JP4336256B2 - Condenser microphone - Google Patents

Description

  The present invention relates to a condenser microphone. More specifically, the present invention relates to a technique for improving the directional frequency response of a condenser microphone to a high range and improving the S / N ratio.

  For example, as described in Patent Document 1, a capacitor microphone basically has a capacitor microphone capsule (capacitor microphone unit) including a diaphragm and a fixed pole that are arranged to face each other via a spacer, and a sound wave. And an audio signal output unit including an impedance converter that converts the vibration of the diaphragm due to the above to an electric signal as a change in capacitance.

  The unidirectional condenser microphone is provided with a front acoustic terminal for directly applying sound waves coming from the sound source to the front side of the diaphragm and a rear acoustic terminal for acting on the back side of the diaphragm. ing.

  Capacitor microphones are classified as small and large according to the diameter of the condenser microphone capsule. Small ones with a diameter of 20 mm or less are classified as small, and those with a diameter exceeding 20 mm, for example, 1 inch (25.4 mm) or more are classified as large. The definition of this classification is applied also in this specification.

  Small condenser microphone capsules with an aperture of 20 mm or less are excellent in high frequency response because the distance between the acoustic terminals of the front acoustic terminal and the rear acoustic terminal can be shortened, but the sensitivity is low because the diaphragm area is small. Inferior in terms of S / N ratio.

  In contrast, large condenser microphone capsules with a diameter of more than 20 mm have a large diaphragm area and are excellent in sensitivity and S / N ratio. However, the distance between the acoustic terminals of the front acoustic terminal and the rear acoustic terminal is long. Therefore, the high frequency response is inferior. Although the S / N ratio depends on the design of the impedance converter, generally, the larger the effective capacitance of the capacitor microphone capsule, the better.

JP-A-2-237300 (FIG. 1)

  Therefore, the object of the present invention is to take advantage of the advantages of a small capacitor microphone capsule and the advantages of a large capacitor microphone capsule, respectively, and to have an excellent directional frequency response up to a high frequency and a good S / N ratio. It is to provide a certain condenser microphone.

To solve the above problems, the condenser microphone of the present invention includes at least three unidirectional condenser microphone capsule diameter is 20mm or less, and a single impedance converter, the respective condenser microphone capsules, their as a the capsule main axis parallel to each other and disposed at a position of each apex portion of a regular polygon having an apex that number fraction, and, with each vibration plate is arranged to lie on the same plane, each of the capacitors The microphone capsule is connected to the one impedance converter.

  According to the present invention, since each condenser microphone capsule has a diameter of 20 mm or less, when viewed as an acoustic mechanical vibration system, it operates as a small condenser microphone capsule excellent in directivity frequency response up to a high frequency range, while being electrically In this case, since the diaphragm and the fixed pole included in each condenser microphone capsule are connected in parallel to one impedance converter, the large effective capacitance is large and the S / N ratio is good. Operates as a condenser microphone capsule. Therefore, a condenser microphone having an excellent directional frequency response up to a high frequency range and a good S / N ratio is provided.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited to this. 1 is a schematic view showing an example of a condenser microphone according to the present invention, FIG. 2 is a cross-sectional view showing one of the condenser microphone capsules included in the condenser microphone, and FIG. 3 is a view of the condenser microphone capsule as seen from the sound source side. It is explanatory drawing which shows the example of arrangement | positioning.

  As shown in FIG. 1, the condenser microphone 1 of the present invention includes a plurality of, in this example, three condenser microphone capsules 10 (10a to 10c). In the present invention, each of the condenser microphone capsules 10a to 10c is a small condenser microphone capsule having a diameter of 20 mm or less, which is excellent in a high frequency response, and the configuration thereof may be the same. One sectional view is shown. The capacitor microphone capsule is synonymous with the capacitor microphone unit.

  According to this, the capacitor microphone capsule 10 includes a diaphragm 11 and a fixed electrode 12 that are arranged to face each other via a spacer ring made of an electrical insulating material (not shown) for the sake of drawing, and a cartridge case (capsule housing) that stores them. Body) 13.

  The cartridge case 13 is made of, for example, a cylindrical body made of a conductive metal material such as brass or aluminum, and has a front acoustic terminal (hole) 13a on one end side (left side in FIG. 2) directed to the sound source side (not shown) during sound collection. It has been drilled. Although only one front acoustic terminal 13a is shown in FIG. 2, in reality, a plurality of such terminals are arranged, for example, on a concentric circle at equal intervals, as shown in FIG.

