An Experimental Transistorized Artificial Larynx

It is sometimes necessary, for the health of an individual, to remove his entire larynx by surgery. His trachea is then terminated at an opening (stoma) in the throat, and no connection between the lungs and the vocal tract remains. Since the normal source of energy for the speech process is provided by the lungs, such an individual loses his natural means of speaking. These persons are usually advised by their surgeons and speech therapists to learn esophageal speech, and classes for this purpose are set up in various centers. In producing esophageal speech, the upper end of the esophagus serves as the substitute larynx and provides the necessary 1337 1338 T H E BELL SYSTEM TECHNICAL J O U R N A L , NOVEMBER 1959 complex tone at an appropriate point in the vocal tract -- the bottom of the pharynx. The esophageal speaker must learn to swallow air, or force air into the esophagus and then control its escape, in such a manner as to cause sustained vibrations of tissues at the upper end of the esophagus. Not all patients can do this successfully. In fact, surveys have shown that about a third of all larnygectomized patients are unable to master esophageal speech for one reason or another. 1 In addition, the quality of speech produced by this method is generally rather unpleassant -- to such a degree that, in a comprehensive comparison test, listeners were unanimous in their preference for speech produced by a reedtype artificial larynx rather than esophageal speech.2 The use of an artificial larynx is therefore frequently desirable, and is often a necessity if the laryngectomized patient is to communicate by speaking.