Hands free sonar for smart phones

Engineers at the University of Washington have developed a sonar-based gesture control system that they claim could enable users to interact with mobile devices by writing or gesturing on any nearby surface or even in mid-air.

The so-called FingerIO system works by using a device's own microphones and speakers to emit an inaudible sound wave. This signal bounces off the users finger, and these "echoes" are recorded by the device's microphones and used to calculate the finger's location in space.

The team claims that the system can accurately track two-dimensional finger movements to within 8mm, which is sufficiently accurate to interact with today's mobile devices. What’s more, because sound waves travel through fabric and do not require a line of sight, users can even interact with a phone inside a front pocket or a smartwatch hidden under a sweater sleeve.

"You can't type very easily onto a smartwatch display, so we wanted to transform a desk or any area around a device into an input surface," explained lead author of a paper on the project Rajalakshmi Nandakumar, a UW doctoral student in computer science and engineering. "I don't need to instrument my fingers with any other sensors - I just use my finger to write something on a desk or any other surface and the device can track it with high resolution."