Narrow-band noise behaves like a randomly amplitude-modulated pure tone.

Evidence

As narrow-band noise shows a self-modulation with an effective modulation frequency of 0.64 times the bandwidth, its fluctuation strength also depends on the bandwidth of the noise. In this demonstration, narrow-band noises with different bandwidths of 2, 6, and 50 Hz are presented. The noises have a center frequency of 1 kHz and a level of 70 dB. The largest fluctuation strength is reached for a noise with a bandwidth of 6 Hz producing an effective modulation frequency of about 4 Hz. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3336 (#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 (#exemplifies, via linked claim)

Categorization

• XREF: connects to: Narrow-band noise self-modulates at 0.64 times its bandwidth — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3336; 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; Amplitude-modulated noises alone can carry recognizable melodies. (+2 more)

Broader Connections

• Narrow-band noise self-modulates at 0.64 times its bandwidth #expands (0.85) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3336
• Random envelope fluctuations in 100-Hz-wide noise bands produce strong roughness #exemplifies (0.75) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1446
• Speech-shaped noise can carry intelligible masked signals through amplitude modulation #expands (0.72)
• Amplitude-modulated noises alone can carry recognizable melodies. #corroborates (0.70)