# US 2019/0174218 A1 · Headphone off-ear detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0174218 A1 - Document ID: US20190174218A1 - Status: Published application - Kind: A1 - Application number: 16/174,067 - Filed: 2018-10-29 - Published: 2019-06-06 - Earliest claimed: 2016-10-24 - Assignees: Avnera Corporation - Applicants: Avnera Corporation - Inventors: Amit Kumar; Shankar Rathoud; Mike Wurtz; Eric Etheridge; Eric Sorensen - Web page: https://patentgrep.com/patent/US20190174218A1 ## CPC - H04R 1/1041: {Mechanical or electronic switches, or control elements (switches in general H01H)} - G10K 11/178: by electro-acoustically regenerating the original acoustic waves in anti-phase - G10K 11/17827: {Desired external signals, e.g. pass-through audio such as music or speech} - G10K 11/17881: {the reference signal being an acoustic signal, e.g. recorded with a microphone} - H04R 1/1008: {Earpieces of the supra-aural or circum-aural type} - H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) - H04R 29/001: {for loudspeakers (H04R29/007 takes precedence)} - G10K 2210/1081: Earphones, e.g. for telephones, ear protectors or headsets - G10K 2210/3026: Feedback - G10K 2210/3027: Feedforward - H04R 2460/01: Hearing devices using active noise cancellation - 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 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. ## Claims ### Claim at position 1 1-11. (canceled) ### Claim 12 A signal processor circuit assembly for off-ear headphone detection comprising: an audio generator configured to generate a tone signal at a specified 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. ### Claim 13 (depends on 12) The signal processor circuit assembly of claim 12 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. ### Claim 14 (depends on 12) The signal processor circuit assembly of claim 12 wherein the tone signal is less than 100 Hz. ### Claim 15 (depends on 12) The signal processor circuit assembly of claim 12 wherein the tone signal is between 15 and 30 Hz. ### Claim 16 (depends on 12) The signal processor circuit assembly of claim 12 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. ### Claim 17 (depends on 16) The signal processor circuit assembly of claim 16 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. ### Claim 18 (depends on 17) The signal processor circuit assembly of claim 17 wherein the off ear detection processor is further configured increase an amplitude of the audio signal after the noise floor increases. ### Claim 19 (depends on 17) The signal processor circuit assembly of claim 17 further comprising: a left feedforward microphone input to receive a left feed forward signal from a left feed forward microphone; a right feed forward microphone input to receive a right feed forward signal from a right feed forward microphone, the left and right feed forward signals based on ambient now at the location of the respective left and right feed forward microphones, the off ear detection signal processor further configured to select a weaker of the left and right feed forward signals to determine the noise floor. ### Claim 20 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. ### Claim 21 (depends on 20) The method of claim 20 further comprising reducing power consumption in a system using the feedback microphone to determine if the headphone is positioned on a user's ear. ### Claim 22 (depends on 20) The method of claim 20, further comprising generating a control signal in response to detecting the headphone being disengaged. ### Claim 23 (depends on 21) The method of claim 21 wherein the control signal turns off a noise cancellation feature providing noise cancellation in the audio signal transmitted to the headphone. ### Claim 24 (depends on 21) The method of claim 21 wherein the control signal turns off the headphone. ### Claim 25 (depends on 21) The method of claim 21 wherein the control signal turns off a media player connected to the headphone. ### Claim 26 (depends on 21) The method of claim 21 wherein the control signal pauses a media player connected to the headphone. ### Claim 27 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 a 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. ### Claim 28 (depends on 27) The headphone system of claim 27 wherein the tone signal is less than 100 Hz. ### Claim 29 (depends on 27) The headphone system of claim 27 wherein the tone signal is between 15 and 30 Hz. ### Claim 30 (depends on 27) The headphone system of claim 27 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. ### Claim 31 (depends on 27) The headphone system of claim 27 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.