Cabin Resonance from Exhaust...Dampening?

[celly]

I'm a big fan of Flowmaster catback systems, but it definitely a little droney at between 2500-3000 rpm in my '00 Sport. My Flowmaster SUV 50 series is mated to 2.5" pipes from the cats back. OEM resonator was cut off and not replaced. Pipes follow stock routing.

I'm looking to quieten the ride inside the cabin a bit (with some Dynomat or similar). Where does resonance originate, i.e. where should I focus the matting? I want to keep it fairly simple to start with (i.e. no panels taken off). I just want to do perhaps the under the seats, "trunk" etc.

Any insight, experiences would be appreciated.

 

[terdrocket]

Do your pipes run straight back or off to the side? Meaning, do the tips exit straight back under the bumper or out under the rear quarter panel.

If they run straight back, pull up the rear carpet (It flips up easily and is not attached except at the rear seats and just pressure fit under the rear moulding at the hatch.) and put a layer or three of sound deadening and replace the carpet.

If they exit to the sides, take each side panel loose and sound deaden the metal behind them. (Floor, side sheet metal and fender wells)
Its a huge open cavity under there to resonate and amplify the noise.

For even more effect, go to Walmart in the sewing section and buy a 5lb box of polly-fill and stuff some behind the panels.

I have true duals with straight through race mufflers, 2.5" piping and 3" tips pointing out under the rear quarter panels. The exaust was just as loud with the windows up or down. I did the above and it made a huge difference. I forget how loud it is until I let someone borrow my car and I hear it drive off.

 

[celly]

My pipe does follow stock routing, i.e. under the bumper. I was thinking about dampening up the area you mentioned. Sometimes the sound comes like it's coming right in the back seat so was wondering it if needed it there. I'll probably start in the areas you mentioned.

Thanks for the input.