Examining potential sources of variability in behavioral measures of cochlear gain and gain reduction in listeners with normal hearing or minimal cochlear hearing loss

This study examined the relationship between clinical measures of auditory function and psychoacoustic measures related to cochlear function. Listeners’ audiometric thresholds for long tones ranged from well within the clinically normal range to just above this range. Where thresholds were elevated, other clinical tests were consistent with a cochlear origin. Because the medial olivocochlear reflex decreases cochlear gain in response to sound, measures were made with short stimuli. Signal frequencies were from 1 to 8 kHz. One point on the lower leg of the input/output function was measured by finding threshold masker level for a masker almost one octave below the signal frequency needed to mask a signal at 5 dB SL. Gain reduction was estimated by presenting a pink broadband noise precursor before the signal and masker and measuring the change in signal threshold as a function of precursor level. In a previous presentation, it was shown that the estimate of gain reduction decreased as quiet threshold increased, but was not solely determined by the amount of gain. In this presentation, the relationship between gain reduction and clinical otoacoustic emission and middle-ear muscle reflex measurements was examined to determine whether these explained some of the variability. [Work supported by NIH (NIDCD) R01 DC008327 (EAS) and NIH(NIDCD) T32 DC016853 (WBS).]