Spectral weights for sample discrimination as a function of overall level

Doherty and Lutfi [(1996). "Spectral weights for overall level discrimination in listeners with sensorineural hearing loss," J. Acoust. Soc. Am. 99, 1053-1058] examined the weights assigned to individual components of a six-tone complex during a sample discrimination task and reported that hearing-impaired subjects gave the most weight to components in the region of their high-frequency hearing loss. In contrast, weighting patterns varied for normal-hearing subjects. In the current study, the same six-tone complex, comprised of the octave frequencies from 0.25 to 8 kHz, was presented to three subjects with normal hearing in high-pass noise, in low-pass noise, and in quiet at two overall levels. Consistent with Doherty and Lutfi, subjects assigned more weight to the 4-kHz component in the high-pass noise condition, but roughly equal weight to all components in the lower-level quiet condition. Weights in the low-pass noise and higher-level quiet conditions, however, were similar to those in the high-pass noise condition. A second experiment compared weights for seven subjects in quiet at four different mean levels. Weights for the highest-frequency components increased as the overall level of the complexes was increased. These results suggest that overall level, rather than degree of hearing loss or sensation level, was the primary cause of the effect that Doherty and Lutfi observed.