Pitch Perception of Two-Frequency Stimuli

Experiments on the pitch of complex tones produced by two frequency components are reported. An exploratory experiment revealed that subjects perceive the pitches of individual part-tones or the stimulus as a whole with a pitch corresponding to about the fundamental frequency. The latter pitch was investigated more thoroughly. In case of adjacent harmonics, the pitch corresponded to the (absent) fundamental frequency. A shift of the frequencies away from such a harmonic situation while maintaining a constant frequency difference resulted in a pitch shift. For higher harmonic numbers, the pitch shift was larger than could be met by current theories. The large pitch shift was explained by taking into account an auditory nonlinearity which generates combination tones of the type f1−k(f2−f1). Sound-pressure level dependence of the pitch shift could be explained in the same manner. When the combination tones were masked, the large pitch shift diminished. With regard to the pitch mechanism, the results suggested that detection of the low pitch of the complex tone requires spectral information.