Production of bite-block vowels: acoustic equivalence by selective compensation

Acoustic and articulatory data are reported for steady state vowels produced both normally and with a bite block. The formant patterns of the bite-block vowels were found to approximate those of the naturally spoken vowels. Measurements derived from lateral view still x-ray films showed that the bite blocks induce drastic articulatory reorganization. Using a mandibular frame of reference, we found that speakers compensated for a large bite block by using supershapes of the tongue and the lips (for [u] and [o]). Comparing the two productions using a maxillary frame of reference, we noted that compensation was maximum at the points of maximum constriction and incomplete or partial at points where the vocal-tract area was large. A computer simulation of our speakers' compensatory strategy revealed that they behaved optimally according to acoustic theory. These findings suggest that a vowel target is coded neurophysiologically in terms of acoustically significant area-function, specifically, by information related to cavity configuration at points of maximum constriction.