SU24003A1 - Electrostatic microphone - Google Patents

Description

In conventional electrostatic microphones, either a membrane is tightly tensioned when the microphone is used as a pressure microphone, or a free-hanging light membrane is used if the effect of moving air particles is used in the microphone. Microphones of the first type are more convenient in the sense that they directly provide more or less the same amplitude for the entire frequency spectrum and do not require special selection of high frequencies and suppression of low ones in the amplification structure, making them difficult because the materials must be strong enough to withstand the high tension / necessary to obtain a membrane's own oscillation period above the sound frequency spectrum. Therefore, it would be more advantageous to use a relatively thin metal film or plate as the membrane, to make the size of the membrane very small, increasing its period by reducing the geometrical dimensions. This requires a significant approximation of the membrane, which serves as a capacitor plate, to the electrode, which serves as another capacitor plate. Experiments made in this direction showed that the airbags obtained in such small chambers extremely strongly limit the movement of the membrane and nullify the expected effect.

The present invention aims to eliminate this drawback, for which it is proposed to make a microphone with reduced pressure between the plates.

In the schematic drawing of FIG. 1 depicts the proposed microphone in section; FIG. 2 - a detail of it.

The massive disc A is covered with a lattice or perforated thin plate B of an air-tight insulating material tightly glued to the disk A. A very thin metal plate or bar C is stuck on top of plate B, with a sticker operation performed under the air pump bell. Because of this, in the chambers formed between A and C, the air pressure will be greatly reduced (Fig. 2). The same membrane will receive due to the pressure of external air on it. Damage to the parts of the membranes corresponding to the individual chambers should not play a big role, since each chamber is separated from another airtight layer.

The subject matter of the invention.

An electrostatic microphone, characterized in that air is evacuated from the space that surrounds the caps A and C of the capacitor forming the microphone.

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