Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room’s response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? In our paper, Acoustic Echoes Reveal Room Shape, which is to appear at the Proceedings of the National Academy of Sciences (PNAS), we present algorithms that reconstruct the full three-dimensional geometry of the room from a single sound emission, and with an arbitrary geometry of the microphone array. Besides answering a basic question about the inverse problem of room acoustics, our results find applications in areas such as architectural acoustics, indoor localization, virtual reality and audio forensics.