Rate of loudness growth for pure tones in normal and impaired hearing.

The present article provides an analysis of loudness growth rates in normal and cochlear-impaired hearing for diverse groups with respect to age and backgrounds. Slopes are obtained from absolute magnitude estimation and magnitude production of loudness (measured values), and from cross-modality matching and absolute magnitude estimation of apparent length (predicted values). Consistent with an earlier study [R. P. Hellman and C. H. Meiselman, J. Acoust Soc. Am. 88, 2596-2606 (1990)], slopes calculated within the 15-30 dB stimulus range above the elevated threshold increase in size with the degree of hearing loss. The corresponding range of loudness values in normal hearing yields a slope near 0.60 independent of the threshold levels. This pattern of loudness growth holds for individuals and groups. But the intersubject variability of the slope is more labile, being larger across than within groups and larger for the measured slopes than for the predicted values. Determined from the predicted slopes, the coefficient of variation, sigma/m, is approximately constant in normal and impaired hearing ranging from 20%-27%. In contrast, sigma/m, obtained from the measured slopes, increases with the degree of hearing loss to a value of almost 50% for a 75-dB loss. The overall stability and systematics of the observed effects further demonstrate that the loudness-intensity relation can be specified with reasonable precision and accuracy from cross-modality matching.