Abstract: Examples of systems and methods are described for detecting heart beats of a subject. The systems and methods may be based on motion of the subject due to cardiac activity, and may operate without contact with the subject. Example systems may provide an interrogation signal to the subject. Reflected signals from the subject are incident on a microphone array. The reflected signals may be processed and beamformed using a set of beamforming weights. The beamforming weights may be selected in a manner to reduce components of the reflected signals due to breathing motion of the subject while increasing the relative contribution of the reflected signals due to cardiac activity. The beamformed signal may provide a waveform indicative of heart beats. Inter-beat intervals, heart rates, and/or other health metrics may be calculated based on the waveform.