Wearable device and signal processing method

1 . A wearable device, comprising:

a sound producing device, a first sound sensing device, a second sound sensing device and a signal processing circuit;

wherein the sound producing device produces a front radiating wave and a back radiating wave while producing a sound;

wherein the first sound sensing device is disposed on a first nodal position corresponding to the sound producing device, and the second sound sensing device is disposed on a second nodal position corresponding to the sound producing device;

wherein on the first and second nodal positions, the front radiating wave and the back radiating wave cancel each other;

wherein the signal processing circuit comprises a discrepancy estimator;

wherein the discrepancy estimator is configured to estimate a discrepancy between the front radiating wave and the back radiating wave produced by the sound producing device and generate a discrepancy estimate.

2 . The wearable device of claim 1 , comprising:

a first port and a second port;

wherein the front radiating wave propagates outward via the first port and the back radiating wave propagates outward via the second port.

3 . The wearable device of claim 1 ,

wherein the first sound sensing device is configured to receive a voice from a user;

wherein the second sound sensing device is configured to receive an ambient sound from an ambient.

4 . The wearable device of claim 1 ,

wherein the wearable device produces the sound toward an open field when a user wears the wearable device.

5 . The wearable device of claim 1 ,

wherein the wearable device is an earbud or a smart glass.

6 . The wearable device of claim 1 ,

wherein the sound producing device comprises an air pulse generating device;

wherein the sound producing device produces the sound by generating a plurality of air pulses at an ultrasonic pulse rate.

7 . A wearable device, comprising:

a sound producing device, a sound sensing device and a signal processing circuit;

wherein the signal processing circuit receives a sensed signal produced by the sound sensing device;

wherein the signal processing circuit performs an operation on the sensed signal and produces a cleaned ambient signal;

wherein the operation is configured to mitigate a sound signal component corresponding to a sound produced by the sound producing device;

wherein the signal processing circuit comprises a discrepancy estimator;

wherein the discrepancy estimator is configured to estimate a discrepancy between a front radiating wave and a back radiating wave produced by the sound producing device and generate a discrepancy estimate.

8 . The wearable device of claim 7 ,

wherein the wearable device produces the sound toward an open field when a user wears the wearable device.

9 . The wearable device of claim 7 ,

wherein the signal processing circuit removes the sound signal component from the sensed signal and produces the cleaned ambient signal.

10 . The wearable device of claim 7 ,

wherein the signal processing circuit subtracts the discrepancy estimate from the sensed signal to produce the cleaned ambient signal.

11 . The wearable device of claim 7 ,

wherein the discrepancy estimator generates the discrepancy estimate according to a driving signal for the sound producing device.

12 . The wearable device of claim 7 ,

wherein the discrepancy estimator corresponds to a transfer function related to a difference between a first transfer function and a second transfer function;

wherein the first transfer function corresponds to a front channel from a front side of the sound producing device to the sound sensing device;

wherein the second transfer function corresponds to a back channel from a back side of the sound producing device to the sound sensing device.

13 . The wearable device of claim 7 ,

wherein the signal processing circuit comprises an anti-ambient block;

wherein the anti-ambient block produces an anti-ambient signal according to the cleaned ambient signal;

wherein a driving signal for the sound producing device comprises the anti-ambient signal.

14 . The wearable device of claim 7 ,

wherein the signal processing circuit comprises a digital IIR (Infinite Impulse Response) filter.

15 . The wearable device of claim 7 ,

wherein the sound producing device comprises an air pulse generating device;

wherein the sound producing device produces the sound by generating a plurality of air pulses at an ultrasonic pulse rate.

16 . A wearable device, comprising:

a sound producing device, a sound sensing device and a signal processing circuit;

wherein the signal processing circuit receives a sensed signal produced by the sound sensing device;

wherein the signal processing circuit performs an operation on the sensed signal and produces a cleaned ambient signal;

wherein the operation is configured to mitigate a sound signal component corresponding to a sound produced by the sound producing device;

wherein the signal processing circuit comprises a feedback loop with a forward block and a feedback block;

wherein the feedback block has a transfer function related to a difference between a first transfer function and a second transfer function;

wherein the first transfer function corresponds to a front channel from a front side of the sound producing device to the sound sensing device;

wherein the second transfer function corresponds to a back channel from a back side of the sound producing device to the sound sensing device.

