Patent ID: 6757395
Filing Date: 2004-06-29
Classification: G10L

Abstract:
A method for reducing noise in audio processing applications, the method comprising:separating audio signals through an analysis filter into a plurality of processing bands, wherein each said processing band processes said audio signals within a predetermined frequency band; generating a gain function for noise reduction in each said processing band, wherein said gain function comprises a gain scale function providing a predetermined amount of gain as a function of a ratio of a signal envelope to a noise envelope and a maximum attenuation function providing a predetermined maximum attenuation; combining the output of each said gain function with the input of each said gain function in a multiplying circuit; and combining the outputs of said multiplying circuits in a synthesis filter to produce a stream of processed audio samples, wherein said generating a gain function for noise reduction in each said processing band comprises: (1) calculating the magnitude of each of a stream of input samples; (2) converting the output of step (1) into the decibel domain; (3) estimating the signal envelope of the output of step (2); (4) estimating the noise envelope based on the output of step (3); (5) generating a decibel domain gain scale function for noise reduction as a function of the outputs of steps (3) and (4); (6) generating a decibel domain maximum attenuation function; (7) combining the outputs of steps (5) and (6); and (8) converting the output of step (7) from the decibel domain to the magnitude domain.