Stable laboratory-standard capacitor microphone

One basic design, embodying a spring-loaded rear electrode assembly, provides models suitable for pressure-type or free-field type of response. Its overall dia. is 1frac18 in., height 1frac18 in. and weight 2.8 oz. It is suitable for operation with artificial ears and with couplers as used in telephone receiver work. Above 3.5 kc/s the response can be raised, lowered or maintained relatively flat according to the angle of incidence of the sound. Behaviour under excessive sound pressure and temperature changes is described. Performance limitations are specified.