The technique, called CovertBand, looks beyond the obvious possibility of using a microphone-equipped device for eavesdropping. It explores how devices with audio inputs and outputs can be turned into echo-location devices capable of calculating the positions and activities of people in a room.

In a paper [PDF] titled "CovertBand: Activity Information Leakage using Music," Rajalakshmi Nandakumar, Alex Takakuwa, Tadayoshi Kohno, and Shyamnath Gollakota describe a way to transmit acoustic pulses in the 18‑20 kHz range, masked by music, from the speaker and tracking sound reflected by the human body using microphones