Towards a comprehensive model of binaural processing

Abstract

Most classic models of binaural processing are partly built on assumptions that have been challenged or even contradicted by physiologic or psychoacoustic data. For example, that delay lines encode interaural time difference (ITD), that “binaural filters” are wider than auditory filters, or that the binaural system is sluggish and cannot encode rapidly changing ITDs. While these assumptions have been motivated by psychoacoustic data, they have also been contradicted by other psychoacoustic data. The present study revisits and challenges the respective reasonings. One result is that the psychoacoustic proof of delay lines contained an unmet assumption. Instead of “sometimes wider filters” we propose a spectral incoherence interference mechanism that appears to resolve the impasse of inconsistent filter bandwidth requirements. In the temporal domain, we model fast ITD encoding and binaural sluggishness is realized by slow reformation of the interaural statistics of auditory objects. The resulting model still has some unproven assumptions; however, it does not need to change its parameters depending on the type of stimulus or task. As the binaural filter bandwidths and processing speeds are now equivalent to their monaural counterparts and consistent with physiological findings, the model may be instrumental in moving to a more unified understanding of auditory processing.