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Abstract

A method and a system are disclosed for normalizing a speech signal prior to a speech recognition process. In a preparatory procedure, a sample interval of speech is separated into thirty-one frequency bands and an amplitude histogram is generated for each band. From these histograms, the 5% percentile amplitude value P(05) and the 95% percentile amplitude value P(95) are extracted for each band and these values are stored for later reference. For actual normalization, the current speech signal is also divided into the same frequency band as in the preparatory procedure, and consecutive input amplitude values A(in) of each frequency band are modified, using the percentile values of the respective band, to obtain output values according to ##EQU1## The essential effect of this normalizing treatment is that the resulting long-term spectrum is given by the P(95) values and the spectrum of silence is given by the P(05) values. After normalization, all speech has the same silence spectrum and long-term spectrum.

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First Claim