Design and evaluation of an electrolarynx with tonal control function for Mandarin.

OBJECTIVE: To improve the speech quality of laryngectomized speakers of Mandarin, we designed an electrolarynx with tonal control function (tone-EL) by using the movement of a trackball. The performance of the tone-EL in producing Mandarin was evaluated. METHODS: The performance of tone-EL was evaluated via a listening experiment. The perceptual accuracies of monosyllabic words, different categories of phrases with different cues were measured and compared with that produced with a conventional EL. The acceptability of sentences was also measured. RESULTS: The perceptual accuracies of monosyllabic words and tones associated with the words produced with the tone-EL were significantly higher than those of monotonic EL speech. The perceptual accuracy of phrases was significantly higher than in monotonic EL speech when no categorical cue for listeners was provided, whereas they were at a close level when categorical information of the phrases was provided in advance. The acceptability of sentences was higher than that of monotonic EL speech. CONCLUSION: Using the tone-EL can produce Mandarin tones effectively and the quality of rehabilitated Mandarin is better than using a conventional-EL. To balance speech intelligibility and ease of use, a strategy -producing tonal speech when few informative cues are available to listeners is preferred.