Noise reduction system having a combination unit, method of operating the system and use of the same

A method of operating a noise reduction system for actively compensating background noise generated by a noise source in a noise reduction area in a passenger transport area of a vehicle, the noise reduction system comprising a controller comprising hardware, a sound generator, which generates anti-noise for superimposing the anti-noise with the background noise in the noise reduction area for active reduction of the background noise, an error microphone picking up background noise emitted by the noise source and anti-noise emitted by the sound generator, and a plurality of reference sensors, which detect the background noise of the noise source, the plurality of reference sensors being arranged at different positions in the vehicle, wherein each reference sensor of the plurality of reference sensors generates a reference signal, at least two reference sensors of the plurality of reference sensors being coupled to the controller, the method comprising:

• implementing a noise canceling algorithm to generate an anti-noise signal for driving the sound generator;
• receiving reference signals of the at least two reference sensors;
• decorrelating the reference signals of the at least two reference sensors;
• determining a virtual reference signal from the decorrelated reference signals;
• and
• generating the anti-noise signal on a basis of the virtual reference signal,
• wherein the error microphone is a virtual error microphone implementing a monitor microphone array having a plurality of monitor microphones and a virtual sensing technique implemented in the controller to estimate an error signal at a position of a virtual microphone, wherein the virtual error microphone is located in the noise reduction area and the error signal is indicative of a summation between the background noise and the anti-noise at the position of the virtual microphone, and the method further comprises updating parameters for driving the sound generator based on the error signal to minimize the error signal.

A processing apparatus for actively compensating background noise generated by a noise source in a noise reduction area in a passenger transport area of a vehicle, the processing apparatus comprising:

• a controller comprising hardware, the controller being configured to:
• implement a noise canceling technique to generate an anti-noise signal for driving a sound generator for generating anti-noise for superimposing the anti-noise with the background noise in the noise reduction area for active reduction of the background noise;
• receive reference signals of at least two reference sensors of a plurality of reference sensors for detecting the background noise of the noise source, the plurality of reference sensors being arranged at different positions in the vehicle, wherein each reference sensor of the plurality of reference sensors is configured to generate one of the reference signals, the at least two reference sensors of the plurality of reference sensors being coupled to the controller;
• decorrelate the reference signals of the at least two reference sensors;
• determine a virtual reference signal from the decorrelated reference signals;
• and
• generate the anti-noise signal, for driving the sound generator, on a basis of the virtual reference signal.