https://honda-tech.com/zerothread?id=691704

 

If I cared at all about how loud my car is, then I would definately give it a try.

 

good idea. I definately have the uber nasty 3-4k moan. But, like dc231 said, I don't care enough to do anything about it.
Good thinking though

 

I'm not too sure about using that egg crate only in the spare tire area will make a big difference, but it's worth a shot. Otherwise if you don't mind removing the carpet, I'd lay some of that dynamat down, along the exhaust path, hopefully it will help. This is only to say if the car doesn't already have its own sound deadening. Also, dynamat is mainly for absorbing vibrations and eliminating rattles, etc. I don't know how well it will get rid of your exhaust noise.

btw for reference, my friend has a 2002 civic ex sedan with a greddy extreme cat-back, and you hear a pretty loud deep note inside the car, almost more than outside. I know his car has factory sound deadening...

 

Try some "Jute" or carpet padding for cheap light sound deadening. As eastbay said, asphault sheeting only does good for dampening lower resonating vibrations... your floor is not resonating, trust me, if anything your big door panels are resonating, think sheet metal rattles. Heavy floor material merely transmit the noise. You need a diffusing material like fiberglass (jute is a cheap substitute). I gutted my EP3 when I got it and put jute everywhere, it helps tremendously, just make sure it's not getting wet or it can mildew.
Asphault sheeting (dynamat, fatmat, brownbread et all...) for think sheet metal, jute for 90% of the rest of higher frequency noises.. Grace "Ice and Water Guard" make a great product for asphault sheeting 65$ for 100 sq ft. more than enough for any car.

 

A couple of rolls of Dynamat or Brown-Bread (-stops sound dead) would do the Job. Easy to install, just strip whole interior. Put mat down square it up then get the Heat gun on to seal it to the floor/roof
On the doors you will have to take the cards off and seal the sound deadening material to the panel. Only thing is, this stuff when done proffesionally (i.e. everywhere neatlys joined up) will add some weight.
So no good for a track motor but there'll hardly be any road noise