Wide Bandwidlt Fetal Phonography Using a Sensor Matched to the Compliance of the Mother's Abdominal Wall

A transducer has been developed which, by improving the sound coupling efficiency between the surface of the maternal abdomen and the sensor, allows a major part of the acoustic output of the fetus to be examined. This has been achieved by a system of compliance matching using a ceramic cantilever beam transducer. The principle is equally applicable to the use of a simple ceramic beam or other active elements.