t’s me, B.
Warning: There’s a lot of reading here. I’m no Stephanie Meyer, but read on if you want the detailed information, or just scroll to the pretty pictures if you so desire.
I’m new to the world of Porsche, but downright decrepit when it comes to car audio and aftermarket noise control. Recently picked up this 991.2, and love it to pieces, but not so much the high levels of scratching, sand-papery tire noise from the Michelins. On anything but perfect surfaces they rudely interrupt the PSE like an angry toddler suddenly materializing and demanding your attention in a critical Zoom meeting.
Now, before someone quite witty comes along and and asks: But B, if you wanted a quieter car, why didn’t you buy a (lexus|bmw|mercedes)?
Well, far be it from me to deny someone the chance of being clever.On to the why: Excessive road noise is a major migraine trigger for me. Also, who wouldn’t want a better listening environment for that Bose sound system? (This is sarcasm.)

Moving on.
The project will consist of phases. Not only does this give the opportunity to observe changes made by doing some sections of the car. I’d prefer to modify this specific post with updates, but I do believe Rennlist has a time limit on editing. I’m not sure the duration, but I believe it to be just before I notice horrendous errors in my post.

Now, a note on measuring results.Obtaining quantitative data from adding sound control materials ranges from pointless to overly optimistic. There’s too many variables. The smallest change the human ear can discern is about 3 decibels. That could be accounted for by warmer tires, a windier day, or poor lunch decisions. One probably could try and control all the variables and use a real time analyzer with a calibrated microphone to at least create some comparisons. It ain’t me.
I’m all about qualitative data here. Fortunately, I do believe I am climbing the Slope of Enlightenment on the subject, and have already crested and tumbled from the Peak of Mount Stupid. (See: Dunning-Kruger effect.)

Having done this so many times in my cars now, I do believe that I’m not as affected by expectation bias as most people are. If you’re not familiar with expectation bias, it’s the reason that people often find $8000 speaker cables sound so much better than generic OFC-on-a-spool from Walmart. As the kid’s say, “Don’t @ me” about the speaker wire.
How am I judging results?I am driving around the same areas before and after. Neighborhood speeds. Worn road with 45mph speed limit near home. Smooth and rough sections of highway.

Hint: Cup your ears forward, then cup your ears backwards. Which is louder?
With no treatment, the rear was louder.
Let’s talk about material selection. We need to keep a few things in mind:

• Much of the sound in these cars is structure-borne. Sound is also quite good at getting around things and traveling through voids.
  
• Blocking sound is hard. High frequency sounds can be blocked with relatively thin material, such as foam or carpet padding. Blocking low frequency sounds can require 2” thick material around the 200hz range, up to 10” thick under 100hz. Thickness can be substituted for density, and 1lb/ft^2 of material performs quite well.
  

Damping mat:

We need to address butyl damping mat abuse. (Read: Not dampening mat, we’re not trying to make things wet here.)

I’ve gone through the phase where I slap Dynamat on every single surface it will bond to. In so many layers I’ve had trouble getting panels back on the car. Here’s the skinny: Damping mat is for damping.

• It is best applied to 50-80% of the center of large, flat, metal panels. Again: Metal panels.
  
• The difference in effective damping between a panel with 80% coverage and 100% coverage is microscopic.
  
• Damping material is not sound blocking material. It will contribute to sound blocking slightly, just by being dense and in the way. Something I’m accused of frequently.
  
• Damping mat will lower the resonant frequency of the surface it’s applied to, which also means it takes a bit more energy to get it excited. This means you can rap on the panel with your fingers and demonstrate to your unimpressed partner that it goes ‘thud’ instead of ‘thunk’ therefore justifying the time, effort, and cost.
  
• I prep by cleaning the panel with alcohol. I then use a prep solution sprayed on and wiped off. In this case, Optimum Paint Prep. Always do plenty of prep work. The surface must be clean and free of any residues.Poorly prepped surfaces can end up with the mat peeling off and sticking to things in the door you don’t want it stuck to.
  

