Harman Becker Automotive Systems Gmbh

Michael Wurm

Markus E Christoph

Michael Perkmann

The present disclosure relates to an active noise control (ANC) system. In accordance with one aspect of the invention, the ANC system includes a plurality of microphones and a plurality of loudspeakers. Each microphone is configured to provide an error signal that represents a residual noise signal. Each loudspeaker is configured to receive a loudspeaker signal and to radiate a respective acoustic signal. The ANC system further includes an adaptive filter bank, which is supplied with a reference signal and configured to filter the reference signal to provide the loudspeaker signals as filtered signals. The filter characteristics of the adaptive filter bank are adapted such that a cost function is minimized. The cost function thereby represents the weighted sum of the squared error signals.

Active noise control system

A method for determining an estimation of a secondary path transfer characteristic in an ANC system is described herein. In accordance with one example of the invention, the method includes the positioning of a microphone array in a listening room symmetrically with respect to a desired listening position and reproducing at least one test signal using a loudspeaker arranged within the listening room to generate an acoustic signal. The acoustic signal is measured with the microphones of the microphone array to obtain a microphone signal from each microphone of the microphone array, and a numerical representation of the secondary path transfer characteristic is calculated for each microphone signal based on the test signal and the respective microphone signal. The method further includes averaging the calculated numerical representations of the secondary path transfer characteristic to obtain the estimation of the secondary path transfer characteristic to be used in the ANC system.

Adaptive noise control system with improved robustness

An active noise control system and method for tuning an acoustic noise signal at a listening position are disclosed in which a first weighting element is connected in the filter coefficient copy path and/or a second weighting element is connected in the microphone path.

Tunable active noise control

Adaptive noise control for reducing power of an acoustic noise signal radiated from a noise source to a listening position comprises providing an electrical reference signal correlated with the acoustic noise signal; filtering the electrical reference signal with an adaptive filter to provide an electrical output signal; multiplying the electrical output signal of the adaptive filter by a gain factor to provide a first electrical compensation signal; filtering and multiplying the electrical output signal of the adaptive filter by the inverse of the gain factor to provide a second electrical compensation signal, the second gain factor being equal to 1 subtracted by the first gain factor; radiating the first electrical compensation signal to the listening position with an acoustic transducer; sensing a residual electrical error signal at the listening position; adding the second electrical compensation signal to the electrical error signal to provide a compensated error signal; and adapting filter coefficients of the adaptive filter as a function of the compensated error signal and the reference signal.

Adaptive noise control

A system for actively reducing noise at a listening point, includes an earphone housing, a transmitting transducer, a receiving transducer and a controller. The transmitting transducer converts a first electric signal into a first acoustic signal, and radiates the first acoustic signal along a first acoustic path having a first transfer characteristic and along a second acoustic path having a second transfer characteristic. The receiving transducer converts the first acoustic signal and ambient noise into a second electrical signal. The controller compensates for the ambient noise by providing a noise reducing electrical signal to the transmitting transducer. The noise reducing electrical signal is derived from a filtered electrical signal that is provided by filtering the second electrical signal with a third transfer characteristic. The second and the third transfer characteristics together model the first transfer characteristic.

Active noise reduction system

An active noise cancellation system includes an adaptive filter, a signal source, an acoustic actuator, a microphone, a secondary path and an estimation unit. The adaptive filter receives a reference signal representing noise, and provides a compensation signal in response to the received reference signal. The signal source provides a measurement signal. The acoustic actuator radiates the compensation signal and the measurement signal to the listening position. The microphone 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. The secondary path includes a secondary path system that represents a signal transmission path between an output of the adaptive filter and an output of the microphone. The estimation unit estimates a transfer characteristic of the secondary path system in response to the measurement signal and the microphone signal.

Adaptive noise control system with secondary path estimation

An active noise cancellation system that reduces, at a listening position, power of a noise signal radiated from a noise source to the listening position. The system includes an adaptive filter, at least one acoustic actuator and a signal processing device. The adaptive filter receives a reference signal representing the noise signal, and provides a compensation signal. The at least one acoustic actuator radiates the compensation signal to the listening position. The signal processing device evaluates and assesses the stability of the adaptive filter.

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Straubing, Germany

Michael Wurm