A new technique for measuring spectral shape discrimination.

A new technique is described for studying the ability of listeners to discriminate between sounds on the basis of spectral shape, a process called "auditory profile analysis." The advantage of the technique is that it reduces the range of the random rove in level necessary to provide a specified limit on the performance which listeners could achieve by "level detection;" that is, by employing a detection strategy based solely on comparisons of stimulus level. Thresholds were measured for the just-discriminable "ripple" (a pattern of alternating intensity increments and decrements) in an equal-amplitude, multitone reference spectrum for a group of normal-hearing listeners. Broadband, high-pass and low-pass filtered conditions were tested. The results indicated that the thresholds obtained using the new technique were well below the lowest level achievable by level detection (referred to as the "level-detection limit") in all conditions using a 20-dB random within-trial rove in overall level. The lowest threshold occurred for the broadband stimulus while the highest threshold was observed for the most extreme high-pass filtered condition. The new technique appears to be well-suited for study of profile analysis in hearing-impaired listeners where stimulus bandwidth and rove range are limited.