Foam or padding:

• Much of the sound in these cars is structure-borne. Sound is also quite good at getting around things and traveling through voids. We can’t do much about structure-borne noise, but we can block the voids and gaps.
  
• Blocking sound is hard. High frequency sounds can be blocked with relatively thin material, such as foam or carpet padding. Blocking low frequency sounds can require 2” thick material around the 200hz range, up to 10” thick under 100hz. Thickness can be substituted for density, and 1lb/ft^2 of material performs quite well.
  

The Subject:

• 2017 Carrera S coupe
  

Complaints:

• Scratchy, sandpaper-like sound from the tires
  
• Just too much noise overall, really
  
• Seat leather squeaks like a dolphin rolling around in rubber sheets
  
• Seat creaks and cracks
  
• Touch surfaces of steering wheel exhibits loads of plastic creaking
  
• Just a lot of little rattles here and there
  

The Goal:

• Reduce annoying sounds while preserving good sounds, like the PSE
  
• Apply material efficiently and effectively
  

Materials:
Annoying Noises:

• Self adhesive 1mm thick felt
  
• Probably some hot glue or silicone glue
  
• Ensolite (It’s just ⅛ neoprene)
  

Sound Control:

• 3M Thinsulate
  
• Damping Mat - Aluminum backed butyl
  
• Second Skin sludge
  
• Heavy vinyl sound barrier with open cell foam backing (I may not end up using this.)
  

Misc:

• Nano tape
  
• Alcohol (For surface prep, not for me)
  
• Surface prep
  
• So many paper towels
  
• So many utility blades. The edge of a Milwaukee blade is ephemeral at best
  

The work.

All work performed with the battery disconnected.
Generally Annoying Areas:

____
Addressing the noisy seats:

A generous application of adhesive-backed felt everywhere the seat came in contact with another surface. Simple and effective.
I also attempted the spray lubrication in the seat mechanisms as detailed in other threads. It made no difference to the creaking. I have no desire to fully disassemble the seats, so putting a pin in that for now.



Taking photos of a car interior creates dust.

____

Doors:
The Musicar video is quite good for disassembly instructions. I also enjoyed the tutorial from Pelican Parts about the door guides. I replaced the noisy door guards while I was in here. Requires a spline bit to remove.I’ll also note: Invest in good panel pulling tools. I used plastic spudgers for most of it, but a good set of metal tools is great, too. Especially with the little pink door clips.

Hint: Get them right in the crevice of the tool, pull to pop, pull again to launch the clip into low orbit.

Door body:Upper section: 7” height, applied the length of the door. Additional 3-4” strip applied over the top of that because I just have just so much of this stuff laying around. Wrote something on the material to confuse future archaeologists..

Lower section: Added a square to each side of the factory damping mat.

Moisture barrier/plastic panel/whatever:

First, I didn’t put any damping mat on this. There’s no point and it’s messy.Second, that speaker is mounted to an unstable surface. Definitely contributing to its terrific sound quality. I can’t be bothered to try and correct this, so I won’t.

I carefully attached the barrier to the loose door card to find voids. In my experience, voids in the door can let a lot of noise through.

Cut a piece of 3M Thinsulate in a way that wouldn’t interfere with door handle operation (A lesson learned from experience) and attached it with nanotape. The nano tape doesn’t need to hold it perfectly, it’s just there to keep it from falling off before you put the door card back in.



3M thinsulate

I dont remember if this is second skin or raamat


___

Interior:

Rear shelf:I noticed that the ‘lip’ under the rear window can be easily removed. Underneath it, is a cavity with an undersized piece of factory foam. I removed the foam. Then, I cut a 6”x60” strip of 3M Thinsulate and ran it behind the metal panel and inside the void. It’s only abut 48” in there, so the ends where the void was larger I folded the material over. Finally, I placed the factory foam pad back between the Thinsulate and the metal supports. Sorry, no after pictures of the material installed. Being 6’7 in the back of a Porsche puts a real damper on the time you spend there.


Right there, where the red arrow is.


Exterior:

– Sludge to be applied to rear wheel wells. Maybe the front if I have spare material.

