Patent ID: 7552049

Claim:
A noise adaptation system of speech model for adapting a speech model for any noise to speech to be recognized in a noisy environment, said speech model being learned by using clean speech data, said system comprising: clustering means for clustering noise-added speech; speech model space generating means for generating a tree-structure noisy speech model space based on the result of the clustering performed by said clustering means; parameter extracting means for extracting a speech feature parameter of input noisy speech to be recognized; selecting means for selecting an optimum model from the tree-structure noisy speech model space generated by said speech model space generating means; and linear transformation means for applying linear transformation to the model selected by the selecting means so that the model provides a further increased likelihood, wherein said clustering means generates said noise-added speech by adding said noise to said speech in accordance with a signal-to-noise ratio condition, subtracts the mean value of speech cepstral of the generated noise-added speech, generates a Gaussian distribution model of each of pieces of generated noise-added speech, and calculates the likelihood between the pieces of noise-added speech to generate a likelihood matrix to provide a clustering result.