Effect of frequency transposition on the discrimination of amplitude envelope patterns

The effects of systematic training on listeners' ability to compare the amplitude envelopes of signals differing in frequency was tested. Listeners indicated which of two comparison signals had the same amplitude envelope as the target signal. During training, center frequencies of comparison signals were gradually increased or decreased relative to target signal center frequencies of 500, 1600, and 3160 Hz. After training, performance was still worse when target and comparison signals were at different frequencies rather than at the same frequency, except possibly when comparison signals were higher in frequency than the 1600-Hz target. Thus the amplitude envelopes of signals do not appear to be perceived independently of the signal itself. Listeners who received no training performed similarly to the trained listeners, except that their performances declined when comparison signals were higher in frequency than the 1600-Hz target. Training did not reduce interlistener differences in overall performance or in the extent of the decline in performance when frequency differences between the target and comparison signals were introduced. The effects of frequency lowering on amplitude envelope discrimination do not appear to be related to the reduced efficacy of frequency-lowered speech-derived amplitude envelopes in supplementing speechreading.