Removal of signal bias for surely recognizing voice, heard over telephone

PURPOSE: To minimize the influence of an unknown signal bias in a voice signal by calculating a bias evaluating value, based on the minimization of a likelihood function and separating the bias evaluating value from the input voice signal. CONSTITUTION: A distorted signal Y(ω) from a telephone channel is inputted to a feature analyzing block 22, and an output signal Y'(ω) is inputted to a signal bias-removing(SBR) block 26. In the SBR block 26, a bias-evaluating value is calculated, based on the maximization of a likelihood function. Then a tentative voice value is obtained by subtracting the bias evaluating value from a voice signal. By repeating this operation a prescribed number of times, a reduced bias voice signal value is obtained. Then the code book for a center of gravity is generated, and the bias evaluating value is recalculated and resubtracted from the tentative voice signal, until the optimum set of centers of gravity is generated. The reduced bias voice signal value and the optimum center of gravity are inputted to a voice-recognizing device 24. COPYRIGHT: (C)1995,JPO