Abstract: A medical device includes an acoustic transducer, which is configured to sense infrasonic waves emitted from a body of a living subject with a periodicity determined by a periodic physiological activity and to output an electrical signal in response to the sensed waves. At least one speaker is configured to output audible sounds in response to an electrical input. Processing circuitry is configured to process the electrical signal so as to generate a frequency-stretched signal in which infrasonic frequency components of the electrical input are shifted to audible frequencies while preserving the periodicity of the periodic physiological activity in the frequency-stretched signal, and to input the frequency-stretched signal to the at least one speaker.

Abstract: Described embodiments include a system (74), including a garment (76), configured to cover at least a portion of a body of a subject, one or more sound transmitters (92) coupled to the garment, configured to transmit sound (128) through the body of the subject, and a plurality of sound detectors (22, 96) coupled to the garment. The sound detectors are configured to detect the transmitted sound following passage of the transmitted sound through the body of the subject, to detect body sound (25) emanating from the body of the subject, and to generate a plurality of sound-detector outputs in response to detecting the transmitted sound and the body sound. The system further includes a processor (98), configured to process the sound-detector outputs, and to generate a processor output in response thereto. Other embodiments are also described.