ADAPTIVE FEED-FORWARD NOISE REDUCTION

• US 20120250873A1
• Filed: 03/31/2011
• Published: 10/04/2012
• Est. Priority Date: 03/31/2011
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Bakalos, Pericles, Parthasarathi, Anand
• Granted Patent: US 8,693,700 B2
• Time in Patent Office: Days
• US Class Current: 381/71.6
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• 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 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/30391 Resetting of the filter parameters or changing the algorithm according to prevailing conditions
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06

Abstract

In an aspect, the invention features an active noise reduction device including an electronic signal processing circuit. The electronic signal processing circuit includes a first input for accepting a first signal, a second input for accepting a second signal, an output for providing a third signal, a feed-forward path from the first input to the output, and a feed-forward controller for determining the control parameter by calculating a control signal using the first signal and the second signal and then using the control signal to determine the control parameter. The feed-forward path includes a fixed compensation linear filter and a variable compensation filter having an input for receiving a control parameter that applies a selected linear filter from a family of linear filters that vary in both gain and spectral shape and are selectable by the control parameter.

Claims

1. An active noise reduction device comprising:

an electronic signal processing circuit including;

a first input for accepting a first signal;

a second input for accepting a second signal;

an output for providing a third signal; and

a feed-forward path from the first input to the output including;

a fixed compensation linear filter; and

a variable compensation filter having an input for receiving a control parameter that applies a selected linear filter from a family of linear filters that vary in both gain and spectral shape and are selectable by the control parameter; and

a feed-forward controller for determining the control parameter by calculating a control signal using the first signal and the second signal and then using the control signal to determine the control parameter.

2. The device of claim 1, further comprising:

a device body configured to form a cavity when coupled to the anatomy of a wearer;

a first microphone configured to sense the sound pressure level outside of the cavity and generate the first signal;

a second microphone configured to sense the sound pressure level inside of the cavity and generate the second signal; and

a driver configured to receive the third signal and provide sound pressure to the inside of the cavity.

3. The device of claim 2, wherein the device body comprises an earcup.

4. The device of claim 2, wherein the device body comprises an in-ear headphone interface.

5. The device of claim 2, wherein each linear filter in the family of linear filters represents a deviation from an average of a plurality of different positions of the device body on the anatomy of the wearer.

6. The device of claim 1, wherein monotonically changing the value of the control parameter causes the gain at any particular frequency of the frequency response of the selected linear filter to change monotonically.

7. The device of claim 1, further comprising a feed-back path from the second input to the output, the feed-back path including a feed-back compensation filter.

8. The device of claim 7, wherein the outputs of the variable compensation filter and the feed-back compensation filter are combined to generate the third signal.

9. The device of claim 1, wherein the feed-forward controller includes an error minimization algorithm that determines the control parameter.

10. The device of claim 9, wherein the error minimization algorithm is the LMS algorithm.

11. The device of claim 1, further comprising a band limiter configured to band limit the first signal and the second signal before they are provided to the feed-forward controller.

12. The active noise reduction device of claim 1, wherein the parameter includes a plurality of values.

13. A method for active noise reduction comprising:

accepting a first signal from a first input;

accepting a second signal from a second input;

producing a third signal; and

providing the third signal to an output;

wherein producing the third signal comprises;

processing the first signal using a feed-forward path from the first input to the output, the processing of the feed-forward path including;

filtering using a fixed compensation filter; and

filtering using a variable compensation filter controlled by a control parameter that applies a selected linear filter from a family of filters that vary in both gain and spectral shape and are selectable by the control parameter; and

determining the control parameter that controls a feed-forward controller by calculating a control signal using the first signal and the second signal and then using the control signal to determine the control parameter.

14. The method of claim 13, wherein producing the third signal further comprises processing the second input using a feed-back path from the second input to the output.

15. The method of claim 14, wherein the second input is processed in the feed-back path by a feed-back compensation filter.

16. The method of claim 15, wherein the output of the variable compensation filter and the feed-back compensation filter are combined to form the third signal.

17. The method of claim 13, further comprising determining the control parameter using an error minimization algorithm.

18. The method of claim 17, wherein the error minimization algorithm is the LMS algorithm.

19. The method of claim 13, further including band limiting the first signal and the second signal before providing them to the feed-forward controller.