Place Dependence of Timbre in Reverberant Sound Fields

The sound-pressure level of a simple tone in a diffuse sound field varies from point to point with a theoretical standard deviation of 5.57 dB. This variability affects the timbre of complex tones in reverberant sound fields, Experiments have shown that the timbre dissimilarity at any two positions is rather well correlated with the difference in sound spectrum, whereas the effect of the randomness of phase is negligible for complex tones with fundamental frequencies above 100 Hz. The analysis of recordings of steady-state organ tones in a large concert hall gives results which are in excellent agreement with the theory. It is shown that the variance of sound spectra measured in dB^2 per one-third octave band is a good measure of the extent to which the characteristic timbres of complex tones are blurred by reverberation.