My work area is roughly 375 sq ft. and is directly below the living room and kitchen/dining room. Because of stuff already in the way of the joints, a drop ceiling would be inefficient. My joists are 9" deep and for the most part are all open.
I have read that high frequencies will travel right through the joists. To do the whole ceiling with R30 (9.5" thick) it will be around $350. This will leave no air gap though.
Should I go with a lower R value to get an air gap?
Also if the joists themselves will let high frequencies through, at what point are the uninsulated joist bays no longer the weakest link in the chain? In other words, is R30 even necessary or would there be no noticeable difference between this and, say, R15?
thanks,
DW