Methods and systems for controlling noise cancellation

A system for detecting failure in a noise cancellation system, the noise cancellation system configured to at least partially cancel an environmental noise within an enclosed space, comprising:

• a computer having a microprocessor and a computer-readable medium coupled to the microprocessor;
• a sensing device located at a target noise source outside of the enclosed space, the sensing device dedicated to receiving a target noise from the target noise source;
• and
• a program stored in the computer-readable medium, the program, when executed by the microprocessor, operable to:
• receive 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 enclosed space, is operable to at least partially cancel the target noise in the enclosed space;
• receive an error signal approximately representing a portion of the target noise remaining after the cancellation noise and the target noise are combined;
• determine whether the signal level changed or remains unchanged for each of the received cancellation noise signal and the error signal;
• and
• based on the determination, assign a failure state of the noise cancellation system and initiate a remedial measure corresponding with the assigned failure state.

A method for detecting failure in an active noise cancellation system operable to at least partially cancel an unwanted noise in a compartment of a vehicle, the unwanted noise including a target noise produced by a target noise source located outside of the compartment, the method comprising:

• sensing the target noise with a dedicated sensor disposed proximate the target noise source and remote from the compartment;
• receiving a cancellation noise signal from the active noise cancellation system of the vehicle, the cancellation noise signal representing a cancellation noise that, when combined with the target noise in the compartment, is operable to substantially cancel the target noise;
• receiving a pure error signal representing only the portion of the target noise remaining after the cancellation noise and the target noise are combined;
• determining that the signal level of the cancellation noise signal is increasing and above a first threshold;
• determining that the signal level of the pure error signal is increasing at a time when the signal level of the cancellation noise signal is increasing and above the first threshold;
• indicating that the active noise cancellation system is unstable;
• and
• initiating at least a partial deactivation of the active noise cancellation system.