An in vitro acoustic analysis and comparison of popular stethoscopes

PURPOSE: To compare the performance of various commercially available stethoscopes using standard acoustic engineering criteria, under recording studio conditions. MATERIALS AND METHODS: Eighteen stethoscopes (11 acoustic, 7 electronic) were analyzed using standard acoustic analysis techniques under professional recording studio conditions. An organic phantom that accurately simulated chest cavity acoustics was developed. Test sounds were played via a microphone embedded within it and auscultated at its surface by the stethoscopes. Recordings were made through each stethoscope’s binaurals and/or downloaded (electronic models). Recordings were analyzed using standard studio techniques and software, including assessing ambient noise (AMB) rejection. Frequency ranges were divided into those corresponding to various standard biological sounds (cardiac, respiratory, and gastrointestinal). RESULTS: Loudness and AMB rejection: Overall, electronic stethoscopes, when set to a maximum volume, exhibited greater values of perceived loudness compared to acoustic stethoscopes. Significant variation was seen in AMB rejection capability. Frequency detection: Marked variation was also seen, with some stethoscopes performing better for different ranges (eg, cardiac) vs others (eg, gastrointestinal). CONCLUSION: The acoustic properties of stethoscopes varied considerably in loudness, AMB rejection, and frequency response. Stethoscope choice should take into account clinical conditions to be auscultated and the noise level of the environment.