Combined monaural and binaural masking release.

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing in hearing

Background:

• Auditory masking occurs when a signal is made inaudible by a masker.
• Across-frequency (comodulation masking release, CMR) and across-ear (binaural masking-level difference, BMLD) cues can reduce masking.
• The interaction between CMR and BMLD is not fully understood.

Purpose of the Study:

• To investigate the combined effects of comodulation masking release (CMR) and binaural masking-level difference (BMLD) on auditory masking.
• To determine if listeners can utilize both CMR and BMLD cues simultaneously for enhanced masking release.
• To explore the influence of modulation frequency on the combination of these cues.

Main Methods:

• Stimuli were presented under conditions with both CMR and BMLD cues available, or with only one cue type.
• Comodulation masking release was manipulated by modulating a masking noise's bandwidth or using two comodulated noise bands.
• A 500-Hz pure-tone signal was masked by noise, with signal and masker phase relationships varied (S0 or Sπ).

Main Results:

• Four out of six subjects demonstrated a greater masking release when both BMLD and CMR cues were available compared to when only one cue was present.
• Two subjects did not show an additional benefit from combining both cue types.
• For subjects who could combine cues, the additional masking release was more pronounced at lower modulation frequencies.

Conclusions:

• The findings suggest that listeners can, to some extent, combine across-frequency (CMR) and across-ear (BMLD) auditory cues for improved signal detection in noise.
• The ability to combine cues varied among individuals.
• A component of comodulation masking release may rely on processing envelope comparisons across frequencies after binaural analysis.