DE2134661B2 - ELECTROSTATIC ELECTROACOUSTIC CONVERTER - Google Patents

Description

3 4

trode 112 together. Appropriate holes 113 for the In the F i g. 3 are like parts with the same

Acoustic emissions are through this reference numerals as in FIG. 2 provided. Also is

going provided. A further fixed electrode 17 is provided on the other side. The fixed one

the vibrating membrane 12 consists of the electret 121 and electrode 17 consists of an electret 171 and

in the form of a film or a foil and from the 5 a counter electrode 172 together, which is attached to this

Counter electrode 122 together, which is film or attached and has many holes 173 through which

Has foil shape and is attached to this. Let the solid before acoustic radiation pass. The one

Electrode 11 and the vibrating membrane 12 are the connection of the secondary winding of the uptransfor-

by holding parts 13 and 14 made of insulating material mierend transformer 15 is with the two

attached. One connection of the secondary winding ίο electrodes 112 and 172 connected and the other connection

of a transformer 15 that is going up is connected to the counter electrode 122 of the oscillating

with the counter electrode 112 of the fixed electrode 11, the film 12 is connected.

Connected and the other port is to the receiving If an AC signal from the signal source Electrode 122 of the vibrating membrane 12 is connected 16 into the transformer 15 which is transformed upwards closed. The primary winding of the step-up transformer 15 is fed, the counter electrodes 112 and 172 The transformer 15 is charged in the opposite direction to the counter electrode 122 via a signal source 16. the tied together. three electrets 111, 121 and 171 are separated from each other an alternating current signal from the signal source of opposite charge sign, as in FIG. 3 ge-16 to the step-up transformer 15 shows, compared. This creates the charges is obtained, the counter electrodes 112 and ao gene of the I laugh of the electrets 111 and 122 is reduced 122 opposing charges. Both and the charges of the electrets 171 and 121 become Electets 111 and 121 are previously increased with opposite - during one half cycle of the signal, th charge sign, as in FIG. 2 will be shown during the next half cycle of the signal the opposite. Thereby occurs during each then the surface charges of the electrets 111 and Half-period of the signal increases an electrostatic tensile 25 122 and those of the electrets 171 and 121 force on, and the vibrating membrane 12 vibrates. are reduced. This process is repeated cyclically

The F i g. 3 explains the basic structure repeatedly, so that the diaphragm 12 vibrates,

and the operation of an electrostatic counter- The invention can also be applied to microphones.

clock speaker according to the invention. find application.

1 sheet of drawings

Claims (3)

spatially small, light in weight and in the manufacture Patent claims: be cheap. If the voltage of the signal source is high enough, the intermediate transformer can even be used. 1. Electrostatic electroacoustic wall to be left, so that according to an advantageous ler with a fixed and an oscillatory 5 development according to the invention, the signal source membrane-like electrode, which is connected directly to the counter electrode from a, foil-like electrets and a thin counter- Preferably two, each made of one electret electrode consists, thereby marked and a counter electrode existing fixed electrodes net that the fixed electrode (11) is provided from a, between which the from a film-like Consists of electrets (111) and a counter electrode (112) and a thin counter electrode, wherein the facing surfaces facing membrane-like electrode is arranged. of the electrets (111 and 121) are oppositely charged are. Drawing of the illustrated exemplary embodiments 2. Converter according to claim 1, characterized marked- explained. draws that two each from an electret 15 F i g. 1 is a perspective view of the ground plan (111 or 171) and a counter electrode (112 or construction of an electrostatic electroacoustic «! Wand-172) existing fixed electrodes (11 or 17) previously according to the invention; are seen, between which the from a foil F i g. 2 is a cross-sectional view of an electrical like electrets (121) and a thin counter-static electroacoustic single transducer, side electrode (122) existing membrane-like electronics, for example an electrostatic loudspeaker, in trode (12) is arranged. a preferred embodiment according to the invention 3. Converter according to claim 1 or 2, characterized in that; indicates that the counter electrodes (112, 122; Fig. 3 is a cross-sectional view of an electro- 172,122,112) directly to a signal source (16) of a static electroacoustic counter-converter, both are bound. 35 e.g. for an electrostatic loudspeaker, in a preferred embodiment according to Invention. In Fig. 1, an electret 111 and a counter electrode 112 attached to it form a fixed one The invention relates to an electrostatic electrode 11 and a film-like electret 121 and see electroacoustic transducers with a fixed and a thin counter-electrode 122 of an oscillatable membrane-like electrode, an oscillating membrane 12, attached to it.
which consists of a sheet-like electret and a counter electrode. The electrets 111 and 121 are in the correct thinning. faced each other. The force factor A this There are mainly two types of electrostatic electroacoustic transducers see electroacoustic transducers with an electre- can be obtained by the following equation in which the th known which, with regard to their structure, size in electrostatic units of the CGS system strongly differ from each other, namely a wall is indicated: ler, which the electret in the form of an oscillating 4πCo (M - ΑΠ Foil used and a transducer that gives the electret 40 A = - - (1) used as a fixed electrode. Especially in the last ^Thu Case, the thickness of the electret can be sufficiently large be made to carry a high amount of cargo and So del do del maintain high stability; since the electret is not as ^Co = ——— ^{and Do} = —r H 1 T Use vibrating foil instead as a fixed electrode. 45 * π Do eel ε ο eel need the mechanical and acoustic del del Characteristics of the electret disregarded for ^M i = - _y ' ^{ael M} z = - ~ ^ae2 so that any electret can be selected ^{ε ε} can. do = air gap length, From the German patent specification 864 696 and the 50 del = thickness of the electret 111, British patent 832 276 are electrostatic del = thickness of the electret 121, Transducer known with one fixed and one oscillating So = face, flexible membrane-like electrode, where single- eel = dielectric constant of the electret 111, lent the membrane-like electrode made of a folienarti- eel = dielectric constant of the electrets 121, gen electrets and a thin loading counter electrode 55 σ el - surface charge density of the electret 111 stands. ael - surface charge density of the electret 121. The invention is based on the problem of converters of this species to improve their sensitivity. In equation (1), the quantities M ₁ and According to the invention, this is added together in a converter M _t when it is achieved in the manner mentioned at the outset in that the 60 has a prefixed sign. That is, if the electrons solid electrode, an electret and an object 111 and 121 are so opposed to each other, electrode is made, with the mutually facing that the charges have opposite signs to one another. Surfaces of the electrets are oppositely charged. other, the force factor A reaches the maximum This makes the voltage sensitivity the len value. Converter increased significantly. An increase in tension 65 The F i g. 2 shows the principle of a preferred embodiment sensitivity in turn has the advantage that an electrostatic single-sound the turns ratio of the input transformer speaker according to the invention. The fixed electrode 11 tors can be small. Therefore this transformer is made up of the electret 111 and the counter-elec-