Recovery from on- and off-frequency forward masking in listeners with normal and impaired hearing

The aim of this study was to investigate the possible mechanisms underlying an effect reported earlier [Wojtczak, M., and Oxenham, A. J. (2009). J. Acoust. Soc. Am. 125, 270-281] in normal-hearing listeners, whereby recovery from forward masking can be slower for off-frequency tonal maskers than for on-frequency tonal maskers that produce the same amount of masking at a 0-ms masker-signal delay. To rule out potential effects of confusion between the tonal signal and tonal masker, one condition used a noise-band forward masker. To test whether the effect involved temporal build-up, another condition used a short-duration (30-ms) forward masker. To test whether the effect is dependent on normal cochlear function, conditions were tested in five listeners with sensorineural hearing loss. For the 150-ms noise maskers, the data from normal-hearing listeners replicated the findings from the previous study that used tonal maskers. In contrast, no significant difference in recovery from on- and off-frequency masking was observed for the 30-ms tonal maskers in normal-hearing listeners, or for the 150-ms tonal maskers in hearing-impaired listeners. Overall, the results are consistent with a mechanism based on efferent feedback that affects the recovery from forward masking in the normal auditory system.