Detection of Opposed Interaural-Time and Interaural-Intensity Differences as a Function of Over-all Level
Samuel C. Carrier, Ervin R. Hafter · The Journal of the Acoustical Society of America · 1971
The binaural trading ratio (Δt/ΔI) is traditionally measured by opposing an interaural time difference (Δt) with an interaural intensity difference (ΔI) in proportions sufficient for apparent cancellation of the perceptual effects of the two cues. In a previous paper [E. R. Hafter and S. C. Carrier, J. Acoust. Sac. Amer. 46, 125 (A) (1969)], we showed that no combination of Δt and ΔI produces a dichotic tone which cannot be detected as different from an otherwise comparable diotic. In that paper we proposed a “dual-threshold” model in which intensive and temporal information are encoded by peripheral dual-threshold devices. The two sets of information are then weighted and recombined by a central processor. An important test of the model is the response to signals of levels sufficiently low as to render the high threshold device functionless. In this study, we measured the tradability of Δt and ΔI at overall levels of 20 and 40 dB SPL. At these levels, Δt and ΔI apparently do cancel, but the signal remains detectably different from diotic owing to the observer's use of monaural intensity increments. Whereas at high over-all levels monaural cues are negligible, here they are of major importance. An extension of the previous model that incorporates this feature will be presented.