____
Results in chronological order:

Felt for leather contact points:
No more squeaks.
Lubricating the seat mechanisms/rails:
No result.

Insulation strip at the rear of the car:
Higher frequency/scratching sound reduced. Road noise shifted more to the front half of the car.

Door treatment: (Butyl on interior side of exterior door surface, thinsulate between door card and moisture barrier, replacement door guides.)
Door guides fixed the squeaking.
More mid-high frequency reduction. This is obvious partially because the lower frequency tire rumble is easier to hear.
The road noise has slightly shifted to the rear of the car again.



Stay tuned.

Edited to add: The original title included "Dangerously close to too much information.
The irony of this being truncated for being too long is not lost on me. Nor have I learned anything.

 

Wow. This almost makes me thankful for my tinnitus and hearing loss.

 

My audiologist told me I have the hearing of a teenager. This fact has not only cost me a lot of money by giving me a blank check to upgrade my home audio setup, but it also got me in a great deal of trouble with my wife.

But the real sick thing is I enjoy this kind of work.

 

Thanks for the post and please keep it coming. I've sort of had doing some noise reduction work on my list for a winter project. Several winter have come and gone with no progress as yet, but I think another winter will be coming along.
A couple of questions:
1. What is the "door card"? The interior door panel that is removed??
2. Can you clarify what is meant by "new door guides"??
MusicarNW has been in my doors to install their kit so I expect those are OK; but I would like to look inside and see what they've done.
My thoughts are to treat the wheel wells (sludge or dynamat), and put mass loaded vinyl under all the carpeting.
While I realize it might be a fools errand I do want to try and take measurements/recordings with a calibrated mic.

 

Wow...thanks for the info. Excellent write up!

 

1. Yep, the plastic/leather interior part.
2. 991.1 and apparently some 991.2 have creaky door guides. (pn 00) and there's an updated version (pn 01) that is on the later cars and is silent. I got mine from Suncoast I think. https://www.suncoastparts.com/product/SKU9X1GUIDE.html



Sludge has been done in the rear wheel wells now.

I removed the wheel well liners (real PITA if I'm being honest)
Be sure you MASK if you do this. Detach the wiring bracket from the car and put it in a plastic bag. Maybe add some plastic wrap around all of it so it doesnt get messed up.
Cover your suspension. Cover the lip of your wheel wells so you dont get it on paint. The stuff can be chipped off, but it's a pain.

Take some masking tape and wrap the threads of every bolt. After curing 24 hours, you can twist the tape off.

For prep i did diluted APC with a stiff bristle brush, rinsed it well, and then used a paint prep spray. Finally, alcohol wipes.





Green arrow points to a similar factory material. Red arrow points to nothing.



Note: This is halfway through and slapped on. Once it was done i did a very thin careful roller layer to even out the texture. It dries matte black.


Over the two wheel wells I applied about 3/4 of a gallon and just got tired of doing it.

I used a 3" roller to apply most of it. A foam brush for hard to reach areas. It took a couple days with frequent thin coats to use up 3/4 of a gallon.
|
Notes:
1. These panels are already damped pretty well. Knocking on them will show that.
2. If I did it again, I think I'd just use CLD (constrained layer damping mat) in the smooth untreated areas.
3. Time involvement was having the car out of commission for about 36 hours, and a lot of labor cleaning/prepping/applying.
4. Put a bag over your suspension/brakes. It gets messy.
5. Mask the seam in the body. Getting the material on it makes it a real hassle to get the liners back in.

Questions:
1. Why does this car have an entire quarry worth of gravel packed in every crevice?
2. How in the world do you snap the splash guards back in?

Results:
This was subtle. So subtle I don't want to say for certain that it did much. It does seem like the sound has now shifted 'centrally' in the car.
Note on result: It takes 7 days to cure. I am now 3 days in to curing. Spectrum is noted to be more effective up to 7 days of curing. I don't expect a dramatic difference.

This is going to be part of a system, I will have some CLD on the other side, then a combination of Ecowool in large voids and Thinsulate otherwise.


