Context-independent dynamic information for the perception of coarticulated vowels

Most investigators agree that the acoustic information for American English vowels includes dynamic (time-varying) parameters as well as static "targe t" information contained in a single cross section of the syllable. Using t he silent-center (SC) paradigm, the present experiment examined the case in which the initial and final portions of stop consonant-vowel-stop consonan t (CVC) syllables containing the same vowel but different consonants were r ecombined into mixed-consonant SC syllables and presented to listeners for vowel identification. Ten vowels were spoken in six different syllables, /b Vb, bVd, bVt, dVb, dVd, dVt/, embedded in a carrier sentence. Initial and f inal transitional portions of these syllables were cross-matched in: (1) si lent-center syllables with original syllable durations (silences) preserved (mixed-consonant SC condition) and (2) mixed-consonant SC syllables with s yllable duration equated across the ten vowels (fixed duration mixed-conson ant SC condition). Vowel-identification accuracy in these two mixed consona nt SC conditions was compared with performance on the original SC and fixed duration SC stimuli, and in initial and final control conditions in which initial and final transitional portions were each presented alone. Vowels w ere identified highly accurately in both mixed-consonant SC and original sy llable SC conditions (only 7%-8% overall errors). Neutralizing duration inf ormation led to small, but significant, increases in identification errors in both mixed-consonant and original fixed-duration SC conditions (14%-15% errors), but performance was still much more accurate than for initial and finals control conditions (35% and 52% errors, respectively). Acoustical an alysis confirmed that direction and extent of formant change from initial t o final portions of mixed-consonant stimuli differed from that of original syllables, arguing against a target+offglide explanation of the perceptual results. Results do support the hypothesis that temporal trajectories speci fying "style of movement" provide information for the differentiation of Am erican English tense and lax vowels, and that this information is invariant over the place of articulation and voicing of the surrounding stop consona nts. (C) 1999 Acoustical Society of America. [S0001-4966(99)05107-3].