# Worth it to do sound deadening on Tesla Model Y?



## PhotonMiles (May 1, 2021)

I've got a 2021 Tesla Model Y, and it has a serious "body boom" road noise rumble problem. Here is a brief video showing my decibel meter set to dBC (in order to accurately capture the low frequency noise level) while I drive just 20 MPH on a somewhat bumpy neighborhood road. The meter averages in the high 90's and goes as high as 105dB at one point! Yikes!






The boomy bass-y road noise is super-low frequency, centering between 35Hz and 40Hz. And it's loud and irritating, and making me nuts. It's like I'm driving inside a sub woofer! The whole car just resonates with this loud rumble on anything but the smoothest of road surfaces.

At this point I'm trying to decide if it's worth trying to tackle the problem with sound deadening treatment since the car basically has zero soundproofing from the factory, or if it is a huge waste of time. This seemed to be a great place to ask! If I could achieve even 6dB or 9dB of improvement I think it'd be worthwhile, but I don't know that it's possible.

Do folks think that a meaningful improvement could be achieved with the standard methods of dampening the metal (dynamat, damplifier, etc), then closed-cell foam, then sheets of MLV? Or is this a huge waste of time since the problem frequencies are so low and just can't be tamed?

Thanks for any thoughts!!


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## Holmz (Jul 12, 2017)

I was going to write to identify the SPL meter, so you are doing well so far by measuring it.

iPads do not have great bass response, so it is hard to tell.


Does it sound loud?
Or is that meter bouncing around?
Was it dB(A) or dB(C)?


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## lithium (Oct 29, 2008)

Oooof, that's a hard one to address with a DIY solution. First you would need to identify the panel(s) or structure which are vibrating at the 30-40 hz. Then apply a CLD product. However, you might get unlucky and find that the resonant panel is a window or glass roof.

Alternatively, you could figure out the source or signal path and address that way. This isn't something anyone could reasonably DIY. Shame the NVH guys are Tesla would let a car ship with this issue.

edit: you wouldn't happen to be running non stock tires? Could be the tread pass frequency if you swapped to something a little more aggressive...


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## lithium (Oct 29, 2008)

I remember this one guy added a bunch of deadener to his car and shifted a panel resonance to a frequency that was excited while driving at particular speeds. Basically undid the work of NVH test and simulation team at the OEM. Kinda funny but super unlucky.


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## Mullings (Jan 31, 2016)

I would start off with treating the wheel wells with mlv since I know that they’re always a trouble spots , if that doesn’t help then you’ll have to drive around while someone is listening for the trouble spots which will be kinda hard because surface panels would rattle and squeak while big flat panels like the roof, floor or doors would produce those frequencies


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## jrwalte (Mar 27, 2008)

Have you talked to Tesla? I see it a '21 so you must have recently bought it. Any road noise in the 90s should be deemed unsellable. It could be considered borderline illegal, subjecting you to over 85dB excessively (even tho it's the low end, you can still argue it to them). Get Tesla's opinion on the noise. Maybe it's something they screwed up in manufacturing. Test drive another Tesla and take your sound meter, if you have to.


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## PhotonMiles (May 1, 2021)

Thank you to everyone for your thoughts! To answer a few questions:

This car is 100% stock, and I intentionally chose the smaller regular wheels in the hopes of reducing road noise. They come with “ContiSilent” tires that supposedly reduce road noise by 9dB! (Hah! Yeah right)

Good observation that the dB meter is just sitting in the cup holder without any bracing. However I’ve redone the experiment with the dB meter wrapped in a microfiber cloth to decouple it from the vehicle, as well as just holding it, and the numbers are the same.

I agree that NVH really screwed up royally here. But apparently they aren’t unique. I don’t have personal experience with other vehicles, but thru my investigation of the issue I’ve been told that the Audi e-tron and Mercedes EQC suffer from the same “body boom” bass rumble road noise issues. I’ve test driven a mustang Mach e and it is similar but much less. So potentially there is something fundamental about AWD EVs in an SUV configuration that leads to this. For comparison apparently the sedan-style Tesla model 3 does not suffer from this.