Was it worth?
I like applying the stuff. It's fun. Like frosting a cake. But if I redid it, I'd just put CLD in the untreated areas, as mentioned above.
If you do spectrum, you CAN put CLD on the metal, then spectrum on TOP of the CLD. But not the other way around.

 

You may have seen it already, but there is a great thread with a lot of tips on chasing down interior vibration/squeaks/rattles:

https://rennlist.com/forums/991/1308...-interior.html

 

I presume Dynamat is one type of CLD? Found this by search:
https://www.pyroteknc.com/products/d...idamp-cld-pro/
Some paint on (sludge?) types also shown.

This link suggests paint on better than applying sheets, and thin better than thick re converting vibration to heat:
https://www.soundproofingcompany.com...r-damping-work

A bit disappointing that all that work sludging did not produce more benefit. Your writeup certainly dissuades me from doing sludge and points me in the direction of CLD on the wheel wells.
You say you will be doing "Thinsulate". I looked that up (https://www.3m.com/3M/en_US/thinsulate-us/) and that seems to be for thermal insulation.

Are you going to pull up the carpeting and put something underneath that? I was thinking mass loaded vinyl (MLV) such as:
https://www.secondskinaudio.com/soun...xury-liner-pro
https://www.secondskinaudio.com/soun...xury-liner-pro

 

I've done much the same to my 15 turbo. Did the doors with dynomat and mass loaded vinyl, (MLV) that moved the noise from everywhere to mostly from the rear. The next winter I did a rear seat delete and again the entire rear with the dynomat and MLV. Prior to all this it was difficult to even carry on a conversation with my passenger. Today it's now possible to talk in normal volumes for discussions. I've also done the rear wheel wells, but noticed little improvement. I was planning to do the sludge to the rear w/w's but from your comments, I'm now reconsidering. Please let us know the results after the seven day cure time has elapsed. Lastly, I changed tires from 265/325 MPS4's to Continental all season in stock sizes. This made a noticeable difference in the cabin noise. Funny occurrence; my son-in-law and I just drove to Porsche Parade in Birmingham, AL and back. While driving the SIL mentioned a squeak, I leaned over and turned the volume up on the radio. "There, problem solved." We both had a laugh with that.

 

Yes it is. Dynamat is really the big original player in this space. I've always liked Raamat and Second Skin myself. That's not based on any data, just used to know the people involved with the companies in my car audio days.
As long as the CLD you use is butyl with a stiff foil back, you're in good shape. In the past people have used asphalt products which is very not good for your health.

As far as paste/sludge/etc vs mat. There is still some debate out there.

The site you linked brings up an excellent point:
"...not intimately bonded well enough to the substrate."

Bubbles, gaps, wrinkles, etc will severely hamper the effectiveness of CLD. It has to be fully adhered to the panel. Sludge is better than poorly applied CLD full stop.

So some things to consider:
- CLD installs in minutes. Sludge will require your vehicle is disassembled for days.
- CLD can be one layer and done. Sludge is a lot of labor to get to a minimum effective level of 3mm thick.
- Its hard to verify that you got 3mm evenly. A small metal pick as it cures could be one way.
- Sludge can be put in very hard to reach places. If you're looking for total panel coverage, it's way easier to do this
- no one has ever sliced their hand open on sludge (CLD with thick aluminum sheets can get you)

So as far as effectiveness goes. I think the benefit would have been far greater had the panels not already been treated by the factory. I think we're running into diminishing returns here. the wheel well area is already very solid. If you rap on yours, you'll notice most of it thuds, and even the thinnest areas that don't have the factory treatment aren't that bad.

This is the thinsulate you want: https://www.3m.com/3M/en_US/p/d/b40068152/
I got mine from a van living website.
It has a sound absorption coefficient of .5 @ 400hz and hits 1 @ 630hz. Blocking anything lower than that requires a lot of thickness or mass.
There's products MLV (mass loaded vinyl) or even lead. I've done the MLV before. But it's very thick, a pain to work with, and at 1-1.15lbs per square foot, didn't feel like the right move in the 991.

