Coarticulatory stability in American English /r/

A number of different researchers have reported a substantial degree of variability in how American English /r/ coarticulates with neighboring segments. Acoustic and articulatory data were used to investigate this variability for speakers of "rhotic" American English dialects. Three issues were addressed: (1) the degree to which the F3 trajectory is affected by segmental context and stress, (2) to what extent the data support a "coproduction" versus a "spreading" model of coarticulation, and (3) the degree to which the major acoustic manifestation of American English /r/--the time course of F3--reflects tongue movement for /r/. The f3 formant trajectory durations were measured by automatic procedure and compared for nonsense words of the form /'waCrav/ and /wa'Crav/, where C indicates a labial, alveolar, or velar consonant. These durations were compared to F3 trajectory durations in /'warav/ and /wa'rav/. In addition, formant values in initial syllables of words with and without /r/ were examined for effects of intervening consonant contexts. Results indicated similar F3 trajectory durations across the different consonant contexts, and to a lesser degree across stress, suggesting that coarticulation of /r/ can be achieved by overlap of a stable /r/-related articulatory trajectory with movements for neighboring sounds. This interpretation, and the concordance of F3 time course with tongue movement for /r/, was supported by direct measures of tongue movement for one subject.