The purpose of this study is to determine the acoustic characteristics of dysarthria depending upon the underlying etiology. We used sound spectrography to assess the formant characteristics, phonation time of vowel, and voice onset time of
alveolar
consonants. With Nasometer, we evaluated nasalance which reflects the ratio of nasal and oral acoustic energy. Visi-Pitch was also used to evaluate pitch perturbation, pitch range, and diadochokinetic rates of the articulatory organ.
Underlying etiology of dysarthria included pseudobulbar palsy in 5 patients, bulbar palsy in 2 patients, language delay in 3 patents.
In spectrographic evaluation, most dysarthric patients were characterized by loss of specific characteristics of formants of vowel, increased noise in high frequency range, and reduced duration of phonation. Voice onset time was prolonged in
alveolar
stop consonants in dysarthric patients with pseudobulbar and bulbar palsy.
Nasalance was increased in dysarthric patients with pseudobulbar and bulbar palsy, but decreased in pateints with tonsiiar hypertrophy.
In Visi-Pitch analysis, voice intensity was normal in all types of dysarthria. However, pitch perturbation was increased in dysarthric patients with tonsilar hypertrophy, pseudobulbar and language delay palsy. Diadochokinetic rate was decreased
in
all
dysarthric patients.
Sound spectrography, Nasometer and Visi-Pitch were considered to be useful to determine the specific acoustic characteristics of dysarthria in the patents with neurological involvement and structural lesion, but were not sensitive to delineate
the
pathologic region of neurological involvements.
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