About 5 years ago I used some left over acoustic foam from work. It was used to help with some machine noise and I wasn't involved in the actual use so I can't vouch for any specs. It may just be any brand but was supposed to have some acoustic properties. Any way I just glued on some magnets...
After reading the recent post about problems with high school musical productions I thought I might pose a simular question. I am am a veteran of the school sock hop circuit many, many years ago. About the only sound treatment was "loud and proud". Now as I attend my kid's assemblies, dances...