Patent ID: 8744845

Claim:
A noise estimation method for a noisy speech signal, comprising the steps of: approximating a transformation spectrum by transforming an input noisy speech signal to a frequency domain; calculating a smoothed magnitude spectrum having a decreased difference in a magnitude of the transformation spectrum between neighboring frames; calculating a search spectrum to represent an estimated noise component of the smoothed magnitude spectrum; calculating an identification ratio to represent a ratio of a noise component included in the input noisy speech signal by using the smoothed magnitude spectrum and the search spectrum; and estimating a noise spectrum by using a recursive average method using an adaptive forgetting factor defined by using the search spectrum, wherein the adaptive forgetting factor is defined by using the identification ratio; wherein the adaptive forgetting factor becomes 0 when the identification ratio is smaller than a predetermined identification ratio threshold value, and the adaptive forgetting factor is proportional to the identification ratio when the identification ratio is greater than the identification ratio threshold value.