Puzzles of loudness constancy, loudness adaptation, and speech frequencies

Abstract

Loudness constancy is suggested as a term for the failure to observe simple adaptation above 30 dB, noting however that Miskiewicz et al. [J. Acoust. Soc. Am. 94, 1281–1286 (1993)] indicated that simple adaptation is found at higher intensities above 4 kHz. Conversely, using the ipsilateral comparison paradigm (ICP), Dange et al. [J. Gen. Psychol. 120, 217–243 (1993)] found adaptation at 1000 Hz, from 45 to 75 dB. They saw this as revealing underlying neural adaptation, normally concealed by processes of loudness constancy. As a further test, Hellman [personal communication (1996)] urged that ICP adaptation be attempted without the usual designated modulus. In the present study (N=20), strong ICP loudness adaptation was indeed found with and without the designated modulus. Recently, Janson et al. [Br. J. Audiol. 29, 288–297 (1996)] found that ICP adaptation at 1 kHz was much less consistent for subjects with higher frequency loss than for nonimpaired listeners. Discussion of the possible value of loudness constancy in the speech frequencies will be discussed in light of current data and previous studies.