I can help. Audimute Sound Absorption Sheets will cancel the BOUNCE almost completely. Double layer of this product may be needed for high sound pressure level applications such as drums, a band, large speakers, etc. It depends on many factors.
The best thing is to start with a single layer and then give a listen where things are at. With this approach, you won't over purchase for the sound solution if single layer will take care of things acoustically for you.
The results you can expect with Audimute Sound Absorption Sheets, by simply covering the walls, is exceptional.
Audimute will not only make your neighbors happy by reducing the amount of sound leaving the practice space, but their is a substantial secondary benefit...Simply put, Audimute makes for better music and musicianship. It enables musicians to hear their music in incredible detail (i.e Mistakes, buried in acoustic deflections, will now be heard clearly, etc.). It quickly puts an end to the musical "shouting contest" many bands experience as musicians increase their volume and intensity only to hear themselves. The quality of practice time will be substantially increased and enable a band to focus on musical dynamics. In a short time, there will be noticeable improvements in timing, tune, tone, and instrumental technique, etc. while creating an audibly safe environment.