Coherence function for speech

It is well known that the lateralization of an auditory image depends upon the difference in the time of arrival of the signals at the two ears. Based upon modifications of the procedure used by Cherry and Sayers [J. Acoust. Soc. Am. 28, 889–895 (1956)], a two‐alternative forced‐choice experiment was employed to investigate the DL for lateralization of an ongoing speech stimulus. In one of the stimulus intervals the binaural speech signal was presented diotically, and in the other interval interaural time disparities of 0.0, 0.015, 0.030, 0.060, 0.075, 0.090, 0.250, and 1.0 msec were created between the binaural signals. The listener's task was to indicate the interval in which the Δt was present. The results show that listeners were able to detect small interaural time differences with 75% performance being reached at a Δt of 0.021 msec. The data has been plotted in terms of a coherence function for speech which is discussed. [Supported by a grant from NINCDS.]