An Ultrasonic Approach to Proximity Detection

Mobile phones must detect when a device is held close to the user's face to listen to a call, typically disabling touchscreen functionality (which also saves power) to avoid misinterpreting an accidental touch of the screen as a command or gesture. Optical sensing, currently the most widely-used proximity-detection strategy, requires extra hardware (the sensor) and unsightly holes in the phone's faceplate. New ultrasound-based proximity-detection software relies on the phone's existing earpiece and microphone. With the ultrasound approach, phone designers can eliminate the sensor and achieve reliable proximity detection - without the holes.

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