Key Spots to Sound Deaden?

[Threehz]

So after reading so many different things about sound deadening/dampening products I realized two things:

1) If you truly want to make a huge difference in your car's environment, get professional studio quality sound dampening/deadening, it'll do five times a better job then brand name car sound dampening/deadening for the same price or cheaper.

2) It's going to be expensive as hell to do it properly no matter what route you take.

So I'm going to do it my style. Walmart/online has memory foam mattress pads in an array of thicknesses for very cheap, like 20$ for a full.

So instead of buying expensive brand name stuff I'm going to use memory foam.

My question is what areas are prone to rattling, vibration or some type of noise making?

I'm going to cut up the foam and use it to dampen those areas the same as normal product would be used. I will also use it as speaker baffles, and probably do a layer across the entire floor under the carpet.

Any ideas/suggestions would be appreciated thanks!

[mrgraphics]

I think you are confusing sound deadening to sound proofing. Sound deadening involves making the door panels have extra mass so that they are harder to vibrate, or vibrate at a lower frequency. Foam does not accomplish this. Only glue / stick on products like dynomat or certain asphalt-based house construction sealers will do this. They physically add weight, and lower the resonate pitch by which everything vibrates.

Sound proofing involves foam, but not just any foam. The foam cells must be created and arranged in a special way, and must be at a certain density. Any old foam will not work. acoustic foam breaks up the sound waves as it travels through, reducing the high and mid frequencies that reach the ears.

In my past 350z, which was terribly loud stock, I was able to attain a near silent cabin by applying an asphalt based coating to all doors, floor, and cabin panels, and adding a layer of sound insulation foam that is used in sound / music studios. The foam was about $150 and was purchased in Modesto - the asphalt peel and stick was from a local construction specialty store. It had a gummy surface with aluminum backing and was about $50 for an entire roll. Something like this (but not exactly this. It has to be rubbery and tacky, not like the Home Depot stuff that is stiffer like asphalt roof tile) http://www.cofair.com/window.aspx

If yo do not follow this procedure, you will do a lot of work without much end result.

[Threehz]

Well my car has a lot of rattles, and I can say that accounts for at least 10% of the noise I hear while driving, if not more.

Secondly that is why I'm choosing memory foam, not only can you buy it in a huge array of density's and cell volumes but also by IFD (indentation force deflection), and heat absorption index.

A high density memory foam, with relatively large cell volumes should of course work perfectly for quieting down rattles, but should actually make a pretty damn good sound barrier. Although the foam will not reflect the majority of the noise, it will absorb quite a bit. Most of the good types of memory foam are made to soften when heated (like someone laying down on it), when vibrations (sound) hits the foam, the foam will absorb quite a bit of it and those vibrations will not travel well through the foam (ever see the glass of wine on the bed with someone jumping on it?) same idea.

I could be totally wrong, but I'm going to doubt that.

Also this should not only quite down sound from the drive-train/outside but it will absorb some of the internal reflections (like your own music). Cars are one of the worst environments for sound for quite a few reasons, one HUGE one being glass. Glass is the bane of good sound quality and our E30's as much as we love them have AMAZING visibility :) Anyhow hopefully the foam should absorb some of my own music bouncing around in the car!

I am going to take high quality sound samples of the car before and after I do the sound "deadening" (dampening, quieting, whatever!) and that will be the true test, of course how it sounds to me and other humans will be the real deal.

However I'll put up the sound samples on here and I'm sure there are many programs that can measure db levels and we can see the difference.

Thank you for your input though man I didn't mean to throw what you say out the door, I'm just confident. Also I plan on spending no more then 40$ total on all my sound dampening, and more likely close to 20$ :D

[dwvw]

Foam is the best thing to use for rattles. Put it between the two panels that contact each other and you fix the rattle, easy right? Just be sure that it won't rot when it encounters moisture, and that it won't hold moisture and cause rusting issues.

As for actual sound dampening, it is terrible. It won't damp any low frequencies (which is what most road noise is, and it has to be very thick to absorb any real amount of high frequencies, like measured in feet not mm.

[dwvw]

Oh and it's damping, not dampening.

[Threehz]

You don't think it will block out any noise though? I mean a simple test is if you just yell at a piece of foam that even an inch or an inch and half. Or play music and put the foam in front it. That damn sure cuts down the noise level quite significantly. I can see it being less effective at very low frequencies. However good memory foam is pretty interesting stuff.

Well so far it's quieted things down a good bit, and it's coming in very handy for sound sealing areas.

[harv]

Fix rattles first.

John