Patent ID: 8644521

Claim:
An active noise cancellation system for reducing, at a listening position, power of a noise signal radiated from a noise source to the listening position, the system comprising: an adaptive filter that receives a reference signal representing the noise signal, and provides a compensation signal in response to the received reference signal; a signal source that provides a measurement signal; an acoustic actuator that radiates the compensation signal and the measurement signal to the listening position; a microphone that receives a first signal that is a superposition of the radiated compensation signal, the radiated measurement signal, and the noise signal at the listening position, and provides a microphone signal in response to the received first signal; a secondary path comprising a secondary path system that represents a signal transmission path between an output of the adaptive filter and an output of the microphone; an estimation device that estimates a transfer characteristic of the secondary path system in response to the measurement signal and the microphone signal; a second microphone, where the first and second microphones are located in different listening positions where the power of the noise signal is to be reduced, the microphones providing a vector of microphone signals; and a second acoustic actuator, where the first and second acoustic actuators radiate a vector of compensation signals provided by the adaptive filter, and radiate a vector of measurement signals provided by the signal source.