Providing Ambient Naturalness in ANR Headphones

• US 20160210958A1
• Filed: 03/29/2016
• Published: 07/21/2016
• Est. Priority Date: 11/02/2012
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Gauger, Daniel M. Jr., Carreras, Ricardo F., Harlow, Jason, Ranney, Neil Adam, Ring, Martin David, Sapiejewski, Roman, Singh, Vikram
• Granted Patent: US 10,074,354 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 during a first operating mode,

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

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.

2. The active noise reducing headphone of claim 1, wherein the second operating mode comprises providing active hear-through in a non-aircraft environment, and the third operating mode comprises providing active hear-through in an aircraft environment.

3. The active noise reducing 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.

4. The active noise reducing headphone of claim 1, wherein the second set of feed-forward coefficients have value K_ht selected to cause the formula

5. The active noise reducing 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.

6. The active noise reducing 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 to apply the coefficients of the second feed-forward filter,

wherein the second signal processor is configured to;

apply a fourth 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 during the first operating mode of the first signal processor,

replace the fourth set of feed-forward coefficients with a fifth 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 during the second operating mode of the first signal processor, and

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

7. The active noise reducing headphone of claim 6, wherein only one of the first or second signal processor applies the respective second or fifth set of feed-forward coefficients to the corresponding first or second feed-forward filter during the second operating mode.

8. The active noise reducing headphone of claim 6, wherein only one of the first or second signal processor applies the respective third or sixth set of feed-forward coefficients to the corresponding first or second feed-forward filter during the third operating mode.

9. The active noise reducing 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.

10. The active noise reducing headphone of claim 9, wherein the signal processor is further configured to:

replace the first set of feedback coefficients with a second set of feedback coefficients during the second operating mode, and

replace the first or second set of feedback coefficients with a third set of feedback coefficients different during the third operating mode.

11. The active noise reducing headphone of claim 1, wherein

during the first operating mode, the first set of feed-forward coefficients cause the feed-forward filter to decrease residual sound in the ear piece over a first frequency range, and

during the second operating mode, the second set of feed-forward coefficients cause the feed-forward filter to decrease residual sound in the ear piece over a first sub-range of the first frequency range and increase residual sound over a second sub-range of the first frequency range, the second sub-range beginning at at least 300 Hz and extending for at least two octaves above 300 Hz.

12. The active noise reducing headphone of claim 1, further comprising a user input, and wherein the signal processor is further configured to select between the first, second or third feed-forward filters based on the user input.

13. The active noise reducing headphone of claim 1, wherein the signal processor is configured to select between the second and third feed-forward filters automatically.

14. The active noise reducing headphone of claim 13, wherein the signal processor is configured to select between the second and third feed-forward filters based on a time-average measurement of the level of the ambient noise.

15. The active noise reducing headphone of claim 14, wherein the signal processor is configured to make the selection between the second and third feed-forward filters upon receipt of a user input calling for activation of a hear-through mode.

16. Active noise reducing headphones comprising:

a first headphone comprising;

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

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

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

a second headphone 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 an 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 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 signal processor configured to apply the coefficients of the first and second feed-forward filters,

wherein the signal processor is configured to;

during an active noise reducing mode,

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

apply a second 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; and

during an active hear-through mode, replace one or both of the first and second sets of feed-forward coefficients with an updated set of feed-forward coefficients to modify the ambient sound detected by one or both of the first and second feed-forward microphones to compensate for changes in the ambient sound resulting from the passive attenuation of one or both of the first and second ear pieces.

17. The active noise reducing headphones of claim 16, wherein during the active hear-through mode, the signal processor is configured to replace only the first set of feed-forward coefficients with the updated set of feed-forward coefficients to modify the ambient sound detected by the first feed-forward microphone to compensate for changes in the ambient sound resulting from the passive attenuation of the first ear piece, the updated coefficients comprising a third set of feed-forward coefficients.

18. The active noise reducing headphones of claim 16, wherein during the active hear-through mode, the signal processor is configured to replace only the second set of feed-forward coefficients with the updated set of feed-forward coefficients 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, the updated coefficients comprising a fourth set of feed-forward coefficients.

19. The active noise reducing headphones of claim 16, wherein during the active hear-through mode, the signal processor is configured to replace both the first and second feed-forward coefficients with the updated set of feed-forward coefficients to modify the ambient sound detected by the first and second feed-forward microphones to compensate for changes in the ambient sound resulting from the passive attenuation of the first and second ear pieces, and wherein the updated coefficients comprise a fifth and sixth set of feed-forward coefficients, the fifth set of feed-forward coefficients replacing the first set of feed-forward coefficients and the sixth set of feed-forward coefficients replacing the second set of feed-forward coefficients.

20. The active noise reducing headphones of claim 16, wherein the updated set of feed-forward coefficients cause one or both of the first and second feed-forward filters to have a zero in the right half plane.

21. The active noise reducing headphones of claim 16, wherein the updated set of feed-forward coefficients have value K_ht selected to cause the formula

22. The active noise reducing headphones of claim 16, wherein the updated set of feed-forward coefficients define non-minimum phase zeros in a transfer function characterizing one or both of the first and second feed-forward signal paths.

23. The active noise reducing headphones of claim 16, wherein

during the active noise reducing mode, the first set of feed-forward coefficients cause the first feed-forward filter to decrease residual sound in the first ear piece over a first frequency range, and the second set of feed-forward coefficients cause the second feed-forward filter to decrease residual sound in the second ear piece over the first frequency range, and

during the active hear-through mode, the updated set of feed-forward coefficients cause one or both of the first and second feed-forward filters to decrease residual sound in one or both of the first and second ear pieces over a first sub-range of the first frequency range and increase residual sound over a second sub-range of the first frequency range, the second sub-range beginning at at least 300 Hz and extending for at least two octaves above 300 Hz.

24. The active noise reducing headphones of claim 16, further comprising a user input, and wherein the signal processor is further configured to select between the active noise reducing mode and the active hear-through mode based on the user input.

25. Active noise reducing headphones comprising:

a first headphone comprising;

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

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

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

a second headphone 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 an 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 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 signal processor configured to apply the coefficients of the first and second feed-forward filters so the first and second feed-forward filters operate in each of three operating modes comprising;

a first operating mode, wherein the signal processor applies a first set of feed-forward coefficients to the first feed-forward filter and a second set of feed-forward coefficients to the second feed-forward filter to generate anti-noise sounds to cancel ambient sound detected by both the first and second feed-forward microphones,

a second operating mode, wherein the signal processor applies a third set of feed-forward coefficients to the first feed-forward filter and a fourth set of feed-forward coefficients to the second feed-forward filter that cause both the first and second feed-forward filters to modify the ambient sound detected by the respective first and second feed-forward microphones to compensate for changes in the ambient sound resulting from the passive attenuation of the respective first and second ear pieces, and

a third operating mode, wherein the signal processor applies a fifth set of feed-forward coefficients to the first feed-forward path to generate anti-noise sounds to cancel ambient sound detected by the first feed-forward microphone, and applies a sixth set of feed-forward coefficients to 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.