sounds of the body The healthy functioning of the human body produces a variety of sounds. We can readily hear the movement of air through the mouth and nose, and in and out of the bronchi and the lungs; the sounds which come from the beating heart as its valves close in sequence; blood pulsating along the arteries; and the rumblings of gas in the alimentary canal. Coughing serves to clear fluid from the airways; hiccuping has no known function. Not so long ago, aural detection of the fetal heartbeat within a swollen female abdomen was the only totally unequivocal clinical indication of pregnancy.

All of the body's normal sounds may become modified in disease. The rhythms of breathing may change, becoming laboured or irregular. The note of the cough alters. Bronchi, inflamed or otherwise constricted, wheeze. The lungs and their membranes may begin to creak, rasp, or hiss, to transmit the voice more clearly or the breath sounds less so. Narrowing of the arteries and valvular disease of the heart both replace the relative quiet of smooth blood flow with the gurgles of turbulence.

Pathological processes may also reveal themselves by the production of sounds unheard in health, such as the creaking of arthritic joints; the crepitus of broken bones; and slopping of abnormal accumulation of fluid in the abdomen. A tinkling sound in the flesh around an infected wound is a dreadful sign, indicative of gas gangrene. The absence of sound may be equally ominous. A blocked artery is quiet downstream of the occlusion. Silence in the bowel demands urgent investigation.

The physicians of ancient Greece knew of the diagnostic value of applying the ear to the chest wall in order to listen to the sounds of the lungs. Sometimes they would shake their patients in an attempt to elicit splashing noises in the thoracic cavity. In the eighteenth century, Leonard Auenbrugger invented the technique of percussion; tapping the thorax with the finger. Regions of the chest that were filled with air resonated; solid or fluid-filled regions did not. The character of the sound elicited by tapping was, thus, indicative of the state of health of the underlying tissues.

The invention of the stethoscope, in 1816, made the clinical study of both normal and pathological sounds much easier, but it was only after considerable research and controversy that the cause and meaning of many of the pathological sounds, and even some of the normal ones, were fully clarified. In the nineteenth century, more than thirty-five different theories were suggested to account for the two principal cardiac sounds. The study of pathological noises was hampered both by deficiencies in the understanding of the physics of sound and by an unduly slavish allegiance to the idea that particular sounds were the characteristic signatures of particular diseases. It only gradually became appreciated that an abnormal sound signifies not necessarily a specific disease but rather a specific alteration of bodily structure.

Malcolm Nicolson

See also auscultation; diagnosis.