Loudness growth in individual listeners with hearing loss

Recent research indicates that there are large individual differences in how loudness grows with level for listeners with sensorineural hearing losses of primarily cochlear origin. Studies of loudness discomfort level suggest that loudness for most of these impaired listeners approaches the loudness experienced by the normal listeners at high levels. Loudness growth at low levels is still controversial. Although it is now well established that loudness at threshold is greater than zero, its exact value is unknown. If this value is the same for normal and impaired listeners, then the loudness growth for the impaired listeners must be steeper in order to catch up to normal at high levels. This phenomenon is called recruitment. If the loudness at threshold for impaired listeners is higher than that for normal listeners, then the impaired listeners will no longer be able to perceive sounds as soft. This phenomenon is called softness imperception. Results from two experiments suggest that: (1) individual differences are more important for impaired listeners than for normal listeners; (2) some impaired listeners seem to show recruitment, others softness imperception; and (3) averaging the results across the impaired listeners will mask these differences. [Work supported by NIH/NIDCD grant R01DC02241.]