The communicative disorders in cleft palate patients have relationship with the acoustic and the physiological phenomena. Generally accepted articulatory disorders are that oral plosives may be substitued by glottal stops. This may occur because
the
glottis may be the only place in the vocal tract where plosives can be achieved.
The acoustic characteristics of a glottal stop demonstrate that a higher utterance intensity and a burst-like waveform can occur at the onset of an vowel following the glottal stops.
Twenty control groups (10 males and 10 females) and ten cleft palates pre-and post-operation are selected by these studies. The test words are composed by bilabial lenis stop consonants followed by one of five vowel /i, e, u, o, a/, and by three
different types of the Korean stops consonants followed by the high vowel /i/. The subjects repeated test words in a sound absorption room on a High-Speed speech analysis system using PC with DSP board.
A flexible laryngeal fiberscope is used for the study of glottal or glottalized stops. The glottal images of the three different types of consonants in word initial position /pipi/, phiphi/ and /pipi/ are examined with respect to the point of the
voice
onset following vowel.
The degree of hypernasality in glottal stops is measured by the Nasomater Model 6200-2. The test words are as followed : alveolar followed by /i/: /titttit/, /tittit/.
@ES The obtained results were as follows:
@EN 1. The average VOT of substituting a glottal stops in cleft palate patients is 20ms. This value is similar to the average. VOT of glottalized stop consonants.
2. First formant and third formant after operation increased and the intensities of higher formant increased also. These mean that the degree of hypernasality decreased after operation.
3. A glottal stops on LPC are characterized by the higher intensity in low frequency areas with negative SES and the highest total burst intensity.
4. The degree of hypernasality decreased after operation, but the width of decreasing hypernasality is small in thwe case of glottal stops.
5. The glottal gestures of glottalized stops show adducted state at the time of burst release, and the oral closure times in glottal or glottalized sops are highest among the three different different types of stops. It means that the force of
articulation is strongest for the glottalized stops.
6. Substituting glottal stops pre operation appeared the oral plosives post operation.
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