Spatial headphone transparency

Patent metadata

Field	Value
Publication number	US-10951990-B2
Application number	US-201816029314-A
Country	US
Kind code	B2
Filing date	Jul 6, 2018
Priority date	Sep 22, 2016
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

Digital audio signal processing techniques used to provide an acoustic transparency function in a pair of headphones. A number of transparency filters can be computed at once, using optimization techniques or using a closed form solution, that are based on multiple re-seatings of the headphones and that are as a result robust for a population of wearers. In another embodiment, a transparency hearing filter of a headphone is computed by an adaptive system that takes into consideration the changing acoustic to electrical path between an earpiece speaker and an interior microphone of that headphone while worn by a user. Other embodiments are also described and claimed.

First claim

What is claimed is:

1. An audio system comprising:
a first adaptive subsystem that is to determine an adaptive path estimation filter, whose transfer function estimates a path from an input of an earpiece speaker to an output of an interior microphone of a headset, using a playback signal that is driving the earpiece speaker and using an output signal from the interior microphone;
a second adaptive subsystem that is to determine an adaptive output filter that has an input coupled to receive a reference signal produced by an exterior microphone of the headset and an output that is driving the earpiece speaker; and
a processor configured to cause the second adaptive subsystem to adapt the adaptive output filter into any one of a plurality of different conditions,
wherein in a first condition the output filter produces an output signal that is to recreate through the earpiece speaker an ambient sound that is sensed in the reference signal,
in a second condition the output filter is being determined using the adaptive path estimation filter and is producing an anti-noise signal to cancel the ambient sound, and
in a third condition the output filter is producing an output signal that is to cancel the ambient sound in a portion of an audio band while recreating the ambient sound through the earpiece speaker in another portion of the audio band.

2. The audio system of claim 1 wherein in the first condition a sum of i) the output signal from the adaptive output filter and ii) the playback signal are converted into sound by the earpiece speaker without acoustic noise cancellation.

3. The audio system of claim 1 wherein the second adaptive subsystem comprises an adaptive filter controller that determines the adaptive output filter, the controller having a first control input to receive a version of the reference signal that is filtered by a copy of the adaptive path estimation filter, and a second control input to receive a version of the reference signal that is filtered by a control filter.

4. The audio system of claim 3 wherein the processor is configured to adjust a response of the control filter in accordance with a user input that affects a transparency function of the audio system.

5. The audio system of claim 4 wherein the user input changes the transparency function from zero transparency to partial transparency to full transparency.

6. A method performed by an audio system for controlling a transparency function, the method comprising:
determining an adaptive path estimation filter whose transfer function estimates a path from an input of an earpiece speaker to an output of an interior microphone of a headset, using a playback signal that is driving the earpiece speaker and using an output signal from the interior microphone;
determining an adaptive output filter that has an input coupled to receive a reference signal produced by an exterior microphone of the headset and an output that is driving the earpiece speaker; and
adapting the output filter into any one of a plurality of different conditions, wherein in a first condition the adaptive output filter produces an output signal that is to recreate through the earpiece speaker an ambient sound that is sensed in the reference signal, in a second condition the adaptive output filter is being determined using the adaptive path estimation filter and is producing an anti-noise signal to cancel the ambient sound, and in a third condition the adaptive output filter is producing an output signal that is to cancel the ambient sound in a portion of an audio band while recreating the ambient sound through the earpiece speaker in another portion of the audio band.

7. The method of claim 6 further comprising converting by the earpiece speaker, in the first condition, a sum of i) the output signal from the adaptive output filter and ii) the playback signal are converted into sound without acoustic noise cancellation.

8. The method of claim 7 wherein determining the adaptive output filter is based on i) a version of the reference signal that is filtered by a copy of the adaptive path estimation filter, and ii) a difference between a version of the reference signal that is filtered by a control filter and an error signal derived from the output signal from the internal microphone.

9. The method of claim 8 further comprising adjusting a response of the control filter in accordance with a user input that affects a transparency function of the audio system.

10. The method of claim 9 wherein the user input changes the transparency function from zero transparency to partial transparency to full transparency.

11. A headset comprising:
an exterior microphone;
an interior microphone;
an acoustic noise cancellation, ANC, subsystem that receives an error signal derived from the interior microphone and produces an anti-noise signal to cancel ambient sound;
a hear through mode filter having an input to receive a reference signal from the exterior microphone and produce an output signal that reproduces an ambient sound environment of the headset; and
a summing unit having a first input to receive the anti-noise signal and a second input to receive the output signal of the hear through mode filter and an output to produce a speaker driver signal.

12. The headset of claim 11 wherein the ANC subsystem is enabled during a phone call to produce the anti-noise signal while the output signal of the filter is disconnected from the summing unit.

13. The headset of claim 12 wherein the summing unit combines the anti-noise signal with a sidetone signal during the phone call.

14. The headset of claim 12 further comprising a compressor that is to produce a dynamic range adjusted version of the output signal of the hear through mode filter, wherein the summing unit combines the anti-noise signal with the dynamic range adjusted version of the output signal.

15. The headset of claim 14 further comprising a processor that adjusts a compression or expansion profile of the compressor and a scalar gain of the output signal, based on analyzing the reference signal from the exterior microphone.

16. The headset of claim 15 wherein the processor adjusts the compression or expansion profile of the compressor and the scalar gain based on analyzing a signal from the interior microphone, a signal from another sensor, and an operating mode of the headset being one of full ANC mode or assisted hearing mode.

17. The headset of claim 16 wherein the analyzing by the processor comprises one of howling detection, wind or scratch detection, microphone occlusion detection, or off-ear detection.

18. The headset of claim 11 further comprising a compressor that is to produce a dynamic range adjusted version of the output signal of the hear through mode filter, wherein the summing unit combines the anti-noise signal with the dynamic range adjusted version of the output signal.

19. The headset of claim 18 further comprising a processor that adjusts a compression or expansion profile of the compressor and a scalar gain of the output signal, based on analyzing the reference signal from the exterior microphone.

20. The headset of claim 19 wherein the processor adjusts the compression or expansion profile of the compressor and the scalar gain based on analyzing i) a signal from the interior microphone, ii) a signal from another sensor, and iii) an operating mode of the headset being one of full ANC mode or assisted hearing mode.

21. The headset of claim 20 wherein analyzing by the processor compris

Assignees

• Apple Inc

Inventors

• Nawfal Ismael H
• Atkins Joshua D
• Nimick Stephen J
• Nicholson Guy C
• Harlow Jason M

Classifications

• H04R2201/401

  2D or 3D arrays of transducers · CPC title

• H04R1/1041

  Mechanical or electronic switches, or control elements (switches in general H01H) · CPC title

• H04R2201/403

  Linear arrays of transducers · CPC title

• H04R5/027

  Spatial or constructional arrangements of microphones, e.g. in dummy heads · CPC title

• H04R2460/01

  Hearing devices using active noise cancellation · CPC title