ACTIVE NOISE CONTROL SYSTEM

• US 20080181422A1
• Filed: 01/16/2008
• Published: 07/31/2008
• Est. Priority Date: 01/16/2007
• Status: Active Grant

• Current Assignee: Harman International Industries Incorporated (Samsung Electronics Co. Ltd.)
• Original Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Inventors: Christoph, Markus
• Granted Patent: US 8,199,923 B2
• Time in Patent Office: Days
• US Class Current: 381/73.1
• CPC Class Codes: G10K 11/17815 between the reference signals and the error signals, i.e. primary path
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• 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

Abstract

An active control of an unwanted noise signal at a listening site radiated by a noise source uses a reference signal that has an amplitude and/or frequency such that it is masked for a human listener at the listening site by the unwanted noise signal and/or a wanted signal present at the listening site in order to adapt for the time-varying secondary path in a real time manner such that a user doesn'"'"'t fell disturbed by an additional artificial noise source.

Claims

1. A system for active control of an unwanted noise signal at a listening site radiated by a noise source where the unwanted noise is transmitted to the listening site via a primary path having a primary path transfer function, the system comprising:

a loudspeaker for radiating a cancellation signal to attenuate the unwanted noise signal, where the cancellation signal is transmitted from the loudspeaker to the listening site via a secondary path;

an error microphone (E) at the listening site for determining through an error signal the level of achieved reduction;

a first adaptive filter for generating the canceling signal by filtering a signal representative of the unwanted noise signal with a transfer function adapted to the primary path transfer function using the signal representative of the unwanted noise signal and the error signal from the error microphone; and

a reference generator for generating a reference signal which is supplied to the loudspeaker together with the canceling signal from the first adaptive filter, where the reference signal has such an amplitude and/or frequency that it is masked for a human listener at the listening site by the unwanted noise signal and/or a wanted signal present at the listening site.

2. The system of claim 1, where amplitude and/or frequency of the reference signal are determined by a psychoacoustic masking model unit which models masking in human hearing in the error signal from the error microphone.

3. The system of claim 2, where the psychoacoustic masking model unit models temporal masking.

4. The system of claim 2, where the psychoacoustic masking model unit models spectral masking.

5. The system of one of claims 1, where the psychoacoustic masking model unit is operated in the frequency domain.

6. The system of claim 1, where the first adaptive filter adapts according to the Least Mean Square (LMS) algorithm.

7. The system of claim 1, where the first adaptive filter adapts according to the filtered X Least Mean Square (filtered X-LMS) algorithm.

8. The system of claim 7, further comprising a second adaptive filter having a transfer function modeling the transfer function of the secondary path, where the second adaptive filter is connected to the first adaptive filter for filtering the signal representative of the unwanted noise signal used for the adaptation of the first adaptive filter.

9. The system of claim 8, where the second adaptive filter adapts according to the Least Mean Square (LMS) algorithm.

10. The system of claim 8, where the signal representative of the unwanted noise signal supplied to the first adaptive filter is derived from the error signal and the signal output by the first adaptive filter and filtered by a third adaptive filter having a transfer function modeling the transfer function of the secondary path.

11. The system of claim 10, where the signal representative of the unwanted noise signal supplied to the first adaptive filter is derived further from the reference signal filtered with a fourth adaptive filter having a transfer function modeling the transfer function of the secondary path.

12. The system of claim 11, where the fourth filter is operated in the frequency domain;

the fourth filter having a time-to-frequency converter connected upstream and a frequency-to-time converter connected downstream.

13. The system of claim 1, where the signal representing the unwanted noise signal supplied to the first adaptive filter is derived from a non-acoustic sensor and the non-acoustic sensor provides a sensor signal and is arranged near the unwanted-noise source.

14. The system of claim 13, further comprising a fundamental calculation unit connected downstream of the non-acoustic sensor for calculating a fundamental signal from the sensor signal and a signal generator connected downstream of the fundamental calculation unit for generating the signal representative of the unwanted noise signal from the fundamental signal.

15. The system of claim 14, further comprising a band pass filter having filter coefficients for filtering the error signal supplied to the first adaptive filter;

the filter coefficients are controlled by a coefficient calculation unit connected downstream of the fundamental calculation unit.

