A method for detecting failure in a noise cancellation system is provided. The noise cancellation system is operable to at least partially cancel an unwanted noise produced by a noise source. The method includes receiving a cancellation noise signal from the noise cancellation system. The cancellation noise signal represents a cancellation noise that, when combined with a target noise, is operable to at least partially cancel the target noise. The method also includes receiving an error signal approximately representing a portion of the target noise that remains after the cancellation noise and the target noise are combined. The method also includes determining whether the signal level changed or remains unchanged for each of the received cancellation noise signal and the error signal. The method also includes assigning a failure state of the noise cancellation system based on the determination and initiating a remedial measure that corresponds with the assigned failure state.