. I'm going to be fairly P'd is it's not quieter afterwards. But I know it will be.

Sent from my SM-G960F using Tapatalk


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## Rrrrolla (Nov 13, 2008)

Hanatsu said:


> I've missed Bateman's threads, so much fun
> 
> 
> There are methods to attenuate low frequencies (even in cars) actively though... by using a second driver bandpassed selectively playing out of phase. My experiments showed that it actually works quite good to get rid of modes. Quite different to simply use EQ.
> ...


You actually made this work? Would love for you to expand on it a bit! I assume you would delay it by some amount of time then play it out of phase to "delete" the reflection? How did you figure out how much to delay by?


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## captainbuff (Mar 11, 2017)

First up; apologies for the stupidest post ever; but sound isolation relative to whom? People in the car? People outside the car? People 100m down the road (like ~120 yards sorry; I'm Aussie!)....? Sound isolation for whom dictates how to approach the treatment....



Patrick Bateman said:


> sound deadening doesn't do much to make the body panel stiffer.


'Stiffer' or 'denser'? Possibly they mean the same to people; but when it comes to sound isolation: MASS is the winner. How much sound do you hear though a metre thick piece of concrete...? Bingo. 'Sound deadener' is also what again...I think later it is confirmed as CLD...in which case it would contribute to increasing the sound isolation (denser panels).


Patrick Bateman said:


> Arguably the ideal way to make the panels more rigid is to use a dual pane composite.


Not 100% what dual pane composite is so excuse my ignorance; however from the diagram given you are targeting sound isolation...all good! Wjere I will raise an argument is that a car does not include such treatments; and again I query the rigidity vs density argument. Making something more rigid lowers the resonant frequency and starts to go into stuff that is over my head. It does not isolate sound (ALBEIT: as effectively as other means)


Patrick Bateman said:


> But there's just so many damn variables to this hobby.


I take this excerpt from a comment that included loudspeaker modelling and a reference to home theater. I agree! However...the variables in car audio are illimitable and (IMHO only) are ridiculous to try and identify past a certain point. In home theater...that is totally different....


Holmz said:


> That said, it is somewhat out of character to not study the evidence to the contrary.


Intriguing...I do this often as well. I know that I will be despised for what I write so I disclaimer what I say; but doing so lessens the intended point of the statements made. Why say what you are saying if you cannot prove it and are just going to be hated on for speaking? A good lesson! Also worth noting that evidence and logic and proof are the champions of any discussion.



Patrick Bateman said:


> Closed cell foam attenuates sound. Open cell foam attenuates sound. Fiberglass insulation attenuates sound. Rockwool attenuates sound.
> 
> In my experiments, fiberglass insulation works really REALLY well. It is hard for me to describe how much better it works; it's not a difference of 10-20%, it's a difference of 200-400% versus closed cell foam.


'Your experiments' have been done by many guys before and there are a TONNE of results. In fact kudos goes to Canada for their research into sound isolation through brick walls (to my knowledge it stands alone...?). However...the results are there to be found in 'pro audio' (and home audio)...they are not relevant to car audio (well...not as much! I do not wish to start an argument with anything I say; but the attenuation of certain treatments is of paramount importance in a recording studio...in a car it _*MAY*_ not make a difference if chosen incorrectly. It MAY make a decent difference if chose well...but you will never turn a car into Abbey Roads...). 

This is a mobile audio site, not a pro audio or home theater site. Not bashing on the knowledge side of what you are saying - as I would put money on the fact that you know more about this stuff than me - just querying relevance mate. Head to 'gearslutz' and start this topic up...I was annihilated within seconds and I was only after some assistance!

Peace mate


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## Holmz (Jul 12, 2017)

captainbuff said:


> First up; apologies for the stupidest post ever; but sound isolation relative to whom? People in the car? People outside the car? People 100m down the road (like ~120 yards sorry; I'm Aussie!)....? Sound isolation for whom dictates how to approach the treatment....
> ....


One would assume that the insertion loss would the same in both directions...
Unless the device acted like some some acoustic diode?




captainbuff said:


> ....
> Intriguing...I do this often as well. *I know that I will be despised for what I write* so I disclaimer what I say; but doing so lessens the intended point of the statements made. Why say what you are saying if you cannot prove it and are just going to be hated on for speaking? A good lesson! Also worth noting that evidence and logic and proof are the champions of any discussion.
> ...
> Peace mate


In a debate it seems wise to,know the oppositions perspective.

In a conversation, it is not a bi direction discussion unless one understands the point the other party is making. Otherwise one is just talking and not listening.

It cannot be an honest discussion without both parties understanding each other and appreciating their perspective.

Which... *I am basically saying, at least I do not despise you for that.*


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## captainbuff (Mar 11, 2017)

Holmz said:


> One would assume that the insertion loss would the same in both directions...
> Unless the device acted like some some acoustic diode?