16. The system of claim 14, where the reference signal includes a wanted signal provided by a wanted-signal source.

17. The system of claim 1, where the signal output by the first adaptive filter is split into at least two partial signals multiplied with weighting factors, where one of the partial signals is supplied to the loudspeaker and an other is supplied to a fifth adaptive filter modeling the secondary path whose output signal is added to the error signal.

18. The system of claim 17, where the sum of the weighting factors is one.

19. The system of claim 17, further comprising a sixth adaptive filter for modeling the primary path, where the sixth adaptive filter provides an output signal supplied to the loudspeaker and being supplied with the sum of its output signal and the reference signal.

20. A method for active control of an unwanted noise signal at a listening site radiated by a noise source where the unwanted noise is transmitted to the listening site via a primary path having a primary path transfer function, the method comprising the steps of:

radiating a cancellation signal to reduce or cancel the unwanted noise signal, where the cancellation signal is transmitted from a loudspeaker to the listening site via a secondary path;

determining through an error signal the level of achieved reduction at the listening site;

first adaptive filtering for generating the canceling signal by filtering a signal representative of the unwanted noise signal with a transfer function adapted to the primary path transfer function using the signal representative of the unwanted noise signal and the error signal; and

generating a reference signal which is supplied to the loudspeaker together with the canceling signal from the first adaptive filtering step, where the reference signal has an amplitude and/or frequency such that it is masked for a human listener at the listening site by the unwanted noise signal and/or a wanted signal present at the listening site.

21. The method of claim 20, where amplitude and/or frequency of the reference signal are determined by a psychoacoustic masking modeling step which models masking in human hearing in the error signal.

22. The method of claim 21, where the psychoacoustic masking modeling step models temporal masking.

23. The method of claim 21, where the psychoacoustic masking modeling step models spectral masking.

24. The method of claim 21, where the psychoacoustic masking modeling step is performed in the frequency domain.

25. The method of claim 20, where the first adaptive filter step adapts according to the Least Mean Square (LMS) algorithm.

26. The method of claim 25, where the first step adapts according to the filtered X Least Mean Square (filtered X-LMS) algorithm.

27. The system of claim 26, further comprising a second adaptive filtering step using a transfer function modeling the transfer function of the secondary path, where the second adaptive filter is connected to the first adaptive filter for filtering the signal representative of the unwanted noise signal used for the adaptation of the first adaptive filter.

28. The method of claim 27, where the second adaptive filter adapts according to the Least Mean Square (LMS) algorithm.

29. The method claim 20, where the signal representative of the unwanted noise signal used in the first adaptive filtering step is derived from the error signal and the signal output by the first adaptive filtering step and filtered in a third adaptive filtering step having a transfer function modeling the transfer function of the secondary path.

30. The method of claim 29, where the signal representative of the unwanted noise signal used in the first adaptive filtering step is derived further from the reference signal filtered in a fourth adaptive filtering step having a transfer function modeling the transfer function of the secondary path.

31. The method of claim 30, where the fourth filtering step is performed in the frequency domain, and the fourth filtering step includes a time-to-frequency conversion step in advance to and a frequency-to-time conversion step following the fourth filtering step.

32. The method of claim 20, where the signal representing the unwanted noise signal used in the first adaptive filtering step is derived from a non-acoustic sensor, and the non-acoustic sensor provides a sensor signal and is arranged near the unwanted-noise source.

33. The method of claim 32, further comprising a fundamental calculation step for calculating a fundamental signal from the sensor signal and a signal generation step for generating the signal representative of the unwanted noise signal from the fundamental signal.

34. The method of claim 33, further comprising a band pass filtering step using filter coefficients for filtering the error signal used in the first adaptive filtering step, where the filter coefficients are controlled by a coefficient calculation step using the fundamental signal.

35. The method of claim 34, where the reference signal includes a wanted signal provided by a wanted-signal source.

36. The method of claim 20, where the signal output by the first adaptive filtering step is split into at least two partial signals multiplied with weighting factors, where one of the partial signals is supplied to the loudspeaker and an other is used by a fifth adaptive filtering step modeling the secondary path whose output signal is added to the error signal.

37. The system of claim 36, where the sum of the weights is one.

38. The system of claim 20, further comprising a sixth adaptive filtering step for modeling the primary path, where the sixth adaptive filtering step provides an output signal supplied to the loudspeaker and being input with the sum of its output signal and the reference signal.