Design of a Tactile Vocoder

A tactile vocoder is designed for the feedback of acoustic cues for detection by the sense of touch. Design objectives based on speech signal properties are generated. An existing spectrum channel vocoder is the starting point of the design. The follow-on modulation stage after the filter channels of the spectrum channel vocoder is built up in a breadboard model and tested. The transfer function of the modulation stage has an input dynamic range of 68 decibels, being linear over 38 decibels of this range. The complete breadboard model using one of the filter channels has an input dynamic range of 40 decibels, being able to process the maximum signal level differences between first and third formant frequencies in vowels. The circuit can process signals of durations down to 33.3 milliseconds which is the area of stop consonants