Wider noise bandwidths decrease detectable amplitude modulation via multi-band cooperation

Evidence

For spectral widths of the band-pass noise larger than a critical band, the just-noticeable degree of amplitude modulation decreases. This decrease results from the cooperation of several critical bands. Whether this cooperation can be accounted for by adding up the available variations in a coherent fashion across critical bands, or by some other strategy used by the ear remains unclear. However, all psychoacoustical data relevant to this question show a decrease in the just-noticeable amplitude modulation, with an increase in the number of critical bands involved. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1032

Categorization

• DEFINE: Clarifies what ‘cooperation of critical bands’ means for amplitude-modulation detection — the mechanism, though unidentified, improves detection as more bands engage.
• QUESTION: The unstated mechanism — coherent summation across bands vs. another strategy — is an open question worth chasing in later chapters or the literature.