Spectral integration based on common amplitude modulation

Abstract

The perceptual integration of a mixture of two complex tones was studied in experiments on adult subjects. Each tone was formed by amplitude modulation (AM) of a carrier sinusoid of frequency (CF) by a raised sinusoid with modulation frequency (MF). One tone always had CF = 1500 Hz and MF = 100 Hz. The other had different CFs around 500 Hz and different MFs around 100 Hz. Both harmonic and inharmonic partials, produced by AM, were employed. The method involved studying the competition between two perceptual organizations: (1)the fusion of the two complex tones, and (2) the tendency of the higher tone to be stripped out of the mixture by a competing sequential organization. Fusion was best when the higher and lower complex tones had the same MF, even when the resulting partials did not form part of the same harmonic series. When MF was the same for the higher and lower tones and all partials were harmonically related, the tones fused best when the AM applied to the two tones was in phase. Results are discussed in relation to the problem of perceptual separation of two simultaneous voices and are seen as favoring a theory in which basilar membrane outputs that are amplitude-modulated by the same glottal pulse will be allocated to the same voice. © 1985 Psychonomic Society, Inc.