Patent Document ID: 8504362
Application ID: 12506705

Base Claim:
1. A speech recognition system, comprising: a microphone receiving a noise signal of a moving object; a speed level classifier for measuring a moving speed of the moving object by using the noise signal at an initial time of speech recognition to determine a speed level of the moving object; a first speech enhancement unit for enhancing sound quality of an input speech signal of the speech recognition by using a Wiener filter, if the speed level of the moving object is equal to or lower than a specific level; and a second speech enhancement unit enhancing the sound quality of the input speech signal of the speech recognition by using a Gaussian mixture model, if the speed level of the moving object is higher than the specific level.

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Claim 4:
4. The speech recognition system of claim 1 , wherein the first speech enhancement unit includes: a transform unit for performing fast Fourier transform on a single frame of the input speech signal; an adder for calculating a sum of signals in a specific frequency band of the fast Fourier transformed signal; a divider for dividing the sum of the signals by a number of fast Fourier transform bins of the transform unit; and a feature extraction unit for converting the divided sum into a log-scale form to extract therefrom voice activity detector characteristics, wherein filter values of the Wiener filter are calculated based on the voice activity detector characteristics extracted by the feature extraction unit, and the input speech signal is filtered by using the calculated filter values.