ADAPTIVE NOISE CONTROL SYSTEM

• US 20100195844A1
• Filed: 01/29/2010
• Published: 08/05/2010
• Est. Priority Date: 01/30/2009
• Status: Active Grant

• Current Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Original Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Inventors: Christoph, Markus, Wurm, Michael
• Granted Patent: US 8,644,521 B2
• Time in Patent Office: Days
• US Class Current: 381/71.11
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/3022 Error paths

Abstract

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.

Claims

1. 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; and

an estimation unit that estimates a transfer characteristic of the secondary path system in response to the measurement signal and the microphone signal.

2. The system of claim 1, where the estimation unit attenuates at least one measurement signal component in the microphone signal to provide an error signal.

3. The system of claim 2, where the estimation unit comprises a second adaptive filter that is responsive to the measurement signal and the error signal, and provides an estimation of the measurement signal as received by the microphone.

4. The system of claim 3, where the estimation unit subtracts the estimation of the measurement signal from the microphone signal to at least partially suppress the one or more measurement signal components in the microphone signal.

5. The system of claim 1, where:

a second microphone, where the first and second microphones that 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.

6. The system of claim 5, where the estimation unit attenuates one or more measurement signal components in the vector of microphone signals.

7. The system of claim 6, where the estimation unit comprises a multi-input/multi-output adaptive filter that is responsive to the vector of measurement signals and the vector of error signals, and provides an estimation of the measurement signals as received by the microphones, where the estimation comprises a matrix of estimated measurement signals, where each matrix component represents the estimated measurement signal of a corresponding pair of a respective one of the acoustic actuators and a respective one of the microphones.

8. The system of claim 7, where the estimation unit subtracts the matrix components of the estimated measurement signals from corresponding components of the vector of microphone signals to provide a matrix of error signals, each component of which corresponds to a pair of a respective one of the acoustic actuators and a respective one of the microphones.

9. The system of claim 1, further comprising:

a first processing unit that superposes the measurement signal and the compensation signal, and supplies at least one resulting sum signal to the at least one acoustic actuator.

10. The system of claim 9, further comprising a second signal source that provides a second measurement signal, where the first processing unit superposes the measurement signal, the second measurement signal and the compensation signal, and supplies one or more resulting sum signals to the at least one acoustic actuator.

11. The system of claim 9, where the measurement signal is sampled at a sample rate, and the first processing unit comprises a sample rate converter that adjusts the sampling rate of the measurement signal to match a sample rate of an audio system driving the at least one acoustic actuator.

12. The system of claim 9, where the measurement signal is sampled at a sample rate, and the first processing unit comprises a sample rate converter that adjusts the sampling rate of the measurement signal to match a sample rate of the estimation unit for estimating the transfer characteristic of the secondary path system.

13. The system of claim 10, where the first processing unit comprises an all-pass filter that compensates for phase differences between different measurement signals.

14. The system of claim 1, further comprising a pre-processing unit connected upstream of the at least one acoustic actuator and downstream of the adaptive filter, the pre-processing unit comprising a unit for imposing a frequency dependent gain on the measurement signal.

15. The system of claim 3, further comprising a control unit that monitors and assesses quality of the estimation of the secondary path system.

16. The system of claim 15, where the control unit provides a control signal for controlling frequency dependent gain of a pre-processing unit, the control signal depending on the quality of the estimation.

17. A method for reducing, at a listening position, power of a noise signal radiated from a noise source to the listening position, the method comprising:

adaptively filtering a reference signal representing the noise signal via an adaptive filter to provide a compensation signal;

providing a measurement signal;

radiating the compensation signal and the measurement signal to the listening position via at least one acoustic actuator;

receiving a first signal via at least one microphone, where the first signal is a superposition of the radiated compensation signal, the radiated measurement signal, and the noise signal at the listening position; and

estimating a transfer characteristic of a secondary path system responsive to the measurement signal and the first signal;

where the secondary path system represents a signal transmission path between an output of the adaptive filter and an output of the at least one microphone.

18. The method of claim 17, where the step of estimating the transfer characteristic comprises:

at least partially suppressing in the first signal one or more measurement signal components to provide an error signal.

19. The method of claim 17, where the step of estimating the transfer characteristic comprises:

adaptively filtering the measurement signal to provide an estimation of the measurement signal as received by the at least one microphone.

20. The method of claim 19, where the step of estimating the transfer characteristic further comprises:

subtracting the estimation of the measurement signal from the first signal to at least partially suppress one or more measurement signal components in the first signal to provide an error signal.