I'm starting this thread to document my approach on adding sound treatment materials to the interior of my Stingray with the goal of making the cabin quiet enough to support me taking work calls VIA bluetooth while driving.

Disclaimer: I completely understand most folks don't care about the road noise, and many will say "turn the radio up", or "install an aftermarket exhaust", or "It's a Corvette, road noise is part of the experience", etc, etc ... And for those folks, this thread isn't for you . This is my daily driver, and I have enough experience with sound treatments in previous vehicles to know I can significantly reduce the road and wind noise in the cabin with proper materials and treatment; so I am going to tackle it.

I will use my audio calibration microphone and software to take measurements before and after, so folks can see the impact this has.

Understanding sound treatment materials is important for this sort of project, so I'll take just a few minutes to explain what things are and what they do:

• CLD (Constraint Layer Damping) materials. This is true "Sound Deadening" material, and is typically a very thin sheet of metal with a butyl rubber backing. It gets applied to vehicle panels which are prone to resonating, and it essentially changes the resonating frequency of the panel to stop it from vibrating. This DOES NOT block sound, but what it does is make it so panels stop vibrating and producing additional sound. A lot of folks misunderstand this material and think it is sound blocking material, and therefore when they use it, become disappointed in its effectiveness. Again, CLD does not block sound, but stops panels from resonating and producing more noise/sound. This does not need full 100% coverage, but is applied to vehicle panels which are large, flat, and not rigid. Think floor panels, outer door skins, firewalls, roof, etc, etc ...
• CCF (Closed Cell Foam): This material is a decoupler, and is designed to stop two components from rattling against each other. Like where a panel clips into the body, and the plastic is touching the aluminum or fiberglass. CCF applied in between the two materials stops them from generating a rattling noise. There is some sound absorbing characteristics of CCF, but that is not really its typical purpose in a car, as it would need to be really thick to be effective if used for that purpose.
• MLV (Mass Loaded Vinyl): This is a true airborne sound blocking material. It is sheets of thick vinyl which has additional mass added to it. The heavier the material, the better it is at blocking sound. The thickness doesn't really help block more sound but the density does. Thicker MLV blocks more sound simply because the thicker it is, the more mass it has. This needs to be applied in a way which provides 100% coverage without any gaps. Think of being inside a room with a window to the outside, and the window is open. Someone is mowing the grass outside, so you close the window 50% ... the sound is still loud. You close the window 80%, the lawnmower sound is still loud. It's not until you close the window 100%, and it seals, that you then reduce the sound coming into the room. This is the same concept at work here and is why sound blocking material requires 100% coverage.
• Lead sheet: This is a very effective sound blocking material (like MLV) but you can use a MUCH thinner lead sheet due to the high density/mass of lead, and achieve the same result as you would get from a much thicker sheet of MLV. Therefore you can achieve the same weight and blocking characteristics in a much thinner and more easy to work with material when using lead sheet vs MLV.

In two of my existing vehicles, I did CLD + CCF + MLV, and the results were absolutely fantastic; game changing I would say. For the C8, I am going to try CLD + CCF + Lead Sheet instead. The lead sheet is more expensive than MLV, but it will be much easier to work with and cause less of a problem with the interior panels fitting back together properly.

Here's a video of a guy who added treatments to his C8. His goal was to address the engine ticking sound, while my goal is road noise. In his video, toward the end ... he states the cabin is now eerily quiet after his treatments though. He used CLD and some foam based product. The foam based product is not sound blocking material but is sound absorbing material. It has its purpose (like in wheel wells, etc ..) and it is cheap, so a lot of folks will use this sort of material instead of a true sound blocking layer. I am not a fan of the brand or products he used, and he used the CLD incorrectly (most likely thinking it was sound blocking material), but he achieved his desired result for about $100 ... so you can't really fault him for it. The CLD doesn't need full coverage like he shows, it just needs to be applied to resonating panels. The foam he used is not anywhere near effective at addressing road noise as MLV or lead is (since the foam absorbs sound waves while MLV or lead blocks sound), but his end result makes me think the lead sheet I plan to use will absolutely deliver my desired outcome.


