Acoustic characterization of stethoscopes using auscultation sounds with synchronized electrocardiography recordings as test signals

The modern stethoscopes implement different technologies and features in order to better transmit the sounds from the inside of a body of a patient to the doctor’s ears. However, the objective evaluation of the actual influence of various solutions on the acoustic parameters of the diagnostic device is difficult. This is due to the fact, that the acoustic coupling between the body of an auscultated patient and the chest piece of a stethoscope can significantly alter the determined parameters, and due to the variable and noisy nature of the auscultation signals. The present study introduces a detailed methodology for acoustic characterization of the stethoscopes using the auscultation sounds as test signals. Information obtained from additional, synchronized electrocardiography measurements is used to extract short, specific fragments of recordings, defined as acoustic events. Analysis of the spectral characteristics of many acoustic events allows to compare the acoustic properties of various stethoscopes and to estimate the measurement uncertainty. The determined statistical acoustic parameters of the auscultation signals are presented, showing relatively large variation even within a single patient examination. The example results concerning various commonly used acoustic stethoscopes are introduced, showing discrepancies between the declared and the actual acoustic properties.