Nonspectral pitch

The spectrum of amplitude-modulated wide-band noise is invariant with changes in modulation frequency, and consequently such waveforms cannot convey melodic information by spectral changes. The results of several experiments indicate, however, that sinusoidally amplitude-modulated wide-band noise does have pitchlike properties. Simple melodies can be identified when the “notes” correspond to different modulation frequencies. More importantly, musically trained observers can immediately recognize melodic muscial intervals composed of such waveforms. The pitchlike properties of modulated noise are maintained when the modulated noise is bandpass filtered and when an unmodulated band-reject masker is added to the bandpass noise. Presumably the perception of pitch elicited by modulated noise is based upon temporal information in the envelope of the waveform. This “temporal pitch” is less salient than the pitch elicited by pure tones. Also, temporal pitch can be elicited only over a restricted range of modulation frequencies. The upper limit (approximately 850–1000 Hz) appears to reflect the inability of the auditory system to follow rapid temporal changes.