For materials, I'm a fan of Second Skin products, and in my previous projects, I used their CLD, CCF and MLV products. They don't offer a lead sheet product though, so for the C8 I ordered CLD from them. I also ordered some radiant heat barrier while I am at it for treating the trunk space to cut down on the heat.

• 40 sq/ft of Damplifier CLD Sheets
• 14 sq/ft of Radiant Shield heat barrier

For the sound block layer, I am going to give ResoNix Barrier a shot. This is a thin lead sheet sandwiched between two layers of CCF. It is very moldable, and since the CCF is already part of the material, I won't need to add additional CCF to decouple the interior panels. This stuff is not cheap, but has become widely accepted as the best in the business for this purpose, especially when dealing with high end vehicles where precise molding and tight tolerances are a consideration.

• 40 sq/ft of ResoNix Barrier

I also have some butyl rope on hand, as well as installation tools and various other materials left over from my previous projects.

The materials have been ordered, and I'm hoping I can spend next Saturday on this project (assuming I can dedicate the day for it). As stated above, I'll take some measurements before tackling the project, so I can have before and after road noise sound measurements. I'll be sure to position the mic in the same place for all measurements, and use the same stretch of road, under the same driving conditions, so it can be a true A:B comparison.

As a point of reference, here are the before and after measurements from my 2005 GTO:

Before measurement:



After CLD + CCF + MLV measurement:




This completely transformed the driving experience in the GTO and I am hoping I can achieve the same reqult in the C8

 

I'll be interested in seeing (hearing?) the results. In the C7 a lot of the road noise came from the back panels since the wheels were right there. In the C8 I suspect a lot of it comes from the front tires since they are right there at the front of the cabin and there are fuel tanks between the rear tires and the cabin. I have a HTC and don't mind the engine noise that reaches the cabin. I'll also be interested in seeing how much weight it adds.

 

I’m in like Flynn

I definitely would like lesser road noise in the cabin. Are you going to tackle the tires themselves? Some say the RF tires are noisy.

 

I don't plan to change the tires at this point. I have the Z51 with the OEM tires, so yeah, they definitely aren't quiet. I'll do the cabin treatments 1st, and see how well that addresses things. Then when the OEM tires are due for replacement, I'll consider options at that time. I'm hoping the cabin treatments will be enough though, and if so, I'll end up going with the all season run flats when it comes time (as again, this is my daily driver).

I was driving to work the other day, and needed to be n a conference call during the drive. I was on the highway, doing about 75 MPH, and every time I had to come off mute to talk, the participants had a hard time hearing me. I'm hopeful the treatments as I've outlined them, will reduce the road noise enough to not only be a more enjoyable driving experience, but make it where I can effectively take calls while driving.

This will add about 100lbs to the car. The lead sheet is 2lbs per sq/ft, so there's 80 lbs right there assuming I use all 40 sq/ft of the ResoNix Barrier. The CLD I'm using is 0.35lbs per sq/ft. So if I use all 40 sq/ft of it (doubtful), it would add 14 lbs.

 

Not a hard job, just takes time and is a good winter project while the car is down for the winter. I did a full sound deadening on my C7 coupe with Dynamat and the result was amazing. I disassembled the doors and did the inside of the door and the outside where the door panel attaches to the door itself. You must do every surface to get a good result. This can take many hours to get full coverage but worth it.The wifey didn't complain about the noise anymore. I think the cost was around $800 seven years ago.

 

Doesn't the Iphone have noise cancelling? I thought all Smart phones did. People on the other end shouldn't be hearing your car or it should be really muffled when you are speaking .

