No more than "slight" hearing loss and degradations in binaural processing.

Listeners having, at most, "slight" hearing loss may exhibit substantial deficits in binaural detection [Bernstein and Trahiotis. (2016). J. Acoust. Soc. Am. 140, 3540-3548; (2018). J. Acoust. Soc. Am. 144, 292-307]. This study assessed whether such listeners also exhibit deficits discriminating interaural temporal disparities (ITDs) or interaural intensitive disparities (IIDs) and whether any deficits observed in those discrimination tasks would be accounted for by the interaural cross-correlation based model that successfully accounts for binaural detection. Thresholds were measured for detection of tones masked by noise in the NoSπ configuration and discrimination of ITD or IID. Gaussian noises (100 Hz-wide), served as maskers in the detection task and as reference and target stimuli in the discrimination tasks. Stimuli were centered at 500 Hz or 4 kHz. The latter were transpositions of stimuli centered at 125 Hz. Results demonstrate that listeners having, at most, slight hearing loss and who exhibit deficits in binaural detection, also exhibit deficits in ITD- and IID-discrimination. Coupled with appropriate decision variables, the cross-correlation-based model that accounts for elevated binaural detection thresholds among such listeners also accounted for their elevated ITD- and IID-thresholds. The deficits in all three tasks appear to stem from increased levels of stimulus-dependent, additive internal noise.