Patent ID: 7133824

Claim:
A noise reduction method for dividing input noise speech into a plurality of continuous frames, determining a noisy speech spectrum for each frame, and partitioning a frequency band into multiple sub-bands to determine a clean speech spectrum from the noisy speech spectrum on each sub-band, the method comprising: (A) estimating a noise spectrum |W r (k)| 2 of an r-th frame at a k-th frequency component from the noisy speech y r (k) of the r-th frame by silence detection and noise spectrum estimation; (B) estimating a signal-to-noise ratio (SNR) value SNR r (i) of an i-th sub-band for the r-th frame by applying a regression process to the SNR of the i-th sub-band for the (r−1)-th frame after noise reduction, the noisy speech spectrum, and the noise spectrum of the i-th sub-band for the r-th frame; (C) determining an over-subtraction factor α r (i) of sub-band i based on the estimated SNR r (i); and (D) determining a clean speech spectrum estimate by performing, on each sub-band, a spectral subtraction |Ŝ r (i,k)| 2 =|Y r (i,k)| 2 −α r (i)·|W r (i,k)| 2 , wherein Y r (i,k)| 2 is the noisy speech spectrum of the r-th frame at the k-th frequency component of the i-th sub-band, |W r (i,k)| 2 is the corresponding noise spectrum and |Ŝ r (i,k)| 2 is the clean speech spectrum at sub-band i for the r-th frame.