I just took the car in for service to repair all the defects from factory and shipping (Tesla is notorious for shoddy build quality needing repair after delivery) and to inform them of the rumble issue. A mechanic did a 15-minute ride along with me and my trusty SPL meter where it frequently hit 100 dBC and he said basically “that’s how these cars are, this is no different from any other”.

So I’m on my own here to address this. It seems like the odds of improvement aren’t great, huh?


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## diy.phil (May 23, 2011)

Probably should ask this in a tesla forum if others hear a similar issue. 90+ dB is way too high.


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## dgage (Oct 1, 2013)

I just want to state that a gas lawn mower is near 90 dB so I have a hard time believing driving down a normal road (with all windows closed) is as loud as a lawn mower inside. Here is a CDC hearing loss table that shows if that truly is the case, then you’d have some hearing loss in a matter of hours.






What Noises Cause Hearing Loss? | NCEH | CDC


Noise is a significant source of hearing loss, but you can protect your hearing. An important first step is to understand how noise causes hearing loss.




www.cdc.gov





I’d really suggest getting a SPL calibrator and using your computer with a microphone to determine the loudness and frequency. I know you said near 40 Hz but how are you identifying that? And I’m assuming you’re using C-weighting as that focuses more on low frequencies while A-weighting focuses more on the middle frequencies. A-weighting is what OSHA uses to identify harmful noise levels for workers. So it would be interesting to see results for both weighting with similar conditions.

I’m not saying I don’t believe you but I’m having a hard time believing it is at the levels you mention. And at least for me, it is hard to move on to the remediation stage if we’re working with levels this high. Because even if you do a great job, you’re only looking at 4, maybe 6 dB of improvement, which still has the sound level firmly in the long-term hearing loss range.

EDIT - And I’m jealous of you as I want to get a Model 3 or Y Performance but still holding on to my car a little longer as my kids graduate high school this year. But your results definitely have me leaning towards the 3 and I was already leaning that way. Only reason for the Y would be hatchback (better bass) and seat height (ease of entry/exit).


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## lithium (Oct 29, 2008)

dgage said:


> I just want to state that a gas lawn mower is near 90 dB so I have a hard time believing driving down a normal road (with all windows closed) is as loud as a lawn mower inside. Here is a CDC hearing loss table that shows if that truly is the case, then you’d have some hearing loss in a matter of hours.
> 
> 
> 
> ...


His measurements may not be 100% accurate but if he's describing booming than I wouldn't be surprised if that 90+ dB (thanks cabin gain). He would have to remeasure with the dBA setting on the meter but since this is mostly a low frequency noise issue the overall level will be reduced significantly. For example, A weighting at 40hz would reduce the level about 30 dB vs dBC.





dBA weighting filter frequency to dBA and dBC dB(A) and dB(C) A weighted sound calculate DIN IEC 651 calculator equal-loudness contours - sengpielaudio Sengpiel Berlin


dBA weighting filter calculator calculate frequency to dBA and dBC dB(A) and dB(C) A weighted sound DIN IEC 651 equal-loudness contours - Eberhard Sengpiel sengpielaudio




www.sengpielaudio.com





If OP had this issue at highway speed that would be a huge issue but he will likely just have to deal with it at the specific speeds this occurs.


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## PhotonMiles (May 1, 2021)

Indeed these are accurate dBC measurements, not dBA. As indicated by the previous poster, the numbers are dramatically lower on the dBA scale. The same meter measuring the same events in dBA shows numbers in the mid-to-high 60's. 

This is very much a low-frequency problem, as indicated by an FFT analysis of the noise. It centers between 35Hz and 40Hz. It's so low that it is more "felt" than "heard," although it is most certainly audible! It's because the noise is so heavily biased towards the low end of the frequency spectrum that there is such a dramatic difference between the dBA numbers and dBC numbers. It really feels like riding inside a bass drum.

