Frequency-dependent absorption makes reverberation time vary with frequency, altering timbre.

Evidence

Equations 6.17 and 6.18 show that the reverberation time depends on the volume, surface area, and the average absorption coefficient in the room. However, the absorption coefficients of real materials are not constant with frequency. This means that, assuming that the room’s volume and surface area are constant with frequency, which is not an unreasonable assumption, the reverberation time in the room will also vary with frequency. This will subjectively alter the timbre of the sound in the room due to both the effect on the level of the reverberant field discussed earlier and the change in timbre as the sound in the room decays away. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1876

Categorization

• XREF: Connects to earlier reverberation-time material (Sabine equations) and the reverberant-field-level discussion in this chapter.