NOISE CONTROLLER FOR DETECTING/ATTENUATING BREAK NOISE

摘要

This invention is a noise controller for use in a probe (11) in a hand-held ultrasonic Doppler fetal heart beat detection and monitoring system where the probe (11) includes a crystal (21) for generating an input signal as a function of the ultrasonic energy in received ultrasonic wave, and a detector for generating a first signal from the input signal. The noise controller comprises a volume controller (19, 20) for receiving the first signal and for processing the first signal to produce an analog signal as the output of the probe. A detector generates a second signal whenever break noise is detected in the first signal. A muting circuit immediately lowers the amplitude of the analog signal upon detection of break noise by the detector, thereby substantially attenuating in the analog signal the break noise which occurred in the first signal.