| Schwa is the most commonly occurring English vowel, yet it has received little attention in phonetics literature. It is generally regarded as a short, centralized, quiet vowel that varies perceptually between /ih/ and /ah/ (as in "bit" and "but"). The primary goal of this study was to test these notions using acoustic data, and to investigate factors that govern schwa's variation. Because naturally occurring data from conversations were used, a secondary goal was to design a methodology that employs statistical techniques to uncover meaningful patterns in inherently uncontrolled speech.;Data were taken from recordings of two male speakers using three speaking modes: spontaneous conversations, reading of sentences from the conversations, and reading of words from the conversations. 200 schwas in non-function words were selected from each mode for each speaker. These tokens occurred in a wide variety of contexts, but were matched according to contexts across modes. Smaller numbers of stressed /ih/ and /ah/ tokens were selected from the wordlist-reading mode.;For each vowel token, the following acoustic measurements were obtained: duration; frequency of Fl, F2 and F3 at vowel onset, midpoint and offset; peak amplitude, absolutely and relative to the primary stressed vowel; and timing of the peak amplitude, absolutely and relative to the duration. Analyses revealed effects on these acoustic representations from the following linguistic factors: speaker, speaking mode, nearby consonants and vowels, position within a word, syllable type, position relative to a primary stress, and orthography.;The traditional assumptions about schwa are true only with qualifications. In general, schwa's acoustic features are more /ih/-like than /ah/-like. Its duration is extremely sensitive to syllable position and phrase-boundary factors. Formant frequency and amplitude data indicate that it is articulated with a rapid, variable jaw-opening gesture but a fairly precise tongue gesture. There appears to be a single target vowel with a neutral jaw position and a fronted tongue position. Coarticulation with surrounding segments, which is related to duration, is usually asymmetrical. Some speakers decrease the amplitude difference between schwa and stressed vowels in casual speech. |
