Sound Deadening

>Should I use it on the doors, floor, ceiling, or engine firewall?

The old technology is some form of adhesive bitumen sheet such as dynamat. One of the better newer sound deadening approaches is 3M Damping Foil 2552. It is also water resistant and quite thin. It's important to remember that bitumen sheets and 2552 use different methods to deaden sound in the cabin. Thus choosing between the two is quite different than say a choice of "should I use dynamat with or without foil"....

Bitumen sheets typically are used in places that vibrate. If used on doors, it should reduce the amount of sound getting out from the car. 3M Damping Foil 2552 should ALSO be used on places where the sound is transmitted into the cabin. The points where the suspension transmits the road noise of the tires are good places to apply 2552 in order to change the sound transmission property of the metal at that location.

>hyundai

Apparently OP couldn't afford a higher-res picture with fewer jpeg artifacts . . . .

>I haven't really tried to pinpoint the source.

HUH? You must have noticed noise level changes on fresh new roads versus older road surfaces versus rutty road surfaces where the larger rocks bulge out and slap the tires harder?

If you are going the same speed on two different roadways and the noise level is vastly different, then it is probably road noise (RN). RN has multiple forms of transmission. Number 1 is it physically goes through the stiff sidewall as vibrations (after all your tire is a stiff resonance chamber) into the rim and then through the metal suspension and then into your cabin. Number two is the sound from the tread blocks slapping the pavement (because that is what a treadblock is doing when you go past a certain speed) bounces up and hits the bottom of the car and gets in that way.

For such a car, quieter tires would make a big difference. For example, if you use AA traction rated dunlop sport performance tires (like I did in my previous car), it would be quite loud. In that same car, I switched to a general all season touring tire and the noise level dropped quite a bit.

If you are using the "more is better" logic, that is not always good. Some people new to cars will think that getting higher speed tires for their car is better than low speed rated tires for that same model of tire. Certainly, various tires have different max speed ratings. But the higher speed ratings usually mean a stronger sidewall and that translates as a stiffer sidewall after the tire is pressurized by the weight of the car sitting on the tire. That stiffer sidewall transmits a lot more road noise into the rim and through that into the rest of the car.

I didn't think people would really feel the need to save the picture since I just se it as a way for people skimming through the pages to easily identify the topic of the thread. It's not like you'd want a high res version of the image for your computer's background.

I usually care more about higher threadwear because I'm cheap and higher threadwear means less wear on the tires, which translate to higher tire life. Or at least that's what I think.

Peel and seal is a cheap alternative thats used for roofing. Can be bought at home depot and lowes. Works fairly well but can smell a little like tar for a month or two. Not sure about exterior use but I've used it inside my car with good results.

Since you sound like you know what the hell you're talking about, what about the spray foam sound dampening materials, are they worth it?

I saw a youtube video yesterday against it and it seemed very reasonable to not use it from his explanation.
youtube.com/watch?v=7hWDx6rt6Xc

Im interested in this too.

>what about the spray foam sound dampening materials

Foam doesn't stop road noise from wheels coupled thru the suspension into the cabin. That's why you have to determine all the sources of sound pollution and determine their level. Then you can deal with each.

Foam is lightweight. It doesn't dampen. It blocks sound transmission through the air and lightweight things that are vibrating. While it may help some if applied on an internal door surface, I believe the foam is more trouble than its worth especially if if water pools on its uneven surfaces, it blocks air flow needed to let things dry out faster, or if you accidentally block certain openings with it like a drainage hole at the bottom of a door.

I found this roofing flashing stuff at lowes that works well, pretty similar to dyanamat but obviously not as good. I think it was 25$ for a roll. Ive done it to two cars to try and reduce vibrations from my system and it seems to work well for the price.

Thin sheets like that are best at deadening high range noise which isn't that prevalent. You want a thicker dense pad.