Systems and methods for using a speaker as a microphone in a mobile device

1. A mobile device comprising:

an enclosure adapted such that the enclosure is readily transported by a user of the mobile device;

a speaker associated with the enclosure for generating sound;

a capacitive microphone; and

a controller within the enclosure, communicatively coupled to the speaker and the capacitive microphone, and configured to:

receive a first signal from the speaker, the first signal induced at least in part by sound incident on the speaker other than sound generated by the speaker;

receive a second signal from the capacitive microphone, the second signal induced by sound incident on the capacitive microphone;

process at least one of the first signal and the second signal to determine at least one characteristic of sound incident upon at least one of the speaker and the capacitive microphone; and

select at least one of the capacitive microphone and the speaker as a signal source for incident sound based on the characteristic.

2. The mobile device of claim 1 , wherein the first signal is a voltage signal.

3. The mobile device of claim 1 , wherein the controller is further configured to:

operate the speaker in a first mode wherein the controller communicates an output signal to the speaker for generating sound; and

operate the speaker in a second mode wherein the controller deactivates the speaker from emitting sound and receives the first signal induced by sound incident on the speaker other than sound generated by the speaker and processes the first signal.

4. The mobile device of claim 1 , wherein the controller is further configured to transition the mobile device from a low-power state to a high-power state responsive to a determination that the first signal induced by sound incident on the speaker corresponds to stimulus for transitioning the mobile device from a low-power state to a high-power state.

5. The mobile device of claim 1 , wherein the controller is further configured to:

perform frequency equalization on the first signal and the second signal in order to account for differences in the frequency responses to sound incident upon the speaker and the capacitive microphone.

6. The mobile device of claim 1 , wherein the at least one characteristic comprises a sound level.

7. The mobile device of claim 1 , wherein the controller is further configured to, based on sound incident at the speaker and sound incident on the capacitive microphone, perform beamforming to determine spatial selectivity of sounds incident on the mobile device.

8. The mobile device of claim 1 , wherein the speaker is a dynamic speaker.

9. A method comprising:

generating, by a speaker within an enclosure adapted such that the enclosure is readily transported by a user of a mobile device, a first signal, the first signal induced at least in part by sound incident on the speaker other than sound generated by the speaker;

receiving a second signal from a capacitive microphone within the enclosure, the second signal induced by sound incident on the capacitive microphone;

processing at least one of the first signal and the second signal to determine at least one characteristic of sound incident upon at least one of the speaker and the capacitive microphone; and

selecting at least one of the capacitive microphone and the speaker as a signal source for incident sound based on the characteristic.

10. The method of claim 9 , wherein the first signal is a voltage signal.

11. The method of claim 9 , further comprising:

operating the speaker in a first mode wherein a controller within the enclosure communicates an output signal to the speaker for generating sound; and

operating the speaker in a second mode wherein the controller deactivates the speaker from emitting sound and receives the first signal induced by sound incident on the speaker other than sound generated by the speaker and processes the signal.

12. The method of claim 9 , further comprising transitioning the mobile device from a low-power state to a high-power state responsive to a determination that the first signal induced by sound incident on the speaker corresponds to stimulus for transitioning the mobile device from a low-power state to a high-power state.

13. The method of claim 9 , further comprising:

performing frequency equalization on the first signal and the second signal in order to account for differences in the frequency responses to sound incident upon the speaker and the capacitive microphone.

14. The method of claim 9 , wherein the at least one characteristic comprises a sound level.

15. The method of claim 9 , further comprising:

based on sound incident at the speaker and sound incident on the capacitive microphone, performing beamforming to determine spatial selectivity of sounds incident on the mobile device.

16. The method of claim 9 , wherein the speaker is a dynamic speaker.

17. The method of claim 9 , wherein selecting at least one of the capacitive microphone and the speaker as a signal source for incident sound based on the characteristic comprises selecting at least one of the capacitive microphone and the speaker as a signal source based on a volume of sound incident on at least one of the capacitive microphone and the speaker and an operational mode of the mobile device.

18. The mobile device of claim 1 , wherein the controller is further configured to select at least one of the capacitive microphone and the speaker as a signal source for incident sound based on the characteristic comprises selecting at least one of the capacitive microphone and the speaker as a signal source based on a volume of sound incident on at least one of the capacitive microphone and the speaker and an operational mode of the mobile device.