Sound Deadening, A little more technical question Options

[r_towle]

Hi,
I have been reading lots on the Internet, and the more I read, the more I find that no-one has done any real analysis.

What type of sound does a motor make?
Is it vibration, or soundwaves?

I guess what I am looking for is not the Use Dynamat, Use Brown Bread type of answer.

What if I combined both the ceramic spray on products, and the peal and stick products?
Aside from throwing alot of money at the problem, am I really stopping any more sound waves from coming through?

Are there any discussions of what sound waves Dynamat stops, and what sound waves a spray on ceramic sound deadening system stops?
Are they the same waves?

It seems to me that when you use two of the correct products, each designed to stop a certain type of sound wave, you will get a much better result.

But, where is the info telling me which sound wave is stopped by what product?

Rich

[McMark]

All sound is transmitted by vibration of panels. There are two types of sound deadening, blocking the sound waves from hitting the panel (think foam 'egg-crates') and keeping the panel from vibrating. Dynamat, BrownBread, and all the spray on sound deadeners work by adding mass to the panel. The more mass the panel has, the harder it is to move it, and thus, the less affected it is by sound waves. So sound hits the big heavy panel and is bounced back instead of passing through. The downside is that mass is weight. The weight issue can be combated by selectively adding Dynamat (etc). It is rarely necessary to completely cover a panel in that stuff. What you want to do is add mass at the most flexible point. That's why you see a 'small' piece of sound deadening on the back of a door skin. That's where it flexes the most.

You can kill the sound coming through the back wall. But you'll still have to deal with the sound coming through the rear window.

Does that help any?