Detecting breathing in babies has an extra wrinkle: the movement of their chests is so tiny that the smart speaker needs to know exactly where the babies are to be able to “see” them breathing. “The breathing signal is so weak that we can’t just look for a change in the overall signal we get back,” Wang said. “We needed a way to scan the room and pinpoint where the baby is to maximize changes in the white noise signal. Our algorithm takes advantage of the fact that smart speakers have an array of microphones that can be used to focus in the direction of the infant’s chest. It starts listening for changes in a bunch of potential directions, and then continues the search toward the direction that gives the clearest signal.” - scienceblog.com