On Cardiovascular Sound

Abstract

Spectral phonocardiography, an adaptation of the method of sound spectrography devised at the Bell Telephone Laboratories, differs from conventional oscillographic phonocardiography principally in the fact that frequency spectrum is displayed as well as the dimensions of time and intensity. The display of frequency spectrum is responsible for three advantages of the method: (1) Quality, or timbre, is given physical definition, (2) resolution in the time dimension is improved, and a (3) a better display of the wide dynamic range of cardiovascular sound is attained. This method can do, or can be made to do, all the ear can, and can probably emulate the performance of the ear because 1) it is not wed to a particular frequency-intensity response curve, 2) it suffers from no "psychoacoustic" impediments, 3) it provides better resolution in the time dimension, and 4) it produces permanent, quantifiable records. Discussed here are selected features of mitral valve disease, aortic valve disease, gallops, systolic clicks, and extracardiac sounds. In general, intensity and peak frequency (or frequency range) vary in a parallel manner in sound of cardiovascular origin. Artefacts due to noncardiovascular ambient noise and to electrical interference can be identified and disregarded in the heart sound analysis.