Figure 1.

The three basic perceptual qualities experienced during listening to AM tones, based quantitatively on the magnitude scaling data of Fastl (1983; Fastl and Zwicker 2007). All results were obtained at a comfortable listening level (e.g., 70 phon), with 100% AM modulation depth. Note that the periodicity pitch and roughness ranges overlap (purple color). The peak of pitch strength is always experienced when f_m = f_c/2, because in this case the lower sideband is positioned at precisely the fundamental frequency. Roughness is defined relative to a standard of f_c = 1 kHz and f_m = 70 Hz. Similar overall results are obtained for AM noise and FM tones, except that pitch strength is much weaker for AM noise, and roughness is much stronger for FM tones. Note that the identical percepts are elicited by speech stimuli in so far as the spectrogram exhibits modulations in the appropriate ranges. For speech, ‘periodicity pitch’ is ‘voice fundamental’, and ‘fluctuation’ is sometimes called ‘rhythm’.