JP2009100251A - Condenser microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor microphone capable of preventing distortion of the impedance transducer when excessive low-band sound pressures such as wind and vibration are applied to the microphone unit. <P>SOLUTION: The condenser microphone unit is equipped with an electrostatic microphone unit 10 containing a diaphragm and a fixed pole which are disposed oppositely at preset intervals and an impedance transducer 20 for transducing a change in electrostatic capacitance output from the microphone unit 10 into a current or voltage signal, wherein a low-cut circuit 30 comprising capacitor elements C1, C2 and resistor elements R1, R2 is connected between the microphone unit 10 and the input portion (gate terminal G of the FET) of the impedance transducer 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a condenser microphone, and more particularly to a low cut circuit of a condenser microphone that reduces noise generated by wind or vibration.

  Condenser microphones have an electrostatic microphone unit that includes a diaphragm and a fixed pole that are arranged opposite to each other with a predetermined interval. However, since the electrical impedance is extremely high, the impedance immediately after the microphone unit A transducer is connected. In many cases, an FET (field effect transistor) is used as the impedance converter, but a vacuum tube is rarely used.

  When a large sound pressure is applied to the microphone unit and an excessive electric signal is applied to the impedance converter, the impedance converter generates distortion. Further, noise is generated when wind or vibration is applied to the microphone unit.

  Since the frequency components of these noises are low frequencies, the low-frequency level can be reduced by a low cut circuit (high-pass filter) composed of C (capacitor element) and R (resistive element). This type of low-cut circuit is effective in reducing noise because the lower the higher the order, the lower the frequency range.

  However, conventionally, as described in Patent Document 1, for example, the low cut circuit is connected to the subsequent stage (output side) of the impedance converter.

  Therefore, a large low-frequency signal due to wind or vibration is added to the input side of the impedance converter, and as described above, when the impedance converter is distorted, even if it is low-cut at the subsequent stage of the impedance converter, The harmonic component of distortion generated by the impedance converter is output from the microphone.

  By the way, wind noise is a sound of a low component such as “go-go”, but noise such as “pocopoco, pocopocoo” may remain even after low cut. This is due to the harmonics that are derived by the impedance converter being distorted by the large amplitude input.

JP 2001-238287 A (FIG. 4)

  Accordingly, an object of the present invention is to prevent the impedance converter from being distorted even if an excessive sound pressure in a low frequency range due to, for example, wind or vibration is applied to the microphone unit.

  In order to solve the above-described problems, the present invention provides, as described in claim 1, an electrostatic microphone unit including a diaphragm and a fixed pole that are opposed to each other with a predetermined interval, and the microphone. In a condenser microphone comprising an impedance converter that converts a change in capacitance output from the unit into a current or voltage signal, a capacitor element and an input between the microphone unit and the impedance converter are provided. A low cut circuit comprising a resistance element is connected.

  According to a second aspect of the present invention, the microphone unit is included in the low-cut circuit as a capacitor element.

  According to the present invention, a low-cut circuit including a capacitor element and a resistance element is connected between the microphone unit and the input unit of the impedance converter, so that, for example, the wind Since the low frequency component due to excessive low sound pressure due to vibration or vibration is reduced, it is possible to reliably prevent the impedance converter from being distorted.

  Further, by including the microphone unit as a capacitor element in the low cut circuit, the configuration of the low cut circuit can be further simplified.

  Next, an embodiment of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this. FIG. 1 is a circuit diagram showing a condenser microphone according to an embodiment of the present invention.

  As shown in FIG. 1, the condenser microphone 1 according to this embodiment includes a microphone unit 10, an impedance converter 20, and a low cut circuit 30 as a basic configuration.

  In addition, three terminals T1 to T3 connected to an output connector (not shown) are provided. Of these, the terminal T1 is included in the power supply system, the terminal T2 is included in the signal output system, and the terminal T3 is grounded (ground). Included in the system.

