Sound localization in noise in hearing-impaired listeners

The present study assesses the ability of four listeners with high-frequency, bilateral symmetrical sensorineural hearing:loss to localize and detect: a broadband click train in the frontal-horizontal plane; in quiet and in the presence of a white noise. The speaker array and, stimuli are identical to those described-by Lorenzi et at tin press). The results show that: (1) localization performance is only slightly poorer in hearing-impaired listeners than in normal-hearing listeners when noise is at 0 deg azimuth,(2) localization performance begins to decrease at higher signal-to-noise ratios for hearing-impaired listeners than for normal-hearing listeners when-noise is at +/-90 deg azimuth,and (3) the performance of hearing-impaired listeners is less consistent when noise is at +/-90 deg azimuth than at 0 deg azimuth. The effects of a high-frequency hearing loss were also studied by measuring the ability of normal-hearing listeners to localize the low-pass filtered version of the clicks.:The data reproduce the effects of noise on three out: of the four hearing-impaired listeners when noise is at 0 deg azimuth. They reproduce the effects of noise on only two out of the four hearing-impaired listeners when noise is at +/-90 deg azimuth. The additional effects of a low-frequency hearing loss were investigated by attenuating the low-pass filtered clicks and the noise by 20 dB. The results show that attenuation does not strongly affect localization accuracy for normal-hearing listeners. Measurements of the clicks' detectability: indicate that the hearing-impaired listeners who show the poorest localization accuracy also show the poorest ability to detect the clicks. The inaudibility of high frequencies; "distortions," and reduced detectability of the : signal are-assumed to have caused the poorer-than-normal localization accuracy for hearing-impaired listeners. (C) 1999 Acoustical Society of America. [S0001-4966(99)04106-5].