Development and perceptual evaluation of pitch controllable electrolarynx

Tone plays an important role in the speech perception for tonal languages. However, the monotonie speech of conventional electrolarynx (EL), which lacks of frequency variation, greatly decreased the intelligibility. For purpose of improving the speech quality of Mandarin Chinese (Mandarin). We designed a new type of EL that can produce the four types of tones in Mandarin, and evaluate its performance through a contrast experiment. A wheel-controlled pitch-adjustable EL was firstly designed and a prototype (W-EL) was manufactured. Then the speech produced by W-EL, and the speech produced by the monotone mode of the commercially available TruTone EL(M-EL), was evaluated objectively and subjectively. The results of objective evaluation showed that the pitch contour of the high-level (HL), middle-rising (MR), and falling-rising (FR) tones produced by W-EL most closely matched the natural speech characteristics of a native speaker. Meanwhile, statistical results showed that the accuracy of W-EL's tone perception and word perception was significantly higher than that of the M-EL. Nevertheless, there were no significant differences in acceptability among the two EL speech types.