Speech recognition and control system for the severely disabled

The availability of microprocessors opens many applications for speech recognition systems where constraints on price, weight, volume and power consumption are imposed, such as in the case of a voice control system for the severely disabled. A microprocessor based speech recognition system for the voice control of wheelchair, touch-tone phone, typewriter and environmental control unit, is described. The finite word length, fixed point arithmetics and relatively slow execution time of the microprocessor introduce several difficulties in the implementation of the recognition process. Algorithms for feature extraction (mainly the autoregressive, or linear prediction coefficients), classification and training are presented. The hierarchical memory organization is discussed. Results with the ten digit set, used to activate a touch-tone phone, are given. With this set the system exhibits less than one percent substitutions and eleven percent rejections.