Frequency-modulated tones grow louder only above roughly 20 Hz modulation

Evidence

This can be proven by using strongly frequency-modulated pure tones and judging their loudness as a function of modulation frequency. Using a frequency shift of ±700 Hz and a centre frequency of 1500 Hz, loudness comparisons show that the loudness level increases as a function of modulation frequency only for modulation frequencies above about 20 Hz. … The model predicts that loudness level should increase for similar modulation frequencies near about 20 Hz. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1297

Categorization

• XREF: The ~20 Hz threshold where FM loudness begins tracking modulation ties to the roughly 45 ms temporal integration window (1/45 ms ~ 22 Hz). — connects to: Frequency-modulated tones lose fluctuation strength above 1 kHz centre frequency; Modulation frequency determines whether sound is heard as fluctuation, roughness, or multiple tones — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1217
• corroborated: 2 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1297

Broader Connections

• Modulation frequency determines whether sound is heard as fluctuation, roughness, or multiple tones #expands (0.80) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1217
• Frequency-modulated tones lose fluctuation strength above 1 kHz centre frequency #qualifies (0.75)