Sound deadening advice?

"Akio Ohtori - RIP Oppo" (akioohtori) 01/22/2018 at 15:03 • Filed to: None

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As part of the Alfa refurb, I need to replace the factory sound deadening on the Spider. Current sound deadening (from factory?) is a layer of butyl-like stuff that is very brittle, a layer of more traditional foil backed butyl deadening (aftermarket?) and several layers of carpet padding.

Looking on Amazon, it appears I have my choice from 30 mil to 300 mil, costing anywhere from $1.2/sqft to $4/sqft.

I’ve also got choices in open cell vs closed and a everything in between.

My goal is to not waste money so... thoughts?

benjrblant > Akio Ohtori - RIP Oppo 01/22/2018 at 15:09

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The foil-backed butyl rubber is only to deaden reverberations of the sheet metal to which it is applied. Contrary to belief, the entire panel does not need to be covered from edge to edge to be effective at reducing vibrations. If you’re looking to reduce noise and heat transmission through the metal you will need to apply a foam insulator such as Dynaliner (or insert alternative adhesive foam insulation here) on top of the butyl mat.

jimz > Akio Ohtori - RIP Oppo 01/22/2018 at 15:19

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I tend to use this stuff:

https://www.parts-express.com/sonic-barrier-lightweight-vinyl-sound-damping-sheet-27-x-40—268-035

it’s mass-loaded vinyl with adhesive backing. reasons?

it doesn’t stink to high heaven like asphalt-based sheets (e.g. DynaMat)

it acts as a limp barrier to both help attenuate low frequencies and damp panel resonances

the adhesive sticks like the dickens

it doesn’t soften when warm like butyl.

I

benjrblant > jimz 01/22/2018 at 15:25

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Dyna-Mat is butyl based, not asphalt. An asphalt based product is something like Peel-N-Seal roofing repair or some other generic sound deadening products.

unclevanos (Ovaltine Jenkins) > benjrblant 01/22/2018 at 15:42

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That’s the common stuff sold at home depot or lowe’s right?

benjrblant > unclevanos (Ovaltine Jenkins) 01/22/2018 at 15:45

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Peel-N-Seal, yes. It’s a roofing repair material with a similar appearance and texture to sound deadening mats. The material is definitely different and I’ve heard mixed things on the longevity of Peel-N-Seal in automotive applications. Asphalt definitely has a different odor and can smell for a long, long time.

ateamfan42 > Akio Ohtori - RIP Oppo 01/23/2018 at 08:41

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I’ve also got choices in open cell vs closed and a everything in between.

Open cell foam is a bad idea in a car, due to moisture collection. Closed cell foam is generally a bit less effective at absorbing sound, but it is more compatible with the automotive environment.

Akio Ohtori - RIP Oppo > ateamfan42 01/24/2018 at 16:34

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So you would suggest closed-cell only? Or closed-cell (butyl in this case) against the metal, then open, then carpet?

ateamfan42 > Akio Ohtori - RIP Oppo 01/25/2018 at 08:35

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If it is an area that isn’t going to get moisture, then the open cell may be okay. Auto manufacturers use that “jute” material under carpets for insulation/sound blocking, which is also a nightmare if it gets wet. So use your judgment on location. I would expect anything in the doors is fair game for water intrusion.

Akio Ohtori - RIP Oppo > ateamfan42 01/25/2018 at 09:33

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Haha this is a convertible so anything is fair game for water intrusion!