Patent ID: 8831239

Claim:
A feedback based active noise reduction system comprising: a feedback component for forming at least part of a feedback loop having an audio path segment, the feedback component including a first signal input for accepting an input signal, a driver output for providing a driver signal to a driver of the audio path segment, a first feedback input for accepting a first feedback signal from a first sensor responsive to a signal on the audio path segment, a control input for accepting a control parameter for adjusting at least one of a gain characteristic and a phase characteristic of the feedback loop, and an instability detector for detecting an instability condition in the feedback component and forming the control parameter based on a result of the detection, the instability detector including a feedback loop signal input for accepting a feedback loop signal, a circuit for detecting an oscillatory signal component in the feedback loop signal not represented in the input signal, the circuit including: a circuit for forming a modified feedback loop signal, the circuit including circuitry for removing a component of the input signal from the feedback loop signal, a circuit for detecting the oscillatory signal component in a specified frequency range in the modified feedback loop signal, and a voltage controlled oscillator and a circuit for combining an output of the voltage controlled oscillator and the modified feedback loop signal, and a control parameter output for providing the control parameter to the control parameter input of the feedback element.