Nine hundred and thirty-three physicians have been tested to evaluate their ability to make cardiac diagnoses by auscultation alone. Fifteen "unknowns," recorded on tape and played back through individual stethophones, with simultaneous presentation of the visual pattern of the sound on the face of an oscilloscope, were used for the test. The "unknowns" were all classic examples of common normal and abnormal auscultatory phenomena and had been pre-tested to assure fidelity of reproduction and the ability of physicians with adequate training in auscultation to identify the examples readily. The highest scores were achieved by those physicians who had been certified in the subspecialty of cardiovascular disease while the lowest scores were made by physicians without specialized training who had been in practice for more than 20 years.
Butterworth JS, Reppert EH. Auscultatory Acumen in the General Medical Population. JAMA. 1960;174(1):32–34. doi:10.1001/jama.1960.03030010034009