Patent ID: 7912231

Claim:
A system for reducing audio noise, comprising: an input component configured so as to receive an input time-domain signal and generate an input frequency-domain signal and a power spectrum of said input frequency-domain signal, wherein said power spectrum comprises N frequency bins corresponding to N sampled values of said input time-domain signal; a noise-activity detector configured to: partition said N frequency bins of the power spectrum into a plurality of bands, obtain a magnitude value for a selected number of said plurality of bands, compare said magnitude value with a threshold value for said selected number of bands, and determine that said noise activity is present in said power spectrum in response to determining that said magnitude value exceeds said threshold value for said selected number of bands; a white noise detector configured to: obtain a current energy value based on a sum of said N frequency bins, obtain a difference between said current energy value from a previous energy value, said difference having a positive value, and generate a white noise indicator indicating presence of white noise in said power spectrum if said difference is greater than a selected value; a network tone detector configured to: identify a selected bin having a maximum value from said N frequency bins, and generate a network tone indicator indicating presence of network tone in said power spectrum if said selected bin has not changed by more than a selected amount and if said selected bin is within a range of frequency corresponding to said network tone; an adjustment component configured so as to: generate an adjustment power spectrum based on detection of said presence of said noise activity, white noise, and network tone, said generating the adjustment power spectrum comprising: scaling said power spectrum by a selected amount if said network tone is not detected by said network tone detector and said noise activity is detected by said noise-activity detector, adjusting said power spectrum for said white noise in place of said scaling if said network tone is not detected by said network tone detector and said white noise is detected by said white noise detector, and if said white noise is not detected by said white noise detector, clipping a gain associated with said scaling if the gain is below a minimum gain or above a maximum gain; combine said adjustment power spectrum with said input frequency-domain signal so as to generate an output frequency-domain signal; and an output component configured so as to generate an output time-domain signal based on said output frequency-domain signal.