ASA 125th Meeting Ottawa 1993 May

4aPP10. Loudness adaptation for high-frequency tones.

Andrzej Miskiewicz

Rhona Hellman

Carol Meiselman

Bertram Scharf

Northeastern Univ., 360 Huntington Ave., Boston, MA 02115

Loudness adaptation was measured for pure tones at 4, 12, 14, 16, and 17 kHz. Loudness adaptation refers to the decline in the loudness of a continuous sound as a function of exposure time. More than 100 students judged---by the method of successive magnitude estimation---the loudness of the tones over a 6-min exposure time. Earlier investigations for frequencies up to 4 kHz had shown that loudness adapts only at sensation levels up to approximately 30 dB [B. Scharf, Hear. Res. Theory, 1--56 (1983)]. The current measurements show that at 12 kHz and above, loudness adapts at sensation levels above 30 dB as well as below. At high frequencies, loudness adaptation becomes greater as frequency increases up to 16 kHz; at 17 kHz adaptation is nearly the same as at 16 kHz. The marked loudness adaptation of steady tones at very high frequencies and relatively high sensation levels is ascribed to a restricted spread of excitation in the auditory system resulting from the steep rise of the threshold curve at the upper bound of hearing. [Work supported by NIH.]