  Although not shown in detail, the microphone unit 10 is an electrostatic acoustoelectric converter including a diaphragm and a fixed pole that are arranged to face each other via an electrically insulating spacer ring, and the diaphragm side is a grounding system. To the terminal T3.

  In this embodiment, a polarization voltage (bias voltage) is applied to the microphone unit 10 from the power supply terminal T1 via the resistance elements Ra and Rb. An electret type microphone unit including an electret dielectric film on either one of the fixed poles may be used.

  An FET (field effect transistor) or a vacuum tube is used for the impedance converter 20. In this embodiment, since an FET is used, the impedance converter is referred to as FET 20 in the following description.

  The drain terminal D of the FET 20 is connected to the power supply system terminal T 1, the source terminal S is connected to the ground system terminal T 3 via the voltage detection resistor element Rc, and the gate terminal G is connected to the fixed pole side of the microphone unit 10. Connected to.

  In the microphone unit 10, when the diaphragm is vibrated by sound waves from a sound source (not shown), the capacitance existing between the diaphragm and the fixed pole changes, and the voltage corresponding to the capacitance is the gate of the FET 20. Applied to terminal G.

  Thereby, the current flowing between the drain terminal D and the source terminal S of the FET 20 is controlled, and a voltage corresponding to the vibration (displacement) of the diaphragm is generated in the voltage detecting resistance element Rc of the source terminal S. The voltage at the voltage detecting resistance element Rc is output to the terminal T2 of the signal output system via the amplifier A1.

  In the present invention, the low cut circuit 30 is connected between the microphone unit 10 and a gate terminal G which is an input portion of the FET 20.

  The low cut circuit 30 in this embodiment includes the first and second capacitor elements C1 and C2 and the first and second resistance elements R1 and R2. In this case, The capacitance of the microphone unit 10 is assigned to the capacitor element C1.

  That is, the microphone unit 10 (first capacitor element C1) and the second capacitor element C2 are connected to the gate terminal G of the FET 20 in series.

  One end of the first resistance element R1 is connected to a connection point between the microphone unit 10 and the second capacitor element C2, and the other end is connected to the source terminal S of the FET 20 and the + of the amplifier A1 through the electrolytic capacitor Ca for cutting DC. Connected to the input terminal.

  One end of the second resistance element R2 is connected to the second capacitor element C2 and the gate terminal G of the FET 20, and the other end is connected to the grounding terminal T3 via the electrolytic capacitor Cb for direct current cut. Yes.

  As described above, the low cut circuit 30 is connected between the microphone unit 10 and the gate terminal G of the FET 20, so that, for example, a low frequency band caused by wind or vibration is provided in front of the gate terminal G (input unit) of the FET 20. Since the low frequency component due to excessive sound pressure is reduced, the FET 20 can be prevented from being distorted.

  Further, by including the microphone unit 10 in the low cut circuit 30 as a capacitor element, the configuration of the low cut circuit 30 can be further simplified. In the above embodiment, the microphone unit 10 may be used for the second capacitor element C2.

1 is a circuit diagram showing a condenser microphone according to an embodiment of the present invention.

Explanation of symbols

1 Condenser microphone 10 Microphone unit 20 Impedance converter (FET)
30 Low cut circuit 30
A1 Ambu C1, C2 Capacitor element R1, R2 Resistor element T1 Feeding system terminal T2 Signal output system terminal T3 Grounding system terminal

Claims (2)

An electrostatic microphone unit including a diaphragm and a fixed pole that are arranged opposite to each other with a predetermined interval, and an impedance converter that converts a change in capacitance output from the microphone unit into a current or voltage signal In a condenser microphone unit equipped with
A capacitor microphone, wherein a low cut circuit including a capacitor element and a resistance element is connected between the microphone unit and the input section of the impedance converter.   The condenser microphone according to claim 1, wherein the microphone unit is included in the low cut circuit as a capacitor element.

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