Vocal efficiency of electrolaryngeal speech production

From the perspective of efficiency, this article studied the energy transfer and conversion in the process of electrolaryngeal (EL) speech production. An overall vocal efficiency of EL speech production was defined as the ratio of the acoustic power of the EL speech to the electric power supplied by the battery. The measurements of a commercial EL showed that the actual utilization efficiency of the battery energy was no more than 0.1%. The energy transfer process was divided into three successive stages. The corresponding efficiencies of these stages were defined and estimated to analyze potential power losses and possible impact of two factors (EL cap and vowel) on the vocal efficiency. It was concluded that the non-linear transducer of the EL device and the physiological features of the neck tissue were the main reasons for the high power losses and low vocal efficiency. Furthermore, both EL cap and phonation vowel showed significant effects on the EL vocal efficiency. Thus, improvement of EL linear vibrator and compatible cap will be beneficial to raising the vocal efficiency and improving the EL speech quality.