We have seen many patients with a voice disorder due to vocal abuse. However, there is little information about the speaking behaviour of such patients. The object of this study was to analyze speaking behaviour and to evaluate the relationship between the cause of voice disorders and its effects on speech. We had previously measured phonation time with a speech time accumulator. Recently, we have developed a speech intensity/speech time accumulator. We obtained data by accumulating the phonation time at 4 degrees of vocal intensity, ranging from weak to strong. By using this instrument, we measured the speaking habits of 29 subjects for 131 days and collected data about the criteria for vocal abuse. Our results showed that the office workers exhibited a phonation time (33.6 +/- 13.6 min for 8 h) three times shorter than that of teachers and patients with vocal fold nodules (102.1 +/- 22.9 min for 8 h). For the teachers and patients with a long phonation time, half of the total phonation time was at high intensity.

In 1953, Calvet first displayed the fundamental frequency (pitch) and sound pressure level (intensity) of a voice on a two-dimensional plane and created a voice range profile. This profile has been used to evaluate clinically various vocal disorders, although such evaluations to date have been subjective without quantitative assessment. In the present study, a quantitative system was developed to evaluate the voice range profile utilizing a personal computer. The area of the voice range profile was defined as the voice volume. This volume was analyzed in 137 males and 175 females who were treated for various dysphonias at Kyushu University between 1984 and 1990. Ten normal subjects served as controls. The voice volume in cases with voice disorders significantly decreased irrespective of the disease and sex. Furthermore, cases having better improvement after treatment showed a tendency for the voice volume to increase. These findings illustrated the voice volume as a useful clinical test for evaluating voice control in cases with vocal disorders.

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