Apparatus, system and method for detecting physiological motion from audio and multi-modal signals

Methods and apparatus provide for detecting physiological motion with active sound generation. In some versions, a processor may detect breathing and/or substantial body movement. The processor may control generation of a sound signal including a proximity of a user by a speaker coupled to the processor. The processor may control sensing of reflected sound signals through a microphone coupled to the processor. The reflected sound signal is a reflection of a sound signal from a user. The processor may process the reflected sound, such as by a demodulation technique. A processor may detect respiration from the processed reflected sound signal. The sound signal may be produced as a series of tone pairs in a time slot frame, or as a phase-continuous repeating waveform (e.g., a triangle or ramped zigzag) with varying frequencies. Evaluation of the detected motion information may determine sleep state or score, fatigue indication, subject identification, chronic disease monitoring/prediction, and other output param