Vibrophonocardiograph

Claim 1

Apparatus for monitoring cardiac dynamics of a subject comprising: a piezoelectric microphone of a total weight of the order of 1.8 grams having an enclosure of a total volume of the order 25 X 10- 3 cubic inches with an opening in one face for receiving acoustic energy in the form of air pressure waves and adapted to be placed exTernally on the chest of said subject with said opening against said subject, said microphone having: a piezoelectric element inside of said enclosure and away from any contact with said subject through said opening, said element having one end secured to said enclosure and another end free to move relative to said enclosure; a flexible diaphragm attached inside said enclosure to separate said element from said opening; means attaching an area of said diaphragm directly over said hole to said free end of said element; and an output terminal connected to said element to obtain piezoelectric signals in response to air pressure waves against said diaphragm; utilization means having an input terminal adapted to receive signals which vary as a function of said subject''s cardiac activity; and an amplifier having an input stage with a very high input impedance of the order of 1,000 megohms coupling said output terminal of said piezoelectric microphone to said input terminal of said utilization means.