I haven't heard that the life detector uses the principle of sound speed. The life detector is actually a breathing and motion detector. The radar signal transmitter continuously emits electromagnetic signals and scans a certain space, and the receiver continuously receives the reflected signals and performs algorithm processing on the returned signals. If the detected person remains still, the return signal is the same. If the target is moving, the signal is different. By comparing the signals received in different time periods with other algorithms, we can judge whether the target is moving.

Because people's breathing frequency is very low, usually 1 2 times per second, breathing action can be distinguished from other high-frequency actions. The principle of measuring motion is basically the same. The antenna of Supervisory Safety System Company is one of the two kinds of ground penetrating radar antennas of Mars probe designated by NASA, which can capture very weak motion very sensitively, and with powerful algorithm processing, it is the best helper for safety and life-saving departments.