A device for recording heart sounds at the body surface through the heart's actions which cause vibrations that are transmitted through organs and tissue to the body surface. These are detected by microphones, processed in an electroacoustic transducer, and give sound characteristics in a phonocardiogram. This is used to assess the low frequency sounds (atrial and ventricular gallops), and high frequency sounds (mitral regurgitation and ventricular septal defect). Some also record subsonic frequencies (a few Hertz) considered as vibrations, typically recorded by an apexcardiograph. This method may also be integrated in other electrocardiograph (ECG) devices.
aventusoft.com