OFF-EAR DETECTOR FOR PERSONAL LISTENING DEVICE WITH ACTIVE NOISE CONTROL

• US 20150310846A1
• Filed: 07/14/2014
• Published: 10/29/2015
• Est. Priority Date: 04/23/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Andersen, Esge B., Goldstein, Andre L.
• Granted Patent: US 9,486,823 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B05B 7/0884 the outlet orifices for jets constituted by a liquid or a mixture containing a liquid being aligned
• CPC Class Codes: B05B 7/2429 the carried liquid and the main stream of atomising fluid being brought together after discharge B05B7/2435 takes precedence
• CPC Class Codes: B05B 7/2464 a liquid being fed by mechanical pumping from the container to the nozzle
• CPC Class Codes: B05B 7/2491 characterised by the means for producing or supplying the atomising fluid, e.g. air hoses, air pumps, gas containers, compressors, fans, ventilators, their drives
• CPC Class Codes: G10K 11/178 by electro-acoustically regenerating the original acoustic waves in anti-phase
• CPC Class Codes: H04R 1/22 for obtaining desired frequency characteristic only circuit for combining transducers having different responses H04R3/00; for hearing aids H04R25/407
• CPC Class Codes: H04R 2410/03 Reduction of intrinsic noise in microphones
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

In a personal listening device, an ANC system can benefit from a mechanism to detect an off-ear condition, which may be a situation in which the user of the personal listening device has moved an earphone or handset housing away from her ear. A detector may detect such a condition using signals from a touch sensor and/or a vibration sensor that are integrated in the earphone or handset housing, and in response power down the ANC system, or in the case of an adaptive ANC system slow down, or even freeze, the adaptation of one or more adaptive filters. The detector may operate during for example a phone call or during media file playback. Other embodiments are also described.

Claims

1. A method for acoustic noise cancellation (ANC) in a personal listening device, comprising:

performing an acoustic noise cancellation (ANC) process during in-the-field use of a personal listening audio device using a control filter to produce anti-noise by the device;

detecting an off-ear condition using one or more signals from one or more of a touch sensor and a vibration sensor that is integrated in a earphone or handset housing of the device; and

one of a) slowing down or freezing adaptation of the adaptive control filter, or b) disabling the ANC process so as to power down the process, in response to the off-ear condition being detected.

2. The method of claim 1 wherein performing the ANC process comprises identifying a signal path between an earpiece speaker of the device and an error microphone that are at a user'"'"'s ear.

3. The method of claim 2 wherein identifying the signal path comprises computing an adaptive S_hat filter that estimates a transfer function of the signal, in accordance with an adaptive filter control algorithm.

4. The method of claim 1 further comprising:

detecting an on-ear condition using one or more signals of the touch sensor and vibration sensor; and

one of a) speeding up or unfreezing adaptation of the adaptive control filter, or b) activating the ANC process, in response to the on-ear condition being detected.

5. The method of claim 3 wherein detecting the off-ear condition comprises analyzing the S_hat filter in frequency domain by comparing strength of a frequency band to a threshold.

6. The method of claim 3 wherein analyzing the S_hat filter comprises computing an L2 norm of the S_hat filter and comparing the L2 norm to a threshold.

7. The method of claim 3 wherein analyzing the S_hat filter comprises:

bandpass filtering a response of a copy of the S_hat filter while stimulating the copy of the S_hat filter with a known signal;

computing strength of the bandpass filtered response; and

comparing the strength to a threshold.

8. A personal listening device comprising:

an acoustic noise cancellation (ANC) controller having an adaptive filter control engine that updates an adaptive control filter which produces an anti-noise signal;

one of a vibration sensor and a touch sensor that is integrated in a earphone or handset housing of the device; and

an off ear detector that uses one or more signals from one or more of the touch sensor or the vibration sensor, to declare an off-ear condition for the device, wherein the ANC controller responds to the declared off-ear condition by one of a) slowing down or freezing the updating of the adaptive control filter, or b) becoming deactivated so as to save power.

9. The device of claim 8 wherein the ANC controller comprises a further adaptive filter control engine that performs an online identification of a secondary signal path between an earpiece speaker and an error microphone that are at a user'"'"'s ear, by updating an adaptive S_hat filter that estimates a transfer function of the secondary signal path.

10. The device of claim 9 wherein the ANC controller further responds to the off-ear detector by slowing down or freezing the updating of the adaptive S_hat filter.

11. The device of claim 9 wherein the off-ear detector analyzes the S_hat filter, in addition to analyzing a signal from the touch sensor or the vibration sensor, in inform its decision to declare the off-ear condition.

12. The device of claim 11 wherein the off-ear detector analyzes the S_hat filter in frequency domain by comparing strength of a frequency band to a threshold.

13. The device of claim 11 wherein the off-ear detector analyzes the S_hat filter by computing an L2 norm of the S_hat filter and comparing the L2 norm to a threshold.

14. The device of claim 11 wherein the off-ear detector analyzes the S_hat filter by bandpass filtering a response of a copy of the S_hat filter while stimulating the copy of the S_hat filter with a known signal, computing strength of the bandpass filtered response, and comparing the strength to a threshold.

15. The device of claim 9 further comprising said error microphone within the earphone housing or mobile phone handset housing.

16. A personal listening device comprising:

an acoustic noise cancellation (ANC) controller having an adaptive filter control engine that updates an adaptive control filter which produces an anti-noise signal when an ANC process is running;

one of a vibration sensor and a touch sensor that is integrated in a earphone or handset housing of the device; and

an on-ear detector that uses one or more signals from one or more of the touch sensor or the vibration sensor, to declare an on-ear condition for the device, wherein the ANC controller responds to the declared on-ear condition by one of a) speeding up or unfreezing the updating of the adaptive control filter, when the ANC process is running, or b) activating the ANC process, when the ANC process is not running.

17. The device of claim 16 wherein the ANC controller comprises a further adaptive filter control engine that performs an online identification of a secondary signal path between an earpiece speaker and an error microphone that are at a user'"'"'s ear, by updating an adaptive S_hat filter that estimates a transfer function of the secondary signal path.

18. The device of claim 17 wherein the ANC controller further responds to the on-ear detector by speeding up or unfreezing the updating of the adaptive S_hat filter.

19. The device of claim 17 wherein the on-ear detector analyzes the S_hat filter, in addition to analyzing a signal from the touch sensor or the vibration sensor, in inform its decision to declare the on-ear condition.

20. The device of claim 17 wherein while the ANC process is running and an on-ear condition has been declared, the ANC controller is to speed up or unfreeze its continuing adaptation of the adaptive control filter, and while the ANC process is inactive and an on-ear condition is declared based on the vibration and/or touch sensor data, the ANC controller is activated in response.