Headphone off-ear detection

Patent metadata

Field	Value
Publication number	US-10448140-B2
Application number	US-201816174067-A
Country	US
Kind code	B2
Filing date	Oct 29, 2018
Priority date	Oct 24, 2016
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

Disclosed is a signal processor for headphone off-ear detection. The signal processor includes an audio output to transmit an audio signal toward a headphone speaker in a headphone cup. The signal processor also includes a feedback (FB) microphone input to receive a FB signal from a FB microphone in the headphone cup. The signal processor also includes an off-ear detection (OED) signal processor to determine an audio frequency response of the FB signal over an OED frame as a received frequency response. The OED processor also determines an audio frequency response of the audio signal times an off-ear transfer function between the headphone speaker and the FB microphone as an ideal off-ear response. A difference metric si generated comparing the received frequency response to the ideal off-ear frequency response. The difference metric is employed to detect when the headphone cup is disengaged from an ear.

First claim

What is claimed is:

1. A signal processor circuit assembly for off-ear headphone detection comprising:
an audio generator configured to generate a tone signal at a specified frequency bin, the tone signal included in an audio signal transmitted toward a headphone speaker;
a feedback microphone input to receive a feedback signal from a feedback microphone in a headphone, the feedback signal based in part on the audio signal including the tone signal; and
an off ear detection processor configured to determine a received frequency response from the feedback signal, determine a difference metric between the received frequency response and a modeled off-ear frequency response, and use the difference metric to detect when the headphone is in an off-ear state.

2. The signal processor circuit assembly of claim 1 wherein the off ear detection processor is further configured to determine on-ear to off-ear, or off-ear to on-ear, headphone state changes by determining and comparing successive difference metrics.

3. The signal processor circuit assembly of claim 1 wherein the tone signal is less than 100 Hz.

4. The signal processor circuit assembly of claim 1 wherein the tone signal is between 15 and 30 Hz.

5. The signal processor circuit assembly of claim 1 further comprising a feedforward microphone input to receive a feedforward signal from a feedforward microphone outside of the headphone, the off ear detection processor further configured to remove a correlated frequency response between the feedforward signal and the feedback signal to determine the received frequency response.

6. The signal processor circuit assembly of claim 5 wherein the off ear detection processor is further configured to determine a noise floor based on the feedforward signal, and the audio generator is further configured to generate the tone signal to have an amplitude greater than the noise floor.

7. The signal processor circuit assembly of claim 6 wherein the off ear detection processor is further configured to increase an amplitude of the audio signal after the noise floor increases.

8. The signal processor circuit assembly of claim 6 further comprising:
a left feedforward microphone input to receive a left feedforward signal from a left feedforward microphone;
a right feedforward microphone input to receive a right feedforward signal from a right feedforward microphone, the left and right feedforward signals based on ambient noise at the location of the respective left and right feedforward microphones, the off ear detection signal processor further configured to select a weaker of the left and right feedforward signals to determine the noise floor.

9. A method of headphone off-ear detection comprising:
generating a tone signal at a specified frequency;
including the generated tone signal in an audio signal transmitted toward a headphone speaker;
receiving a feedback signal from a feedback microphone in a headphone, the feedback signal based in part on the audio signal;
determining a received frequency response from the feedback signal;
determining a difference metric between the received frequency response and a modeled off-ear frequency response, the difference metric based in part on the tone signal; and
detecting when the headphone is in an off-ear state using the difference metric.

10. The method of claim 9 further comprising reducing power consumption in a system using the feedback microphone to determine if the headphone is positioned on a user's ear.

11. The method of claim 10 wherein the control signal turns off a noise cancellation feature providing noise cancellation in the audio signal transmitted to the headphone.

12. The method of claim 9 , further comprising generating a control signal in response to detecting the headphone being disengaged.

13. The method of claim 12 , wherein the control signal turns off the headphone.

14. The method of claim 12 , wherein the control signal turns off a media player connected to the headphone.

15. The method of claim 12 , wherein the control signal pauses a media player connected to the headphone.

16. A headphone system comprising:
a speaker;
an audio generator configured to generate a tone signal at a specified frequency bin, the tone signal included in an audio signal transmitted to the speaker;
a feedback microphone positioned in the headphone, the feedback microphone configured to generate a feedback signal based in part on the audio signal;
an off ear detection processor coupled to the feedback microphone, the off ear detection processor configured to determine a received frequency response from the feedback signal, determine a difference metric between the received frequency response and a modeled off-ear frequency response, and use the difference metric to detect when the headphone is in an off-ear state.

17. The headphone system of claim 16 wherein the tone signal is less than 100 Hz.

18. The headphone system of claim 16 wherein the tone signal is between 15 and 30 Hz.

19. The headphone system of claim 16 further comprising a feedforward microphone positioned to generate a feedforward signal from outside of the headphone, the off ear detection processor further configured to remove a correlated frequency response between the feedforward signal and the feedback signal to determine the received frequency response.

20. The headphone system of claim 16 wherein the off ear detection processor is further configured to generate a control signal to turn off a noise cancellation feature providing noise cancellation in the audio signal transmitted to the headphone in response to detecting the headphone being disengaged.

Assignees

• Avnera Corp

Inventors

• Kumar Amit
• Rathoud Shankar
• Wurtz Mike
• Etheridge Eric
• Sorensen Eric

Classifications

• H04R1/1041 Primary

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

• G10K2210/1081

  Earphones, e.g. for telephones, ear protectors or headsets · CPC title

• H04R1/1008

  Earpieces of the supra-aural or circum-aural type · CPC title

• G10K2210/3026

  Feedback · CPC title

• H04R2460/01

  Hearing devices using active noise cancellation · CPC title