A method of diagnosing a failure of an active noise control system of the present invention may receive a sound wave transmission function A and a sound wave transmission function Afrom a controller, measure a sound wave transmission function a while a vehicle is stationary and a sound wave transmission function a while the vehicle travels, determine whether an active noise control system operates normally on the basis of similarity between a and A and similarity between a and A, and notify a user of a failure state of the active noise control system when the active noise control system is determined as not operating normally.

A method of detecting singing of a user of a personal audio device, the method comprising: receiving a first audio signal comprising bone-conducted speech of the user from a first transducer of the personal audio device; monitoring a second audio signal output to a speaker of the personal audio device; and determining whether the user is singing based on the first audio signal and the second audio signal.

A method performed by an audio output device is provided for detecting instabilities and taking mitigating actions. Specifically, an A-weighted dBA level of a raw feedback signal exceeding a threshold level trigger, at least, muting the driver. The described methods apply to detecting instabilities across a broad frequency spectrum.

Embodiments of a diagnostic tool for an active noise cancelling system are presented. The diagnostic tool may generate an output from the active noise cancelling system and capture input to the active noise cancelling system that results from the output of the active noise cancelling system. The diagnostic tool may generate visual output to aid in evaluation of active noise cancelling systems.

A playback audio signal is combined with a feedback signal from a feedback microphone to provide a first combined signal. The first combined signal is filtered with a feedback filter to provide a driver command signal. The driver command signal is provided to an acoustic transducer for transduction to acoustic energy. The first combined signal is compared with the feedback signal to detect a feedback instability based upon the comparison.