To the commenter mentioning posting in a Tesla forum regarding this concern, there were 18 pages of comments on this issue before I came along (including several people suffering ear aches, tinnitus, and ultimately getting rid of the car because of it):

Ear pain/Pressure help

Wish I had found this before bothering to buy the car!! On my brief test drive I was so wowed by the new high-tech EV experience and trying to figure out one-pedal driving that I didn't pay too much attention to the rumble, although I did notice it. 

In any event, here it is. Now I still need to decide if it's worth any effort to try to tackle it, or if I should just sell the car as several others have done before me.


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## Holmz (Jul 12, 2017)

Well my leaf blower says 89dB, and in the small print it says at 50 feet.

My truck is in that range, but dB(C) is a bit different than dB(A)...


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## JCsAudio (Jun 16, 2014)

You could always drive down the road with your UMIK microphone and REW and measure the actual response. That would be pretty accurate, lol.


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## dgage (Oct 1, 2013)

JCsAudio said:


> You could always drive down the road with your UMIK microphone and REW and measure the actual response. That would be pretty accurate, lol.


It still needs a SPL calibrator as you‘ll know the frequency but not necessarily an accurate SPL scale.

As a matter of fact OP, PM me and I’ll let you borrow an SPL calibrator since I have an extra one as I’d really like to see an accurate set of measurements on this issue. And thanks for the link to the Tesla forum. This may have saved me a lot of money from making a similar mistake.


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## lashlee (Aug 16, 2007)

I got my Model 3 Performance just over a month ago (stupid fast, just like you think it is!) but already a decent amount of deadener to go in. Like someone else noted above, the wheel wells seem to be where the most of the noise comes in the cabin and the place to start first. My '21 even has some pieces of deadener peeking out from under the wheel well liners, letting me know that Tesla is at least following the lead of some of the aftermarket/end users trying to quiet down a "noisy" car. FWIW, I haven't gotten out my UMIK to see where the sounds land in my car but will probably do a before and after once it comes time to deaden the car.


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## PhotonMiles (May 1, 2021)

I got an SPL calibrator to check my dB meter and it was hot by 0.7dB, so pretty darn good. Basically my numbers are pretty much accurate. It really is a boomy vehicle. 

So does anyone think that this is a resolvable problem? Or is this just too big of a mountain to climb?


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## lithium (Oct 29, 2008)

I mean you could gut the car, apply deadener, and get lucky.. No good way for a DIYer to really diagnosis this issue.

If you haven't already, maybe someone on a forum somewhere has already deadened the crap out of their model Y and they could share their results with you..


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## dgage (Oct 1, 2013)

PhotonMiles said:


> I got an SPL calibrator to check my dB meter and it was hot by 0.7dB, so pretty darn good. Basically my numbers are pretty much accurate. It really is a boomy vehicle.
> 
> So does anyone think that this is a resolvable problem? Or is this just too big of a mountain to climb?


The short answer is this can’t be fixed, not to an appreciable degree.

I’d still like to see numbers with A-weighting as more of a level set but that is secondary to the deep bass issue at hand.

But you’re really saying the Model Y is a drum that you’re inside of. This isn’t external noise you’re trying to block. This isn’t panel vibration on a small scale that you can address.

The steps to address would be to pull the interior out, put down some CLD, which is really more for panel vibration attenuation, then put down a sound barrier such as MLV, and then isolate with CCF. But I doubt that would do much for the frequencies and loudness you’re describing. You could probably make a good first pass on the doors and wheel wells but for the boominess, there really isn’t anything we could prescribe for that as we‘re not sure of the source.

And that really sucks!


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## PhotonMiles (May 1, 2021)

dgage said:


> And that really sucks!


Yes. Yes it does.


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## LBaudio (Jan 9, 2009)

it is cheaper to try to solve that with deadening/sound barieres than selling the car and buying new one,....which will still need to be sound treated. This low freq noise is hard to block, but there will definitelly be some more positive outcome.


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## lithium (Oct 29, 2008)

LBaudio said:


> it is cheaper to try to solve that with deadening/sound barieres than selling the car and buying new one,....which will still need to be sound treated. This low freq noise is hard to block, but there will definitelly be some more positive outcome.


