Formant frequencies and lip position in American English vowels
Wendy Linker · The Journal of the Acoustical Society of America · 1977
In order to determine which parameters of lip position could best be determined from formant frequencies, simultaneous frontal and lateral photographs were taken of the lips of ten speakers producing nine American English vowels, while their production was tape recorded. Formant frequencies were obtained using an LPC program and by measuring spectrograms. For the frontal view, horizontal and vertical distances of the mouth opening were measured, and the area was calculated. Laterally, protrusion was measured with reference to three points: (1) a fixed point at the upper front teeth, (2) the most forward point of lip contact, and (3) the corner of the mouth. Center-line measurements were taken from these points to one another and to (a) the most forward points of the upper and lower lips and (b) the line connecting these points. Also measured were the distances along the inner-lip surface from the most forward point of lip contact to the most forward points on the lips. Multiple regression techniques were employed to determine the correlation between the lip parameters and the formant frequencies.