Hearing groups frequency bands by shared envelope modulation, reducing masking

Evidence

Co-modulation masking release is the decrease in the masking effect when the masker is amplitude-modulated with the same modulating function at all frequencies. Let us consider the case where the signal is a single sinusoid and the masker is a noise band around the frequency of the sinusoid. If the noise band is not modulated, the masking effect grows stronger when the noise bandwidth is extended. Interestingly, if the masker is amplitude-modulated coherently in all frequencies of the masker at the rate of 10–20 Hz, the masking effect deviates from the non-modulated case when the bandwidth of the masker exceeds 100 Hz (Hall et al., 1984). This can be seen to imply that the hearing system groups different frequency bands together based on the similarity of the variation of the level in the bands. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1013

Categorization

• DEFINE: Defines co-modulation masking release as a named phenomenon before explaining its mechanism.
• XREF: Explains how hearing groups simultaneous sounds by common modulation — a mechanism behind auditory scene analysis, connecting to cocktail-party-effect literature.