Frequency modulation within a resonance peak produces visible amplitude modulation

Evidence

Thus the effect of a frequency modulation is to additionally produce amplitude modulation in any component that is within a resonance peak of the sound modifier. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1469

Categorization

• DEFINE: Clarifies the FM-to-AM coupling mechanism that underlies modulated timbres.
• QUESTION: Does this coupling explain why vibrato sounds fuller or louder, not just higher and lower?
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1469