Auditory filter asymmetry in the hearing impaired

Abstract

Thresholds for 2-kHz sinusoidal signals were determined in the presence of a notched-noise masker, for 6 normal-hearing listeners and 12 listeners with cochlear hearing losses. Conditions were used where the notch was placed both symmetrically and asymmetrically about the signal frequency. The auditory filter shape for both the low- and high-frequency side of the filter was calculated using the rounded-exponential form of the filter. In 6 hearing-impaired listeners, the auditory filter shapes showed a shallow low-frequency skirt indicating pronounced susceptibility to the upward spread of masking. In 2 hearing-impaired listeners, the filter shape showed a shallow high-frequency skirt, indicating pronounced susceptibility to the downward spread of masking. Two other listeners with mild threshold losses had steeper and more symmetric filters than normal, suggesting either a small conductive loss or an attenuation factor of sensorineural origin not associated with a degradation of frequency resolution. In the remaining 2 listeners, the auditory filter had too little selectivity for its shape to be reliably determined.