Synchronized mode transition

1. A first device configured to be worn at an ear, the first device comprising a processor configured to:

in a first contextual mode, produce an audio signal based on audio data, wherein active noise cancellation is enabled in the first contextual mode;

in the first contextual mode, exchange a time indication of a first time with a second device; and

at the first time, transition from the first contextual mode to a second contextual mode based on the time indication, wherein the active noise cancellation is disabled in the second contextual mode.

2. The first device of claim 1 , wherein the first contextual mode corresponds to a first operational mode of an active noise cancellation (ANC) filter that is distinct from a second operational mode of the ANC filter corresponding to the second contextual mode.

3. The first device of claim 1 , wherein the second contextual mode corresponds to a quiet mode.

4. The first device of claim 1 , wherein the second contextual mode corresponds to a transparency mode.

5. The first device of claim 1 , wherein the processor is configured to:

based on detecting a first condition of a microphone signal, cause transmission of a change indication of a change from the first contextual mode to the second contextual mode; and

receive an answer to the change indication, wherein the transition from the first contextual mode to the second contextual mode is further based on receiving the answer.

6. The first device of claim 5 , wherein the processor is configured to cause transmission of the time indication concurrently with transmission of the change indication.

7. The first device of claim 5 , wherein the processor is configured to receive the time indication concurrently with receiving the answer.

8. The first device of claim 5 , wherein the processor is configured to detect the first condition based on detecting an environmental noise condition.

9. The first device of claim 5 , wherein the processor is configured to detect the first condition based on determining that environmental noise indicated by the microphone signal remains below a first noise threshold for at least a first threshold time.

10. The first device of claim 5 , wherein the processor is configured to:

based on detecting a second condition of the microphone signal, cause transmission of a second change indication of a change from the second contextual mode to the first contextual mode; and

at a second time, transition from the second contextual mode to the first contextual mode.

11. The first device of claim 10 , wherein the processor is configured to detect the second condition based on determining that environmental noise indicated by the microphone signal remains above a second noise threshold for at least a second threshold time.

12. The first device of claim 10 , wherein the processor is configured to receive a second answer to the second change indication, wherein the transition from the second contextual mode to the first contextual mode is based on receiving the second answer.

13. The first device of claim 10 , wherein the transition from the second contextual mode to the first contextual mode is independent of receiving any answer to the second change indication.

14. The first device of claim 1 , further comprising one or more antennas configured to send to the second device, or receive from the second device, modulated data based on the time indication.

15. The first device of claim 14 , further comprising one or more modems coupled to the one or more antennas, the one or more modems configured to demodulate the modulated data to determine the time indication or generate the modulated data based on the time indication.

16. The first device of claim 1 , further comprising one or more loudspeakers configured to render an anti-noise signal in the first contextual mode.

17. A method comprising:

producing, at a first device in a first contextual mode, an audio signal based on audio data, wherein active noise cancellation is enabled in the first contextual mode;

exchanging, in the first contextual mode, a time indication of a first time with a second device; and

transitioning, at the first device, from the first contextual mode to a second contextual mode at the first time, the transition based on the time indication, wherein the active noise cancellation is disabled in the second contextual mode.

18. The method of claim 17 , wherein the first contextual mode corresponds to a first operational mode of an active noise cancellation (ANC) filter that is distinct from a second operational mode of the ANC filter corresponding to the second contextual mode.

19. The method of claim 17 , wherein the second contextual mode corresponds to a quiet mode.

20. The method of claim 17 , wherein the second contextual mode corresponds to a transparency mode.

21. The method of claim 17 , further comprising:

based on detecting a first condition of a microphone signal, causing transmission of a change indication of a change from the first contextual mode to the second contextual mode; and

receiving, at the first device, an answer to the change indication, wherein transitioning from the first contextual mode to the second contextual mode is further based on receiving the answer.

22. The method of claim 21 , further comprising causing transmission of the time indication concurrently with transmission of the change indication.

23. The method of claim 21 , further comprising receiving the time indication concurrently with receiving the answer.

24. The method of claim 21 , further comprising detecting the first condition based on detecting an environmental noise condition.

25. The method of claim 21 , further comprising detecting the first condition based on determining that environmental noise indicated by the microphone signal remains below a first noise threshold for at least a first threshold time.

26. The method of claim 21 , further comprising:

based on detecting a second condition of the microphone signal, causing transmission of a second change indication of a change from the second contextual mode to the first contextual mode; and

transitioning, at the first device, from the second contextual mode to the first contextual mode at a second time.

27. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to:

produce, in a first contextual mode, an audio signal based on audio data, wherein active noise cancellation is enabled in the first contextual mode;

exchange, in the first contextual mode, a time indication of a first time with a device; and

transition from the first contextual mode to a second contextual mode at the first time, the transition based on the time indication, wherein the active noise cancellation is disabled in the second contextual mode.

28. The non-transitory computer-readable medium of claim 27 , wherein the instructions, when executed by the processor, further cause the processor to exchange the time indication with the device based on detecting an environmental noise condition.

29. The non-transitory computer-readable medium of claim 27 , wherein the second contextual mode corresponds to a quiet mode.

30. An apparatus comprising:

means for producing an audio signal based on audio data, the audio signal produced in a first contextual mode, wherein active noise cancellation is enabled in the first contextual mode;

means for exchanging a time indication of a first time with a device, the time indication exchanged in the first contextual mode; and

means for transitioning from the first contextual mode to a second contextual mode at the first time, the transition based on the time indication, wherein the active noise cancellation is disabled in the second contextual mode.

31. The apparatus of claim 30 , wherein the means for producing, the means for exchanging, and the means for transitioning are integrated in an earphone.

32. The apparatus of claim 30 , wherein the second contextual mode corresponds to a transparency mode.