Abstract

An electronic stethoscope for reproducing at a user's ear as exactly as possible the sound pressure signals originating from a conventional diaphragm or bell type of chestpiece. The subject electronic stethoscope utilizes a signal processing approach which relies upon acousto-electronic feedback to provide an error or adjustment signal to amplifier gain control circuits. A pickup microphone detects audible sounds from a patient and produces an output signal representative thereof, and a variable gain amplifier amplifies the output signal of the pickup microphone. The amplifier drives an acoustic transducer in a headset which converts the amplified signal to audible sounds for audible detection by the user. A feedback microphone is placed near the acoustic transducer to detect the audible sounds produced thereby, and provides a feedback output signal. A control circuit compares the feedback output signal with the output signal produced by the pickup microphone, and in dependence thereon controls the transfer function of the variable gain amplifier, such that the audible output of the acoustic transducer is substantially the same as the audible input to the pickup microphone.