MICROPHONE CIRCUIT FOR THE LINEARIZATION OF THE PROXIMITY EFFECT IN A DYNAMIC DIRECTIONAL MICROPHONE

Abstract

A microphone circuit characterized in that an impedance element can be connected in parallel with the microphone for the purpose of damping resonance and linearizing the proximity effect. The impedance of this element is preferably between 20 and 1000 ohms.

Claims

1. A microphone circuit including a microphone capsule, the microphone circuit being configured for linearizing a proximity effect in a dynamic directional microphone, wherein the microphone circuit has at least one inductive impedance element that can be connected in parallel with the microphone capsule.

2. The microphone circuit according to claim 1, wherein the at least one inductive impedance element is arranged in parallel and can be switched in via a switch.

3. The microphone circuit according to claim 1, wherein the at least one inductive impedance element is a hum bucking coil or noise suppression coil that is connected in series with the microphone capsule of the dynamic directional microphone when in a non-damping state.

4. The microphone circuit according to claim 1, wherein an impedance of the at least one inductive impedance element is between 20 and 1000 ohms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows a standard version of a circuit for a dynamic microphone with a hum bucking coil;

[0011] FIG. 2 shows another standard version of a circuit for a dynamic microphone with a hum bucking coil;

[0012] FIG. 3 shows a microphone circuit according to the present disclosure with a microphone capsule and an impedance connected in parallel;

[0013] FIG. 4 shows another microphone circuit according to the present disclosure with a microphone capsule and a hum bucking coil or noise suppression coil that can be connected either in series or in parallel;

[0014] FIG. 5 shows a variant embodiment of a circuit of a dynamic microphone according to the present disclosure according to FIG. 3 and an amplifier;

[0015] FIG. 6 shows a variant embodiment of a circuit of a dynamic microphone according to the present disclosure with a switchable hum bucking coil according to FIG. 4 and an amplifier; and

[0016] FIG. 7 shows the differences in the amplitude response of an output signal that can be achieved according to the present disclosure, normalized at 1 kHz.

DETAILED DESCRIPTION

[0017] In accordance with technical jargon, the term “impedance element” is often replaced by simply “impedance” in the following and in the claims.

[0018] The presently disclosed microphone circuit for a directional microphone has at least one impedance element with inductive properties. The impedance element can be any passive electronic component that is connected in parallel with the microphone capsule and has an effective resistance and an inductive reactance. The value of the impedance connected in parallel is preferably between 20 and 1000 ohms, more preferably between 300 and 700 ohms.

[0019] In contrast to classical filters, the impedance element used in the microphone circuits of the present disclosure disproportionately damps the self resonance or quality of the oscillating dynamic microphone system. The shape of the amplitude response of the microphone returns to its original shape on both sides outside its effective range. The self-resonance damping of the oscillating dynamic system in the described application is performed at the electrical level using components that are already present in the system. These components can, for example, be a hum bucking coil, noise suppression coil or EMC components and thus take on a dual function in the system. The value of the parallel connected impedance is also between 20 and 1000 ohms, whereby the active resistance can be small. In this context, small means approximately the ohmic resistance of a commercially available hum bucking coil for dynamic microphones.

[0020] FIG. 1 shows a standard version of a circuit of a dynamic microphone 1, as is known from prior art, with a hum bucking coil 2 which is connected in series upstream of a moving coil 3. The microphone 1 has no integrated amplifier.

[0021] FIG. 2 shows another standard version of a circuit of a dynamic microphone 1, known from prior art, with a hum bucking coil 2, which is connected in series downstream of a moving coil 3. The microphone 1 has no integrated amplifier.

[0022] FIG. 3 shows an example of a circuit of a microphone 1 according to the present disclosure, in which a microphone capsule 4 can be connected in parallel with an inductive impedance 5 via a switch S1. For the signal occurring at the signal output 6 and the differences resulting from the circuit states, reference is made to FIG. 7, in which the representation shown, with an open switch S1, corresponds to undamped behavior.

[0023] FIG. 4 shows an example of a circuit of a microphone 7 according to the present disclosure, comprising a microphone capsule 4 and an inductive impedance 5, which can be, for example, a hum bucking coil, a noise suppression coil, or more generally a mechanically oscillating system that dampens mechanical noises (handling noises, impact noise, etc.). This also consists of a membrane/coil system without sound inlet. In the position shown, the impedance 5 and the microphone capsule 4 are connected in series. This position corresponds to the undamped behavior of FIG. 7 at the signal output 6. If the switch S2 is closed, the impedance 5 and the microphone capsule 2 are in parallel connection, which corresponds to the damped behavior of FIG. 7 at the signal output 4.

