Absorbers of any kind work best when fastened to a surface, with an air gap between the 'quilt' and the wall or ceiling. The thicker the quilt, and the wider the air gap, the lower the range of frequencies will be that are absorbed. Since the more destructive sound reflections occur in the corners of a room, fixing an absorber straight across the corner, leaving a triangular gap behind it is the best use of a limited amount of absorption. Secondly, the weight of the absorber is important, and heavy is good. Thin and light absorbers will do nothing except absorb the highest frequencies- you know, the ones that allow you to hear consonants or the sparkly tones from new guitar strings! Finally, do think hard about hanging up anything that is not fireproof. Professional absorbers are made of High-Density Rockwool. There are also Helmholtz absorbers and flexible panel absorbers, but It gets technical at that point! Personally, with only a dozen small quilts to work with in a big concrete room, I would stretch each one across a light wooden frame and hang them at 45 degrees along the angle between the top of the wall and the ceiling. Then I'd go round any theatres in the region, to see if they had any old heavy stage curtains that they were willing to donate to line the rest of the walls. Rugs and carpet on the floor will help too. Even a suspended wooden floor will improve things ( it acts as a panel absorber). It won't turn the place into a sound studio or a concert hall, but it will be a lot more comfortable to be in. It is important to note that this is all acoustic treatment of the room, it has nothing to do with sound proofing. Cheers Dave
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