Study fora Practical Use of an Electolarynx with a Pitch Control Function Using Expiration

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An electrolarynx is one of the artificial larynges for people who have failed to master the other substitute speech. However, this prosthesis makes it difficult to produce phonetic information such as intonation and accent. In order to improve a conventional electrolarynx, we have proposed a new method that can allow laryngectomees to control voice intonation by using their respiration.This device consists of three parts. The first part is a pressure sensor that can detect expiration air pressure produced from a stoma made by a surgical incision into the neck. The second part is a transformation circuit that can convert air pressure into a pitch frequency for voice. The third part is an electromechanical vibrator that can be attached to the neck. This method was evaluated through the following two experiments as a parameter of a transform function. The first one was an experiment to measure the accuracy of pitch control using the respiration of laryngectomees and the second one was psychophysical experiments regarding the degree of naturalness of the electrolarynx voice.From the experimental results, the optimal transform function was found to be F=60+25xP,where F is the pitch frequency in Hz and P is the expiration pressure in cmH20. The pitch pattern of the electric larynx voice became clearly similar to the pattern produced from a normal subject after one day training. We have decided to manufacture the new device for the people who can not master the substitute speech or have just had their larynx removed.