High frequency noise - sound reduction

[Madsen203]

I’d like to stuff something under the rear passenger seats to muffle to 4-6khz sound emitting from the electronics. Service center said noise is normal and penthouse seal is aligned properly (which it visually appears to be). The noise is most noticeable driving without music or music at low volume greater than 30mph.

I’ve ordered some mass loaded polyurethane to put in there but I want something there to absorb the sound as the MLV will only be reflecting it away.

What flexible, semi-heat resistant options are there? I looked at mineral wool to go under the MLV but I’m concerned if you drove with the windows open and air flows through there that it will spit fiberglass all around the car—bad news bears if that were to happen.

There are mats under the floor carpet of some cars (looks like wool/cotton mix—often gray in color) that would possibly work and are flexible which is key. I found something similar to this on Soundproof cow but for a $30 sheet they wanted $150+ In shipping.

Any other ideas or recommendations? Thanks I’m advance!

 

[GOVA]

OP, can't offer any recommendations on material, but please DO report back once you finish up the project.

Is this coming from 'electronics' or motor?

 

[DanDi58]

"The noise is most noticeable driving without music or music at low volume"

Who does that?!

 

[Madsen203]

"The noise is most noticeable driving without music or music at low volume"

Who does that?!

I have a pregnant wife who has always been sensitive to noise. Day to day driving alone is not an issue.


I will report back. Look forward to any other suggestions.

The noise appears to be from the battery/inverter or something as it can be heard under very light throttle at slower pace (25-45mph).

Going to try a cotton mat that is flame/heat rated and then cover it with MLV. For the MLV to be effective, it needs to be airtight which I won’t be able to do. Anything to drop it 10-20db though would be great!

 

[Madsen203]

Ordered some sound insulation from Sound Proof Cow. 2” thick cotton mixture in a 2’x4’ pad. I’ll stuff two of these in there with some mass loaded vinyl. Will report back when everything gets delivered.

 

[Madsen203]

Alright so I just finished stuffing 2” sound deadening mat under the seat and then added 1# mass loaded vinyl on top as best I could. I’ll test it out later this morning to see if there was any benefit.

 

[Madsen203]

Alright so I just finished stuffing 2” sound deadening mat under the seat and then added 1# mass loaded vinyl on top as best I could. I’ll test it out later this morning to see if there was any benefit.

Sound absorbing cotton

Mass loaded vinyl

When I played a YouTube video that had a 6k frequency note playing, the MLV dropped the volume significantly. The cotton didn’t do as much but the cotton will help prevent it from echoing as the MLV doesn’t absorb sound-only blocks it. So any gaps would allow noise to come through. Hoping the combination helped reduce the high frequency noise.

I only hear the noise at highway speeds with low volume music or if I’m on a phone call. Hoping this helps as my newborn will be sitting right above the noise maker.

 

[Madsen203]

I can say this worked 80%. Vastly reduced. I think some of the noise is now echoed through the rear of the car above the motor (need to remove the sub trunk and not sure how yet) and through the side trim that runs along the edge of the seat. Overall, much better. It sounds like it should (minimal, faint noise).

 

[chamshaw]

Madsen203; we all hope for a healthy baby for you and as a VERY retired opera singer (I no longer even try to sing in the shower) I comment that your wife's sensitivity to noise can be a painful problem for some of us. I always drive in absolute silence (I once raced) and enjoy my Baroque favourites at home. Popping small hard items into a new car during assembly is a nasty old-time trick which one hopes is no longer common. Well-found, never-the-less.

 

[Madsen203]

Final note: I tightened the rear DU ground to frame until the threads about stripped. Somehow this fixed the noise almost entirely. It’s still very slightly audible but hardly so (like new car quiet). Found a few threads in the Model S/3 forums talking about this being the culprit and tightening beyond the 10nm spec resolved much of the noise.

I will pull the rear wheel and tighten the DU side once I receive the jack pucks. Then check the front motor as well. I was able to get another 1/3-3/4 turn from the bolt that was holding to the frame.

