PROVIDING AMBIENT NATURALNESS IN ANR HEADPHONES

• US 20140341387A1
• Filed: 08/05/2014
• Published: 11/20/2014
• Est. Priority Date: 11/02/2012
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Gauger, Daniel M. Jr., Harlow, Jason
• Granted Patent: US 9,953,626 B2
• Time in Patent Office: Days
• US Class Current: 381/71.6
• CPC Class Codes: G10K 11/17821 characterised by the analysis of the input signals only
• CPC Class Codes: G10K 11/17837 by retaining part of the ambient acoustic environment, e.g. speech or alarm signals that the user needs to hear
• CPC Class Codes: G10K 11/17853 of the 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 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/3026 Feedback
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters
• CPC Class Codes: G10K 2210/3036 Modes, e.g. vibrational or spatial modes
• CPC Class Codes: G10K 2210/3055 Transfer function of the acoustic system
• CPC Class Codes: G10K 2210/3056 Variable gain
• CPC Class Codes: H04R 1/1008 Earpieces of the supra-aural or circum-aural type
• 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
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2460/05 Electronic compensation of the occlusion effect
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits

Abstract

In an active noise reducing headphone, a signal processor applies filters and control gains of both the feed-forward and feedback active noise cancellation signal paths. The signal processor is configured to apply first feed-forward filters to the feed-forward signal path and apply first feedback filters to the feedback signal path during a first operating mode providing effective cancellation of ambient sound, and to apply second feed-forward filters to the feed-forward signal path during a second operating mode providing active hear-through of ambient sounds with ambient naturalness.

Claims

1. An active noise reducing headphone comprising:

an ear piece configured to couple to a wearer'"'"'s ear, the ear piece providing passive attenuation of ambient sound into the wearer'"'"'s ear;

a feed-forward microphone acoustically coupled to an external environment and electrically coupled to a feed-forward active noise cancellation signal path having a feed-forward filter with configurable coefficients;

an output transducer acoustically coupled to the wearer'"'"'s ear canal when the ear piece is coupled to the wearer'"'"'s ear and electrically coupled to the feed-forward active noise cancellation signal path; and

a signal processor configured to apply the coefficients of the feed-forward filter;

wherein the signal processor is configured to;

apply a first set of feed-forward coefficients to the feed-forward filter that cause the feed-forward filter to generate anti-noise sounds to cancel ambient sound detected by the feed-forward microphone, decreasing residual sound in the ear piece over a first frequency range, during a first operating mode, and

replace the first set of feed-forward coefficients with a second set of feed-forward coefficients in the feed-forward filter that cause the feed-forward filter to modify the ambient sound detected by the feed-forward microphone to compensate for changes in the ambient sound resulting from the passive attenuation of the ear piece, decreasing residual sound in the ear piece over a first sub-range of the first frequency range and increasing residual sound over a second sub-range of the first frequency range, during a second operating mode, the second sub-range beginning at at least 300 Hz and extending for at least two octaves above 300 Hz.

2. The headphone of claim 1 wherein the second set of feed-forward coefficients cause the feed-forward filter to have a zero in the right half plane.

3. The headphone of claim 1, wherein the second set of feed-forward filters cause the headphone to have a total system response at the wearer'"'"'s ear that is smooth and piecewise linear within the second sub-range.

4. The headphone of claim 3, wherein the second set of feed-forward filters cause the headphone to have a total system response at the wearer'"'"'s ear that decreases with a gentle roll-off above the second sub-range.

5. The headphone of claim 4, wherein the second sub-range extends to at least 3 kHz before the roll-off begins.

6. The headphone of claim 4, wherein the second sub-range extends to at least 5 kHz before the roll-off begins.

7. The headphone of claim 1, wherein the second sub-range begins at at least 140 Hz.

8. The headphone of claim 1, wherein the second set of feed-forward filters have value K_ht selected to cause the formula

9. The headphone of claim 1, wherein the second set of feed-forward coefficients define non-minimum phase zeros in a transfer function characterizing the feed-forward signal path.

10. The headphone of claim 1, wherein the signal processor is further configured to:

replace the first or second set of feed-forward coefficients with a third set of feed-forward coefficients during a third operating mode providing active hear-through of ambient sounds with a different total response than is provided in the second operating mode.

11. The headphone of claim 1, wherein the signal processor is a first signal processor and the feed-forward signal path is a first feed-forward signal path, the headphone further comprising:

a second ear piece configured to couple to a wearer'"'"'s second ear, the second ear piece providing passive attenuation of ambient sound into the wearer'"'"'s second ear;

a second feed-forward microphone acoustically coupled to the external environment and electrically coupled to a second feed-forward active noise cancellation signal path having a second feed-forward filter with configurable coefficients;

a second output transducer acoustically coupled to the wearer'"'"'s second ear canal when the ear piece is coupled to the wearer'"'"'s second ear and electrically coupled to the second feed-forward active noise cancellation signal path; and

a second signal processor configured apply the coefficients of the second feed-forward filter;

wherein the second signal processor is configured to;

apply a third set of feed-forward coefficients to the second feed-forward filter that cause the second feed-forward filter to generate anti-noise sounds to cancel ambient sound detected by the second feed-forward microphone, decreasing residual sound in the second ear piece over the first frequency range, during the first operating mode of the first signal processor, and

replace the third set of feed-forward coefficients with a fourth set of feed-forward coefficients in the second feed-forward filter that cause the second feed-forward filter to modify the ambient sound detected by the second feed-forward microphone to compensate for changes in the ambient sound resulting from the passive attenuation of the second ear piece, decreasing residual sound in the second ear piece over the first sub-range of the first frequency range and increasing residual sound in the second ear piece over the second sub-range of the first frequency range, during the second operating mode of the first signal processor.

