Active noise reduction engine speed determining

Abstract

An active noise reduction system using adaptive filters. A method of operation the active noise reduction system includes smoothing a stream of leakage factors. The frequency of a noise reduction signal may be related to the engine speed of an engine associated with the system within which the active noise reduction system is operated. The engine speed signal may be a high latency signal and may be obtained by the active noise reduction system over audio entertainment circuitry.

1 . A method for operating an active noise reduction system comprising:
 receiving a high latency signal representative of engine speed;   providing a noise reduction audio signal at a reference frequency, the reference frequency related to the engine speed; and   generating a noise reduction audio signal at a frequency corresponding to a predetermined multiple of the reference frequency.   
     
     
         2 . A method in accordance with  claim 1 , further comprising:
 transducing acoustic energy in an enclosed space to provide a noise signal representative of the noise in the enclosed space, and   determining, responsive to the noise signal, a phase and a magnitude of the noise reduction signal.   
     
     
         3 . A method in accordance with  claim 2 , wherein the determining the phase and magnitude of the noise reduction signal is performed by circuitry comprising an adaptive filter. 
     
     
         4 . A method in accordance with  claim 3 , wherein the enclosed space is a vehicle cabin. 
     
     
         5 . A method for operating an active noise reduction system comprising:
 receiving from a bus associated with an audio entertainment system a signal representative of engine speed; and   responsive to the signal representative of engine speed, generating a noise reduction audio signal having a frequency related to the engine speed.   
     
     
         6 . A method in accordance with  claim 5 , further comprising
 receiving from the bus, an entertainment audio signal.   
     
     
         7 . A method in accordance with  claim 5 , wherein the receiving the signal representative of engine speed comprises receiving a high latency signal. 
     
     
         8 . A method in accordance with  claim 7 , further comprising
 processing the entertainment audio signal to provide a processed entertainment audio signal; and   combining the processed entertainment audio signal with the noise reduction audio signal.   
     
     
         9 . A method in accordance with  claim 5 , further comprising receiving from the bus an entertainment system control signal. 
     
     
         10 . A method in accordance with  claim 9 , further comprising
 receiving from the bus, an entertainment audio signal.   
     
     
         11 . A method in accordance with  claim 10 , further comprising
 processing the entertainment audio signal to provide a processed entertainment audio signal; and   combining the processed entertainment audio signal with the noise reduction audio signal.   
     
     
         12 . An audio system comprising:
 an input element for receiving a signal representative of engine speed and an entertainment audio control signal; and   circuitry for generating a noise reduction signal of a frequency related to the signal representative of engine speed.   
     
     
         13 . Apparatus in accordance with  claim 12 , further comprising
 audio signal processing circuitry for processing the entertainment audio signal to provide a processed entertainment audio signal; and   an acoustic driver, for radiating acoustic energy corresponding to the noise cancellation signal and also corresponding to the processed entertainment audio signal.   
     
     
         14 . An audio system in accordance with  claim 12 , wherein the active noise reduction system is associated with a vehicle.