Methods, apparatus and systems for biometric processes

1. A method comprising:

monitoring for an event initiated by a user of a personal audio device, the event being a user activity producing an associated audio artefact;

detecting the event;

in response to detecting the event, applying the acoustic stimulus to the user's ear during a masking period in which the acoustic stimulus is masked in the user's hearing by the audio artefact; and

extracting, from a response signal of the user's ear to the acoustic stimulus, one or more features for use in a biometric process;

wherein the event comprises one or more of:

(i) a physical interaction with the personal audio device;

(ii) tapping of the personal audio device;

(iii) a voice interaction between the user and the personal audio device;

(iv) a heartbeat of the user;

(v) a footfall of the user; and

(vi) a footstep of the user.

2. The method of claim 1 , wherein the event is detected using one or more of an accelerometer, a button, a microphone, or a transducer of the personal audio device.

3. The method of claim 1 , further comprising generating the acoustic stimulus for application to the user's ear.

4. The method of claim 3 , further comprising:

determining one or more properties of the audio artefact, wherein the acoustic stimulus is generated in dependence on the one or more properties of the audio artefact.

5. The method of claim 4 , wherein the one or more properties comprises one or more of a frequency response and an amplitude of the audio artefact.

6. The method of claim 4 , wherein generating the acoustic stimulus based on the one or more properties of the audio artefact comprises one or more of:

(i) modifying the gain of the acoustic stimulus;

(ii) increasing the duration of the acoustic stimulus;

(iii) applying an additional instance of the acoustic stimulus;

(iv) shifting the pitch of the acoustic stimulus such that content of the response signal is better aligned with one or more resonances of the user's ear;

(v) adding a masking noise to the acoustic stimulus;

(vi) amplifying ambient noise and/or user voice via hear through mode or sidetone path;

(vii) using a masking model to add additional content to the acoustic stimulus that is inaudible to the user;

(viii) adding harmonic content to the acoustic stimulus.

7. The method of claim 1 , wherein detecting the event initiated by the user comprise predicting the event based on two or more historic user initiated events, each historic user initiated event having an associated historic audio artefact.

8. The method of claim 1 , wherein the masking period at least partially coincides with the audio artefact.

9. The method of claim 1 , wherein the biometric process is one of on ear detection, in ear detection, biometric enrolment and biometric authentication.

10. The method of claim 9 , wherein biometric enrolment comprises generating and storing a unique model for the user based on the one or more features and wherein biometric authentication comprises comparing the one or more features to a unique model for the user.

11. The method of claim 1 , further comprising detecting the response signal at a microphone of the personal audio device.

12. An apparatus, comprising processing circuitry and a non-transitory machine-readable which, when executed by the processing circuitry, cause the apparatus to:

monitor for an event initiated by a user of a personal audio device, the event being a user activity producing an associated audio artefact;

detect the event;

in response to detection of the event, apply an acoustic stimulus to a user's ear using the transducer during a masking period in which the acoustic stimulus is masked in the user's hearing by the audio artefact; and

extract, from a response signal of the user's ear to the acoustic stimulus detected by the microphone, one or more features for use in a biometric process;

wherein the event comprises one or more of:

(i) a physical interaction with the personal audio device;

(ii) tapping of the personal audio device;

(iii) a voice interaction between the user and the personal audio device;

(iv) a heartbeat of the user;

(v) a footfall of the user; and

(vi) vi a footstep of the user.

13. The apparatus of claim 12 , comprising:

a transducer configured to apply the acoustic stimulus; and

a microphone configured to detect the response signal of the user's ear, wherein the microphone is further configured to detect an error signal for use in an active noise cancellation system.

14. The apparatus of claim 12 , comprising:

a transducer configured to:

apply the acoustic stimulus; and

detect the response signal of the user's ear.

15. An electronic device, comprising the apparatus of claim 12 .

16. A non-transitory machine-readable medium storing instructions which, when executed by one or more processors, cause an electronic apparatus to:

monitor for an event initiated by a user, the event being a user activity producing an associated audio artefact;

detect the event;

in response to detecting the event, applying an acoustic stimulus to the user's ear during a masking period in which the acoustic stimulus is masked in the user's hearing by the audio artefact;

extracting, from a response signal of the user's ear to the acoustic stimulus, one or more features for use in a biometric process;

wherein the event comprises one or more of:

(i) a physical interaction with the personal audio device;

(ii) tapping of the personal audio device;

(iii) a voice interaction between the user and the personal audio device;

(iv) a heartbeat of the user;

(v) a footfall of the user; and

(vi) vi a footstep of the user.