Noise fluctuations within narrow critical bands raise the masking index

Evidence

Sound of a given frequency can block our ability to hear softer sounds at nearby frequencies, but distant frequencies are not affected. The threshold for detecting the softer sound is raised by the presence of a louder sound within the same critical bandwidth. Even if the softer sound is audible, it will not seem as loud as it would if played alone. Similarly, two tones that fall within the same critical bandwidth will appear to be less loud together than two tones of the same total energy that fall outside each others’ critical bandwidths. — Eric J. Heller, Why You Hear What You Hear- An…, 2009 (#expands, via linked claim)

Bands of noise often sound rough, although there is no additional amplitude modulation. This is because the envelope of the noise changes randomly. These changes become audible especially for bandwidths in the neighbourhood of 100 Hz, where the average rate of envelope change is 64 Hz (see Sect. 1.1). Therefore, roughness is particularly large at such bandwidths. For increasing bandwidth, the creation of roughness is limited by frequency selectivity. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1446 (#expands, via linked claim)

Categorization

• XREF: 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; Random envelope fluctuations in 100-Hz-wide noise bands produce strong roughness — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1446 (+5 more)

Broader Connections

• Masking acts within critical bandwidths, leaving distant-frequency sounds unaffected #expands (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 2009
• Random envelope fluctuations in 100-Hz-wide noise bands produce strong roughness #expands (0.80) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1446
• Narrowband noise at a given frequency masks nearby tones much more than distant ones #corroborates (0.80)
• Narrow-band noise self-modulates at 0.64 times its bandwidth #expands (0.75) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3336