And yes. I'm going to pull the rear carpet out at some point, hit the big areas with CLD (probably 80% coverage in large panels). I'll fill voids with Knauf Ecose (its a non toxic rockwool) and put the thinsulate anywhere that can support it.
That might not be until the fall though.Gets really hot in my garage.

 

note: hardening of sludge hasn't seemed to change the sound, but too many variables.


OK, going to abandon my tweeter thread. No reason for two threads.
https://rennlist.com/forums/991/1418...-improved.html

tldr, i built a crossover+lpad for the tweeter which improved the sound with the Dayton tweeter.

I then noticed that covering the midranges resulted in the elimination of terrible harshness in the audio system.
I didn't have a chance to measure it, so: give it a try.
Throw some insulation over each midrange, listen to something loud (preferably something with a lot of harshness, like metal, electric guitar, etc) then suddenly pull the insulation off the nearest side. Should immediately illustrate the problem with the midrange reflections. What you're listening for is a highly localized sound. Sort of like all the tinny bits of the music played slightly out of time over a clock radio.

You can do it with your hand, too. Though that will block it all.





Note: The square of thinsulate is really too much material. It cuts out a lot. However, it works fantastic in the presence of road noise. Mostly a problem standing still listening with the car off. Don't do that. Go inside. Listen to better speakers.

So, I decide to crack open the doors again. I had more time to poke around.

I cut a 4x6 square of thinsulate and stuffed it into the grill.

I was worried about mechanical interference, but it was fine.



Then I noticed the door panel is just completely open to the woofer. Generally, you want the woofer to only enter the cabin and not bounce around in a cavernous door card. Because of the shape of the grill, I couldn't just put a ring around it.

So I stuffed all the voids I could find with thinsulate. There were a lot. I pretty much put it anywhere that wouldn't interfere with the airbag or any moving parts in the door.



Some of the insulation i added

Folded over a few pieces for these voids


The result isn't a perfect seal, but a greatly improved one. More care and time would have resulted in less chunks of insulation, and better cut-to-fit sheets. I'm too lazy for that though.

Sound reduction while driving was noticeable. No more door rattles with bass. (I still have a few rattles with REW sweeps, but I haven't put felt on the buttons yet.)

And the sound system?

It's actually enjoyable now. It's gone from offensively bad, to somewhat tolerable if a bit harsh, to: Actually, that's really nice for OEM+.

Better bass, tamed midranges, detailed highs. Minimal sibilance. There's a crispiness to it that needs to be addressed by a DSP, but for now that's out of scope.


Note for people still fully bose: Try just the insulation over the midranges. I bet it would sound a lot more pleasant even with the stock tweeters.

 

pulled the rear bit out again and noticed its full of holes. probably for the sound symposer.

since this leads to a big chamber thats also the firewall, i decided to stuff it.

used the thinsulate and shoved it in. not pretty.




the difference in road noise is immediate and apparent. for almost no effort it makes a real big difference.


however, it also kills a lot of the engine/exhaust noise you might want.

anyway this is a temporary solution until I can pull the rear of the car apart.

I think my long-term solution here is going to be damping mat on the firewall, thinsulate on all surfaces under the carpet. then build a cover that goes under this piece where i can pipe the symposer tubes in (or not)

 

So, I was chasing down a rattle last night and ended up tearing the interior out.
I was really surprised by the amount of factory sound deadening - the carpets had thick, dense foam everywhere.

So I added some butyl mat to key places, and filled empty voids with the thinsulate.

Result?

Very minor. I wasn’t expecting much from the butyl, given how it works, but I’m surprised filling all those voids didnt help much.
Filling wheel well voids and spare tire tools in my 4runner made a huge impact!

The tone of the road noise is definitely an octave lower. I can hear myself talk a little louder. I’m not sure it was worth being a 6’7 out of shape middle aged man doing 3 hours of gymnastics in the back of a 911.
But I’m glad it’s done.

I did reduce the rattles thanks to the other thread, but managed to break the clips in the c-pillar. My awesome wife heard me complain about it and tracked down their part numbers so I can replace them.

 

Whatever you're on, it's a helluva drug!