Acoustic cues to vowel-schwa sequences for high front vowels

Abstract

In a landmark-based model of lexical access [K. N. Stevens, J. Acoust. Soc. Am. 111, 1872–1891 (2002)], the presence of a vowel is marked by a peak in energy in the first formant region. However, when a vowel is followed by a schwa, the schwa frequently appears as a shoulder on the peak associated with the first vowel [W. Howitt, MIT (2000)]; two landmarks are not present. The purpose of this study is to examine duration and F2 movement as possible cues to the presence of a vowel-schwa sequence for [+high, +front] vowels. This subset of vowels presents at least two challenges to the detection of a vowel-schwa sequence: (1) duration is expected to contribute to the difference between /i/ and /I/, and (2) an F2 off-glide toward schwa is expected for /I/ in American English. For 613 tokens from the phonetically labeled TIMIT database, equally distributed between /i■/, /i/, and /I/, a measure of F2 curvature is a stronger cue than duration in classifying the tokens. Using F2 curvature, over 93% of the tokens are correctly classified. Using duration, 67% are correctly classified. F2 curvature may reflect a more extreme articulation for the /i/ prior to the schwa. [Work supported by NIH Grant DC02978.]