DE1044169B - Magnetic-electric acoustic transducer - Google Patents

Description

GERMAN

The invention relates to a magneto-electric acoustic transducer, in particular for use "is suitable as a microphone and a tongue plate as a spring-elastic, magnetic has conductive material which has at least two cut legs on a web, of which one is clamped in the air gap of a magnet, while the other with its free leg end is arranged swinging freely in front of or in the air gap of the magnet.

There are already known transducers of this type whose tongue plates have an E-shape and with their both outer legs are clamped in the air gap of a permanent magnet. These known arrangements however, have the disadvantage that their tongue plates also still connect to their legs common web are clamped. The invention is based on the idea that one Much higher sensitivity and a better frequency response with magneto-electric converters of these Art receives if it is possible to train the tongue plate in such a way that of two adjacent ones Only one of the legs is clamped at one end, the other at the other end is coupled with a membrane. One then has the advantage that with every swinging movement elastic bending claimed length in this case from the clamping point over the length of one Leg the connecting web and from there to the freely swinging end of the other leg extends. This can be achieved with a converter of the type described at the outset, in which according to of the invention, the otherwise freely oscillatable tongue plate exclusively on at least one its leg ends is clamped in the air gap of the magnet.

In the drawing, a magneto-electric acoustic transducer is shown.

Fig. 1 shows the converter in a three-dimensional representation,

FIG. 2 shows a graph for the frequency response of the converter according to FIGS. 1 and

3 shows an electrical equivalent circuit diagram of the mode of operation of the converter according to FIG. 1.

The transducer has an E-shaped, thin tongue plate 3 made of resilient, magnetically conductive Material that on a common web 4 has three trimmed legs. The two outer ones Legs 6 are with the interposition of bronze sheets 7 in the air gap 2 of a horseshoe-shaped Permanent magnet 1 clamped, while the middle leg, designated 8, of the tongue plate protrudes into the air gap 2 of the magnet, but in the magnet electrical acoustic transducer

Applicant:

German electronics

Company with limited liability,

Berlin-Wilmersdorf, Forckenbeckstr. 9-13

Dr. Werner Puhlmann, Darmstadt,
has been named as the inventor

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this can swing freely back and forth. Near its free end, the middle leg 8 is over a plunger 9 connected to a membrane, not shown.

With this type of clamping, in which the tongue plate is only attached to both of its leg ends 6 is clamped, there are at least two possibilities for the formation of a fundamental oscillation, in analogy to the electrical oscillations of the Lecher system as common-mode and differential-mode oscillation should be designated. In the case of the push-pull oscillation, the middle part 8 oscillates Tongue with an antinode at the open end and a knot at the closed end, d. H. at the Web 10 of the E-shaped tongue. In the common-mode case, the entire E-piece 3 vibrates as one-sided clamped Tongue, the two outer legs 6 at the point of restraint 7 have a knot and have an antinode on the web 10. The middle, unrestrained part 8 of the tongue runs in the direction of the tangent to the deflected end of the swinging tongue and thus moves in the desired way in the gap.

The position of the natural frequencies can be reached individually by weighting the tongue. the The resonance of the common mode oscillation is set by weighting the Ouersteg of the tongue the push-pull oscillation by weighting the unclamped tongue handle. Through the width of the tongue bridge, the resonance of the common mode oscillation can be independent of the differential mode oscillation move. The damping of the common mode oscillation can be independent of the differential mode oscillation with the help of a damping means attached to the closed end (web) of the tongue can be set.

In order to expand the transmission range of the electroacoustic transducer, one is preferably Resonance oscillation to the lower frequency limit

, 809 67J / 201

and the other resonance oscillation is placed in the middle of the transmission range.

The success of this measure in the case of a microphone can be seen from the curve shown in FIG. To record this curve, a microphone was acoustically measured while idling, in which the damping means for leveling the individual resonance peaks were omitted in order to clearly demonstrate the idea of the invention. A pronounced minimum arises between the two resonance peaks 11 and 12 of the tongue. The origin of this minimum can be explained from the electrical equivalent circuit diagram (Fig. 3) of the mechanical system. In this equivalent circuit diagram, the impedance of the membrane is indicated by L _M and C _M , while C _{L represents} the capacitance formed by the air cushion located behind the membrane. The tongue vibrating in unison forms a series resonance circuit or guide circuit L ₇₁₁ -C ^; a guide circle L _Z2 -C _Zz parallel to this corresponds to the tongue parts oscillating in push-pull. The resonance frequencies of the two guide circles correspond to the tips 11 and 12 in FIG. B. L _Zl -C _Zv acts as an inductance and results with the capacitive component of the lower frequency excited circuit, z. B. -L ₂₂ -C ₂₂ , a parallel resonance which causes the minimum between the peaks 11 and 12 in FIG. The resonances can be leveled by damping materials, e.g. B. by vaseline, felt, fabric, silicone paste, as shown in Fig. 2 by dashed lines.

Claims (11)

PATENT CLAIMS: 1. Magneto-electric acoustic transducer, in particular For use as a microphone, with a tongue plate made of resilient, magnetic conductive material that has at least two cut legs on a web, of one of which is clamped in the air gap of a magnet, while the other with a membrane connected and swinging freely with its free leg end in front of or in the air gap of the magnet is arranged, characterized in that the otherwise freely oscillatable tongue plate (3) exclusively on at least one of its leg ends (6) in the air gap (2) of the magnet (1) is clamped. 2. Electroacoustic transducer according to claim 1, characterized in that the one resonance oscillation to the lower frequency limit and the other resonance oscillation to the upper frequency limit of the transmission range is laid. 3. Electroacoustic transducer according to claim 1 or 2, characterized in that the location of the Natural resonances each set for itself by weighting down the tongue. 4. Electroacoustic transducer according to claim 3, characterized by a weighting of the transverse web the tongue to adjust the natural resonance of the common mode oscillation. 5. Electroacoustic transducer according to claim 3, characterized by a weighting of the not clamped leg of the tongue to adjust the natural resonance of the push-pull oscillation. 6. Electroacoustic transducer according to claim 1 and one of the following, characterized in that that the mutual position of the natural resonances is set by the width of the Ouersteges of the tongue is. 7. Electroacoustic transducer according to one or more of the preceding claims, characterized by a dampening means acting on the web of the tongue, e.g. B. silicone paste for Damping of the common-mode oscillation independent of the other form of oscillation. Considered publications:
U.S. Patent Nos. 2,163,161, 2,454,425. 1 sheet of drawings © 809 679/201 11. S »