Step Spy

Fingerprints are not the only biometric traits that set individuals apart. Each person’s walking gait is unique—and it can serve not only as an identifier but also as an indicator of mood and health. A team of researchers has developed remote sensors that analyze footsteps by measuring tiny floor vibrations. They used this technology to identify specific individuals walking through a building and to test a new method of hands-off wellness monitoring.

The way you walk is “a very unique signature of yourself,” says Hae Young Noh, who performed the research as a civil and environmental engineer at Carnegie Mellon University. Gait can reveal “who you are, where you are, what kinds of activities you’re doing, or even your cognitive state.” If hardware sensors detect a pattern of footsteps, software can analyze them to verify an individual’s identity.

And walking patterns can provide more than a simple ID. If somebody starts placing more weight on one side or another, for example, the change in balance might indicate a neurological problem. This information could help doctors monitor seniors and other at-risk people who want to live independently: tracking subjects’ gait could keep tabs on health without directly impinging on their space.

To measure this data-rich signature, Noh, along with electrical and computer engineer Pei Zhang of Carnegie Mellon and their colleagues, wanted to develop portable footstep sensors that would work remotely. The scientists took advantage of the fact that typical walls and floors pick up even faint vibrations from activity in the space they contain.

Sensing vibrations from a mere foot-step requires extremely sharp detectors. “To give you an idea of how sensitive our sensors are: when you sit in the chair a meter away, we put the sensor on the ground,” Zhang says, and “we can sense your heartbeat.”

The ability to conduct this kind of monitoring raises obvious privacy concerns, and the researchers suggest their technology should be used only for consensual health care applications. Such monitoring systems, they note, can help caregivers who need to know when elderly people might be likely to fall. They could also alert children’s hospitals to symptoms of chronic diseases, such as muscular dystrophy, as early as possible. The developers contend that in such cases, footstep sensors would preserve privacy better than, say, a camera.

“This was actually created because of the privacy concerns of the other type of monitoring mechanisms,” Zhang says. And in health-related scenarios, he adds, “I’m willing to trade off a little bit of my data to prevent falls and to detect diseases.”

from Scientific American July, 2020