Patent Document ID: 5416887
Application ID: 08201093
Patent Status: 1

Claim One:
1. A speech recognition device for use in recognition of speech mixed with background noise, comprising: a reference memory for keeping a plurality of reference patterns; an input unit for converting an input sound signal derived from the speech mixed with the background noise to an input pattern having an input level; a noise level detector for receiving the input pattern from the input unit, finding a threshold point where the input pattern first exceeds a threshold level, calculating a noise level from a portion of the input pattern preceding the threshold point, and for producing a noise signal representative of the noise level; a speech detector unit for receiving the input pattern from the input unit, for comparing the input level with the noise level to detect a portion of the input pattern having a level exceeding the noise level, and for outputting the portion detected as a speech pattern; a reject value calculator supplied with said noise signal for calculating a reject value corresponding to the noise level of said noise signal to produce a reject value signal representative of the reject value; and a pattern matching unit supplied with the reference patterns from the reference memory, the speech pattern from the speech detector unit, and the reject value signal from the reject value calculator, for selecting as a result of recognition of the speech one of the reference patterns that has a best degree of pattern match relative to the speech pattern, and accepting the selected pattern as a correct pattern when a difference between the speech pattern and the selected pattern is not greater than said reject value.