Overshoot in subjects with sensorineural hearing impairment

Abstract

Overshoot was measured in both ears in subjects with normal hearing and in subjects with unilateral high‐frequency, sensorineural hearing loss by measuring threshold for a 10‐ms signal presented 1 or 195 ms after the onset of a 400‐ms broadband noise masker. Masker spectrum level was 20, 30, or 40 dB SPL. At 4.0 kHz, where absolute thresholds were elevated in the impaired ears, overshoot (the difference between thresholds at 1 and 195 ms) was small or absent. This may indicate that hearing loss alters a mechanism contributing to overshoot, or it may reflect the fact that sufficient amounts of masking (greater than about 20 dB) could not be produced except at high masker levels, where overshoot can be small or absent in normal ears [S. P. Bacon, J. Acoust. Soc. Am. (in press)]. In addition, overshoot was smaller at 1.0 kHz in the impaired ear than in the normal ear of the unilaterally impaired subjects, despite the fact that absolute thresholds were normal at that frequency. This, too, may reflect a damaged peripheral mechanism, or it may reflect the normal consequence of a relatively narrow, “effective” masker bandwidth. [Work supported by NIDCD.]