No one here can say that for sure. It's totally possible for it to be an issue with the glass.


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## LBaudio (Jan 9, 2009)

lithium said:


> No one here can say that for sure. It's totally possible for it to be an issue with the glass.


True. If it is the glass, then,....good luck, lol, but if it is produced by panel/floor resonating/road noise it could be at least partly solveable....better than nothing


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## DiamondFanatic (Dec 26, 2007)

The biggest concern I would have is the comments in that Tesla thread about the one piece rear casting... if it’s not the hatch adjustment for buffeting and it’s really an increase in NVH from the road/tires being transmitted through the suspension and chassis design you may likely never resolve it. At least not with anything practical

In reading the thread it seems like fairly low risk/effort to do a high quality CLD (not the Noico) on the floor, tub, and a couple spots on the hatch skin and see what the result is? Even with Resonix the cost would be around $200. I was also confused why there was never a good test of that modelyshelf in there but I may have missed it.

The one owner seems to have a hyper sensitivity and the pump part may be at play but it seems like you’re specifically concerned about the low frequency not the ~10k mentioned in the thread?


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## DiamondFanatic (Dec 26, 2007)

I’ll add I really appreciate you posting this and bringing this up because I really like the model Y and see them around town all the time. If not my next car (YOLO gas?) the car after will be an EV so of course I’m strongly considering Tesla (MY or MS) and this is really good to know.

Of the contributors to the thread you are one that’s able to actually take some really solid before and after measurements with the same car/roads etc and detail what you changed. If nothing else giving it a shot with a reasonable level of work would sort out if it’s fixable or not for everyone else.


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## cowdog360 (Jan 17, 2021)

I wanted to toss in an option here. There’s a company called RoadStage Audio that is coming out with a complete kit to sound dampen and entire Model 3 and Y. I’ll be reviewing one of the first kits here shortly on my Model 3. It’s a complete solution with CLD, CCF, MLv and cotton all custom cut to easily install yourself throughout the entire vehicle. If you’re interested let me know and I can get you some more information with one of the owners of the company.


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## PhotonMiles (May 1, 2021)

cowdog360 said:


> I wanted to toss in an option here. There’s a company called RoadStage Audio that is coming out with a complete kit to sound dampen and entire Model 3 and Y. I’ll be reviewing one of the first kits here shortly on my Model 3. It’s a complete solution with CLD, CCF, MLv and cotton all custom cut to easily install yourself throughout the entire vehicle. If you’re interested let me know and I can get you some more information with one of the owners of the company.


Well this is certainly somewhat compelling. All I can find about them is that they are here in Los Angeles where I am. Any ETA on this sound dampening kit, or any promised results? 

I'm awfully gun-shy to start tearing this car apart with no guarantee of any meaningful results. The few folks who've posted over at the Tesla forums after doing some CLD work either make very vague statements about "it's a bit better" or somewhat more honest (?) statements that it really didn't do much. No one has objective measurements of any kind. 

I also fear that the issue is inherent to the design, potentially the unicast rear shell of the vehicle. Audi's various technical documents about their similar E-Tron "body boom" problem sure seem to point the finger at the new requirements of mounting rear-wheel EV motors to the subframe. I suspect no amount of CLD can make up for something so fundamental. 

From what I can tell this issue plagues SUV-format RWD or AWD EVs, but not sedans or FWD EVs. The affected cars that I'm aware of are the Model Y, E-Tron, and Mercedes EQC, as well as the Mustang Mach-E to a somewhat lesser extent. 

The other thing that's got me disinclined to go nuts modifying the car is the current used value is actually MORE than the retail price. It's insane. If I took it to CarMax today, I'd lose a few grand because of sales tax but the offer is about $2500 HIGHER than MSRP! So it's really a matter of deciding whether or not to cut my losses and get the heck out of this situation.


