Advanced electronic technology has resulted in the ability to objectively analyzed and display speech characteristics.
The mandibular prognathism patients had modified the place of articulation in comparison to preoperation. The acoustic characteristics appeared in the acoustic resonance. Assessment of resonance was measured by a High Speed Analysis System using
PC
with
DSP. This personal computer-based speech analysis system performs spectrographic analysis in real time. The testing words consisted of the simple vowels-/i/,/e/,/u/,/a/-, and the CVC phonetic contexts containing the bilabial consonants both
fricative
and lateral.
Separately from the spectrographic analysis, a Nasometer was used for measuring the indirect assessment of vocal tract physiology. This device measures the oral and nasal components of a subject's speech: the components are picked up by
microphones
on
either side of sound separator that rests on the upper lip. The signal from each of the micro-phones is filtered and digitalized by custom electronic modules. The resultant signal ratio multiplied by 100 and is expressed as a "nasalance" score.
The tested utterances were selected by simple words containing the vowels /i/,/e/,/u/,/o/,/a/, and CVC phonetic environments containing the nasal consonants /m/ and /n/ with the high vowel /i/ and low vowel /a/.
The three different types of nasal phrases were used to test no nasal passage, mild nasal passage and high nasal passage.
The three different types of nasal phrases were used to test no nasal passage, mild nasal passage and high nasal passage.
@ES The author obtained the results using these acoustic methods as follows:
@EN 1. The first formant of the mandibular prognathism pre-operation group was higher the control group than post-operation. This varation of F1 is most responsive to changes in mouth opening. Opening mouth sounds are characterized by relatively
high
frequency first formants.
The second formant of the mandibular prognathism pre-operation group was lower than that of the control group: this means that the vocal tract of the mandibular prognathism group was longer than the control group. The vocal tracts of these
patients
were
affected after the mandibular prognathism operation. Therefore the F2 was higher after operation.
On the vowel chart, the author found that athe place of articulation after operation moved backward.
The Voice Onset Time, Vowel duration and total duration after operation increased in comparison with pre-operation, these results were assessed by the delayed of the articulation reaction time.
Nasalance of post-operation increased in comparison with the preoperation, this means that the velopharyngeal function was acted in these cases.
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