Non contact ultrasound stethoscope

Abstract

Heartbeat and respiration are very important vital signs that indicate health and psychological states of a person. Recent technologies allow to detect both physical parameters on a human subject by using different techniques with and without contact. Noncontact systems often use electromagnetic waves for contactless measurement but approaches based on ultrasound waves, laser or video processes are also proposed. In this abstract an alternative ultrasound system for non-contact and local measurement is presented. The system works in echographic mode and ultrasound signals are processed using two methods. The experimental setup uses an elliptic mirror to focus ultrasonic waves onto the skin surface. Backscattered waves are recorded by a microphone located close to the emitting transducer. Heartbeat and respiration signals are determined from the skin displacement caused by the chest-wall motion. For comparison purpose, the cross-correlation method, which uses broadband signal, and the Doppler method, which uses narrowband signal, are applied to measure the skin displacement. Sensitivity and accuracy parameters of the two methods are compared. At least, as the measurement is local, the system can act as a noncontact stethoscope to listen the internal sounds of the human body even through the light clothes of the patient.