Remote masking for listeners with cochlear impairment.

Abstract

Remote masking in ears with cochlear impairment was investigated, According to one theory, remote masking results from unsymmetrical mechanical action in the inner ear that generates a broad-band noise within the inner ear. The broad-band noise is said to mask tones at frequencies remote from and below the narrow-band masker. A second theory proposes that remote masking is the result of attenuation provided by the acoustic reflex. Two noise bands were presented at three levels to a group of listeners with normal hearing and two groups with high-frequency hearing losses of presumed cochlear origin. From these results, it appears that, when a noise band is located at frequencies of hearing loss, listeners with presumed cochlear impairment require a higher level of noise for remote masking to occur than do normal-hearing listeners; and their remote masked thresholds are at a lower SPL and there is less remote masking than for normal-hearing listeners. It was observed that remote masking is not necessarily at a constant sensation level across frequency, with the greatest amount of remote masking occurring near 800 Hz. The similarities between results of this investigation and known parameters of the acoustic reflex lead us to the conclusion that a dual mechanism of middle-ear plus inner-ear activity is a more suitable explanation of remote masking than either theory alone.