Abstract It is axiomatic that to hear a faint cardiac murmur one should listen in a quiet environment. In the average busy hospital, clinic, or office environment there is a more or less constant level of background noise which, though we become acclimated and somewhat oblivious to it, does interfere with auscultatory examination. Particularly, faint heart murmurs, those which often are of the greatest importance in early diagnosis of heart disease and which reach the ear in intensities far lower than those of ordinary conversation and the other sounds to which the ear is more accustomed, are readily masked by extraneous room noises. This masking effect is well known to clinicians. Perhaps less well known is the degree to which the background noise levels actually present in hospital wards and examining rooms can impair one's ability to hear heart murmurs through the stethoscope. The purpose of this study was to measure the degree of this impairment under conditions simulating those of ordinary cardiac auscultation. We have been unable to find in the medical literature references to any study of this aspect of auscultation.