COHERENCE MASKING PROTECTION IN BRIEF NOISE COMPLEXES - EFFECTS OF TEMPORAL PATTERNS

Three experiments examined listeners' thresholds for classifying the p itch of a target signal in a masking noise when it was presented alone as compared to when it was presented with a ''cosignal.'' The target signal was a narrow band of noise centered on either 375 or 625 Hz and the masker was noise low-pass filtered at 1000 Hz. The cosignal provi ded no information about the pitch of the target signal but could pote ntially combine with it to form an auditory object; it was spectrally well separated from the target signal, consisting of a band of noise r anging from 2200 to 2900 Hz. Experiment 1 showed that identification t hresholds were lower when the target signal was paired with the cosign al than when it was presented alone if the onsets and offsets of the t arget signal and cosignal were temporally synchronous. This is an inst ance of ''coherence masking protection,'' a phenomenon that has previo usly been established in the perception of vowels [p. c. Gordon, Perce pt. Psychophys. 59, 232-242 (1997)]. The effect disappears when the co signal leads and lags the target signal by short durations, a finding that also matches that observed previously with vowels. The finding th at temporal relations between the components of a stimulus have simila r effects on the perception of nonspeech noise complexes and speech so unds suggests that speech perception makes use of general auditory mec hanisms for perceptual integration of this sea. Experiments 2 and 3 ex amine further the role of temporal relations between the onsets and of fsets of the target signal and the cosignal in producing coherence mas king protection. The results show that either onset synchrony or offse t synchrony is sufficient to produce the effect when the cosignal is o f greater duration than the target signal, but that only onset synchro ny produces the effect when the target signal has greater duration tha n the cosignal. This pattern indicates that the target signal and cosi gnal do not contribute equally to the formation of auditory objects. ( C) 1997 Acoustical Society of America. [S0001-4966(97)03609-6] PACS nu mbers: 43.66.Dc, 43.66.Mk [RHD].