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We propose the use of the pitch rate of free-form speech recorded by smartphones as an index of voice disability. This research compares the effectiveness of pitch rate, jitter, shimmer, and harmonic-to-noise ratio (HNR) as indices of voice disability in English, German, and Japanese. Normally, the evaluation of these indices is performed using long-vowel sounds; however, this study included the recitation of a set passage, which is more similar to free-form speech. The results showed that for English, the jitter, shimmer, and HNR were very effective indices for long-vowel sounds, but the shimmer and HNR for read speech were considerably worse. Although the effectiveness of jitter as an index was maintained for read speech, the pitch rate was better in distinguishing between healthy individuals and patients with illnesses affecting their voice. The read speech results in German, Japanese, and English were similar, and the pitch rate showed the greatest efficiency for identification. Nevertheless, compared to English, the identification efficiency for the other two languages was lower.

We have been developing a method of evaluating the mental health condition of a person based on the sound of their voice. Currently, we have applied this technology to create a smartphone application that shows the vitality and the mental activity as mental health condition indices. Using voice to measure one’s mental health condition is a non-invasive method. Moreover, this application can be used continually through a smartphone call. Unlike a periodic checkup every year, it could be used for monitoring on a daily basis. The purpose of this study is to compare the vitality index to the widely used Beck depression inventory (BDI) and to evaluate its validity. This experiment was conducted at the Center of Innovation Program of the University of Tokyo with 50 employees of one corporation as participants between early December 2015 and early February 2016. Each participant was given a smartphone with our application that recorded his/her voice automatically during calls. In addition, the participants had to read and record a fixed phrase daily. The BDI test was conducted at the beginning of the experimental period. The vitality index was calculated based on the voice data collected during the first two weeks of the experiment and was considered as the vitality index at the time when the BDI test was conducted. When the vitality and the mental activity indicators were compared to BDI score, we found that there was a negative correlation between the BDI score and these indices. Additionally, these indices were a useful method to discriminate a participant of high risk of disease with a high BDI score. And the mental activity index shows a higher performance than the vitality index.