Compensation of own voice occlusion

1. A method of equalising sound in a headset comprising an internal microphone configured to generate a first audio signal, an external microphone configured to generate a second audio signal, a speaker, and one or more processors coupled between the speaker the external microphone, and the internal microphone, the method comprising:

while the headset is worn by a user:

determining a first audio transfer function between the first audio signal and the second audio signal in the presence of sound at the external microphone; and

determining a second audio transfer function between a speaker input signal and the first audio signal with the speaker being driven by the speaker input signal;

determining an electrical transfer function of the one or more processors;

determining a closed-ear transfer function based on the first audio transfer function, the second audio transfer function and the electrical transfer function; and

equalising the first audio signal based on a comparison between the closed-ear transfer function and an open-ear transfer function to generate an equalised first audio signal.

2. The method of claim 1 , wherein the comparison is a frequency domain ratio between the closed-ear transfer function and the open-ear transfer function, or wherein the comparison is a time-domain difference between the closed-ear transfer function and the open-ear transfer function.

3. The method of claim 1 , wherein:

a) the open-ear transfer function is a measured open-ear transfer function between an ear-entrance or an eardrum of the user; or

b) the open-ear transfer function is a measured open-ear transfer function between an ear-entrance and an ear-drum of a head simulator; or

c) the open-ear transfer function is an average open-ear transfer function of a portion of the general population.

4. The method of claim 1 , further comprising:

a) measuring the open-ear transfer function between an ear-entrance or an eardrum of the user; or

b) measuring the open-ear transfer function between an ear-entrance and an ear-drum of a head simulator; or

c) determining the open-ear transfer function based on an average open-ear transfer function for a portion of the general population.

5. The method of claim 1 , wherein the step of determining the first audio transfer function is performed with the speaker muted.

6. The method of claim 1 , wherein the step of determining the second audio transfer function is performed in the presence of little or no sound external to the headset.

7. The method of claim 1 , wherein determining the electrical path transfer function comprises determining a frequency response of a feedforward ANC filter implemented by the one or more processors and/or a frequency response of a feedback ANC filter implemented by the one or more processors.

8. The method of claim 4 , wherein determining the electrical path transfer function comprises determining a gain associated with the one or more processors.

9. The method of claim 1 , wherein determining an open-ear transfer function between an ear-entrance and an eardrum of the user comprises approximating the open-ear transfer function of the user.

10. The method of claim 1 , further comprising:

outputting the equalised first audio signal to the speaker.

11. The method of claim 1 , further comprising:

determining a third audio transfer function between the first audio signal and the second audio signal while the headset is worn by the user and the user is speaking; and

further equalising the equalised first audio signal based on the third transfer function.

12. The method of claim 11 , further comprising:

on determining that the user is speaking, outputting the voice equalised first audio signal to the speaker.

13. The method of claim 11 , further comprising:

determining that the one or more processors is implementing active noise cancellation (ANC); and

adjusting the further equalisation to account for the one or more processors implementing ANC.

14. The method of claim 11 , further comprising:

requesting that the user to speak a phoneme balanced sentence or phrase, wherein the third audio transfer function is determined while the user is speaking the phoneme balanced sentence.

15. An apparatus, comprising:

a headset comprising:

an internal microphone configured to generate a first audio signal;

an external microphone configured to generate a second audio signal; and

a speaker; and

one or more processors configured to:

while the headset is worn by a user:

determine a first audio transfer function between the first audio signal and the second audio signal in the presence of sound at the external microphone; and

determine a second audio transfer function between a speaker input signal and the first audio signal with the speaker being driven by the speaker input signal;

determine an electrical transfer function of the one or more processors;

determine a closed-ear transfer function based on the first audio transfer function, the second audio transfer function and the electrical transfer function; and

equalise the first audio signal based on a comparison between the closed-ear transfer function and an open-ear transfer function to generate an equalised first audio signal.

16. The apparatus of claim 15 , wherein the comparison is a frequency domain ratio between the closed-ear transfer function and the open-ear transfer function, or wherein the comparison is a time-domain difference between the closed-ear transfer function and the open-ear transfer function.

17. The apparatus of claim 6 , wherein:

a) the open-ear transfer function is a measured open-ear transfer function between an ear-entrance or an eardrum of the user; or

b) the open-ear transfer function is a measured open-ear transfer function between an ear-entrance and an ear-drum of a head simulator; or

c) the open-ear transfer function is an average open-ear transfer function of a portion of the general population.

18. The apparatus of claim 15 , wherein the one or more processors are further configured to:

a) measuring the open-ear transfer function between an ear-entrance or an eardrum of the user; or

b) measuring the open-ear transfer function between an ear-entrance and an ear-drum of a head simulator; or

c) determining the open-ear transfer function based on an average open-ear transfer function for a portion of the general population.

19. A non-transitory computer-readable storage medium storing instructions which, when executed by a computer, cause the computer to carry out a method of equalising sound in a headset comprising an internal microphone configured to generate a first audio signal, an external microphone configured to generate a second audio signal, a speaker, and one or more processors coupled between the speaker the external microphone, and the internal microphone, the method comprising:

while the headset is worn by a user:

determining a first audio transfer function between the first audio signal and the second audio signal in the presence of sound at the external microphone; and

determining a second audio transfer function between a speaker input signal and the first audio signal with the speaker being driven by the speaker input signal;

determining an electrical transfer function of the one or more processors;

determining a closed-ear transfer function based on the first audio transfer function, the second audio transfer function and the electrical transfer function; and

equalising the first audio signal based on a comparison between the closed-ear transfer function and an open-ear transfer function to generate an equalised first audio signal.