Perception of the low pitch of frequency-shifted complexes

Abstract

When all of the components in a harmonic complex tone are shifted in frequency by delta f, the pitch of the complex shifts roughly in proportion to delta f. For tones with a small number of components, the shift is usually somewhat larger than predicted from pitch theories, which has been attributed to the influence of combination tones [Smoorenburg, J. Acoust. Soc. Am. 48, 924-941 (1970)]. Experiment 1 assessed whether combination tones influence the pitch of complex tones with more than five harmonics, by using noise to mask the combination tones. The matching stimulus was a harmonic complex. Test complexes were bandpass filtered with passbands centered on harmonic numbers 5 (resolved), 11 (intermediate), or 16 (unresolved) and fundamental frequencies (FOs) were 100, 200, or 400 Hz. For the intermediate and unresolved conditions, the matching stimuli were filtered with the same passband to minimize differences in the excitation patterns of the test and matching stimuli. For the resolved condition, the matching stimulus had a passband centered above that of the test stimulus, to avoid common partials. For resolved and intermediate conditions, pitch shifts were observed that could generally be predicted from the frequencies of the partials. The shifts were unaffected by addition of noise to mask combination tones. For the unresolved condition, no pitch shift was observed, which suggests that pitch is not based on temporal fine structure for stimuli containing only high unresolved harmonics. Experiment 2 used three-component complexes resembling those of Schouten [J. Acoust. Soc. Am. 34, 1418-1424 (1962)]. Nominal harmonic numbers were 3, 4, 5 (resolved), 8, 9, 10 (intermediate), or 13, 14, 15 (unresolved) and F0s were 50, 100, 200, or 400 Hz. Clear shifts in the matches were found for all conditions, including unresolved. For the latter, subjects may have matched the "center of gravity" of the excitation patterns of the test and matching stimuli.