Methods and apparatus for biometric processes

1. A method for generating an acoustic stimulus for use in an ear biometric process on a user, the method comprising:

receiving an indication of stimulation frequencies for use in the ear biometric process;

grouping the stimulation frequencies into bands of a psychoacoustic scale;

generating the acoustic stimulus, the acoustic stimulus comprising a masked bandpass component within each band of the psychoacoustic scale that comprises one or more of the stimulation frequencies.

2. The method of claim 1 , wherein the indication of frequencies is extracted from a model generated from one or more ear canal frequency responses.

3. The method of claim 2 , wherein the model is a generic model generated from an analysis of ear canal frequency responses from a subset of the general population.

4. The method of claim 2 , wherein the model is a user-specific model generated from an analysis of an ear canal frequency response of the user.

5. The method of claim 4 , wherein the ear canal frequency response of the user is obtained during a biometric enrolment process performed on the user.

6. The method of claim 2 , wherein frequencies in the indication of frequencies align with ear canal acoustic modes in the one or more ear canal frequency responses.

7. The method of claim 1 , wherein the psychoacoustic scale comprises a bark scale or an equivalent rectangular bandwidth, ERB, scale or a mel scale or a logarithmic scale or an octave scale.

8. The method of claim 1 , wherein the acoustic stimulus further comprises one or more adjacent masked bandpass components within adjacent bands of the psychoacoustic scale, the adjacent bands being adjacent to bands of the psychoacoustic scale that comprises one or more of the stimulation frequencies.

9. The method of claim 1 , further comprising determining a time duration for each of the masked bandpass components based on an ambient noise level in a microphone signal used in the ear biometric process.

10. The method of claim 9 , wherein the time duration is determined for each of the masked bandpass components based on the ambient noise level in a respective band of the psychoacoustic scale.

11. The method of claim 1 , wherein one or more of the masked bandpass components are temporally ordered with respect to each other.

12. The method of claim 11 , further comprising varying the temporal order to reduce perceptual intrusiveness of the acoustic stimulus to a user.

13. The method of claim 1 , wherein generating the acoustic stimulus comprises:

generating each of the masked bandpass components; and

combining the masked band pass components to generate the acoustic stimulus.

14. The method of claim 1 , further comprising determining a signal level of each of the masked bandpass components based on one or more of:

a) an expected signal-to-noise ratio (SNR);

b) a measured ambient noise level;

c) a spectral shape of ambient background noise;

d) a measured level of noise leakage into an ear canal of the user;

e) playback signal information.

15. The method of claim 1 , further comprising combining the acoustic stimulus with a comfort stimulus.

16. The method of claim 15 , wherein the comfort stimulus comprises one or more of:

a) one or more random tones;

b) music;

c) one or more triad progressions;

d) one or more arpeggios;

e) a voice call signal;

f) a hearing augmentation signal;

g) a passthrough audio signal;

h) an audio signal notifying the user when a device is placed in or on the user's ear.

17. The method of claim 1 , further comprising adding white noise to the acoustic stimulus.

18. The method of claim 1 , further comprising applying the acoustic stimulus to the ear canal of a user.

19. An apparatus comprising processing circuitry and a non-transitory machine-readable medium storing instructions which, when executed by the processing circuitry, cause the apparatus to perform a method for generating an acoustic stimulus for use in an ear biometric process on a user, the method comprising:

receiving an indication of stimulation frequencies for use in the ear biometric process;

grouping the stimulation frequencies into bands of a psychoacoustic scale; and

generating the acoustic stimulus, the acoustic stimulus comprising a masked bandpass component within each band of the psychoacoustic scale that comprises one or more of the stimulation frequencies.

20. An electronic device comprising the apparatus of claim 19 .