Phase effects in masking by harmonic complexes: detection of bands of speech-shaped noise.
When phase relationships between partials of a complex masker produce highly modulated temporal envelopes on the basilar membrane, listeners may detect speech information from temporal dips in the within-channel masker envelopes. This source of masking release (MR) is however located in regions of unresolved masker partials and it is unclear how much of the speech information in these regions is really needed for intelligibility. Also, other sources of MR such as glimpsing in between resolved masker partials may provide sufficient information from regions that disregard phase relationships. This study simplified the problem of speech recognition to a masked detection task. Target bands of speech-shaped noise were restricted to frequency regions containing either only resolved or only unresolved masker partials, as a function of masker phase relationships (sine or random), masker fundamental frequency (F0) (50, 100, or 200 Hz), and masker spectral profile (flat-spectrum or speech-shaped). Although masker phase effects could be observed in unresolved regions at F0s of 50 and 100 Hz, it was only at 50-Hz F0 that detection thresholds were ever lower in unresolved than in resolved regions, suggesting little role of envelope modulations for harmonic complexes with F0s in the human voice range and at moderate level.
Department of Otolaryngology, Johns Hopkins University School of Medicine, 818 Ross Research Building, 720 Rutland Avenue, Baltimore, Maryland 21205.
Mickael L D
ML
Deroche
School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff, CF10 3AT, United Kingdom.
John F
JF
Culling
Auditory Prostheses and Perception Laboratory, Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131.
Monita
M
Chatterjee
D000328:Adult; D004056:Differential Threshold; D006801:Humans; D008962:Models, Theoretical; D009622:Noise; D046709:Pattern Recognition, Physiological; D010470:Perceptual Masking / Q000502:physiology*; D010507:Periodicity; D010700:Phonetics; D013016:Sound; D013061:Speech Acoustics; D013065:Speech Intelligibility; D055815:Young Adult