Lateralization of sine tones—Interaural time versus interaural phase

Abstract

Five listeners estimated the lateral positions of 50 sine tones in a headphone experiment designed to determine whether the human sense of sound location correlates better with the interaural phase difference (IPD) or the interaural time difference (ITD). In any experimental block the IPD values ranged from −150 to +150 degrees, and the frequencies were chosen such that the ITDs ranged from −1000 to +1000 microseconds. The frequencies were all in the range where human listeners are known to be able to lateralize tones based on the ITD in the waveform fine structure. It was found that the lateralization responses correlated with the ITD much better than with the IPD. The average variance was five times smaller for the ITD hypothesis compared to the IPD hypothesis, and only the ITD hypothesis led to a well-fitting (compressive) function. For the ITD function, individual compressive exponents varied considerably and averaged 0.75. For the IPD function the exponents were too small to be meaningful. Comparison with previous lateralization studies indicates the importance of presenting the entire range of stimulus parameters in all experimental blocks because it appears that listeners tend to use the entire range of allowable responses in any block. [Work supported by the NIDCD.]