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To the Editor:—
My article dealt primarily with the acoustic characteristics of stethoscopes used in general practice, and it brought out the fact that they do not amplify sound. The statement under criticism, "Amplification of heart and lung sounds is neither practical, nor desirable, nor needed for the physician with normal hearing," is challenged by your correspondent, who states that amplification is desirable as being (1) possible of graphic recording (2) or in showing fine differences (a) unaffected by the "danger of the personal equation" and (b) the complication of "lack of uniformity in terminology." Undoubtedly, acoustic analysis of heart and chest sounds will advance to a science, but it will have to pass through a long period of development similar to the study of hearing across the frequency range. The latter has been intensively considered by a small group of otologists for at least ten years and is not
Macfarlan D. AMPLIFICATION OF HEART AND LUNG SOUNDS-Reply. JAMA. 1938;111(12):1123. doi:10.1001/jama.1938.02790380065025