is a combined hard- and software system designed to locate and track multiple unmodified mobile devices on any regular table using passive acoustic sensing.

Barely audible sound pulses are emitted from mobile devices, picked up by four microphones located in the corners of the surface and processed in a low-latency pipeline to extract position data. It has an average positional accuracy and precision of about 3 cm on a table of 1 m x 2 m size.

The prototype set-up consists of the following:

• TTT Sine Emitter Android applicaton which lets a smartphone emit a modified sine signal
• Emitter Locator Linux application using the ALSA sound library which locates the emitted signals

• 4 t.bone EM700 microphones
• Behringer U-PHORIA UMC404 sound-card
• notebook with an Intel Core i7-2630QM 2Ghz CPU.
• Nexus 4 devices as sound emitters.

For details about the system about the initial setup, the parameters, calibration of the system or know issues, please refer to the Wiki.