Determining earpiece presence at a user ear

1. A computer-implemented method, comprising:

playing, with an audio processing device, a source audio signal, including causing the source audio signal to be audibly output by an electroacoustic transducer of a user earpiece;

recording, with the audio processing device, an aural signal using same said electroacoustic transducer of the user earpiece concurrent with the playing of the source audio signal by the electroacoustic transducer;

determining values of one or more features of the aural signal that indicate, as a result of playing the source audio signal, a characteristic of a space in which the user earpiece is located;

comparing the determined values of the one or more features of the aural signal with defined values; and

based on a result of comparing the determined values of the one or more features of the aural signal with the defined values, determining whether the user earpiece is located at a user's ear.

2. The computer-implemented method of claim 1 , further comprising determining whether to perform a specified action based on whether the user earpiece is located at the user's ear.

3. The computer-implemented method of claim 1 , further comprising:

determining, at a first time, that the user earpiece is located at the user's ear;

determining, at a second time after the first time, that the location of the user earpiece is changed from being at the user's ear to not being at the user's ear; and

in response to determining that the location of the user earpiece is changed from being at the user's ear to not being at the user's ear, performing a specified action.

4. The computer-implemented method of claim 3 , wherein the specified action comprises at least one of playing a media file, pausing the media file, stopping the media file, resuming play of a paused media file, activating an electronic display, adjusting a brightness setting of a backlight of the electronic display, transitioning a device into a locked mode, transitioning a device out of a locked mode, initiating a telephone call, ending a telephone call, launching an application, or closing an application.

5. The computer-implemented method of claim 1 , further comprising:

determining, at a first time, that the user earpiece is not located at the user's ear;

determining, at a second time after the first time, that the location of the user earpiece is changed from being not at the user's ear to being at the user's ear; and

in response to determining that the location of the user earpiece is changed from being not at the user's ear to being at the user's ear, performing a specified action.

6. The computer-implemented method of claim 5 , wherein the specified action comprises at least one of playing a media file, pausing the media file, stopping the media file, resuming play of a paused media file, activating an electronic display, adjusting a brightness setting of a backlight of the electronic display, transitioning a device into a locked mode, transitioning a device out of a locked mode, initiating a telephone call, ending a telephone call, launching an application, or closing an application.

7. The computer-implemented method of claim 1 , further comprising repeatedly determining whether the user earpiece is located at the user's ear over a period of time to monitor for a change in location of the user earpiece from (i) not being at the user's ear to being at the user's ear or (ii) from being at the user's ear to not being at the user's ear.

8. The computer-implemented method of claim 1 , wherein the one or more features of the aural signal comprise an impulse response of an acoustic echo of the space in which the user earpiece is located.

9. The computer-implemented method of claim 1 , wherein the defined values comprise a model that characterizes a space in the user's ear.

10. The computer-implemented method of claim 1 , wherein the defined values are determined based at least in part on previously determined values of the one or more features of aural signals that resulted from playing the source audio signal or another audio signal when the user earpiece was determined to be located at the user's ear.

11. The computer-implemented method of claim 1 , wherein the defined values are determined based at least in part on values of the one or more features of aural signals that resulted from playing the source audio signal or another audio signal when the user earpiece was located at the respective ears of one or more users other than the user.

12. The computer-implemented method of claim 1 , wherein the earpiece comprises a headphone or an earbud.

13. The computer-implemented method of claim 1 , wherein the audio processing device comprises a portable digital media player, a smartphone, a tablet computing device, a notebook computing device, a desktop computing device, or a wearable computing device.

14. The computer-implemented method of claim 1 , wherein playing the source audio signal comprises playing white noise.

15. The computer-implemented method of claim 1 , wherein playing the source audio signal comprises playing a song or spoken content to the user of the audio processing device.

16. The computer-implemented method of claim 1 , wherein playing the source audio signal comprises playing sound having an average frequency that is greater than 20 kilohertz, such that the played sound is above a normal frequency limit for human hearing.

17. The computer-implemented method of claim 1 , wherein determining the values of the one or more features of the aural signal that indicate the characteristic of the space in which the user earpiece is located includes determining the values based on a change between said source audio signal that is audibly output by the electroacoustic transducer and the aural signal that is concurrently recorded using same said electroacoustic transducer.

18. A computing system, comprising:

one or more processors; and

one or more computer-readable media having instructions stored thereon that, when executed by the one or more processors, cause performance of operations that comprise:

playing, with an audio processing device, a source audio signal, including causing the source audio signal to be audibly output by an electroacoustic transducer of a user earpiece;

recording, with the audio processing device, an aural signal using same said electroacoustic transducer of the user earpiece concurrent with the playing of the source audio signal by the electroacoustic transducer;

determining values of one or more features of the aural signal that indicate, as a result of playing the source audio signal, a characteristic of a space in which the user earpiece is located;

comparing the determined values of the one or more features of the aural signal with defined values; and

based on a result of comparing the determined values of the one or more features of the aural signal with the defined values, determining whether the user earpiece is located at a user's ear.

19. One or more non-transitory computer-readable media that have instructions stored thereon that, when executed by one or more processors, cause performance of operations that comprise:

playing, with an audio processing device, a source audio signal, including causing the source audio signal to be audibly output by an electroacoustic transducer of a user earpiece;

recording, with the audio processing device, an aural signal using same said electroacoustic transducer of the user earpiece concurrent with the playing of the source audio signal by the electroacoustic transducer;

determining values of one or more features of the aural signal that indicate, as a result of playing the source audio signal, a characteristic of a space in which the user earpiece is located;

comparing the determined values of the one or more features of the aural signal with defined values; and

based on a result of comparing the determined values of the one or more features of the aural signal with the defined values, determining whether the user earpiece is located at a user's ear.