The Economist’s Technology Quarterly describes how mobile phone microphones are being used as versatile sensors with myriad health applications. Examples follow:
1. Professor Tanzeem Choudhury of Cornell has created StressSense to capture and analyze voice characteristics such as amplitude and frequency. Her team concluded that “it is feasible to implement a computationally demanding stress-classification system on off-the-shelf smartphones”.
2. BeWell’s sleep-tracking feature, also by Professor Choudhury, determines whether the phone’s user is awake or not by analyzing usage, light and sound levels, and charging habits. Physical activity is monitored using built-in accelerometers for motion-detection. Social activity is measured by sounds that indicate that the user is talking to someone, either in person or over the phone.
3. Professor John Stankovic of the University of Virginia uses microphones to capture heartbeats. Researchers in his group use earphones modified with accelerometers and additional microphones that detect the pulse in arteries in the wearer’s ear. This makes it possible to collect physical state information, including heart rate and activity level, which is transmitted to the smartphone via the audio jack.
4. Shwetak Patel of the University of Washington uses a smartphone to measure lung function when users blow on its microphone. His team has developed the SpiroSmart app, which simulates a digital spirometer, to measure the volume of air a person can expel from his or her lungs. Spirometers help doctors better understand the health status of patients with conditions like asthma, chronic obstructive pulmonary disease and cystic fibrosis.