Acoustical Analyses of Maxillary Prosthetic Patients with the Aid of a Digital Signal Processor.

Vowel sounds spoken by patients having maxillary defects were compared and evaluated with a digital signal processor that was capable of automatically recognizing the formant frequencies of Japanese vowels before and after wearing a maxillary prosthesis.The automatic recognition rate for formant frequencies for this system was 91.6%, and immediate recordings and analyses of sound waveforms were recorded on floppy discs.Results showed that a sexual difference of formant frequency existed among normal subjects, but no age difference for those over 20 years of age was shown. Patients having maxillary defects showed the vowel sounds for /i/, /u/, and /e/ to be located mostly outside the normal equiprobability ellipsoid. The F 1 value for patients having maxillary defects tended to increase slightly for /i/ and increase as well as decrease for /e/. Vowel sounds /a/, /u/, and /o/ remained within the normal range. On the otherhand, the F 2 value tended to increase for /a/, /u/ and /o/, and decrease for /i/and /e/ for patients having maxillary defects.In conclusion, compared to H 1 type maxillary defects, H 3 and H 4 type showed most vowel sounds to be located outside the normal equiprobability ellipsoid. However, the vowel sounds were found to be within the normal range when the patients wore their dentures.