Picture shamelessly stolen from another thread on this forum. With the Gemini wheels and no covers, my thin arms could reach in with a ratchet to snug it up some.

What a relief! I can say I love this car again. Part of me wonders if it needs a second ground as well but so far, the results are phenomenal! More of an impact than the sound insulation project I did above.

Highly recommend trying this. Worth the 10 seconds of your life (or 10 minutes if you have to remove the wheel).

 

[Todd Turbo S]

Final note: I tightened the rear DU ground to frame until the threads about stripped. Somehow this fixed the noise almost entirely. It’s still very slightly audible but hardly so (like new car quiet). Found a few threads in the Model S/3 forums talking about this being the culprit and tightening beyond the 10nm spec resolved much of the noise.

I will pull the rear wheel and tighten the DU side once I receive the jack pucks. Then check the front motor as well. I was able to get another 1/3-3/4 turn from the bolt that was holding to the frame.

Picture shamelessly stolen from another thread on this forum. With the Gemini wheels and no covers, my thin arms could reach in with a ratchet to snug it up some.

What a relief! I can say I love this car again. Part of me wonders if it needs a second ground as well but so far, the results are phenomenal! More of an impact than the sound insulation project I did above.

Highly recommend trying this. Worth the 10 seconds of your life (or 10 minutes if you have to remove the wheel).View attachment 722985

Nice write up and thank you for the information. Where did you purchase the 1# mass loaded vinyl and how many sf did you end up needing to complete the job?

 

[Madsen203]

Nice write up and thank you for the information. Where did you purchase the 1# mass loaded vinyl and how many sf did you end up needing to complete the job?

Amazon. It was about $50 for 16sqft. 1#. Any heavier and you lose pliability.

I got a 4x4 section. I probably only used 4’x1.5’

 

[gadgetfreaky]

Final note: I tightened the rear DU ground to frame until the threads about stripped. Somehow this fixed the noise almost entirely. It’s still very slightly audible but hardly so (like new car quiet). Found a few threads in the Model S/3 forums talking about this being the culprit and tightening beyond the 10nm spec resolved much of the noise.

I will pull the rear wheel and tighten the DU side once I receive the jack pucks. Then check the front motor as well. I was able to get another 1/3-3/4 turn from the bolt that was holding to the frame.

Picture shamelessly stolen from another thread on this forum. With the Gemini wheels and no covers, my thin arms could reach in with a ratchet to snug it up some.

What a relief! I can say I love this car again. Part of me wonders if it needs a second ground as well but so far, the results are phenomenal! More of an impact than the sound insulation project I did above.

Highly recommend trying this. Worth the 10 seconds of your life (or 10 minutes if you have to remove the wheel).View attachment 722985

hi, what is this? can you explain a little more detail? what's DU?

 

[Mattemsmy]

what's DU?

Drive unit?

 

[maximus96]

Final note: I tightened the rear DU ground to frame until the threads about stripped. Somehow this fixed the noise almost entirely. It’s still very slightly audible but hardly so (like new car quiet). Found a few threads in the Model S/3 forums talking about this being the culprit and tightening beyond the 10nm spec resolved much of the noise.

I will pull the rear wheel and tighten the DU side once I receive the jack pucks. Then check the front motor as well. I was able to get another 1/3-3/4 turn from the bolt that was holding to the frame.

Picture shamelessly stolen from another thread on this forum. With the Gemini wheels and no covers, my thin arms could reach in with a ratchet to snug it up some.

What a relief! I can say I love this car again. Part of me wonders if it needs a second ground as well but so far, the results are phenomenal! More of an impact than the sound insulation project I did above.

Highly recommend trying this. Worth the 10 seconds of your life (or 10 minutes if you have to remove the wheel).View attachment 722985

Can you share the thread for this discussion? I'd like to see where all the locations are that needs tightening. Thanks

 

[Madsen203]

Can you share the thread for this discussion? I'd like to see where all the locations are that needs tightening. Thanks

DIY fix ground strap thread

Thanks to @camalaio for this.