GB276028A - Improvements in or relating to acoustic instruments - Google Patents

Abstract

276,028. Telefunken Ges. f³r Drahtlose Telegraphie. Aug. 13, 1926, [Convention date]. Void [Published under Sect. 91 of the Acts]. Diaphragms; magnetic instruments; microphones.-In acoustic instruments, such as loudspeakers, telephones, microphones &c., transverse vibrations of the diaphragm are produced by longitudinally acting forces and vice versa. Thus, as shown in Fig. 1, transverse vibrations of the diaphragm CBD are produced by forces acting at the points C, D in the directions indicated by the arrows. The membrane is slightly arched so that all movements thereof occur on one side of the plane CAD. In order that it shall always return to its original position of rest, the diaphragm is preferably made of elastic material or a slight tension is imposed at C and D. The actuating means may take the form of an iron core set into longitudinal oscillation by an actuating coil. The core may be made of any suitable material provided with an iron coating and the diaphragm itself is preferably formed of iron plate. Several diaphragms with one or more actuating means may be employed, whilst, in the case of a single diaphragm, any number of actuating means may be provided around its edge or the diaphragm may be clamped along one edge. Fig. 2 shows a construction of microphone in which transverse oscillations of the arched diaphragm M act longitudinally on the cover e of a carbon microphone E. The diaphragm, which in this case is made of the substance known under the registered Trade Mark " Pertinax," is clamped along one edge at b. The diaphragm may be associated with a lever system.