Binaural coherence and the localization of sound in rooms
William M. Hartmann, Zachary A. Constan, Brad Rakerd · The Journal of the Acoustical Society of America · 1998
The absorption coefficient of materials tends to decrease with decreasing frequency. Therefore, the ratio of direct to reverberant sound is normally least favorable at low frequency, and binaural coherence tends to be a minimum. However, the ability to localize sounds using interaural time differences (ITD) in the steady-state waveform requires binaural coherence, especially at low frequency. Lateralization experiments, using a forced-choice staircase technique, indicate that adequate localization based on ITD requires binaural coherence of at least 0.2. Measurements of binaural coherence in rooms find that binaural coherence is often less than that, which means that ITD cues can only be used on the transient portions of a signal. By contrast, interaural level differences are perceptually useful at high frequencies and increasingly dominate the localization of steady-state sounds as the environment becomes more reverberant. [Work supported by the NIDCD, Grant No. DC00181.]