Mobile device localization using audio signals

1. A computer-implemented method of localizing a mobile device, comprising:

receiving, at a processor, a first audio signal captured by a microphone located at the mobile device;

receiving, at the processor, a second audio signal captured from a further microphone;

computing a correlation value for the first audio signal and second audio signal; and

determining whether the mobile device is in proximity to the further microphone using the correlation value.

2. A method according claim 1 , wherein the step of computing the correlation value comprises calculating a cross-correlation between the first audio signal and second audio signal.

3. A method according to claim 1 , wherein the first audio signal comprises ambient noise from the vicinity of the mobile device, and the second audio signal comprises ambient noise from the vicinity of the further microphone.

4. A method according to claim 1 , wherein the further microphone is non-mobile and is associated with a predefined location.

5. A method according to claim 4 , wherein the predefined location is a room of an indoor environment.

6. A method according to claim 4 , wherein the processor is located at a server, and wherein the step of receiving the first audio signal comprises receiving the first audio signal via a wireless interface, and the step of receiving the second audio signal comprises receiving the second audio signal via and analog-to-digital converter.

7. A method according to claim 4 , wherein the processor is located at the mobile device, and wherein the step of receiving the second audio signal comprises receiving the second audio signal via a wireless communication interface at the mobile device.

8. A method according to claim 1 , wherein the processor is located at the mobile device, and the further microphone is located in a further mobile device, such that the step of determining determines whether the mobile device is in proximity to the further mobile device.

9. A method according to claim 1 , further comprising the steps of: receiving, at the processor, a third audio signal captured from an additional microphone; and

computing a further correlation value for the first audio signal and third audio signal.

10. A method according to claim 9 , further comprising the step of comparing the correlation value and the further correlation value, and wherein the step of determining comprises determining that the mobile device is in proximity to the further microphone if the second audio signal has a higher degree of correlation with the first audio signal than the third audio signal.

11. A method according to claim 1 , further comprising the step of determining an audio fingerprint for the first and second audio signals prior to computing the correlation.

12. A method according to claim 1 , further comprising the step of at least one of normalizing and filtering at least one of the first and second audio signals prior to computing the correlation.

13. A method according to claim 1 , further comprising the step of transforming the first and second audio signals into frequency domain signals prior to computing the correlation.

14. A method according to claim 1 , further comprising the step of applying a time-shift to at least one of the first and second audio signals prior to computing the correlation.

15. A mobile device, comprising:

a microphone arranged to capture a first audio signal from the vicinity of the mobile device;

a communication interface arranged to receive a second audio signal captured from a further microphone;

a processor connected to the microphone and the communication interface, and arranged to compute a correlation value for the first audio signal and second audio signal, and determine whether the mobile device is in proximity to the further microphone using the correlation value.

16. A mobile device according to claim 15 , wherein the further microphone is located at a further mobile device, and the processor is arranged to determine whether the mobile device is in proximity to the further mobile device.

17. A method according to claim 1 , wherein the further microphone is non-mobile and is associated with a predefined location, and the processor is arranged to determine whether the mobile device is in proximity to the predefined location.

18. A mobile device according to claim 15 , wherein the mobile device is a mobile telephone or laptop computer.

19. An indoor positioning system, comprising:

a plurality of fixed microphones, each located in a different room of an indoor environment, and each arranged to capture audio signals from its respective room;

a wireless interface arranged to receive an audio signal from a mobile device having a microphone arranged to capture the audio signal from the vicinity of the mobile device; and

a computing device connected to the plurality of fixed microphones and the wireless interface, and arranged to receive each of the fixed microphone audio signals and the mobile device audio signal, compute a correlation between the mobile device audio signal and each of the fixed microphone audio signals, determine a selected fixed microphone providing the audio signal having the highest degree of correlation with the mobile device audio signal, and outputting the room associated with the selected fixed microphone as the mobile device location.

20. An indoor positioning system according to claim 19 , wherein at least one of the plurality of fixed microphones is located in a landline telephone or telephone conferencing device.