The preferences of experiences listerners for pitch and formant frequency dispersion in unison choir sounds were explored using synthesized stimuli. Two types of dispersion were investigated: (a) pitch scatter, which arises when voices in an ensemble exhibit small differences in mean fundamental frequency, and (b) spectral smear, defined as such dispersion of formants 3 to 5 as arises from differences in vocal tract length. Each stimulus represented a choir section of five bass, tenor, alto, or soprano voices, producing the vowel [u], [a], or [ae]. Subjects chose one dispersion level out of six available, selecting the "maximum tolerable" in a first run and the "preferred" in a second run. The listeners were very different in their tolerance for dispersion. Typical scatter choices were 14 cent standard deviation for "tolerable" and 0 or 5 cent for "preferred." The smear choices were less consistent; the standard deviations were 12 and 7%, respectively. In all modes of assessment, the largest dispersion was chosen for the vowel [u] on a bass tone. There was a vowel effect on the smear choices. The effects of voice category were not significant.
1993. Vol. 7, no 2, 129-135 p.