Practically inaudible with an acoustic stethoscope.

Acoustic stethoscopes are familiar to most people, and operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the listener's ears.
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An electronic stethoscope (or stethophone) overcomes the low sound levels by electronically amplifying body sounds. However, amplification of stethoscope contact artifacts, and component cutoffs (frequency response thresholds of electronic stethoscope microphones, pre-amps, amps, and speakers) limit electronically amplified stethoscopes' overall utility by amplifying mid-range sounds, while simultaneously attenuating high- and low- frequency range sounds. Currently, a number of companies offer electronic stethoscopes. Electronic stethoscopes require conversion of acoustic sound waves to electrical signals which can then be amplified and processed for optimal listening.
http://en.wikipedia.org/wiki/Stethoscope#Types_of_stethoscop...

Twelve popular acoustic stethoscope models were tested for sound transmission characteristics and clinical utility in checking heart, breath, and vascular sounds and measuring blood pressure. Sound transmission was both measured on human volunteers, and in an acoustic laboratory using sine wave frequency sweeps, and Dirac pulses.
http://www.forusdocs.com/reviews/Acoustic_Stethoscope_Review...

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Note added at 3 Stunden (2011-04-26 11:28:47 GMT)
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I have found a few Google hits for stethacoustic, but mainly in English translations from French or Portuguese, so I would be hesitant to use it.