Methods and apparatus for detecting motion noise and for removing motion noise from physiological signals
A monitoring apparatus includes a housing that is configured to be attached to a body of a subject. The housing includes a sensor region that is configured to contact a selected area of the body of the subject when the housing is attached to the body of the subject. The sensor region is contoured to matingly engage the selected body area. The apparatus includes at least one physiological sensor that is associated with the sensor region and that detects and/or measures physiological information from the subject and/or at least one environmental sensor associated with the sensor region that is configured to detect and/or measure environmental information. The sensor region contour stabilizes the physiological and/or environmental sensor(s) relative to the selected body area such that subject motion does not impact detection and/or measurement efforts of the sensor(s).
1. A method of at least partially removing motion artifacts from physiological signals produced by a physiological sensor of a wearable device, wherein the physiological sensor includes at least one optical emitter and at least one optical detector, the method comprising:
detecting light emitted by the at least one optical emitter that is scattered by a body of a subject wearing the wearable device and producing a physiological information signal therefrom via the at least one optical detector;
detecting light emitted by the at least one optical emitter that is scattered by a light regulating region of the wearable device as a result of movement of the wearable device and producing a motion noise information signal via the at least one optical detector, wherein the light regulating region is configured to block light at one or more selected wavelengths from reaching the body of the subject; and
processing the physiological information signal and the motion noise information signal via at least one processor associated with the wearable device to at least partially remove unwanted motion artifacts from the physiological information signal.
2. The method of claim 1 , wherein the light scattered by the body of the subject and the light scattered by the light regulating region of the wearable device travel through separate first and second regions of the wearable device.
3. The method of claim 2 , wherein the first region of the wearable device is configured to guide light between the sensor and the body of the subject.
4. The method of claim 1 , wherein the light regulating region of the wearable device comprises one of a flap, lever, or membrane that moves in response to subject motion.
5. The method of claim 1 , wherein the light regulating region of the wearable device moves in response to subject motion.
6. The method of claim 1 , wherein the light regulating region of the wearable device comprises an optically reflecting material.
7. The method of claim 1 , wherein processing the physiological information signal and the motion noise information signal comprises subtracting the motion noise information signal from the physiological information signal.
8. The method of claim 1 , wherein the steps of detecting light emitted by the at least one optical emitter that is scattered by the body of the subject and detecting light emitted by the at least one optical emitter that is scattered by the light regulating region of the wearable device are performed substantially simultaneously.
9. A motion noise sensor configured to be attached to a body of a subject, the motion noise sensor comprising:
at least one optical emitter;
at least one optical detector; and
a light regulating region configured to block light from the at least one optical emitter at one or more selected wavelengths from reaching the body of the subject, wherein the light regulating region is configured to move in response to subject motion;
wherein the at least one optical detector is configured to detect light scattered by the light regulating region.
10. The motion noise sensor of claim 9 , wherein the light regulating region comprises one of a flap, lever, or membrane that moves in response to subject motion.
11. A wearable apparatus, comprising:
a physiological sensor comprising at least one optical emitter and at least one optical detector; and
a light regulating region configured to block light from the at least one optical emitter at one or more selected wavelengths from reaching the body of the subject,
wherein the at least one optical detector is configured to detect light from the at least one optical emitter that is scattered by a body of a subject wearing the wearable apparatus and to produce a physiological information signal therefrom, and
wherein the at least one optical detector is configured to detect light from the at least one optical emitter that is scattered by the light regulating region as a result of movement of the wearable apparatus and to produce a motion noise information signal therefrom.
12. The wearable apparatus of claim 11 , wherein the at least one optical detector comprises at least two optical detectors.
13. The wearable apparatus of claim 11 , further comprising at least one processor configured to process the physiological information signal and the motion noise information signal to at least partially remove unwanted motion artifacts from the physiological information signal.
14. The wearable apparatus of claim 11 , wherein the light regulating region is configured to move in response to subject motion.
15. The wearable apparatus of claim 11 , wherein the light regulating region comprises one of a flap, lever, or membrane that moves in response to subject motion.
16. The wearable apparatus of claim 11 , wherein the wearable apparatus is an earbud configured to be positioned within an ear of the subject.
17. The wearable apparatus of claim 11 , wherein the wearable apparatus is a headset configured to be attached at or near an ear of the subject.
18. The wearable apparatus of claim 11 , wherein the wearable apparatus is configured to be attached to a limb, a nose, an earlobe, and/or a digit of the subject.
19. The wearable apparatus of claim 11 , wherein the light scattered by the body of the subject and the light scattered by the light regulating region travel through separate first and second regions of the wearable device.
20. The wearable apparatus of claim 19 , wherein the first region of the wearable device is configured to guide light between the sensor and the body of the subject.