Page 278 - Master Handbook of Acoustics

Flat-panel absorbers using a plywood or other hardboard skin can provide a reasonable amount of
absorption. But wrapping a panel around semicylindrical bulkheads can yield additional benefits.
With polycylindrical elements (polys), it is acoustically possible to achieve a good diffuse field
along with liveness and brilliance, factors that tend to oppose each other in rooms with flat surfaces.

The larger the chord dimension, that is, the larger the width of the semicircular bulkhead, the better
the bass absorption. Above 500 Hz there is little significant difference between the polys of different
sizes.
Polys perform differently, depending on whether they are empty or filled with absorbent material.
Figures 12-26C and D show the increase in bass absorption resulting from filling the cavities with
absorbent. If needed, this increased bass absorption can be easily achieved by simply filling the polys

with glass fiber. If the bass absorption is not needed, the polys can be used empty. This adjustability
can be an important asset in the acoustical design of listening rooms and studios.