One would be grossly incorrect if they thought that *sound isolation* was the same in both directions. In a multilayered system of sound isolation (say CLD, decoupled MLV, CCF) this is somewhat intuitive...?



Holmz said:


> In a debate it seems wise to,know the oppositions perspective.
> 
> In a conversation, it is not a bi direction discussion unless one understands the point the other party is making. Otherwise one is just talking and not listening.
> 
> ...


Yes,,,indeed. The issue is invariably created where the humblest party (or the party actively attempting not to offend and admitting they may be wrong and don't know everything) is taken as weak and assumed to be wrong.

Peace


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## Holmz (Jul 12, 2017)

You might be right about the sound isolation...

If we put an SPL meter in the car and a horn a meter away...
And the horn in the car and an SPL a meter away from the car...
Then we could have some proof of it.

I do not know the answer, but I assumed it is more like shining light through sunglasses from the front and from the back?


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## captainbuff (Mar 11, 2017)

Holmz said:


> You might be right about the sound isolation...
> 
> If we put an SPL meter in the car and a horn a meter away...
> And the horn in the car and an SPL a meter away from the car...
> ...


Well that would depend if they were Polaroids I believe,...come on man...? Neither of us are here to dick measure mate, so we can bail on the patronising metaphors.

Why the inclusion of a decoupled layer by many if sound isolation is only relative to the materials used? The order of materials will affect the final result...in each direction. Though I will agree with you; the affect would not be large!! Where it becomes extremely important (and in reality the source of my statements) is in sound isolating a bedroom for a drum kit...but that is not car audio so I will leave it there  though theoretically correct; practically it isn't relevant for this forum.
Peace


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## bassace (Oct 31, 2011)

Patrick Bateman said:


> At this point in the discussion, someone is probably thinking _"Patrick Bateman you are an idiot, I put sound deadening in my car and it became quieter."/_
> 
> There's two reasons why this happens:
> 
> ...



Yet that is the whole point of "sound deadening". The ears are more sensitive around 3-6kHz, therefore you want to block or change the panel resonance away from those frequencies. 

Also sound absorbing material in the vehicle absorbs frequencies from bouncing everywhere. That minimizes the echoing of noise from bouncing within, creating a more pleasant environment on the ears. 

Using SPL measurements are referencing a scalar point of data. Those auto journalists just use one number, you have to use an RTA on all audible frequencies. Using the "x car has this many dBs" doesn't tell me the whole story, it just gives a general idea.

A 68dB car can actually sound louder than another car measured at 70dB. What isn't seen on the measurements are the frequencies, the magnitude of those frequencies, the time duration of the echoing, and heck maybe even phase. More than likely they are just looking at the peak of all frequencies. 

If car companies didn't think "sound deadening(a loosely used term)" didn't work, they would not be placing material in those cars. 

Also those carbon vehicles have different resonance at different frequencies than steel or aluminum, likely closer to the sensitive frequencies of your ears. Carbon Fiber Reinforced Plastics are stiff, so they'll likely have a higher resonant frequency and maybe even less damping characteristics than metals. They also require their vehicles to be lightweight, so they will not use many materials. 

I'll say it again, don't look that the posted dB number, that won't show the qualitative assessment, only the quantitative. 

Ringing and echoing are unpleasant and are not factored in. The best tool to measure with is your ears, as that is the final sensor.


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## bassace (Oct 31, 2011)

killadawg said:


> Not sure what I agree with here, yet I have an extremely "RIGID" car, built for racing with custom welded bracing, all solid motor and transmission mounts and all spherical stainless steel bearings, solid suspension mounts.. there is no play and no flex.. BTW a similar car without those rigidity modification is 3x quieter than mine!! so making rigid only allows more noise to travel to the interior in my instance! After sound dampening / deadening and running a fluidamper pulley, I managed to remove a moderate amount of NVH from my interior. I'm currently learning how to tune my own system, and I thought I had everything perfect (listening to my car while not running the engine or driving).. then I took it for a ride.. hahahaha well the sound went to hell because the amount of NVH is ridiculous even after 150lbs of sound deadening CLD, CCF, Tesa tape.. (nee to do the butyl rope thing on clips!!) etc.. Tire noise is ridiculous (running rallyX tires for winter, I will put quieter summers on soon). So in my case even tuning gets tricky because of the NVH change due to running the vehicle as compared to just sitting. Yet back to the topic at hand, I think *SkizeR *has the right information on this!



Sounds like what is happening is the stiffer vehicle is more likely transferring higher frequencies. If so, I would "spend", in terms of weight, more on decoupled MLV vs CLD. If the frequencies are higher, the decoupled MLV should fair well in blocking those higher frequencies. 

Then you could add melamine foam or Thinsulate to absorb. Thinsulate should have a pretty good absorption 1500Hz and higher.


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