A Loud-Speaker Stethoscope for Clinical Teaching

An equipment was required that would enable a number of students to listen simultaneously in auscultation of a patient's chest. The method adopted is to pick up the sounds by means of a microphone held on the chest, amplify them elec-trically, and reproduce them at a loud-speaker. The problem differs from that of phonocardiography in two main respects: first, the subjective effect on the listener must be as similar as possible to ausculta-tion with a stethoscope, which means that certain components of the sounds, too small to affect the phonocardiograph record, must be faithfully repro-duced, and at the same time frequencies that are not well picked up by a stethoscope must be corre-spondingly attenuated by the electrical system; and