Patent ID: 7124079

Claim:
In a speech decoder that receives speech and noise information from a communication channel, an apparatus for producing comfort noise parameters for use in generating comfort noise, said apparatus comprising: a first input for providing a plurality of interpolated comfort noise parameter values normally used by the speech decoder to generate comfort noise; a second input for providing values of a background noise parameter from a receiver buffer; a variability estimator coupled to said second input and responsive to the background noise parameter values for calculating variability information, wherein said variability estimator is responsive to a plurality of values of the background noise parameter for calculating a mean value of the background noise parameter over a period of time, wherein said variability estimator includes a variability determiner for producing variability information indicative of how the background noise parameter varies relative to said mean value of the background noise parameter, and is further operable to calculate differences between the mean value and at least some of the background noise parameter values to produce mean-removed values of the background noise parameter; a modifier coupled to said first and second inputs and responsive to the variability information indicative of the variability of the mean-removed values of the background noise parameter to the mean value of the background noise parameter for perturbing the comfort noise parameter values to produce perturbed comfort noise parameter values; and an output coupled to said modifier for selecting at least one of said perturbed comfort noise parameter values for use in generating perturbed comfort noise.