Abstract: This invention provides an electroacoustic transducer and a method of making it. The transducer according to the invention comprises a substrate of a semiconductor material with a recessed portion. A membrane is stretched across the recessed portion, which membrane is set in vibration in response to an input signal comprising audio and/or ultrasonorous frequencies. A pair of electrodes is provided, which form a capacitor, and between which an electric field is present. The electrodes are so arranged relatively to the membrane that the capacitance of the capacitor can vary under the influence of vibrations of the membrane, so that acoustic signals are converted into electric signals. A layer of an electrically insulating material functions as a carrier for an electric charge to provide an auxiliary electric field between the electrodes.

Abstract: This invention provides an electroacoustic transducer and a method of making it. The transducer according to the invention comprises a substrate of a semiconductor material with a recessed portion. A membrane is stretched across the recessed portion, which membrane is set in vibration in response to an input signal comprising audio and/or ultrasonorous frequencies. A pair of electrodes is provided, which form a capacitor, and between which an electric field is present. The electrodes are so arranged relatively to the membrane that the capacitance of the capacitor can vary under the influence of vibrations of the membrane, so that acoustic signals are converted into electric signals. A layer of an electrically insulating material functions as a carrier for an electric charge to provide an auxiliary electric field between the electrodes.

Abstract: An electret transducer and a method for making same. A multiple support between a diaphragm plate and a backplate is provided by a plurality of relatively small spacing disks made of an electrically insulating material and which as separate posts are fixedly attached on the upper surface of the backplate. Such spacing disks are conveniently and accurately punched from a foil of dielectric material which is held opposite and above the backplate, whereafter the spacing disks thus formed are attached on the backplate.

Abstract: A motor assembly for an electret transducer, wherein spacing means supporting the diaphragm plate on the backplate are manufactured from a separate material which is applied on the backplate surface to achieve an accurately defined and reproduceable spacing therebetween. Such spacing means can be formed as a meshlike screen lying on the backplate surface. In an alternative embodiment wherein the backplate is constituted by substantially spherical, conductive particles sintered together, the spacing means are formed by an acoustical porous coating applied on the backplate surface, which coating also acts as an electret.

Abstract: An electro-acoustic transducer in which a diaphragm has a stiffened portion which at the one hand is pivotally connected to a fixed frame portion, and at a location offset from the center of the diaphragm is connected to a U-form armature of an electromagnetic unit at the other, whereby the average amplitude of the movement of said diaphragm caused by a movement of the free end of said armature is greater than the amplitude of the latter movement.