12. The headphone of claim 11, wherein the third set of feed-forward coefficients are not identical to the first set of feed-forward coefficients.

13. The headphone of claim 11, wherein only one of the first or second signal processor applies the respective second or fourth set of feed-forward coefficients to the corresponding first or second feed-forward filter during a third operating mode.

14. The headphone of claim 1, further comprising

a feedback microphone acoustically coupled to the wearer'"'"'s ear canal when the earpiece is coupled to the wearer'"'"'s ear and electrically coupled to a feedback active noise cancellation signal path having a feedback filter with configurable coefficients;

wherein

the output transducer is also electrically coupled to the feedback active noise cancellation signal path, and

the signal processor is further configured to apply a first set of feedback coefficients to the feedback filter during the first operating mode.

15. The headphone of claim 14, wherein the signal processor is further configured to replace the first set of feedback coefficients with a second set of feedback coefficients different from the first set of feedback coefficients during the second operating mode.

16. An active noise reducing headphone comprising:

an ear piece configured to couple to a wearer'"'"'s ear, the ear piece providing passive attenuation of ambient sound into the wearer'"'"'s ear;

a feed-forward microphone acoustically coupled to an external environment and electrically coupled to a feed-forward active noise cancellation signal path having a feed-forward filter with configurable coefficients;

an output transducer acoustically coupled to the wearer'"'"'s ear canal when the ear piece is coupled to the wearer'"'"'s ear and electrically coupled to the feed-forward active noise cancellation signal path; and

a signal processor configured to apply the coefficients of the feed-forward filter;

wherein the signal processor is configured to;

apply a first set of feed-forward coefficients to the feed-forward filter that cause the feed-forward filter to generate anti-noise sounds to cancel ambient sound detected by the feed-forward microphone during a first operating mode, and

replace the first set of feed-forward coefficients with a second set of feed-forward coefficients in the feed-forward filter that cause the feed-forward filter to modify the ambient sound detected by the feed-forward microphone to compensate for changes in the ambient sound resulting from the passive attenuation of the ear piece during a second operating mode; and

wherein the second set of feed-forward coefficients cause the feed-forward filter to have a zero in the right half plane

17. The headphone of claim 16, wherein the second set of feed-forward filters cause the headphone to have a total system response at the wearer'"'"'s ear that is smooth and piecewise linear within the second sub-range, the second sub-range beginning at at least 300 Hz and extending for at least two octaves above 300 Hz.

18. The headphone of claim 17, wherein the second set of feed-forward filters cause the headphone to have a total system response at the wearer'"'"'s ear that decreases with a gentle roll-off above the second sub-range.

19. The headphone of claim 16, wherein the second set of feed-forward filters have value K_ht selected to cause the formula

20. The headphone of claim 16, wherein the second set of feed-forward coefficients define non-minimum phase zeros in a transfer function characterizing the feed-forward signal path.

21. An active noise reducing headphone comprising:

an ear piece configured to couple to a wearer'"'"'s ear, the ear piece providing passive attenuation of ambient sound into the wearer'"'"'s ear;

a feed-forward microphone acoustically coupled to an external environment and electrically coupled to a feed-forward active noise cancellation signal path having a feed-forward filter with configurable coefficients;

an output transducer acoustically coupled to the wearer'"'"'s ear canal when the ear piece is coupled to the wearer'"'"'s ear and electrically coupled to the feed-forward active noise cancellation signal path; and

a signal processor configured to apply the coefficients of the feed-forward filter;

wherein the signal processor is configured to;

apply a first set of feed-forward coefficients to the feed-forward filter that cause the feed-forward filter to generate anti-noise sounds to cancel ambient sound detected by the feed-forward microphone during a first operating mode, and

replace the first set of feed-forward coefficients with a second set of feed-forward coefficients in the feed-forward filter that cause the feed-forward filter to modify the ambient sound detected by the feed-forward microphone to compensate for changes in the ambient sound resulting from the passive attenuation of the ear piece during a second operating mode, wherein

the second sub-range of the first frequency range begins at at least 300 Hz and extends for at least two octaves above 300 Hz,

the second set of feed-forward filters cause the headphone to have a total system response that is smooth and piecewise linear within the second sub-range, and decreases with a gentle roll-off above the second sub-range.

22. The headphone of claim 21, wherein the second sub-range extends to at least 3 kHz before the roll-off begins.

23. The headphone of claim 21, wherein the second sub-range extends to at least 5 kHz before the roll-off begins.

24. The headphone of claim 21, wherein the second sub-range begins at at least 140 Hz.

25. The headphone of claim 21 wherein the second set of feed-forward coefficients cause the feed-forward filter to have a zero in the right half plane.