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## SkizeR (Apr 19, 2011)

absolutely. even though it is an electric car, its probably the loudest car I've driven road noise wise. I even took a video of it on my phone some weeks back making fun of this very issue.


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## cowdog360 (Jan 17, 2021)

SkizeR said:


> absolutely. even though it is an electric car, its probably the loudest car I've driven road noise wise. I even took a video of it on my phone some weeks back making fun of this very issue.


After you guys did the Model Y with sound dampening, would you say there were noticeable improvements?


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## SkizeR (Apr 19, 2011)

cowdog360 said:


> After you guys did the Model Y with sound dampening, would you say there were noticeable improvements?


A little, but not much. The owner of that car only paid for deadening to prevent rattles for the system. He didn't do any soundproofing.


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## cowdog360 (Jan 17, 2021)

SkizeR said:


> A little, but not much. The owner of that car only paid for deadening to prevent rattles for the system. He didn't do any soundproofing.


I feel like the stereo really has to compete with the car's noise floor, especially on the highway (model 3). I'm hoping to lower that quite a bit to see how it helps output/clarity. But I'm also running a lot less power than your install had, so it probably has the volume to overcome it a lot easier.


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## SkizeR (Apr 19, 2011)

cowdog360 said:


> I feel like the stereo really has to compete with the car's noise floor, especially on the highway (model 3). I'm hoping to lower that quite a bit to see how it helps output/clarity. But I'm also running a lot less power than your install had, so it probably has the volume to overcome it a lot easier.


The owner of the one we did does not listen loud. I have a feeling he will be calling to install our new product..






ResoNix Barrier – Moldable Noise Barrier – ResoNix Sound Solutions







resonixsoundsolutions.com





We've actually had 4 model 3/y owners xall in the past few months to do soundproofing. More than any other car lol


Sent from my SM-G998U using Tapatalk


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## PhotonMiles (May 1, 2021)

SkizeR said:


> We've actually had 4 model 3/y owners xall in the past few months to do soundproofing. More than any other car lol


Did your soundproofing work on the Model Y reduce the rumbly bass-y road noise at city speeds at all? Or did it mainly benefit wind noise and such at freeway speeds?


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## SkizeR (Apr 19, 2011)

PhotonMiles said:


> Did your soundproofing work on the Model Y reduce the rumbly bass-y road noise at city speeds at all? Or did it mainly benefit wind noise and such at freeway speeds?


1 is the guy who we didbthe full build for but he passed on doing FULL sound proofing, one is still in talks, one didn't get back to me, and one is just considering selling the car. So, idk

Sent from my SM-G998U using Tapatalk


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## FlyingEagle (Sep 22, 2017)

PhotonMiles said:


> Thank you to everyone for your thoughts! To answer a few questions:
> 
> This car is 100% stock, and I intentionally chose the smaller regular wheels in the hopes of reducing road noise. They come with “ContiSilent” tires that supposedly reduce road noise by 9dB! (Hah! Yeah right)
> 
> ...


If you have ever had the pleasure of removing and patching one of Tesla's tires, factory ones I have had off on model 3 and S's, contained a glued in foam insert across the inner surface of the tire in equivalent area to where the tire tread patch would be. They work. Acura sport utilities like the MDX are coming with large resonator assemblies built into the depression of part of the barrel of the rim, which makes tire removal a bit of a chore to clear it without breakage to the plastic. These technologies work but you may be experiencing light weight body structures and their own set of audible phenomenon while on certain road surfaces which create certain tones in the vehicle.


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## PhotonMiles (May 1, 2021)

Tested: Do Acoustically Insulated Tires Really Hush Road Noise?

Car & Driver doesn’t think too highly of these tires.

Maybe they are quieter than the exact same tire tread without any foam, or perhaps they reduce loudness at a very specific frequency. But overall they apparently don’t do much and they DEFINITELY don’t help at 35-45Hz.

Honda’s approach with integrated resonators seems compelling, but as far as I can tell this tech is proprietary and not available in any aftermarket wheels. Bummer.


