Microsoft Research has developed a new gesture-based motion controller that makes use of the Doppler effect to detect in-air gestures done around the device. The project is called SoundWave and what’s particularly interesting about it is that it doesn’t need any additional hardware in order to work.

Instead of a Kinect-like sensor bar, SoundWave utilizes the existing speakers and microphone built into a PC or notebook to detect gestures. The speakers emit inaudible tones in the 18 - 22 KHz range. SoundWave then uses the microphone on the same system to pick up these tones as they are bounced back by moving objects, such as a hand. These tones are passed through a detection algorithm and any frequency shifts detected are processed to figure out what the gesture made in front of the system was.