Noise controller for automatically detecting and attenuating break noise in a portable hand held doppler fetal heart beat probe

A noise controller for use in a probe in a hand held ultrasonic Doppler fetal heart beat detection and monitoring system, said probe including a crystal 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 said input signal, said noise controller comprising:

• a volume controller for receiving said first signal and for processing said first signal to produce an analog signal as the output of said probe,
• a detector for generating a second signal whenever break noise is detected in said first signal;
• a muting means connected to said volume controller and said detector for immediately lowering the amplitude of said analog signal upon detection of said break noise by said detector sensor to substantially attenuated in said analog signal said break noise which occurred in said first signal.