Pitch perturbations of sustained vowels were examined on ten normal subjects and fifteen deaf children.
Vibrations of the vocal cord were induced by a condenser microphone attached on the skin over the frontal wall of the trachea. Fundamental pitches were extracted by a pitch indicator.
Results obtained were as follows:
(1) In normal subjects
1) Fundamental pith of sustained vowels ranged from 100 to 150 cps in male and 200 to 250 cps in female owing to each suject.
2) Pitch perturbations of fundamental tone were remarkable at the onset and end of voicing but in the intermediate time course they seemed considerably stable.
3) Perturbation widths were measured within ten per cent of the mean fundamental pitch in every subjects.
4) There was some relation between the mean fundamental pitch and perturbation width.
5) Duration of sustained voice gave no effect on perturbations of fundamental pitch.
(II) In deaf children
1) Fundamental pitch showed much difference among vowels and subjects, especially remarkably in younger group.
2) Perturbation widths were mostly from ten to fifteen per cent of the mean fundamental pitch, which far exceeded that of normal subjects.
3) There found positive relationship between the mean fundamental pitch and perturbation width in younger group.
4) In older group pith perurbation grew larger as the duration of sustained voice.
5) In more than seventy per cent of all cases perturbation of pitch and voice pressure were mutually related through voicing.
These results were discussed from a point of the aural regulatory function of phonatory mechanism.
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