Recognition of amplitude-modulation patterns in the presence of a distractor. I. Effects of correlation and frequency relation.
Listeners' ability to compare the amplitude modulation pattern of 200- and 500-Hz targets when distractors that were also amplitude modulated were presented simultaneously was evaluated. The amplitude modulations of the distractors were either uncorrelated, partially correlated, or fully correlated with the amplitude modulations of the comparisons. Relative to the case of no distractor, performance tended to decrease when a distractor was present, and the degree of interference increased as the modulation correlation between the comparisons and distractors decreased. Although the interference was greater when the comparisons and distractors were separated by 50 Hz, there was also significant interference when the separation was 300 Hz. Whether the comparison was higher or lower in frequency than the distractor had no overall effect. However, the effect of modulation correlation was greater when comparisons were higher than distractors rather than lower. Patterns of interference are compared to those found in studies of modulation detection and discrimination interference, and implications for the use of multiple-band signals that carry the amplitude envelopes from different spectral regions of a speech signal to convey speech are discussed.