Axiom Home Page Forums General Discussion Home Theater sound deadening return air ducts

I was talking with a friend about the setup of a home theater sound room in a basement and he advised me about isolating the return air duct.

He had used something like dynamat that has a sticky side and ran it along the exposed bottom side of the return air to deaden metal. It doesn't really remove the sound, but gets rid of the ringing pitch that tends to travel along the air ducts.

Have any of you experts in the HT room building trade used this, or is there a better product that I should be using?

In my installation, I have a two story house. The HT/Sound room is directly below the front sitting room in the house. This is essentially a non used room in daily life at my house. (it gets used when guest come over and we have a party). My thought was that distance reduces sound, and having all the bedrooms on the second floor, sound from the basement will be greatly reduced just by distance from anyone watching a movie or listening to tunes by the fact that there is a complete first floor between them.

I was told the one problem to this is that sound can get into the air ducts then bounce back and forth along the length of the forced air ducts and come out the other end as a tinny amplified version of what is playing in the basement.

Any advise would be much appreciated.