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Sound deadening: Installed; before and after dB measurements

Old 06-05-2015, 05:14 PM
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Hopper12
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Default Sound deadening: Installed; before and after dB measurements

Lots of information on sound deadening in our C7's - but haven't really seen any with real measurements other than 'seat of the pants'. First off, for those who don't really care, and figure this is a sports car and you can just turn up the radio: I get it, no problems.

For the rest of us, we bought the C7 for all the same reasons - great looks, performance, and most of all - to enjoy driving and road trips. I wanted to get it as quiet as possible so that I can enjoy road trips with my wife. So here is my experience:

* Car: '15 Z51 coupe. 1100 miles.
* Sound deadening installed: Crazy Cowboy's extreme kit. Includes Memphis Mat and foil enclosed foam insulation. I know there are cheaper ways to do it, but I'll pay for the convenience of having great instructions and the foam already cut out.
* How much time did it take: about 12 hours or so. I'm pretty detail oriented and just took my time. Was actually kind of fun.
* Base line measurements: I'm going to share the decibel differences. The control vehicle is my '14 Cadillac SRX Premium. I figured this is a good control because it's open to the back like the C7, and it has all the sound insulation/control that Cadillac installs. The freeway stretch I chose was a stretch of concrete - decent pavement.
* Before readings: Same stretch, same day. 75-80 mph, windows up, HVAC off. C7 was 5-6 decibels higher than the SRX. That's quite a bit of difference. When cruising, it does not matter what exhaust mode you have it in at all.
* After readings: Same stretch, same day (about a week later than the original 'before' readings), same speed. C7 now 2-3 decibels higher than the SRX. Then I checked it against a '15 loaded up Impala (rental, nice car) - the C7 was dead on the same readings as the Impala. So I got a 3 decibel improvement from installing the kit and my C7 is now as quiet as a new Impala.
* Am I satisfied: a qualified 'yes'. I say qualified, because I think there could be a bit more material installed around the wheel wells (both the mat and the foam), as the kit only covered part of it (please refer to pictures), and I think this is where much of the road/tire noise comes from. It's pretty easy to access that area, so I may get some additional material and install it. And I would have liked a bit more mat for the front foot areas. But.....3 dB isn't bad.
* Would I do it again? Yes. Definitely noticeable, if not quite as good as I was hoping for. Still, a nice improvement. And I know my C7 MUCH better now.
* Did I run into any difficulties? Yes, one. On the passenger side, you need to be careful to put the wire harness that runs under the aluminum foot plate in a plastic loom so the plate doesn't cut thru the wrapped harness. The mat and foam forces the harness closer to the plate, and the plate is sharp and will cut thru the tape into the wires. Ask me how I know........took me a few hours to trouble shoot it, but I got it.

I hope this helps, and provides some objective results to help decide if you want to tackle it. Have a great day.
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Last edited by Hopper12; 06-05-2015 at 05:16 PM.
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Old 06-05-2015, 05:26 PM
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Thank you so much for the data and practical advice!
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Old 06-05-2015, 05:31 PM
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Nice job. 12 hours! How many beers?
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Old 06-05-2015, 05:35 PM
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Originally Posted by rmorin1249 View Post
Nice job. 12 hours! How many beers?
Thanks. A case of diet Dew and 3 band aids.
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Old 06-05-2015, 06:43 PM
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You did a really nice job and 3db is a pretty noticeable improvement, considering the scale is logarithmic. I don't think you'd gain much more from 100% dynomat coverage. Thanks for the pics and write up.
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Old 06-05-2015, 11:31 PM
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Thanks for doing this! 3dB is about double the power of a speaker so that is a big improvement.

What did you use to measure it?
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Old 06-05-2015, 11:38 PM
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Yes great work but I do not understand about all the noise people are talking about. My C7 seems quite as is.
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Old 06-05-2015, 11:42 PM
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Originally Posted by C2367 View Post
Yes great work but I do not understand about all the noise people are talking about. My C7 seems quite as is.
I think it has to do with the differences in roads, some areas have roads that are much louder than others.

I'm going to try a blockit soon and see if that helps
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Old 06-05-2015, 11:48 PM
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Originally Posted by 10mm_ View Post
I think it has to do with the differences in roads, some areas have roads that are much louder than others.

I'm going to try a blockit soon and see if that helps
I believe that is right. some roads are noisy as hell. Some not at all.
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Old 06-05-2015, 11:56 PM
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Originally Posted by sanantguy View Post
I believe that is right. some roads are noisy as hell. Some not at all.
Yes I can understand that. The roads in California are getting to the third world quality mark.
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Old 06-05-2015, 11:59 PM
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george vee
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Thanks for the post, I'll do this in the winter
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Old 06-06-2015, 12:53 AM
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Originally Posted by 10mm_ View Post
Thanks for doing this! 3dB is about double the power of a speaker so that is a big improvement.

