Abstract: A noise reduction method partitions frequency band into multiple sub-bands and estimates the signal-to-noise ratio (SNR) value for each sub-band. An over-subtraction factor of each sub-band is determined based on the estimated SNR value. Then, the clean speech spectrum estimate is determined by performing spectral over-subtraction on each sub-band, so as to determine the clean speech signal from the estimated clean speech spectrum.

Abstract: A scheme of allocating variable pulses for each frame is proposed to reduce the bit-rate of LP based AbS coders while maintaining the same speech quality. Since speech signal is not stationary, the required pulse count in a speech coder should be variable frame by frame. In this patent the optimal pulse count allocation is provided based on criterion of perceptual distortion analysis. The method comprises receiving source speech data and generating temporary encoded data according to the source speech data, and synthesized speech data according to the temporary encoded data, and adjusting the fixed codebook pulse allocation in temporary encoded data to a minimum required pulse count according to the perceptual disturbance values between the synthesized speech data and the source speech data, and outputting final encoded data accordingly.

Abstract: A noise reduction method partitions frequency band into multiple sub-bands and estimates the signal-to-noise ratio (SNR) value for each sub-band. An over-subtraction factor of each sub-band is determined based on the estimated SNR value. Then. the clean speech spectrum estimate is determined by performing spectral over-subtraction on each sub-band, so as to determine the clean speech signal from the estimated clean speech spectrum.