Thresholds for formant-frequency discrimination of vowels in consonantal context

Abstract

The discrimination thresholds for shifts in formant frequency were shown to be in the range of 1%–2%, in a recent report to this society [Kewley-Port, J. Acoust. Soc. Am. Suppl. 1 87, S159 (1990)]. Thresholds for F1 and F2 obtained from well-trained subjects listening to vowels under minimal stimulus uncertainty were a factor of 3 lower than earlier estimates. The present experiment extends that study to examine the effects of placing a vowel in a consonantal context. The vowel /l/ was synthesized in CVC syllables for the consonants /b/, /d/, /g/, /z/, /m/, and /l/. For F1=450 Hz, the threshold, ΔF, was the same for isolated /l/ as the ΔF averaged over all CVC contexts, about 12 Hz. For F2=2300 Hz, ΔFwas significantly larger (45 Hz) for the vowel in the average CVC context than in isolation (25 Hz). Thresholds for individual CVC's were significantly different from the threshold for isolated /l/, in about one-half of the cases examined. These differences are discussed in terms of the extent of the formant transitions and the durations of the steady-state vowel formants. [Research supported by NIH and AFOSR.]