The lateralization of simple dichotic pitches

Abstract

A "simple" dichotic pitch arises when a single narrow band possesses a different interaural configuration from a surrounding broadband noise whose interaural configuration is uniform and correlated. Such pitches were created by interaurally decorrelating a narrow band (experiment 1) or by giving a narrow band a different interaural time difference from the noise (experiment 2). Using an adaptive forced-choice procedure, listeners adjusted the interaural intensity difference of "pointers" to match their lateralization to that of the dichotic pitches. The primary determinants of lateralization were the interaural configuration of the broadband noise (experiment 1), the center frequency of the narrow band (experiment 1), and its interaural configuration (experiment 2). The ability of two computational models to predict these results was evaluated. A version of the central-spectrum model [J. Raatgever and F. A. Bilsen, J. Acoust. Soc. Am. 80, 429-441 (1986)] incorporating realistic frequency selectivity accounted for the main results of experiment 1 but not experiment 2. A new "reconstruction-comparison" model accounted for the main results of both experiments. To accommodate the variables shown to influence lateralization, this model segregates evidence of the dichotic pitch from the noise, reconstructs the cross-correlogram of the noise, and compares it with the cross-correlogram of the original stimulus.