Design and evaluation of an electrolarynx with Mandarin tone-control function

The lack of frequency variation during voicing with a conventional-electrolarynx (EL) results in a low speech quality, especially for tonal languages, in which tone plays an important role in the speech perception. In order to improve the speech quality of Mandarin, we designed an EL with tone-control function (tone-EL). The movement of a trackball was used to control the fundamental frequency (F0) of the vibration of EL. Users could produce tones by manipulating the trackball to adjust the F0 contour. In the perceptional evaluation, the intelligibility of isolated words produced with tone-EL (44.3%) was much higher than that of words produced with conventional-EL (9.5%), mainly due to the high accuracy of identification of tones for tone-EL speech (83.3%). The acceptability of sentences produced with tone-EL was remarkably improved comparing with sentences produced with conventional-EL. The tone-EL was proved to be effective to produce Mandarin tones.