Methods and results in characterizing electronic stethoscopes

Two methods for characterizing the acoustical properties of electronic stethoscopes are reported. The first method measures the frequency response of the stethoscope using a fluid-filled rubber ball that is excited by a mechanical shaker driven by broadband noise. The acoustic impedance of this phantom is designed to be similar to that of human body tissue. The second method measures the acoustic impedance of the stethoscopes using a standard acoustic impedance tube measurement system. The frequency response and impedance results for six commercially available electronic stethoscopes are reported. It is shown that the stethoscope responses vary considerably as a function of frequency, showing peaks and nulls of as much as 20 dB in the frequency range of 5 Hz to 3 kHz and that the stethoscope responses differ considerably from each other.