A method of controlling a noise cancellation system, for use in an audio device, comprises: generating an ambient noise signal representative of ambient noise; filtering and applying gain to the ambient noise signal to generate a noise cancellation signal; passing the noise cancellation signal to a speaker; and generating an error signal from an error microphone, wherein the gain applied to the ambient noise signal is controlled based on the error signal, and the method further comprises: determining from the error signal whether the audio device is in an off-ear position, and controlling the noise cancellation system based on said determination as to whether the audio device is in the off-ear position.