 

Just give me your address and a good time and I'll bring mine over for you to do too. On certain concrete interstate highways it can be deafening inside the cockpit!

 

I will be interested in your results. I live in an area with Chip seal on all roads. I have an app that I have used to check the noise level while driving on the Chip sea and on the freeway. The app shows 95db at 60 mph when on the Chip seal. 93db when going down the freeway on worn concrete surface at 70mph.
Once I am on new asphalt it’s so quiet.
Would adding a material to the fender liner help me out?

 

Following this thread as I have been there done that. I wasn't nearly as scientific Stoopalini, as I just used a Db sound meter app on my phone for before and after tests. There is a stretch of freeway on the way to work that is especially loud (worn concrete) and my before tests showed a constant reading of 89-90 Db @ 70 MPH.

I started out using a commercially available sound deadening kit for the C8, however I was disappointed with the results only showing a 1 Db reduction in road noise.

Next, I removed the wheelhouse liners and added Dyna-liner (closed cell foam) to the back sides of the wheelhouse liners. The Db results did not show a noticeable reduction in tire noise. After reading the OP's post, in hindsight this probably not the best product to use for this particular location.

For the next step I removed foil backed "bubble wrap" type of insulation that came with the sound deadening kit from the floors and replaced it with Dyna-pad. Dyna-pad is a multi-layer product that is fairly thick and has a dense rubber material in the middle. The Dyna-pad did show a Db reading of about 87-88 on the same stretch of freeway @ 70MPH

I decided to work on the doors next and to my surprise there is virtually no sound deadening in the doors, other than some light insulation on the back side of the interior door panel. So, I lined the inner door structure with Dyna-pad. This reduced the road noise to about 86-87 Db. Interestingly enough after doing the doors the sound system does sound better though

I'm not a sound engineer and was trying products based off of my limited experience/research. I was able to reduce the road noise somewhat, that being said I was hoping for better results and will be interested to see how much success Stoopalini has.

 

Nice ... so a few thoughts on your project.

First, note that a drop of 3dB is not insignificant. 3dB for audio represents a doubling of energy. For example, if you have an amplifier and a speaker playing a sound at 87dB loudness, and you want to increase it to 90dB loudness ... you need to double the amplifier's power output.

That said, how we perceive sound is different ... 10dB is generally accepted as the level in which humans perceive sound levels as being double loud. So while going from 87dB to 90dB takes double the energy, it's not until 97 dB that a person would perceive the loudness as being doubled.

The material you used is essentially a layer of MLV sandwiched between two layers of CCF. They try to market the CCF as sound absorbing (which CCF does do), but it is way too thin to have any real effect for this purpose. The CCF is really acting as a decoupler here, just like the lead based product I plan to use. The Dynapad website states the MLV layer is 1lb per sq/ft, which is on par with industry standards for standard MLV. So it should be pretty effective at blocking sound, but only if you have 100% coverage with no gaps. Any seams need to be sealed to really be effective. Like your doors, that really should have been a single piece of the material, draped from top to bottom. If you needed to use separate pieces, then you really should seal the separate pieces together to be effective. Having the seams not sealed is like my analogy above about te lawn mower ... if the window is closed and sealed, but then you just barely crack the window the slightest amount, the lawnmower sound will penetrate the room immediately.

I used MLV on my inner door skins of the GTO ... this is how I draped it. The C8 door cards may not allow this with thick MLV though, due to tight tolerances, not sure. This is one reason I'm going with the ResoNix lead product instead, because it is so thin.




In that vehicle, I also put MLV at the trailing edge of the front fender, to stop tire noise from entering the leading door edge. Here's a pic from the front wheel well, looking back toward the door. CLD on the fender (right side of pic) to stop if from resonating, and then MLV to stop airborne noise from the tire entering the door.





Not sure how I am going to address the doors or wheel wells in the C8 yet, as I'm not sure 40 sq/ft of the ResoNix Barrier will be enough to do the cabin and the doors. But if doing the cabin alone isn't enough, I'll probably order more material and do the doors (possibly wheel wells) later. Especially since the entire interior doesn't need to come out for those.

