Detection and intensity discrimination of brief tones as a function of duration by hearing-impaired listeners

For normal listeners, difference limens for intensity (DLs) for Gaussian-sh aped tone pulses are largest at medium Pulse durations (corresponding to ab out five cycles of the tonal carrier) when the pedestals are 10 dB above th reshold, either in quiet or in a pink noise background. One explanation for this is that worst performance occurs when the internal representation of the tone pulses is most compact in time and frequency, affording minimial o pportunity for 'multiple looks' (Van Schijndel et al., J. Acoust. Soc. Am. 105 (1999) 3425-3435). However, the mid-duration worsening is largest for m edium overall levels, suggesting an involvement of compression on the basil ar membrane (BM), which is also greatest at medium levels (Baer ct al., J. Acoust. Soc. Am. 106 (1999) 1907-1916). If this is so, the mid-duration wor sening should be reduced when BM compression is reduced by outer hair cell damage. To test this, subjects with sensorineural hearing losses were teste d using 1-kHz or 4-kHz Gaussian-shaped tone pulses, in quiet or in pink noi se that raised thresholds by 10-20 dB. For subjects with mild losses, poore st performance was sometimes found for medium durations. For more severe lo sses, intensity DLs tended to improve monotonically or remain roughly const ant with increasing duration. Performance overall tended to be better for s ubjects with greater hearing losses. The results are more consistent with a il explanation based on BM compression than with an explanation based on mu ltiple looks. (C) 2001 Elsevier Science B.V. All rights reserved.