1. A method, comprising acts of: (A) determining quality of an input signal to a speech recognition system, the determining comprising detecting a signal-to-noise ratio and a loudness of the input signal; and (B) establishing a rejection threshold used in rejecting a speech recognition result for speech included in the input signal based at least in part on the determined quality of the input signal; wherein the speech recognition result has a confidence score indicating a level of confidence in an accuracy of the speech recognition result, and the rejection threshold specifies which confidence scores indicate that the speech recognition result is to be rejected as being incorrectly recognized.