Co-modulation masking release (CMR) in consonant recognition

Abstract

In the psychoacoustic phenomenon of co-modulation masking release (CMR), detection of a target in a narrow-band noise is improved in the presence of a co-modulated flanking noise band. The present study investigates whether CMR could improve speech perception. Consonant recognition scores of bandlimited speech, 1200–2200 Hz, were measured under a modulated noise of the same bandwidth, and a second band of noise (5000–7000 Hz), which was either co-modulated or non-co-modulated with the first band. With a hypothesis that CMR improves discrimination of phonemes that are characterized by temporal cues, i.e., amplitude envelope, rather than spectral cues, two groups of consonants were selected for testing: stop consonants (similar temporal envelopes, but different spectra) and alveolar–dental consonants (similar spectra, but different temporal envelopes). Results agreed with the hypothesis: significantly higher recognition scores were obtained with the co-modulated noise band for alveolar–dental consonants, while the difference was marginal for stop consonants. This indicates that CMR can improve speech perception as well as psychophysical thresholds. Co-modulation in the flanking band seems to enable listeners to better ‘‘hear out’’ subtle temporal speech cues in noise, leading to better recognition. [Work supported by Quota scholarship and NIDCD.]