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## dgage (Oct 1, 2013)

One of my thoughts on the “drum-style” boom PhotonMiles described is that it is likely a big resonant panel such as over or is the battery compartment. I started to suggest potentially pulling the battery out and laying it on a mattress pad and blanket in the back while taking sound measurements (assumes battery and cooling cables are long enough or could be extended with adapters). But that is pretty crazy to do and if you did find out it was the battery area, what do you do since you don’t want to invalidate that warranty? 

What about this? Try putting some barrier behind the back seat like a piece of wood wrapped in a couple blankets so it turns the Model Y in to more of a sedan just to see if that changes anything.


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## PhotonMiles (May 1, 2021)

dgage said:


> One of my thoughts on the “drum-style” boom PhotonMiles described is that it is likely a big resonant panel such as over or is the battery compartment. I started to suggest potentially pulling the battery out and laying it on a mattress pad and blanket in the back while taking sound measurements (assumes battery and cooling cables are long enough or could be extended with adapters). But that is pretty crazy to do and if you did find out it was the battery area, what do you do since you don’t want to invalidate that warranty?
> 
> What about this? Try putting some barrier behind the back seat like a piece of wood wrapped in a couple blankets so it turns the Model Y in to more of a sedan just to see if that changes anything.


Well your first idea sure is thinking BIG! 🤣 

But I tried a variant on your second idea already; I got a 4’ x 4’ sheet of 2LB mass loaded vinyl and laid it in the back. 32 pounds of rubber is awfully awkward to move around! It made absolutely zero difference. None. I then tried hanging it like a screen from the rear jacket hooks and also zero improvement to the rumble. Granted it didn’t make it all the way to the ceiling.

So since that made absolutely no difference whatsoever I’m even less inclined to start spending a bunch of time and money pulling the car apart and installing CLD.

Any chance an aftermarket suspension upgrade or better tires (or both) could reduce the rumble? I figure maybe the best thing is to attack the problem at the source which is clearly road variations being transferred through the wheels and suspension.


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## lithium (Oct 29, 2008)

barrier wont work unless its continuous. And you would have to guess the correct panel. 

You could see if is a cabin mode by opening the windows. Wind noise might mask the booming though...


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## PhotonMiles (May 1, 2021)

lithium said:


> barrier wont work unless its continuous. And you would have to guess the correct panel.
> 
> You could see if is a cabin mode by opening the windows. Wind noise might mask the booming though...


Haha interestingly this is exactly what I just tried next. Driving slowly enough to not cause major wind noise but fast enough on my nearby uneven road to cause the boom (20 MPH) yielded identical results if the windows were opened or closed, and even if the rear hatch was opened or closed. Of course the boom subjectively seemed a bit worse with closed windows since there was no distracting wind noise at all, but the dB meter readings were essentially identical.


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## FlyingEagle (Sep 22, 2017)

Does it change if you load all the empty seats with mass, like sitting on the seats? Kind of like when you put three more people in your car and suddenly, it is quieter minus their breathing and earthly sounds. Maybe you just need to load up the car with rubber filled training dummies?


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## dgage (Oct 1, 2013)

PhotonMiles said:


> Any chance an aftermarket suspension upgrade or better tires (or both) could reduce the rumble? I figure maybe the best thing is to attack the problem at the source which is clearly road variations being transferred through the wheels and suspension.


I doubt the suspension between the Model 3 and Y are THAT different. And I doubt tires would change the frequency of the vibration unless you have a wheel out of balance. You could take your tires and get a RoadForce balance but if they were bad, you’d feel that at higher speeds I’d expect. It also wouldn’t be as bad at lower speeds as you mentioned an issue at 20 mph, which leads me to believe it isn’t tire related.

Every panel has a resonant frequency, which is the frequency where it is most “energetic” or ”excitable”. This is how a singer can break a glass if they’re able to hit the frequency where the glass excites. People walking in unison caused the Millenium Bridge in London to sway so they had to install dampers.

