GB729556A - Electrostatic transducers - Google Patents

Abstract

729,556. Sound receiving or transmitting devices; stethoscopes; loud-speakers. INTERNATIONAL PATENTS TRUST, Ltd. March 27, 1952 [March 27, 1951; May 30, 1951; Jan. 7, 1952], No. 7923/52. Class 40 (4). [Also in Groups VI and XXXVIII] In a mechanico-electric transducer, the transducing element which is a condenser comprises interleaved conducting and insulating elements loosely wound to form a convolute unit which in response to variations of external pressure produces proportionate changes of capacitance. Conducting strips 11, 12, Fig. 1, interleaved with dielectric strips 13, 14, which may be of paper or polystyrene, are wound to form a flat but resilient convolute condenser. Air may be trapped between the layers to give added resilience and a coating of finely divided powder such as talcum applied to prevent sticking between adjacent layers. A condenser in which the strips are corrugated to give added resilience is described with reference to Fig. 19 (not shown). Application of the invention to the measurement of physiological pressure waves in the human body is described with reference to Figs. 3-7, 22 and 23 (not shown) and further applications, using a plurality of elements or a pair of elements in push-pull relationship, include gramophone pick-ups, receivers, loud-speakers, and subaqueous signalling devices. The examples include arrangements wherein the element is operated by tension and compression and also mountings wherein the element is subject to torsional oscillation. Means for calibrating the physiological instruments by known pressures produced mechanically or by a second transducer are described with reference to Figs. 5, 6 and 23 (not shown) and amplifier arrangements designed to enhance specific frequencies in connection with physiological measurements are also described.