Perceptual constancy, reverberation, and grouping: Within-band effects.

Abstract

Perceptual constancy effects are observed when differing amounts of reverberation are applied to a context sentence and a test-word embedded in it. Adding reverberation to members of a “sir”-“stir” test-word continuum causes temporal-envelope distortion, which has the effect of eliciting more sir responses from listeners. If the same amount of reverberation is also applied to the context sentence, the number of sir responses decreases again, indicating an “extrinsic” compensation for the effects of reverberation. Such a mechanism would effect perceptual constancy of phonetic perception when temporal envelopes vary in reverberation. This experiment asks whether such effects precede or follow grouping. Eight auditory-filter shaped noise-bands were modulated with the temporal envelopes that arise when speech is played through these filters. The resulting “gestalt” percept is the appropriate speech rather than the sound of noise-bands, presumably due to across-channel “grouping.” These sounds were played to listeners in “matched” conditions, where reverberation was present in the same bands in both context and test-word, and in “mismatched” conditions, where the bands in which reverberation was added differed between context and test-word. Constancy effects were obtained in matched conditions, but not in mismatched conditions, indicating that this type of constancy in hearing precedes across-channel grouping.