Detection of a microphone

1. A method comprising:

receiving at least two microphone signals from at least two microphones, the at least two microphone signals associated with at least one acoustic source, wherein the at least one acoustic source is from an environment surrounding the at least two microphones;

processing at least part of the at least two microphone signals to determine at least one audio source based on the at least one acoustic source;

determining at least one direction associated with the determined at least one audio source; and

calibrating at least one of the at least two microphone signals based on the at least one direction and further based on a number of times that calibration of the at least two microphone signals has been performed.

2. The method as claimed in claim 1 , wherein processing at least part of the at least two microphone signals to determine the at least one audio source based on the at least one acoustic source comprises filtering each of the at least two microphone signals to generate a respective at least two associated microphone signal parts.

3. The method as claimed in claim 1 , wherein determining the at least one direction associated with the determined at least one audio source comprises:

determining a maximum correlation of a time difference between a pair of the at least part of the two microphone signals; and

determining a direction based on the maximum correlation of the time difference.

4. The method as claimed in claim 3 , wherein calibrating the at least one of the at least two microphone signals based on the at least one direction comprises determining a direction based on the maximum correlation of the time difference in least one determined calibration direction.

5. The method as claimed in claim 4 , wherein determining the direction based on the maximum correlation of the time difference in the at least one determined calibration direction comprises determining that the direction based on the maximum correlation of the time difference is within at least one determined calibration direction sector.

6. The method as claimed in claim 1 , further comprising defining at least one direction for which the at least part of the at least two microphone signals have an expected signal relationship, wherein the expected signal relationship is at least one of signal level relationship and signal phase relationship.

7. The method as claimed in claim 6 , wherein the expected signal level relationship is at least one of:

equal signal levels of the at least part of the at least two microphone signals; and

a predefined ratio between the at least part of the at least two microphone signals.

8. The method as claimed in claim 6 , wherein calibrating at least one of the at least two microphone signals based on the at least one direction comprises calibrating the at least two microphone signals based on the signal levels of the at least part of the at least two microphone signals and the expected signal level relationship.

9. The method as claimed in claim 1 , wherein calibrating at least one of the at least two microphone signals based on the at least one direction comprises determining or updating at least one calibration value associated with a respective microphone signal based on at least one of:

a number of times the operation of calibrating the at least one of at least two microphone signals had been performed;

a signal level associated with the at least part of the at least two microphone signals;

an expected signal level relationship between the at least part of the at least two microphone signals when the at least one audio source is associated with at least one determined direction;

a signal phase difference associated with the at least part of the at least two microphone signals; and

an expected signal phase difference relationship between the at least part of the at least two microphone signals when the at least one audio source is associated with at least one determined direction.

10. The method as claimed in claim 1 , wherein calibrating at least one of the at least two microphone signals based on the at least one direction further comprises calibrating the at least two microphone signals based on a number of times the calibration of the at least two microphone signals has been performed.

11. An apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured to with the at least one processor cause the apparatus to:

receive at least two microphone signals from at least two microphones, the at least two microphone signals associated with at least one acoustic source, wherein the at least one acoustic source is from an environment surrounding the at least two microphones;

process at least part of the at least two microphone signals to determine at least one audio source based on the at least one acoustic source;

determine at least one direction associated with the determined at least one audio source; and

calibrate at least one of the at least two microphone signals based on the at least one direction and further based on a number of times that calibration of the at least two microphone signals has been performed.

12. The apparatus as claimed in claim 11 , wherein the determined at least one audio source based on the at least one acoustic source causes the apparatus to filter each of the at least two microphone signals to generate a respective at least two associated microphone signal parts.

13. The apparatus as claimed in claim 11 , wherein to determine the at least one direction associated with the determined at least one audio source causes the apparatus to determine a maximum correlation time of a difference between a pair of the at least part of the two microphone signals and a direction based on the maximum correlation of the time difference.

14. The apparatus as claimed in claim 13 , wherein to calibrate the at least one of the at least two microphone signals based on the at least one direction comprises determining a direction based on the maximum correlation of the time difference in at least one determined calibration direction.

15. The apparatus as claimed in claim 14 , wherein determining the direction based on the maximum correlation of the time difference in the at least one determined calibration direction comprises determining that the direction based on the maximum correlation of the time difference is within at least one determined calibration direction sector.

16. The apparatus as claimed in claim 11 , wherein the determined at least one direction further comprises the at least part of the at least two microphone signals having an expected signal relationship, wherein the expected signal relationship is at least one of signal level relationship and signal phase relationship.

17. The apparatus as claimed in claim 16 , wherein the expected signal level relationship is at least one of equal signal levels of the at least part of the at least two microphone signals and a predefined ratio between the at least part of the at least two microphone signals.

18. The apparatus as claimed in claim 16 , wherein the apparatus is further caused to calibrate the at least two microphone signals based on the signal levels of at least part of the at least two microphone signals and the expected signal level relationship.

19. The apparatus as claimed in claim 11 , wherein the calibrated at least one of the at least two microphone signals further causes the apparatus to update at least one calibration value associated with a respective microphone signal based on at least one of:

a number of times the operation of calibrating the at least one of at least two microphone signals had been performed;

a signal level associated with the at least part of the at least two microphone signals;

an expected signal level relationship between the at least part of the at least two microphone signals when the at least one audio source is associated with at least one determined direction;

a signal phase difference associated with the at least part of the at least two microphone signals; and

an expected signal phase difference relationship between the at least part of the at least two microphone signals when the at least one audio source is associated with at least one determined direction.

20. A computer program product comprising a non-transitory computer readable storage medium, the non-transitory computer readable storage medium comprising program code, when executed by a processor, to configure the processor to:

receive at least two microphone signals from at least two microphones, the at least two microphone signals associated with at least one acoustic source, wherein the at least one acoustic source is from an environment surrounding the at least two microphones;

process at least part of the at least two microphone signals to determine at least one audio source based on the at least one acoustic source;

determine at least one direction associated with the determined at least one audio source; and

calibrate at least one of the at least two microphone signals based on the at least one direction and further based on a number of times that calibration of the at least two microphone signals has been performed.