The current study examined the association between formant trajectories and tongue and lip movements in the American English diphthongs /aɪ/, /aʊ/, and /ɔɪ/. Seventeen native speakers of American English had electromagnetic sensors placed on their tongues and lips to record movement data along with corresponding acoustic data during productions of the diphthongs in isolation. F1 and F2 trajectories were extracted from the middle 50% of the diphthongs and compared with time-aligned kinematic data from tongue and lip movements. The movement and formant tracks were converted to z-scores and plotted together on a common time scale. Absolute difference scores between kinematic variables and acoustic variables were summed along each track to reflect the association between the movement and acoustic records. Results show that tongue movement has the closest association with changes in F1 and F2 for the diphthong /aɪ/. Lip movement has the closest association with changes in F1 and F2 for the diphthong /aʊ/. Results for the diphthong /ɔɪ/ suggest tongue advancement has the closest association with changes in F2, while neither lip movement nor tongue movement have a clearly defined association with changes in F1. These results suggest that for diphthongs with the lip rounding feature, lip movement may have a greater influence on F1 and F2 than previously considered. Researchers who use formant data to make inferences about tongue movement and vowel space may benefit from considering the possible influence of lip movements on vocal tract resonance.



College and Department

David O. McKay School of Education; Communication Disorders



Date Submitted


Document Type





speech science, formant, diphthong, speech acoustics, kinematic, articulation