i have access to boxes and boxes of polyester air filters and i was thinking about their effectiveness to absorb sound. I would be taking the panel off and stuffing them behind. the only place i'd really use them would be behind the rear side panels in my civic. It seems like its basically the same stuff used to stuff speaker boxes but i'm not sure.

anyone tried this or have any input?

 

Don't waste your time.

Its like trying to block sound with cotton candy.

 

Try those audio mats like Dynamats that the audio retailers sell.

 

It's too light, use something heavier like "Roxul Safe and Sound." It's a treated-wool based insulation sold in big bags of 10 or so sheets. Stuff it tightly in your body panels and be amazed!