7. The method of claim 6 , wherein if the quality of the input signal is determined in the act (A) to be low, then the act (B) comprises increasing skirts of the underlying multivariate Gaussian distribution, and if the quality of the input signal is determined in the act (A) to be high, then the act (B) comprises reducing skirts of the underlying multivariate Gaussian distribution.
6. The method of claim 1 , wherein the act (B) comprises establishing the rejection threshold in an underlying multivariate Gaussian distribution within an acoustic model of the speech recognition system.