PIEZOELECTRIC HEART RATE SENSING FOR WEARABLE DEVICES OR MOBILE DEVICES
Embodiments relate generally to electrical and electronic hardware, computer software, wired and wireless network communications, and wearable computing devices for sensing health and wellness-related information. More specifically, disclosed is a physiological sensor using, for example, acoustic signal energy to determine physiological characteristics, such as a heart rate, the physiological sensor being disposed in a wearable device (or carried device). In one embodiment, a physiological signal generator is disposed substantially in a wearable housing. At least a portion of a skin surface microphone (“SSM”) including a piezoelectric sensor is configured to receive acoustic signals. The wearable housing is configured to position the SSM to receive an acoustic signal originating from human tissue. The physiological signal generator is configured to receive a piezoelectric signal based on an acoustic signal, and to generate a physiological signal including data representing a heartbeat or heart rate.
1 . An apparatus comprising:
a skin surface microphone (“SSM”) comprising:
a piezoelectric sensor configured to receive acoustic signals and generate piezoelectric signals;
a wearable housing including the SSM, the wearable housing configured to position the SSM to receive an acoustic signal originating from human tissue; and
a physiological signal generator configured to receive a piezoelectric signal based on the acoustic signal, and the physiological signal generator being configured further to generate a physiological signal including data representing a heartbeat.
2 . The apparatus of claim 1 , wherein the physiological signal generator is further configured to generate the heart rate signal based on the heartbeat.
3 . The apparatus of claim 2 , wherein the acoustic signal is generated either by blood vessel pulsation or a human heart, or both.
4 . The apparatus of claim 1 , further comprising:
a heart rate processor configured to determine the heart rate; and
an anomaly detector configured to reduce anomalous portions of the acoustic signal that are anomalous to a range of acoustic characteristics associated with the heartbeat.
5 . The apparatus of claim 1 , wherein a portion of the wearable housing is configured to position a surface of the SSM adjacent the surface of the human tissue, a portion of the SSM being formed external to a surface of the wearable housing to contact human tissue.
6 . The apparatus of claim 1 , wherein a portion of the piezoelectric sensor is formed external to a surface of the wearable housing, the portion of the piezoelectric sensor being configured to contact the human tissue.
7 . The apparatus of claim 1 , wherein the SSM is encapsulated in the wearable housing.
8 . The apparatus of claim 7 , wherein the wearable housing further comprising:
an encapsulant having an acoustic impedance value in a range of acoustic impedance values including a value of acoustic impedance for the human tissue.
9 . The apparatus of claim 1 , wherein the SSM further comprising:
a coupler having an acoustic impedance equivalent to the human tissue, at least a first surface of the coupler being formed external to a surface of the wearable housing and second surface of the coupler being configured to communicate the acoustic signal from the first surface of the coupler to the piezoelectric sensor.
10 . The apparatus of claim 1 , further comprising:
a piezoelectric signal characterizer configured characterize portions of the piezoelectric signal; and
an anomalous signal filter to identify a subset of the portions of the piezoelectric signal anomalous to a range of acoustic characteristics associated with the heartbeat.
11 . The apparatus of claim 10 , wherein the anomalous signal filter is configured to deemphasize the subset of the portions of the piezoelectric signal based on context data.
12 . The apparatus of claim 11 , wherein the context data includes one or more of age data, location data, and motion data.
13 . The apparatus of claim 10 , further comprising:
a mask generator configured to mask time intervals in which sampling is suppressed; and
a window interval determinator configure to determine other time intervals in which the portions of the piezoelectric signal include data representing the heartbeat.
14 . The apparatus of claim 1 , further comprising:
a heartbeat identification determinator configured to identify the heartbeat and to identify subsequent heartbeats to determine a heart rate.
15 . A method comprising:
receiving an acoustic signal originating from human tissue, the acoustic signal associated with a physiological characteristic;
generating a piezoelectric signal responsive to the acoustic signal;
determining a portion of the piezoelectric signal associated with a heartbeat derived from the acoustic signal;
identifying a heart rate at a processor based on the portion of the piezoelectric signal; and
causing generation of data representing the heart rate for presentation.
16 . The method of claim 15 , wherein receiving the acoustic signal originating from the human tissue comprises:
receiving the acoustic signal via a coupler configured to communicate the acoustic signal from a surface of the human tissue to a piezoelectric sensor, the coupler having an acoustic impedance equivalent to the human tissue.
17 . The method of claim 15 , further comprising:
deemphasizing a portion of the piezoelectric signal based on context data.
18 . The method of claim 15 , further comprising:
transmitting data representing the heart rate to a device.
19 . A wearable device comprising:
a skin surface physiological device comprising:
a piezoelectric sensor configured to receive signals and generate piezoelectric signals;
a housing including the skin surface physiological device, the housing configured to position the skin surface physiological device to receive a signal originating from human tissue; and
a physiological signal generator configured to receive a piezoelectric signal based on the signal, and the physiological signal generator being configured further to generate a physiological signal including data representing a heartbeat.
20 . The wearable device of claim 19 , wherein the piezoelectric sensor comprises:
an acoustic sensor.