17 . The wearable device of claim 16 ,

wherein the signal processing circuit comprises a subtractor;

wherein the subtractor subtracts an output from the feedback block from a sensed signal from the sound sensing device.

18 . A wearable device, comprising:

a sound producing device and a signal processing circuit;

a first sound sensing device, producing a first sensed signal; and

a second sound sensing device, producing a second sensed signal;

wherein the signal processing circuit receives the first sensed signal and the second sensed signal;

wherein the signal processing circuit performs an equalizing operation on the first sensed signal and the second sensed signal, to mitigate a sound signal component and produce a cleaned ambient signal;

wherein the sound signal component corresponds to a sound produced by the sound producing device.

19 . The wearable device of claim 18 ,

wherein the signal processing circuit performs a subtraction operation on the first and second sensed signals, to capture a voice signal.

20 . A wearable device, comprising:

a sound producing device, a sound sensing device and a signal processing circuit;

wherein the signal processing circuit receives a sensed signal produced by the sound sensing device;

wherein the signal processing circuit performs an operation on the sensed signal and produces a cleaned ambient signal;

wherein the operation is configured to mitigate a sound signal component corresponding to a sound produced by the sound producing device;

wherein the signal processing circuit obtains a difference transfer function between a first transfer function and a second transfer function;

wherein the first transfer function corresponds to a front channel from a front side of the sound producing device to the sound sensing device;

wherein the second transfer function corresponds to a back channel from a back side of the sound producing device to the sound sensing device.

21 . The wearable device of claim 20 ,

wherein the signal processing circuit is controlled to obtain the difference transfer function.

22 . The wearable device of claim 21 , comprising:

a sensor, configured to detect whether the wearable device is mounted on a user;

wherein the signal processing circuit obtains the difference transfer function when the sensor detects the wearable device is mounted.

23 . A signal processing method applied in a signal processing circuit disposed within a wearable device, the signal processing method comprising:

receiving a sensed signal from a sound sensing device disposed within the wearable device; and

performing an operation on the sensed signal, to mitigate a sound signal component corresponding to a sound produced by a sound producing device disposed within the wearable device, and producing a cleaned ambient signal;

wherein the wearable device produces the sound toward an open field when a user wears the wearable device;

wherein the step of performing the operation on the sensed signal to mitigate the sound signal component further comprises:

obtaining a difference transfer function between a first transfer function and a second transfer function;

obtaining a discrepancy estimate according to the difference transfer function and a driving signal for the sound producing device; and

removing the discrepancy estimate from the sensed signal to produce the cleaned ambient signal;

wherein the first transfer function corresponds to a front channel from a front side of the sound producing device to the sound sensing device;

wherein the second transfer function corresponds to a back channel from a back side of the sound producing device to the sound sensing device.

24 . A signal processing method applied in a signal processing circuit disposed within a wearable device, the signal processing method comprising:

receiving a sensed signal from a sound sensing device disposed within the wearable device; and

performing an operation on the sensed signal, to mitigate a sound signal component corresponding to a sound produced by a sound producing device disposed within the wearable device, and producing a cleaned ambient signal;

wherein the wearable device produces the sound toward an open field when a user wears the wearable device;

wherein the step of performing the operation on the sensed signal to mitigate the sound signal component further comprises:

receiving a first sensed signal from a first sound sensing device and a second sensed signal from a second sound sensing device;

performing an equalizing operation on the first sensed signal and producing an equalized signal; and

mitigating the sound signal component according to the equalized signal.

25 . A signal processing method applied in a signal processing circuit disposed within a wearable device, the signal processing method comprising:

receiving a sensed signal from a sound sensing device disposed within the wearable device; and

performing an operation on the sensed signal, to mitigate a sound signal component corresponding to a sound produced by a sound producing device disposed within the wearable device, and producing a cleaned ambient signal;

wherein the wearable device produces the sound toward an open field when a user wears the wearable device;

wherein the step of performing the operation on the sensed signal to mitigate the sound signal component further comprises:

obtaining a ratio of transfer function of a first transfer function and a second transfer function;

receiving a first sensed signal from a first sound sensing device and a second sensed signal from a second sound sensing device;

performing an equalizing operation on the first sensed signal according to the ratio of transfer function and producing an equalized signal; and

combining the equalized signal and the second sensed signal, to mitigate the sound signal component;

wherein the first transfer function corresponds to a first channel from the sound producing device to the first sound sensing device;

wherein the second transfer function corresponds to a second channel from the sound producing device to the second sound sensing device.