  For the diaphragm 11, for example, a synthetic resin thin film having a metal vapor deposition film that forms a capacitor with the fixed electrode 12 is used. The diaphragm 11 is housed on the side of the front acoustic terminal 13a in the cartridge case 13 in a state of being stretched with a predetermined tension on a metal support ring 14. The diaphragm 11 is electrically connected to the cartridge case 13 via the support ring 14.

  The fixed electrode 12 is accommodated in the cartridge case 13 so as to face the diaphragm 11 through the spacer ring while being supported by an insulating seat 15 made of synthetic resin, and then the cartridge case 13 is opened. A locking ring 17 for fixing is screwed to the other end side. The fixed pole 12 is insulated from the cartridge case 13 by an insulating seat 15. An electret film may be attached to the fixed electrode 12.

  The fixed pole 12 and the insulating seat 15 are formed with sound passage holes 12a and 15a for allowing sound waves from a rear acoustic terminal (not shown) to act on the back side of the diaphragm 11. The insulating seat 15 is provided with an extraction electrode 16 for the fixed pole 12. Although not shown, a conductor film for connecting the fixed electrode 12 and the extraction electrode 16 is formed on the inner surface of the insulating seat 15.

  Normally, one impedance converter is used for one capacitor microphone capsule. In the present invention, one impedance converter is used for a plurality of capacitor microphone capsules.

  That is, as shown in FIG. 1, each extraction electrode 16 on the fixed pole 12 side of the condenser microphone capsules 10a to 10c is connected to the input terminal of the impedance converter 21, and each of the condenser microphone capsules 10a to 10c on the diaphragm 11 side is connected. The cartridge case 13 is connected to the ground circuit 22. When the impedance converter 21 is an FET (field effect transistor), each extraction electrode 16 is connected to its gate electrode.

  As a result, in the acoustic mechanical vibration system, each of the condenser microphone capsules 10a to 10c operates as a small (small aperture) condenser microphone capsule having a good directivity frequency response particularly in a high frequency range, and electrically has an S / N ratio. It operates as a large (large diameter) condenser microphone capsule with good effective capacitance.

  In the present invention, the arrangement of the condenser microphone capsules 10a to 10c is important in order to make the characteristics uniform, and it is necessary to arrange the condenser microphone capsules 10a to 10c so as to be substantially equidistant from the sound source.

  In FIG. 2, the capsule main axis of the condenser microphone capsule 10 (the axis passing through the center of the diaphragm 11 and synonymous with the sound collection axis) is X. First, as shown in FIG. 1, each capsule main axis X of the condenser microphone capsule 10a to 10c. Are made parallel to each other. Next, the diaphragms 11 of the condenser microphone capsules 10a to 10c are aligned so as to be on the same plane.

  When the sound source is relatively far away, the capacitor microphone capsules 10a to 10c may be arranged in a line as shown in FIG. 3B, but the capacitor microphone capsule as shown in FIG. It is preferable to arrange 10a to 10c at each vertex of the equilateral triangle. That is, in the case of two, it must be arranged side by side, but in the case of three or more, it may be arranged at each vertex portion of a regular polygon having the number of vertices.

  In the above example, the condenser microphone capsules 10a to 10c having the same diameter are used. However, if the diameter is 20 mm or less, those having different diameters may be combined. included.

The schematic diagram which shows an example of the condenser microphone by this invention. Sectional drawing which shows one of the capacitor | condenser microphone capsules contained in the said capacitor | condenser microphone. Explanatory drawing which shows the example of arrangement | positioning of the said capacitor | condenser microphone capsule seen from the sound source side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor microphone 10 (10a-10c) Capacitor microphone capsule 11 Diaphragm 12 Fixed pole 13 Cartridge case 14 Support ring 15 Insulation seat 16 Lead electrode 17 Lock ring 21 Impedance converter 22 Grounding circuit X Capsule spindle

Claims (1)

Including at least three unidirectional condenser microphone capsules having an aperture of 20 mm or less, and one impedance converter,
Each of the above-mentioned condenser microphone capsules, in parallel to those of the capsule main shaft together and placed in the position of each apex portion of a regular polygon having an apex that number fraction, and such that each diaphragm is present on the same plane And a capacitor microphone, wherein each of the capacitor microphone capsules is connected to the one impedance converter.

Images