DYNAMIC SPECIFICATION OF COARTICULATED GERMAN VOWELS - PERCEPTUAL ANDACOUSTICAL STUDIES

To examine the generality of Strange's Dynamic Specification Theory of vowel perception, two perceptual experiments investigated whether dyn amic (time-varying) acoustic information about vowel gestures was crit ical for identification of coarticulated vowels in German, a language without diphthongization. The perception by native North German (NG) s peakers of electronically modified /dVt/syllables produced in carrier sentences was assessed using the ''silent-center'' paradigm. The relat ive efficacy of static target information, dynamic spectral informatio n (defined over syllable onsets and offsets together), and intrinsic v owel length was investigated in listening conditions in which the cent ers (silent-center conditions) or the onsets and offsets (vowel-center conditions) of the syllables were silenced. Listeners correctly ident ified most vowels in silent-center syllables and in vowel-center stimu li when both conditions included information about intrinsic vowel len gth. When duration information was removed, errors increased significa ntly, but performance was relatively better for silent-center syllable s than for vowel-center stimuli. Acoustical analyses of the effects of coarticulation on target formant frequencies, vocalic duration, and d ynamic spectre-temporal patterns in the stimulus materials were perfor med to elucidate the nature of the dynamic spectral information. In co mparison with vowels produced in citation form /hVt/syllables by the s ame speaker, the coarticulated /dVt/utterances showed considerable ''t arget undershoot'' of formant frequencies and reduced duration differe nces between tense and lax vowel pairs. This suggests that both static spectral cues and relative duration information for NG vowels may not remain perceptually distinctive in continuous speech. Analysis of for mant movement within syllable nuclei corroborated descriptions of Germ an vowels as monophthongal. However, an analysis of first formant temp oral trajectories revealed distinct patterns for tense and lax vowels that could be used by Listeners to disambiguate coarticulated NG vowel s. (C) 1998 Acoustical Society of America.