Intelligibility of electrolarynx speech using a novel actuator

During voiced speech, the larynx provides quasi-periodic acoustic excitation of the vocal tract. Following a laryngectomy, some people speak using an electrolarynx which replaces the excitatory function of the absent larynx. Drawbacks of conventional electrolarynx designs include the buzzing monotonic sound emitted, the need for a free hand to operate the device, and difficulty experienced by many laryngectomees in adapting to its use. Despite these shortcomings, it remains the preferred method of speech rehabilitation for a substantial minority of laryngectomees. In most electrolarynxes, mechanical vibrations are produced by a linear electromechanical actuator, the armature of which percusses against a metal or plastic plate at a frequency within the range of glottal phonation. As part of the ongoing development of a hands-free alternative to the conventional electrolarynx, the authors have developed a novel actuator which is based on a lightweight pager motor similar to those used to produce vibration in many mobile phones. In this paper, the intelligibility of speech produced using the novel actuator is compared to speech produced using a conventional electrolarynx. Three able-bodied speakers (two male, one female) performed a closed response test containing 48 monosyllabic words, once using a conventional electrolarynx and a second time using the novel actuator. The resulting audio recordings were randomized and replayed to four listeners who recorded each word that they heard. The results show that the speech produced using the novel actuator was substantially more intelligible to all listeners than that produced using the conventional electrolarynx. The new actuator has properties (size, weight, shape, cost) which lends itself as a suitable candidate for possible hands-free operation. This is one of the research ideals for the group and this test methodology presented as a means of testing intelligibility. Any further actuators which exhibit desirable characteristics are also to be examined for electrolaryngeal intelligibility using this test procedure.