Surface absorption reduces total sound power, so reflections fall below inverse-square predictions.

Evidence

It is important to note, however, that the total power in the sound will have been reduced by the interaction with the surface. This means that there will be less sound intensity at other positions in the room. Also, any focusing structure must be large when measured with respect to the sound wavelength, which tends to mean that these effects are more likely to happen for highrather than low-frequency components. In general, therefore, the level of direct reflections will be less than that which would be predicted by the inverse square law due to surface absorption. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1703

Categorization

• DEFINE: Explains the physical criterion — focusing structures must be large relative to wavelength — that gates when the effect occurs.