Threshold in quiet depends on total sound intensity within one critical band only

Evidence

In order to characterize the rule for a small number of tones, i.e. smaller frequency separation L1j, the data are plotted in Fig. 6.2b in a different form. The abscissa is the same, but the ordinate is now the overall sound pressure level of the complex of tones. It therefore becomes clear that the overall sound pressure level remains constant at threshold in quiet (or at masked threshold) for bandwidths smaller than the critical band. The overall sound pressure increases for bandwidths above the critical bandwidth, indicating that the components outside the critical band do not contribute either to the threshold in quiet or to the masked threshold. The sound intensity falling into one critical band is responsible for threshold in quiet as well as for masking. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 888

It is interesting to note that in the range between one and eight tones in the complex, the threshold level decreases 3 dB per doubling of the number of tones. This means that, at threshold, the overall sound pressure level of the complex remains constant regardless of the number of tones. This rule holds only up to about nine tones. Beyond this number, threshold expressed as level of each tone in the complex no longer decreases with increasing number of tones, i.e. overall sound pressure level increases. This means that the threshold in quiet is determined in our hearing system by the sound intensity of the total complex, as long as the components of this complex fall within a certain bandwidth. Parts outside that bandwidth do not contribute to threshold in quiet. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 878

As the ear is sensitive to sound pressures, the sound intensity is pro­ portional to the square of the sound pressures, as discussed in Chapter 1. Because the acoustic intensity of the sound is also proportional to the sum of the squared pressure, the loudness of a sound within a critical band is independent of the number of frequency components so long as their total acoustic intensity is constant. — David Howard, Jamie Angus, coustics and Psychoacoustics, 650

Categorization

• DEFINE: Captures the critical-band integration principle: energy within one critical band alone determines threshold.
• XREF: This unifies threshold-in-quiet and masking under a single critical-band model, which is the organizing concept of the chapter. — connects to: Masked threshold of a tone by white noise is computable from critical-band level; Masking acts within critical bandwidths, leaving distant-frequency sounds unaffected — Eric J. Heller, Why You Hear What You Hear- An…, 2009; Uniform exciting noise delivers equal intensity to every critical band — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1189 (+3 more)
• corroborated: 4 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 888; Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 878; David Howard, Jamie Angus, coustics and Psychoacoustics, 650

Broader Connections

• Masking acts within critical bandwidths, leaving distant-frequency sounds unaffected #expands (0.80) — Eric J. Heller, Why You Hear What You Hear- An…, 2009