Amplitude-modulation detection becomes easier once modulation spreads the spectrum beyond one critical band

Evidence

In the case of a sinusoidal carrier, when the modulation frequency reaches about half the width of the critical band, the threshold starts to decrease again. As the spectrum of the modulated signal spreads to an area wider than one critical band, hearing detects the change more easily. For a white noise carrier, the signal is broadband to begin with, and the spectral effect of modulation is not detectable. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1169

Categorization

• XREF: Connects to critical-band theory and spectral vs. temporal cue integration, relevant to cochlear implant and compression-algorithm design.