ASA 127th Meeting M.I.T. 1994 June 6-10

4aPP14. Is ``recalibration'' of loudness related to short-term auditory fatigue?

Lawrence E. Marks

John B. Pierce Lab., 290 Congress Ave., New Haven, CT 06519

After listening to tone sequences containing brief, relatively low-SPL signals at one frequency (f[sub 1]) and higher-SPL signals at another frequency (f[sub 2]), tones at f[sub 1] appear relatively louder than tones at f[sub 2]. Similar changes in loudness occur after exposure to only the higher-SPL signals. Such changes have been called ``recalibration'' [L. E. Marks, J. Exp. Psychol.: Hum. Percept. Perf. 20, 1--15 (1994)], and they resemble the temporary threshold shifts of short-term auditory fatigue. But fatigue is widely viewed to involve peripheral processes, whereas recalibration, a complex phenomenon also observed in other sensory modalities, may rely on central processes. Consequently, two experiments examined whether ``recalibration'' shows interaural transfer. Subjects compared the loudness of 500- and 2500-Hz signals before and after being presented sequences of monaural exposure tones that were themselves either listened to passively or judged for loudness. Both experiments showed substantial recalibration in the ear ipsilateral to the exposure stones, and smaller but still clearly evident recalibration in the contralateral ear. Thus recalibration may involve central mediation and, if so, may then rely on mechanisms differing at least in part from those underlying auditory fatigue. [Work supported by NIH.]