Overclocked smartwatch sensor uses vibrations to sense gestures, objects, and locations

by admin November 21, 2016 at 10:13 pm

Just from patterns of motion, your smart devices know when you’re walking, when you’re riding a bike, and when you lift your wrist to check the time. But it turns out they can also tell when you snap or make a fist, or whether you’re holding a smartphone or steering wheel. All they have to do is listen a little harder — well, about 100 times harder, actually.

Researchers from Carnegie Mellon University created a system called ViBand that supercharges an ordinary smartwatch’s accelerometer, allowing it to sense incredibly tiny variations in vibration frequency. That could be the thrum of an engine, the note being tuned on a guitar, or the slight differences apparent when you move your hand in different ways.

The secret lies in the specs of the accelerometer itself. Normally, they sample motion somewhere around 20-100 times per second — more than enough to tell whether the user is walking or running, for instance.

But CMU’s Chris Harrison and his colleagues noticed something.

viband_diagram“Right there on the data sheet, it says ‘maximum speed 4,000 Hz,’” said Harrison in an interview with TechCrunch. It was capable of polling motion more than a hundred times faster than any smartphone was telling it to. “We saw that and said hmm, bet there’s some interesting stuff there.”

Sure enough, there was. Even when propagated through “a water-filled sack of bones,” as Harrison described the body, just about everything produces a unique high-frequency vibration pattern, a sort of acoustic signature that can be used to identify it almost immediately.