Bare insulation as broadband absorbtion?

Hey guys, please excuse the newbie question.... I tried using the search function... :) I am turning an old garage into a little studio space. The space is probably about 25 x 15 with a gable ceiling. Right now the room is far too reflective, so I am considering different options for broadband room treatment. I know, of course, of the use of rigid fiberglass insulation for this purpose. But how about regular pink insulation?. Since the garage is uninsulated right now, I thought that maybe I could: insulate the room like normal, but rather than covering all of the insulation with poly and then drywall, cover some with a fire-retardant cloth instead. I could also leave the "bare" insulation at intervals in the room so as to minimize parallel surfaces of drywall. Like, maybe leave 40 or 50% bare. Will this result in a room that is too dead? Keep in mind that this is a low budget option (less that $500), not an ideal scenario. Thoughts? Michael Collinge

Standard fiberglass insulation is typically about 0.8 PCF so would require several FEET of thickness to come close to the absorption (at most frequencies) that the rigid stuff (typically 3 PCF and up) will get. Covering most/all your surfaces with this will result in a very boxy, boomy room similar to using carpet. For a better grasp on some of this, go here http://www.saecollege.de/reference_material/index.html and specifically click on the links for acoustics, absorbers, reverb calculator (and any others that may intrigue you) - however, do NOT use the helmholtz calculator there or anywhere else; the one in THIS forum has been corrected to the proper formula. HTH... Steve

Excellent answer. That is exactly the information I was seeking. Thank you!

701, plain 2" (51mm) on wall 1.5 pcf (24 kg/m3) 0.22 0.67 0.98 1.02 0.98 1.00 0.90 Unfaced 2.5" R8 on wall 0.21 0.62 0.93 0.92 0.91 1.03 0.85 703, plain 4" (102mm) on wall 3.0 pcf (48 kg/m3) 0.84 1.24 1.24 1.08 1.00 0.97 1.15 Unfaced 3.5" R11 16" air 0.80 0.98 1.01 1.04 0.98 1.15 1.00