GB1181868A - Microphone having a Variable Directional Characteristic - Google Patents

Abstract

1,181,868. Microphones. AKUSTISCHE U KINO-GERATE G.m.b.H. 19 July, 1967 [19 Aug., 1966], No. 33184/67. Heading H4J. In a microphone having a variable directional characteristic (e.g. cardioid, hypercardioid, supercardioid) a deflecting member in the form of a disc or sleeve between a sound inlet opening communicating with the forward face of the diaphragm and a sound inlet opening communicating with the rear face of the diaphragm is provided and is detachable and/or adjustable in size and/or shape whereby to vary the external acoustic path between the front and rear inlet openings. In a first embodiment, a dynamic microphone capsule 1 (Fig. 1) having front inlets 2, rear inlets 3 and a pressure chamber 5 is provided with a removable deflecting disc 6. Without the disc 6 the acoustic path d 1 between front and rear inlets 2, 3 provides a cardioid characteristic while with the disc 6 in place the acoustic path d 2 provides a supercardioid or hypercardioid characteristic, depending on the size of the disc 6. Alternatively a plastics deflecting disc 6<SP>1</SP> (Fig. 5) has openings 7 which may be closed by a punched metal sheet 8 rotatably mounted in a groove 9 of the disc 6<SP>1</SP>. The sheet 8 is rotatable by a lever 10 and has openings 11 which correspond to the openings 7. Acoustic paths d 1 , d 2 , d 3 provide cardioid, hypercardioid and supercardioid characteristics, respectively. Alternatively, a microphone capsule 1 in a housing 12 (Fig. 7) is provided with a cap 13. Sound enters through a front protective screen 14 and through slots 15 in the cap 13. Frusto-conical member 6 is fitted to the cap 13. The member 6 may be circular, elliptical or star-shaped. It may be used as a microphone rest, either being provided with an elastic ring 17 or with a peripheral pad. The member 6 may be of variable outside diameter and arranged as an iris diaphragm.