Method and system for classifying state of a wearable device

1 . A wearable device configured to be fitted to a user, comprising:

a pair of ultrasonic transducers, each transducer configured to emit ultrasonic pulses and receive returned signals corresponding to the emitted ultrasonic pulses;

wherein the pair of ultrasonic transducers have predetermined positions with respect to the wearable device;

wherein the pair of ultrasonic transducers are in a line of sight relationship when the user is in a first state with respect to the wearable device,

wherein the pair of ultrasonic transducers are not in a line of sight relationship when the user is in a second state with respect to the wearable device, and

wherein the pair of ultrasonic transducers are configured to alternately emit ultrasonic pulses; and

at least one processor coupled with the pair of ultrasonic transducers and configured to:

evaluate the returned signals; and

based at least in part on the evaluation, classify the state of the wearable device as being one of the first state and the second state.

2 . The wearable device of claim 1 , wherein classifying the state of the wearable device comprises a determination of whether the wearable device is being worn by the user.

3 . The wearable device of claim 1 , wherein the at least one processor is further configured to adjust behavior of the wearable device based at least in part on the classification.

4 . The wearable device of claim 1 , wherein the at least one processor evaluates the returned signals at least in part by distinguishing reflected echoes corresponding to an ultrasonic pulse emitted by one ultrasonic transducer of the pair of ultrasonic transducers at a given epoch received by the one ultrasonic transducer and opposing transmissions received by one ultrasonic transducer of the pair of ultrasonic transducers that were emitted by another ultrasonic transducer of the pair of ultrasonic transducers at a previous epoch.

5 . The wearable device of claim 4 , wherein the at least one processor further evaluates the returned signals at least in part by determining whether the opposing transmissions were received directly or after reflection.

6 . The wearable device of claim 5 , wherein the at least one processor further evaluates the returned signals at least in part by determining whether a directly received opposing transmission has been attenuated.

7 . The wearable device of claim 4 , wherein the at least one processor further evaluates the returned signals at least in part by determining whether a distance corresponding to a received reflected echo is consistent with an expected position of the user for at least one of the first state and the second state.

8 . The wearable device of claim 4 , wherein the at least one processor further evaluates the returned signals at least in part by determining whether the opposing transmissions were received directly or after reflection and by determining whether a distance corresponding to a received reflected echo is consistent with an expected position of the user for at least one of the first state and the second state.

9 . The wearable device of claim 4 , wherein evaluating the returned signals further includes identifying at least one characteristic of the retuned signals that indicates a transition state between the first state and the second state.

10 . The wearable device of claim 7 , wherein at least one of the pair of ultrasonic transducers has an extended waveguide configured to prevent an object from being positioned at a distance closer than a ringdown blind spot.

11 . The wearable device of claim 1 , wherein the device comprises a headset.

12 . At least one sensor processing unit comprising:

a pair of ultrasonic transducers, each transducer configured to emit ultrasonic pulses and receive returned signals corresponding to the emitted ultrasonic pulses;

wherein the pair of ultrasonic transducers have predetermined positions with respect to a wearable device configured to be fitted to a user;

wherein the pair of ultrasonic transducers are in a line of sight relationship when the user is in a first state with respect to the wearable device,

wherein the pair of ultrasonic transducers are not in a line of sight relationship when the user is in a second state with respect to the wearable device, and

wherein the pair of ultrasonic transducers are configured to alternately emit ultrasonic pulses; and

at least one sensor processor coupled with the pair of ultrasonic transducers and configured to:

evaluate the returned signals; and

based at least in part on the evaluation, classify the state of the wearable device as being one of the first state and the second state.

13 . The sensor processing unit of claim 12 , wherein at least one of the pair of ultrasonic transducers has an extended audio waveguide configured to prevent an object from being positioned at a distance closer than a ringdown blind spot.

14 . A method for classifying state of a wearable device, wherein the wearable device is configured to be fitted to a user, comprising:

alternately emitting ultrasonic pulses from a pair of ultrasonic transducers, each transducer configured to emit ultrasonic pulses and receive returned signals corresponding to the emitted ultrasonic pulses;

wherein the pair of ultrasonic transducers have predetermined positions with respect to the wearable device;

wherein the pair of ultrasonic transducers are in a line of sight relationship when the user is in a first state with respect to the wearable device,

wherein the pair of ultrasonic transducers are not in a line of sight relationship when the user is in a second state with respect to the wearable device;

evaluating retuned signals received by the pair of ultrasonic transducers; and

classifying the state of the wearable device as being one of the first state and the second state based at least in part on the evaluation.

15 . The method of claim 14 , wherein classifying the state of the wearable device comprises a determination of whether the wearable device is being worn by the user.

16 . The method of claim 14 , further comprising adjusting behavior of the wearable device based at least in part on the classification.

17 . The method of claim 14 wherein evaluating the returned signals is based at least in part by distinguishing reflected echoes corresponding to an ultrasonic pulse emitted by one ultrasonic transducer of the pair of ultrasonic transducers at a given epoch received by the one ultrasonic transducer and opposing transmissions received by one ultrasonic transducer of the pair of ultrasonic transducers that were emitted by another ultrasonic transducer of the pair of ultrasonic transducers at a previous epoch.

18 . The method of claim 17 , wherein evaluating the returned signals is based at least in part on determining whether the opposing transmissions were received directly or after reflection.

19 . The method of claim 17 , wherein evaluating the returned signals is based at least in part on determining whether a directly received opposing transmission has been attenuated.

20 . The method of claim 17 , wherein evaluating the returned signals is based at least in part on determining whether a distance corresponding to a received reflected echo is consistent with an expected position of the user for at least one of the first state and the second state.

21 . The method of claim 17 , wherein evaluating the returned signals is based at least in part on determining whether the opposing transmissions were received directly or after reflection and on determining whether a distance corresponding to a received reflected echo is consistent with an expected position of the user for at least one of the first state and the second state.

22 . The method of claim 17 , wherein evaluating the returned signals further includes identifying at least one characteristic of the retuned signals that indicates a transition state between the first state and the second state.