[0024] FIG. 5 shows an exemplary variant embodiment of a circuit of a dynamic microphone 1 according to the present disclosure with a serial hum bucking coil 2 and a downstream inductive impedance element 5 according to FIG. 3. The latter can be switched on and off as required by using switch S1. Downstream of the actual microphone capsule 4 is an amplifier 8 as part of the dynamic microphone. The microphone is divided into an electronic part 9, which contains the amplifier 8 and the parallel impedance 5, and a purely passive mechano-acoustic part 10, which contains the microphone capsule 4 with the separate hum bucking coil 2.

[0025] FIG. 6 shows an exemplary variant embodiment of a circuit of a dynamic microphone 7 according to the present disclosure with a hum bucking coil as a connectable parallel impedance 5 according to FIG. 4. The switch S2 makes it possible to switch from the standard series circuit of the hum bucking coil as a parallel impedance 5 and moving coil 3 to a parallel circuit. Downstream, an amplifier 8 is shown as part of the dynamic microphone. The microphone is made up of an electronic part 9, which contains the amplifier 8 and the switchable parallel impedance 5, and a purely passive mechano-acoustic part 10, which contains the microphone capsule 4 and the hum bucking coil 2.

[0026] FIG. 7 shows an amplitude response normalized at 1 kHz in each case for an undamped (corresponding to the prior art) and a damped output signal which can be achieved according to the present disclosure for the frequency range from 20 Hz to 20,000 Hz. The amplitude difference between the damped and undamped state for the frequency range 50 Hz-300 Hz can be clearly seen.

[0027] If a higher output signal is desired in the relevant frequency range due to the general conditions, the impedance 5 can either be deactivated via the switches S1 and S2, shown in FIG. 3 or FIG. 5 and FIG. 4 or FIG. 6, respectively, or amplified by means of an amplifier 8 to be connected downstream of the output signal.

[0028] The embodiments according to the present disclosure shown in FIGS. 3 and 4 and their more detailed representations in FIGS. 5 and 6 are to be understood as examples. Although it is advantageous in most cases if the embodiments have the switches S1 or S2 shown in the figures, [[but]] in cases where this is not desired for certain reasons, it is of course also possible to have a microphone circuit without the switches S1 or S2. Analogous to FIGS. 3 and 4, this embodiment then corresponds to permanently closed switches.

[0029] Examples of inductive impedance elements 5 are hum bucking coils (as shown in FIG. 6), but also noise suppression coils or EMC components. The particular advantage is that these components are often already contained in the microphones, but have been connected in series. These existing components can be connected in parallel with a simple circuit, as shown for example in FIG. 6, and can thus be used to dampen the natural resonance of the microphone. The damping of the natural resonance thus leads to a simple and efficient linearization of the proximity effect.

[0030] Measured examples of the ratio of active resistance to reactance of the impedance are:

Example 1: 600 ohm active resistance and 16 ohm reactance, measured at 1 kHz
Example 2: 260 ohm active resistance and 12 ohm reactance, measured at 1 kHz
Example 3: 360 ohm active resistance and 7 ohm reactance, measured at 1 kHz

[0031] However, the explanations are not limited to the examples given, but can in principle assume any ratio of reactance to active resistance, provided that it proves to be expedient for reducing the proximity effect in a dynamic directional microphone based on subsequent measurements. Preferably, the range of impedance resistance is in a range of 20 to 1000 ohms, more preferably between 300 and 700 ohms.

[0032] A parallel connection is understood to mean the connection of a plurality of reactances and/or active resistances, which have the same voltage direction in the steady state (cf. Deimel et al. “Grundlagen der Elektrotechnik 1”, 2000, R. Oldenbourg Verlag, Vienna, p. 82ff. and Deimel et al., “Grundlagen der Elektrotechnik 2”, 2001, R. Oldenbourg Verlag, Vienna, p. 86ff.). In contrast, structures with an opposing member are referred to as negative feedback or feedback (cf. Lutz & Wendt, “Taschenbuch der Regeltechnik”, 2010, Wissenschaftlicher Verlag Harri Deutsch, Frankfurt am Main, p. 34ff.).

[0033] The features and variants specified in the individual configurations and examples can be freely combined with those of the other examples and configurations and used in particular to characterize the invention in the claims without necessarily including the other details of the respective configuration or the respective example.

LIST OF REFERENCE NUMERALS

[0034] 1 Microphone circuit [0035] 2 Hum bucking coil [0036] 3 Moving coil [0037] 4 Microphone capsule [0038] 5 Parallel impedance element [0039] 6 Signal output [0040] 7 Microphone circuit [0041] 8 Amplifier [0042] 9 Electronic part of the microphone circuit [0043] 10 Mechano-acoustic part of the microphone circuit [0044] S1 Switch [0045] S2 Switch