Patent ID: 7933420

Claim:
A method for controlling a noise cancellation system having an adaptive control portion, the noise cancellation system operable to generate a cancellation noise configured to at least partially cancel an unwanted noise in a defined environment, and the adaptive control portion operable to adjust the operation of the noise cancellation system based on a remaining level of unwanted noise remaining when the cancellation noise and the unwanted noise are combined, the method comprising: receiving an error signal representing a portion of a noise not cancelled by a cancellation noise generated from the noise cancellation system; determining whether the level of the error signal exceeds a first threshold value for a first predetermined period of time; calculating a crest factor using the error signal, the crest factor representing the ratio of a peak value of the error signal to the root-mean-square value of the error signal; determining whether the crest factor exceeds a second threshold value; and deactivating the adaptive control portion and continuing to operate the noise cancellation system if the error value exceeds the first threshold value for the predetermined period of time and the crest factor exceeds the second threshold value.