Since the back seat floor is flat, try putting a big blanket down and then put the MLV down on the floor. Essentially I want you to try to put weight on the floor and see if that makes the issue go away or attenuate. My theory is that the floor is what is resonating or what is under the floor (battery pack). It is worth a shot. If that doesn’t work, I’m out of ideas. Wish you the best.


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## lithium (Oct 29, 2008)

dgage said:


> I doubt the suspension between the Model 3 and Y are THAT different. And I doubt tires would change the frequency of the vibration unless you have a wheel out of balance. You could take your tires and get a RoadForce balance but if they were bad, you’d feel that at higher speeds I’d expect. It also wouldn’t be as bad at lower speeds as you mentioned an issue at 20 mph, which leads me to believe it isn’t tire related.
> 
> Every panel has a resonant frequency, which is the frequency where it is most “energetic” or ”excitable”. This is how a singer can break a glass if they’re able to hit the frequency where the glass excites. People walking in unison caused the Millenium Bridge in London to sway so they had to install dampers.
> 
> Since the back seat floor is flat, try putting a big blanket down and then put the MLV down on the floor. Essentially I want you to try to put weight on the floor and see if that makes the issue go away or attenuate. My theory is that the floor is what is resonating or what is under the floor (battery pack). It is worth a shot. If that doesn’t work, I’m out of ideas. Wish you the best.


Tire tread impact frequency might be it. Math is pretty straight forward to figure out. Just need to know number of treads on the tire, tire size (circumference), and ground speed.


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## dgage (Oct 1, 2013)

lithium said:


> Tire tread impact frequency might be it. Math is pretty straight forward to figure out. Just need to know number of treads on the tire, tire size (circumference), and ground speed.


Technically something like that could occur but do you think that would really cause an issue at such a low speed of 20 mph? And if it were tires, wouldn’t it change across speeds? Technically it is possible but I’m assuming there are multiple tire sizes and types involved in this issue based on how long the Tesla thread is but it is a good question. Every possibility should be explored.


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## lithium (Oct 29, 2008)

Tire tread impacts create vibrations that travels through the frame to various panels. Panels with resonant frequencies inline with the input is excited and creates the noise in the cab. When he's traveling at a particular speed the frequency of the tire treads lines up the panel resonance. When he changes the speed it moves the vibe outside the panel resonance, no noise.


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## PhotonMiles (May 1, 2021)

To add some clarity the booming is exacerbated by uneven road surfaces, even at slower speeds. The issue isn’t specifically due to a certain speed, it’s more a matter of how remarkable it is that it’s so bad even at slow speeds. The smoother the road, the less bad the boomy noise.


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## PhotonMiles (May 1, 2021)

So I tossed this link on the thread over at the Tesla Forum, and thought I'd put it here as well to get thoughts from the experts.

I came across this 2017 Swiss study about reducing low-frequency resonances in passenger cars. 

The effectiveness of the suppression of low frequency acoustic resonances with porous sound absorbing structures of multifunctional upholstery materials of car body interior

It's super-academic and hard to understand. But the main message I took from it is that using some good sound-absorbing materials in the interior of the rear area of the vehicle can lower bass-y resonances by 9 to 12 dB. 

If I could get that level of improvement in the Model Y I'd be elated. Even half of that would probably be fantastic.

I'm wondering if anyone here can parse the science-lingo in the study and help me understand a bit better exactly what materials they used to get these results?


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## lithium (Oct 29, 2008)

Well if OP wanted to create something like a giant bass trap or resonator in the car that might help. 

I would be curious if you can apply a home theater design helmholtz resonator to address the booming. In theory it should work. OP just needs to identify frequency of the booming, not sure if his meter can do it but if you have REW and a microphone you should be able to get it. 






Calculate Helmholtz - Resonator







mh-audio.nl





Example: 








DIY helmholtz resonator made easy - Gearspace.com


i've seen a couple of questions here regarding how to tune helmholtz resonators. i think those are very easy to build & tune & very effective f



gearspace.com


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## dgage (Oct 1, 2013)

PhotonMiles said:


> So I tossed this link on the thread over at the Tesla Forum, and thought I'd put it here as well to get thoughts from the experts.
> 
> I came across this 2017 Swiss study about reducing low-frequency resonances in passenger cars.
> 
> ...