What did you use to measure it?
My pleasure. I've learned a lot from those on this forum - found most to be extremely helpful.

I used two devices to measure it. A good friend has an son who is an engineer and I borrowed his professional meter. I checked it against my smartphone meter (Smart Tools). The professional sound meter was about 1-2 dB less than my phone meter across the board on all readings so I used it to recalibrate the smart phone meter. After the recalibration I got virtually the same readings from both meters.
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Old 06-06-2015, 01:11 AM
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Originally Posted by Hopper12 View Post
My pleasure. I've learned a lot from those on this forum - found most to be extremely helpful.

I used two devices to measure it. A good friend has an son who is an engineer and I borrowed his professional meter. I checked it against my smartphone meter (Smart Tools). The professional sound meter was about 1-2 dB less than my phone meter across the board on all readings so I used it to recalibrate the smart phone meter. After the recalibration I got virtually the same readings from both meters.
That's awesome!
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Old 06-06-2015, 02:10 AM
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Nice write-up!! I put crazy cowboy's full kit in my C5 and my first C6.
The rear was pretty easy but the front section was a lot more work with seats and center tunnel and getting parts back on after the additional thickness. I did the rear one weekend and the front the next. Its a long job. Plus the 3M spray gets a little overwhelming. It made a big improvement and was nice to have a kit and instructions and he provided some extra material. On my second C6 I only did the rear section and the center console, but I skipped under the seats. I was still very happy with the sound quality improvement. I want to hear my radio, my exhaust and on occasion my wife (when she's in the car) not road noise. The stock C7 is indeed an improvement over prior generations.
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Old 06-06-2015, 06:29 AM
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Any idea what it weighs?
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Old 06-06-2015, 06:55 AM
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I did not weigh my kit but its not significant. Maybe 15lbs I'd guess if that.

My kit is going in along with my supercharger hopefully in the next week. Maybe the maker of the kit can chime in with adding pieces to the wheel well area in the back.

I went with the extreme kit because I am looking for quiet as possible from the back.

Tire age can also have an affect, the ZP's get much louder as they get older and I've got about 13k on mine now and they are way louder than when new.
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Old 06-06-2015, 11:31 AM
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Originally Posted by pickleseimer View Post
Any idea what it weighs?
I should have mentioned that. The full extreme kit is about 23-24 pounds. The mat is probably 90% of that weight, as the foam is really lite. I usually figure 100 pounds is worth about 1/10 in the quarter if that's where you're headed.

Also, I purchased the 3M adhesive, but didn't use any - the mat is adhesive backed and the foam fit so well I just used aluminum tape to keep it in place as needed.
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Old 06-06-2015, 11:40 AM
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For those who want to measure before/after sound levels, there's some nice phone apps to measure dB:

Windows Phone: CyberX Decibel Meter.

One for Android: Sound Meter

...and even iphone: Decibel Meter
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Old 06-06-2015, 11:57 AM
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Originally Posted by Hopper12 View Post
* Did I run into any difficulties? Yes, one. On the passenger side, you need to be careful to put the wire harness that runs under the aluminum foot plate in a plastic loom so the plate doesn't cut thru the wrapped harness. The mat and foam forces the harness closer to the plate, and the plate is sharp and will cut thru the tape into the wires. Ask me how I know........took me a few hours to trouble shoot it, but I got it.
What symptoms did you notice?

I did mine the other day and now I can't open the doors or hatch with the touchpads (I have to press a button on the FOB). I also have a service keyless start system message in the DIC. I was not looking forward to blindly pulling everything back out. At least now I know where to look

Link to my thread
https://www.corvetteforum.com/forums...rt-system.html
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Old 06-08-2015, 06:19 PM
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Originally Posted by pmzangag View Post
What symptoms did you notice?

I did mine the other day and now I can't open the doors or hatch with the touchpads (I have to press a button on the FOB). I also have a service keyless start system message in the DIC. I was not looking forward to blindly pulling everything back out. At least now I know where to look

Link to my thread
https://www.corvetteforum.com/forums...rt-system.html
Sorry it took me a while to respond - been gone. Nice ride, BTW!!

My symptoms were: everything worked except the passenger door unlock from both inside and outside. When I pushed either button, you could hear the gas door relay working, but the door latch actuator had no current going to it. Turns out the passenger aluminum foot rest had cut into the taped harness that runs under it and shorted one of the wires. Easy fix once I found it. Even though your symptoms are different, this may be it because there a several wires in the harness. I hope you find the issue. And you're right, it was a pain to have to pull everything out again to find it. You might try a battery reset too, just in case that would solve the issues you're experiencing. Let us know what you find!
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