INTENSITY PERCEPTION .14. INTENSITY DISCRIMINATION IN LISTENERS WITH SENSORINEURAL HEARING-LOSS

Intensity discrimination of pulsed tones (also called level discrimina tion) was measured as a function of level in 13 listeners with sensori neural hearing impairment of primarily cochlear origin, one listener w ith a vestibular schwannoma, and six listeners with normal hearing. Me asurements were also made in normal ears presented with masking noise spectrally shaped to produce audiograms similar to those of the cochle arly impaired listeners. For unilateral impairments, tests were made a t the same frequency in the normal and impaired ears. For bilateral-sl oping impairments, tests were made at different frequencies in the sam e ear. The normal listeners showed results similar to other data in th e literature. The listener with a vestibular schwannoma showed greatly reduced intensity resolution, except at a few levels. For listeners w ith recruiting sensorineural impairments, the results are discussed ac cording to the configuration of the impairment and are compared across configurations at equal SPL, equal SL, and equal loudness-level. List eners with increasing hearing losses at frequencies above the test fre quency generally showed impaired resolution, especially at high levels , and less deviation from Weber's law than normal listeners. Listeners with decreasing hearing loss at frequencies above the test frequency showed nearly normal intensity-resolution functions. Whereas these tre nds are generally present, there are also large differences among indi viduals. Results obtained from normal listeners who were tested in the presence of masking noise indicate that elevated thresholds and reduc ed dynamic range account for some, but not all, of the effects of recr uiting sensorineural impairment on intensity resolution.