A central spectrum theory of binaural processing. Evidence from dichotic pitch.

A theory is presented that describes the binaural processing of interaural time or phase differences. It is an elaboration of the central spectrum concept for the explanation of dichotic pitch phenomena [F. A. Bilsen, "Pitch of noise signals: Evidence for a 'central spectrum'," J. Acoust. Soc. Am. 61, 150-161 (1977)]. The generation is postulated for central activity patterns (CAP) due to binaural interaction. From these CAPs the central processor selects specific spectral information that constitutes the information for lateralization, dichotic pitch, binaural masking, etc. Here, a strategy is assumed to be based on central spectra (CS) rather than on interaural cross correlation. For the calculation of the central activity patterns a number of assumptions have been introduced. The peripheral filters are supposed to be infinitesimally narrow. The analog filter outputs from corresponding filters at both ears are thought to interact by means of a linear delay-and-add mechanism. The squared output (power) of such a binaural (addition) network constitutes the CAP. The theory has been tested with lateralization and BMLD measurements using dichotic stimulus configurations characteristic of the perception of dichotic pitch. The predictions of the model concerning the pitch and the lateralization of the pitch images as well as the BMLD patterns for this kind of stimuli are confirmed.