Patent ID: 8068616

Claim:
A method for detecting failure in a noise cancellation system operable to at least partially cancel an unwanted noise within a defined space, wherein the unwanted noise is produced by a target noise source located outside of the defined space, the method comprising: sensing a target noise with a dedicated sensing device located at the target noise source, the sensing device configured to receive noise primarily from the target noise source; receiving a cancellation noise signal from the noise cancellation system, the cancellation noise signal representing a cancellation noise that, when combined with the target noise in the defined space, is operable to at least partially cancel the target noise in the defined space; receiving an error signal approximately representing a portion of the target noise remaining after the cancellation noise and the target noise are combined; for each of the received cancellation noise signal and the error signal, determining whether the signal level changed or remains unchanged; and based on the determination, assigning a failure state of the noise cancellation system and initiating a remedial measure corresponding with the assigned failure state.