 

Interesting on the multiple vs single piece sheets on the doors as I hadn't thought about sealing the pieces together. I did it in multiple sections so that if I ever had to work on the door (I'm a retired Chevy tech), I could still access the adjustments and service holes without dealing with the glued-on Dyna-pad.

Thanks for posting your info!

 

I went with this kit https://www.exoticvette.com/c8_sting...tion_kits.html . You can save money by selecting materials and figuring things out on your own but I wanted to make the install as cut and paste as possible.

Sound deadening wasn't a hard job when I did it to my Subaru WRX or did something much less involved to my Dodge Challenger but I absolutely hated doing the job with the C8. Two or three connectors fought me and eventually I gave up on the waterfall speaker connector and cut the wires then soldered them together on installation. The panel clips on the top and side panels drove me crazy, after trying every shape and type of panel tool known to man and donating skin from my left hand to the car Gods I eventually got them off with about 5 of the clips messed up (Chevy charges a stupid high price for new clips) and the clip mount on one panel broken and in need of repair (epoxy and get-er-done engineering).

At the end of the day I'm glad I did it as it really seems to have helped with the higher frequency tire noise I hate on nearby rough surfaced concrete roads and everything went back together as it should. Don't know if I will ever go back and do doors or anything else as I'm pretty content as is, but I could easily be swayed to go farther as people relay their results, perhaps doing the doors is low hanging fruit.

Someone with more panel removing skill and experience might be able to breeze through the job, just for what it is worth.

 

I am surprised, with my 2023 Z51 and Continental DWS06 Tires in Tour Mode it is very quiet. Almost as quiet and my F150 Lightning. I talk on the car phone all the time and have no issues hearing or being heard. The C7 is another story. I have to yell to be heard in that car.

 

And I thought this was a sports car!

 

Corvettes now come in several flavors; Stingray, Z06. eRay, ZR1, ZR1X. Maybe there's room for a country club cruiser Corvette. Quiet inside, soft ride, easy ingress/egress for the more elderly, still with some snappy performance and the intimacy of a 2 seater.........Actually, I think GM tried to market something similar already. The Cadillac XLR. Unfortunately the car suffered from being (1) ugly and (2) underpowered with a 4.5 liter Northstar engine.

 

I drive a 93 Cadillac Allante with a Northstar motor...that thing floats down the road, lots of cabin space and a large trunk...It's an old mans car but hey, it owes me nothing...I have been driving it for 20 yrs...I have my eye on a 24 2lt but this noise thing might be an issue for me...I plan on driving it when I get back home..

 

The XLR was produced 2004-2009...Two motors...Northstar or supercharged xlr-v

 

For sound blocking material (MLV, Lead, or any other material) it actually needs to be able to vibrate. This you’re not supposed to use glue or anything else which would bond it to any panels.

CLD is different, where you want that bonded very well in order to add mass to the panel and change the resonance properties of it. Sound absobrbing material is also less sensitive to how you install it. But soundblocking material needs to be floating.

The MLV in my GTO door is mounted at the top using dual lock (Velcro type stuff) and the rest is hanging loosely.

if you glued the stuff to the door, then it is significantly hampering the MLV’s sound blocking ability. Add in the gaps, and it’s probably not doing too much.

for serviceability, if the sheet is just affixed at the top, it’s pretty easy to remove or just move out of the way.

 

True, but there is nothing pleasant or appealing about tire noise, now engine exhaust note is a different story!

 

I like the idea of the ResoNix product for the doors. Not sure if you have pulled the door panels off of your car yet, but there are a lot of irregular shapes to work around and in some cases the clearance between the interior door panel and door frame is very tight. (upper tweeter speaker) The fact that ResoNix is moldable will be helpful in this application.