Effects of interaural delay, center frequency, and no more than "slight" hearing loss on precision of binaural processing: Empirical data and quantitative modeling

This study assessed how precision of binaural processing is affected by center frequency (CF), interaural temporal disparity (ITD), and listeners' hearing status. Tonal signals and 100-Hz-wide Gaussian noise maskers were employed at CFs ranging between 250 and 8000 Hz, in octave steps. In addition, for CFs of 2000, 4000, and 8000 Hz, transposed maskers and signals were employed. All listeners had no greater than "slight" hearing losses (i.e., no thresholds greater than 25 dB HL). Across all CFs and ITDs tested, binaural detection thresholds were elevated for listeners whose absolute thresholds at 4 kHz exceeded 7.5 dB HL. That outcome is consistent with results from Bernstein and Trahiotis [(2016). J. Acoust. Soc. Am. 140, 3540-3548]. Quantitative predictions of binaural detection thresholds derived via a comprehensive interaural correlation-based model of binaural processing were highly accurate across the entire set of data. The modeling results suggest that elevated thresholds from listeners having small hearing losses stem from elevated levels of stimulus-dependent, additive internal noise. They do not appear to stem from increased levels of noise within the central binaural comparator or from reduced sensitivity to changes in interaural correlation produced by the addition of the signal to the masker.