I didn't read all of it as I'm not completely sure of the point. I think what they were really trying to say is that vehicle borne noise can be addressed to a degree but it needs to be a multi-pronged (multi-layer) approach. The main thing they kept trying to get across is fibrous material to interfere with more of the acoustical energy. The idea of the fibrous material is similar to putting polyfill in a sealed enclosure to make the enclosure seem a little larger (up to maybe 10%). While this is all true, the frequencies this will assist with are limited to the higher frequencies which it is notable that their charts use kHz as the unit and don't have much improvement until the higher frequencies.

I'm big into home theater and own a home theater subwoofer company that produces 18" and 24" subwoofers. I have worked many times with theater designers and have also researched sound treatments for better sound quality. The problem is that treatments for bass, also known as "bass traps", have to be quite large/thick to be effective. You even have to have several inches of insulation to even start to attenuate the midrange much less deeper bass, which you aren't going to get in an auto environment. And even MLV isn't dense enough to block deep bass. So no, I don't think you'll get anywhere near 9 to 12 dB, if you're talking deep bass, maybe 2-3 dB if you're luck. UNLESS you find the source of the resonance and address. But if it is the cover over the battery or the battery or a suspension part, what is the mitigation that won't interfere with your warranty?

And to back up what I just wrote, a guy named Bob Gold did some testing to determine how different materials with different thicknesses attenuate the various frequencies. Here is the site (https://www.bobgolds.com/AbsorptionCoefficients.htm) and I pulled out the rows on Owens Corning 703, which is a popular insulation used in sound treatments (Roxul 60/80 are also popular). And here is a popular thread on AVSForum that focused on DIY printed sound treatments for theater rooms that used OC703 and he seems to go into much more detail. This essentially shows that 1" and 2" barely do any attenuation of the 125Hz frequency. You really need to get to 3" or 4" to really attenuate lower midbass. Now OC703 isn't that deep so maybe you'd get better results down low with something a little more dense. Well if you go more dense to try to attenuate the 125 Hz, you'll get more bouncing of high frequencies, which takes us back to the document you linked in that multiple layers would be needed.


PRODUCTTHICKNESSMOUNTINGDENSITY125HZ250HZ500HZ1000HZ2000HZ4000HZOC 703, plain1" (25mm)on wall3.0 pcf (48 kg/m3)0.11​0.28​0.68​0.9​0.93​0.96​OC 703, plain2" (51mm)on wall3.0 pcf (48 kg/m3)0.17​0.86​1.14​1.07​1.02​0.98​OC 703, plain3" (76mm)on wall3.0 pcf (48 kg/m3)0.53​1.19​1.21​1.08​1.01​1.04​OC 703, plain4" (102mm)on wall3.0 pcf (48 kg/m3)0.84​1.24​1.24​1.08​1​0.97​

The first step I'd suggest before trying to attenuate is to try blocking the noise. You could potentially use a CONTINUOUS layer of MLV with some dense jute underneath and then some closed cell foam or neoprene before putting down the carpet. That would definitely help for some frequencies and is basically how luxury cars help make their interiors quiet. But really luxury companies attack the noise level in the design phase with quiet suspensions, acoustic (dual-layered) glass, gluing of panels, etc. This is why even if someone goes crazy with sound treatment, it won't turn an econocar into a quiet car. 

Which brings me back to the Model Y. Will a continuous layer of MLV even help? Well, if the source of the noise is under the floor then maybe it might help some. But if it is the suspension or something other than the floor, the MLV won't help much because the job of MLV is to try to BLOCK the source of the noise, which is why it has to be continuous. And if you don't block the source of the noise, you're not going to be able to get a thick enough piece of somewhat dense insulation to be able to absorb near or under 100 Hz.

So without knowing the source of the noise in the bass range under 100 Hz, you're not going to be able to do much by just throwing traditional auto-noise abatement strategies. Sorry.


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