In The Beginning
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The earliest reference we can find in the literature to electrostatic transducers is circa 1912. A British scientist, Lawrence Frederick Richardson, was attempting to detect underwater objects using electrostatic transducers. Alas, I can find no extant record of that patent, if one existed. However, the year was a pertinent one for the detection of "underwater objects", and the captain of the Titanic would no doubt have been grateful for such a device!
Richardson's ideas were picked up by a Russian emigré to France, by the name of Constantin Chilowski. He was able to interest the eminent French physicist Paul Langèvín in this matter, and Langèvín turned the investigations in the direction of electrostatics. They applied for patents in the matter of: "Production of Submarine Signals and the Location of Submarine Objects", and were granted a French Patent (502,913) on March 4, 1920 (application date: May 29, 1916), and the equivalent U.S. Patent ( 1,471,547) on October 23, 1923. The electrostatic transducer was not a great success in this application, and was soon replaced by a piezoelectric device, in about 1916 (shortly after the original application for patent was filed).
As early as 1918, electrostatics were used to build condensor microphones. Edward Wente is credited as the inventor of the first such device, and microphones of this type became precision laboratory equipment.