Discrimination of envelope frequency in one spectral region in the presence of modulation in another.
This paper examines how discrimination of envelope frequency in one spectral region is affected by the presence of either correlated or uncorrelated modulation in another spectral region. Envelope-frequency discrimination thresholds, delta fe's, for a 60-dB SPL two-tone complex centered at 2 kHz were measured in the presence or absence of an auxiliary two-tone complex at another frequency. When present, the auxiliary complex had either the same envelope as the standard signal or an envelope that was uncorrelated with both the standard and variable signal. The results show that listeners can take advantage of correlation between simultaneous envelopes in different frequency regions to improve discrimination of a small change in envelope frequency, whereas the presence of uncorrelated envelopes causes interference with discrimination. Except when the auxiliary complex and the signal are close together in frequency, the discrimination advantage afforded by the correlated auxiliaries appears to reflect across-channel envelope processing. The discrimination interference caused by the uncorrelated auxiliaries, on the other hand, may reflect primarily within-channel interaction such as peripheral masking, although a small amount of across-channel masking also is apparent.