Two tones are perceived as separate when no single filter captures both

Evidence

In terms of the perception of two pure tones illustrated in Figure 2.7, the “critical bandwidth” can be thought of as the bandwidth of the band-pass filter in the bank of filters, the center frequencies of which are exactly halfway between the frequencies of the two tones. This ignores the asymmetry of the basilar membrane response (see Figure 2.5) and the consequent asymmetry in the individual filter response curve-see Figure 2.10(a)-but it provides a good working approximation for calculations. Such a filter (and others close to it in center frequency) would capture both tones while they are perceived as “beats,” “rough fused” or “rough separate,” and at the point where rough changes to smooth, the two tones are too far apart to be both captured by this or any other filter. At this point there is no single filter that captures both tones, but there are filters that capture each of the tones individually, and they are therefore resolved and the two tones are perceived as being “separate and smooth. ” A musical sound can be described by the frequency components that make it up, and an understanding of the application of the critical band mechanism in human hearing in terms of the analysis of the components of musical sounds gives the basis for the study of psychoacoustics. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 597

Such a filter (and others close to it in center frequency) would capture both tones while they are perceived as “beats,” “rough fused” or “rough separate,” and at the point where rough changes to smooth, the two tones are too far apart to be both captured by this or any other filter. At this point there is no single filter which captures both tones, but there are filters which capture each of the tones individually and they are therefore resolved and the two tones are perceived as being “separate and smooth.” — David Howard, Jamie Angus, coustics and Psychoacoustics, 583

Categorization

• DEFINE: The critical bandwidth concept is defined here through the filter-bank model that links physical filter bandwidth to perceptual transitions.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 597; David Howard, Jamie Angus, coustics and Psychoacoustics, 583
• XREF: connects to: Hearing two tones as separate requires separate basilar membrane peaks — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 577