The use of absorbent material in double-leaf wall constructions

Abstract We describe a systematic investigation of the effect of using absorbent material in the cavity of a double panel on the transmission loss of the panel. We attempt to resolve some of the conflicting views, expressed on this subject in previous papers. We found that the first addition of absorbent to a previously undamped cavity has the greatest effect on the transmission loss of the panel, that further addition has less effect, and that the position of a limited amount of absorbent material in the cavity is not important. Finally it is shown that it is useful in the coincidence region to increase the damping of the panel leaves by adding damping material to their inner surfaces.