Better flame spread and smoke density mineral fiber insulation for acoustical usage and yields better bass trapping. Best way to tighten up room's sound in the process is to design it right, build it tight and make the partitions as dense as possible. That's where our specialized mineral fiber sound insulation comes in. It's way more dense than the pink stuff and is specifically designed for acoustical usage. It yields much better bass trapping, overall absorption, thermal characteristics, moisture absorption and sound transmission loss (isolation) than any other product we've found. Highly recommended and is in-use at some of the best-sounding studios and theatres anywhere.