Monitoring of the heartbeat sounds using an optical fiber Bragg grating sensor

Heartbeat is intuitively examined via a stethoscope that amplifies the sound. Diagnosis may be broadened by extracting more information: strength, frequency components, and sound pressure. This paper is on the demonstration of an optical fiber Bragg grating sensor to monitor the heartbeat using sound pressure and possibly extending to application of ballistocardiography (BCG: the heartbeat-associated movements imparted by recoil and impact). To our knowledge, cardiac examination with BCG and sound sensing using FBG technology has not been explored. In this setup, heartbeat sounds are translated into an electrical signal using a strain-sensitive reflective FBG sensor that provides differential changes in the reflection spectrum. For a proof-of-concept demonstration, FBG sensor is glued to the vibrating membrane of a subwoofer of a speaker set. Using recordings of various heartbeat sounds, spectral changes are recorded at a 250-Hz sampling rate. The results show increased sensitivity to: strength of the heartbeat, frequency and temporal content of the oscillatory wave pattern.