Drones can determine the shape of a room by listening
(PHYSorg.com Mathematics)

Imagine a loudspeaker is placed in a room with a few microphones. When the loudspeaker emits a sound impulse, the microphones receive several delayed responses as the sound reverberates from each wall in the room. These first-order echoes-heard after sound impulses have bounced only once on a wall-then bounce back from each wall to create second-order echoes and so on.