GB214609A - Microphone with non-rigid vibrating diaphragm - Google Patents

Abstract

214,609. Soc. des Etablissements Gaumont. April 18, 1923. Microphones; diaphragms.-The diaphragm of a microphone is made of supple material not under tension, so as to be free from resonance, and the resistance material consists of powdered anthracite. A felt block a is cut into the form of a six-spoked wheel to form chambers x which are filled with powdered anthracite capable of passing through a sieve with 80 to 100 meshes to the square centimeter. The diaphragm e is of pure silk muslin coated with rubber, to which is applied, before vulcanization, a sheet of gold leaf or other non-oxidizable and non-sulphurable material. Alternatively, the diaphragm may be of thin unsized paper, india-rubber, gutta percha or other pliable substance. This diaphragm is clamped over the mouth of a metal casing d by means of a split ring l which is sprung into position, a brass disc f being interposed. The diso is cut away at g, Fig. 2, and under the remaining parts h are fixed strips i of rubber .6 m.m. deep and formed with an edge of 30‹ against which the diaphragm rests. Current enters and leaves by the terminal rods n, p, of which the former is insulated by a sleeve o and communicates with a carbon block b supporting the granules, while the rod p communicates with the metal casing d. The active part of the diaphragm has a diameter of 44 mm., but in a modification suitable for use with amplifiers by a person standing at a distance the diameter may be increased to 100 m.m. with a corresponding increase in the number of granulechambers x.