Originally Posted by pitviper33
Question: How efficient is the transfer of sound energy between a slab of concrete and the air? Are there recommended soundproofing treatments for a concrete floor?
Some people cut the concrete slab to decouple it. (possibly with a Concrete K Saw)
As for if that's Building Code approved in your area (e.g. water table concern), or if you'd caulk the joint with acoustic caulk or silicone, I don't know.
You can cut around the furnace, or you can cut around the theatre. Generally, cutting around the theatre is preferred for both ways (into and from the theatre). And many central air conditioner's have drains that go through the slab somewhere near the furnace.
I don't have any stats on the effectiveness. There is still some flanking transmission through the earth under the slab, but that's less.
Sometimes the transmission through whatever is under the slab is strange. I'm thinking of an example where the theatre sound couldn't be heard in the house next door, but it could be heard the house the other side of it, because the bedrock curved touching the two houses where the noise was generated and heard, but dipped under the house in the middle.
Other possibilities include
a) building a floating floor. Another concrete pad raised on pucks or springs, or (not both),
b) covering the home theatre floor in acoustic-mat (a kind of heavy rubber pad).
c) and of course ignoring it.
In the case of (a) and (b), the stud walls would be built on top of the floating floor or on top of the acoustic mat respectively. In the case of acoustic mat, bolts from the wall base plate through the mat to the concrete slab would also be isolated with rubber and washers.