# US 9,967,647 B2 · Off-ear and on-ear headphone detection

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- Number: US 9,967,647 B2
- Document ID: US9967647B2
- Status: Granted
- Kind: B2
- Application number: 14/850,859
- Filed: 2015-09-10
- Published: 2017-01-12
- Granted: 2018-05-08
- Earliest claimed: 2015-07-10
- Assignees: Avnera Corporation
- Applicants: Avnera Corporation
- Inventors: Amit Kumar; Eric Sorensen; Shankar Rathoud
- Web page: https://patentgrep.com/patent/US9967647B2

## CPC

- H04R 1/1041: {Mechanical or electronic switches, or control elements (switches in general H01H)}
- G10K 11/17823: {Reference signals, e.g. ambient acoustic environment}
- G10K 11/17825: {Error signals}
- G10K 11/17827: {Desired external signals, e.g. pass-through audio such as music or speech}
- G10K 11/17833: {by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels}
- G10K 11/17835: {using detection of abnormal input signals}
- G10K 11/17853: {of the filter}
- G10K 11/17855: {for improving speed or power requirements}
- G10K 11/17881: {the reference signal being an acoustic signal, e.g. recorded with a microphone}
- G10K 11/17885: {additionally using a desired external signal, e.g. pass-through audio such as music or speech}
- G10K 2210/1081: Earphones, e.g. for telephones, ear protectors or headsets
- G10K 2210/3021: Eigenfrequencies; Eigenvalues, e.g. used to identify most significant couplings between actuators and sensors
- 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)}
- H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F)
- H04R 29/00: Monitoring arrangements; Testing arrangements {(for hearing aids H04R25/30; detection of loudspeaker connection H04R5/04; sound-field adaptation dependent on speaker detection H04S7/308)}
- H04R 2410/05: Noise reduction with a separate noise microphone
- H04R 2460/03: Aspects of the reduction of energy consumption in hearing devices
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR

## Abstract

A headphone detector including a headphone and a processor. The headphone has a microphone and a speaker, and the microphone is configured to generate an audio signal based on an output of the speaker. The processor is configured to receive the audio signal, determine a characteristic of the audio signal, and assess whether the headphone is on ear or off ear based on a comparison of the characteristic to a threshold. In another aspect, an off-ear detection (OED) system includes a headphone and an OED processor. The headphone has a speaker, a feedforward microphone, and a feedback microphone. The OED processor is configured to determine whether the headphone is off ear or on ear, based at least in part on a headphone audio signal, a feedforward microphone signal, and a feedback microphone signal.

## Claims

### Claim 1

A headphone detector comprising:
a headphone having a microphone and a speaker, the microphone configured to generate an audio signal based on an output of the speaker, in which the microphone includes a feedback microphone configured to sample the output of the speaker;
a processor configured to receive the audio signal, determine a characteristic of the audio signal, and assess whether the headphone is on ear or off ear based on a comparison of the characteristic to a threshold; and
a feedforward microphone configured to generate an ambient noise signal based on a sampled ambient noise level, in which the processor is further configured to receive the ambient noise signal, determine a characteristic of the ambient noise signal, and assess whether the headphone is on ear or off ear further based on a comparison of the characteristic of the ambient noise signal to a parameter,
wherein the threshold and parameter correspond to one or more of an audio response of the audio signal at a corresponding frequency, an audio response of the ambient noise signal at a corresponding frequency, and an audio response of a feedback microphone signal at a corresponding frequency, under one or more known conditions.

### Claim 2 (depends on 1)

The headphone detector of claim 1, further comprising a tone source configured to produce a tone in the output of the speaker.

### Claim 3 (depends on 2)

The headphone detector of claim 2, in which a signal generated by the tone source is mixed with the audio signal.

### Claim 4 (depends on 1)

The headphone detector of claim 1, in which the characteristic of the audio signal is an energy of the audio signal.

### Claim 5 (depends on 1)

The headphone detector of claim 1, in which the characteristic of the audio signal is an energy of a portion of the audio signal.

### Claim 6 (depends on 1)

The headphone detector of claim 1, in which the characteristic of the audio signal is an energy of a low-frequency portion of the audio signal.

### Claim 7 (depends on 1)

The headphone detector of claim 1, in which the threshold relates to a known condition of the headphone.

### Claim 8

A method of detecting whether a headphone is off ear or on ear, the method comprising:
producing an acoustic signal at a headphone based at least in part on a received headphone audio signal;
generating, at the headphone, a feedforward microphone signal and a feedback microphone signal, in which the feedback microphone signal is based at least in part on the acoustic signal;
determining, with the processor, a characteristic of the headphone audio signal, a characteristic of the feedforward microphone signal, and a characteristic of the feedback microphone signal, wherein the characteristics include an audio response at a corresponding frequency; and
assessing, with the processor, whether the headphone is off ear or on ear based at least in part on an audio response of the headphone audio signal, an audio response of the feedforward microphone signal, and an audio response of the feedback microphone signal.

### Claim 9 (depends on 8)

The method of claim 8, further comprising injecting a tone signal into a headphone audio signal.

### Claim 10 (depends on 8)

The method of claim 8, further comprising applying a bandpass filter to the headphone audio signal, the feedforward microphone signal, and the feedback microphone signal before determining the characteristics, the bandpass filter having a center frequency of less than 100 Hz.

### Claim 11 (depends on 8)

The method of claim 8, further comprising iteratively receiving, at the processor, the headphone audio signal, the feedforward microphone signal, and the feedback microphone signal until a preset duration of samples is obtained.

### Claim 12 (depends on 11)

The method of claim 11, in which determining the characteristics includes determining:
a running sum for each of the headphone audio signal, the feedforward microphone signal, and the feedback microphone signal;
a running sum of squares of the headphone audio signal, the feedforward microphone signal, and the feedback microphone signal; and
a running sum of products of the feedforward microphone signal times the feedback microphone signal.

### Claim 13 (depends on 8)

The method of claim 8, further comprising outputting a decision signal from the processor, in which the decision signal is based at least in part on whether the headphone is assessed to be off ear or on ear.

### Claim 14 (depends on 13)

The method of claim 13, further comprising triggering a convenience feature based at least in part on the decision signal.

### Claim 15 (depends on 14)

The method of claim 14, in which the convenience feature includes sending a signal to initiate a power-saving feature.

### Claim 16 (depends on 14)

The method of claim 14, in which the convenience feature includes sending a signal to stop a media player from generating the headphone audio signal.

### Claim 17 (depends on 14)

The method of claim 14, in which the convenience feature includes sending a signal to start a media player, the media player generating the headphone audio signal.

### Claim 18 (depends on 8)

The method of claim 8, further comprising iteratively performing the generating, determining, and assessing processes until a preset number of identical, consecutive assessments is obtained.

### Claim 19 (depends on 18)

The method of claim 18, further comprising a delay period between each iteration, the delay period being substantially longer than a duration of time for performing one iteration of the generating, determining, and assessing processes.

### Claim 20 (depends on 18)

The method of claim 18, further comprising injecting a tone signal into a headphone audio signal for each iteration after a preset number of iterations.

### Claim 21 (depends on 8)

The method of claim 8, in which determining the characteristics includes determining an energy of the headphone audio signal, an energy of the feedforward microphone signal, and an energy of the feedback microphone signal.

### Claim 22 (depends on 8)

The method of claim 8, in which determining the characteristics includes determining a power of the headphone audio signal, a power of the feedforward microphone signal, and a power of the feedback microphone signal.