hi! I've got a somewhat similar issue...looking at buying a new house...there's an upper main floor, a middle floor with master bedroom, and then lower basement level...all three floors have a large cold return vent connecting them like a column in the center of the house..
...I'd like to have a piano on the upper floor, and rent out the lower basement...however, one major problem right now is, I turned on my ipod on the upper floor, not even at a loud volume and down in the basement you can hear it almost as if you are right next to the ipod...you
can hear people's conversations clearly as well...
...i'm thinking about sealing off the basement cold return and closing all vents, and installing a ductless heat pump for heating down there....what do you guys think of this, and how would you suggest to deal with the sound travelling issue? welcome all suggestions!