Room modes and sound absorption: Some practical measurements compared with theoretical predictions

Changes in the amount of sound absorption, which occur when absorbing material is placed at different regions of a standing wave pattern in a reverberant enclosure, are discussed. Theoretical predictions of this change of absorption are compared with practical measurements. The dependence of the degree of excitation of the absorbing surface on the standing wave pattern over its area, the relative importance of the potential and kinetic energy components in the sound field, and the acceptance of energy from regions of the sound field not immediately adjacent to the absorber, are cited as causes of the observed differences between the theoretical and practical results.