Frequency Characteristics of Heart and Lung Sounds

In auscultation, the physician is interested in a variety of normal and abnormal sounds produced within the human body. The nature of organic lesions can often be determined by a careful study of these sounds. The quality of the sounds, as interpreted by the ear, depends on two factors: (1) the relative intensities of the various frequency components that make up the whole, and (2) the relative sensitivity of the ear at these frequencies.1By the term frequency is meant, of course, complete cycles (or vibrations) per second. Although the quality and pitch of the sounds do not indicate directly the conditions that give rise to them, by any process ofa priorireasoning, nevertheless we know by experience, corroborated by postmortem examinations, that these factors have definite significance. It is therefore of interest to know as much as possible about the exact physical characteristics of the sounds commonly