JP5731900B2 - Stereo microphone - Google Patents

Description

  The present invention relates to a stereo microphone. More specifically, the present invention relates to a stereo microphone suitable for a camcorder having a sound pickup shaft opening suitable for the angle of view of the camcorder and having little sensitivity behind the camcorder.

  Of the stereo microphones, a stereo microphone mounted on a camcorder is often a stereo microphone based on an MS stereo system or an XY stereo system.

  In the MS stereo system, a main signal M is obtained from a unidirectional microphone unit arranged in the center, and a direction signal S is obtained from a bidirectional microphone unit arranged on the side thereof, and each of these signals is matrixed. The signals are input to the circuit to generate L and R channel signals (M + S) and (MS) (see, for example, Patent Document 1).

  On the other hand, in the XY stereo system, two unidirectional microphone units are mechanically fixed at an appropriate angle, the left unit output is the L channel, and the right unit output is the L channel (for example, patents). Reference 2).

Japanese Patent Laid-Open No. 2002-374592 (paragraphs [0002]-[0003], FIG. 3) Japanese Utility Model Publication No. 6-35597 (FIG. 4)

  By the way, the angle of view by the standard lens of the camcorder is usually about 25 ° to 50 °. The stereo microphone is attached in the vicinity of the viewfinder of the camcorder, and the operator is located at the rear part of the camcorder during imaging.

  In the MS stereo system, as described above, the bidirectional microphone unit is used as the side unit, and the side unit is oriented at 90 ° with respect to the camera axis. For this reason, the sound from the side of the operator (for example, the voice of the neighbor) may be collected. In addition, since the bidirectional microphone unit has a large proximity effect, it is easy for sound with a low frequency component to be collected from outside the angle of view.

  In the XY stereo system, two unidirectional microphone units are attached so as to be swung to the left and right of ± 45 ° to 60 ° with respect to the camcorder axis. According to this, almost no sound from the lateral direction is collected, but since the directional axes are directed to ± 45 ° to 60 ° to the left and right, the sound from the rear of the camcorder (operator's voice, operation sound, etc.) ) Is easily picked up.

  Accordingly, an object of the present invention is to provide a stereo microphone suitable for a camcorder having an opening of a sound collecting shaft suitable for the angle of view of the camcorder and having little sensitivity behind the camcorder.

In order to solve the above problems, the present invention is a stereo microphone including two first and second microphone units each having directivity that is unidirectional, and includes a baffle plate formed in a flat plate shape, Each microphone unit has a directivity axis parallel to each other, the first microphone unit is disposed on one surface side of the baffle plate, and the second microphone unit is disposed on the other surface side of the baffle plate. A unit cover made of an acoustic resistance material having a through-hole formed coaxially with the directivity axis of the microphone unit is provided on each surface of the baffle plate and arranged symmetrically with the unit. A unit is housed in the through hole of each unit cover, and the baffle plate and each unit. By the bar is constructed and the right front acoustic terminal and the left front acoustic terminal on the distal end side of the respective through-holes, said rear end portions of the unit cover is extend rearward from the rear end of the baffle plate, said The internal spaces of the respective through holes communicate with each other at the rear end portion of each unit cover, and are common to the respective microphone units between the rear end portions of the respective unit covers on the extension line of the baffle plate. The rear acoustic terminal is provided.

  According to the present invention, the right front acoustic terminal and the left front acoustic terminal are formed on the tip side of each through-hole provided in the unit cover by the baffle plate and the unit covers provided on both surfaces thereof, The rear end of the unit cover extends rearward from the rear end of the baffle plate, and between the rear ends of each unit cover on the extension line of the baffle plate, a common rear acoustic terminal for each microphone unit Is provided, the collection of sound waves from the rear (180 ° direction) can be made extremely small.

  Also, since the line connecting the rear acoustic terminal and the right front acoustic terminal is the right sound collection axis, and the line connecting the rear acoustic terminal and the left front acoustic terminal is the left sound collection axis, the rear acoustic terminal and the front acoustic terminal By adjusting the distance between the two, the plane including the baffle plate is set to the 0 ° direction, and the opening angle of the sound collecting shaft can be easily set according to the angle of view of the camcorder.

(A) The front view which shows the stereo microphone which concerns on embodiment of this invention, (b) The rear view FIG. 1A is a right side view of FIG. 1A (left side view of FIG. 1B). FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. The disassembled perspective view which isolate | separates and shows the microphone unit and unit cover which are provided in a baffle board. (A) The circular graph which shows the polar pattern of a right side microphone unit, (b) The graph which shows the directivity frequency response. (A) The circular graph which shows the polar pattern of the left side microphone unit, (b) The graph which shows the directivity frequency response.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 6, but the present invention is not limited to this.

  1 to 3, a stereo microphone 1 according to this embodiment is for a camcorder in which a video camera and a VTR are integrated, and as a basic configuration, a baffle plate formed in a flat plate shape. 10, two microphone units 20, 20 and unit covers 30, 30 for each microphone unit.

  The baffle plate 10 has a rectangular shape, and one short side (the left side in FIGS. 2 and 3) is directed to a sound source side (not shown), and thus one short side is used as a front end portion 10 </ b> F of the baffle plate 10. .

  The other short side opposite to the front end 10F is the rear end. In this embodiment, as shown in FIG. 4, the central portion on the other short side is cut out in a U shape. The bottom of the rear space portion 11 that is cut out is a substantial rear end portion 10E of the baffle plate 10.

  The operator of the camcorder operates the camcorder (not shown) located on the rear end portion 10E side of the baffle plate 10 (the front side of the paper surface in FIG. 1B and the right side in FIGS. 2 and 3). In the description, the left side (L side) and the right side (R side) of the stereo are based on the case of viewing from the operator side.

  The microphone units 20 and 20 are both unidirectional (cardioid) and have substantially the same characteristics such as directional frequency response, and the left microphone unit 20L on one side and the right microphone unit on the other side. As shown in FIG. 3, 20R has left and right surfaces 10L and 10R on the left and right surfaces 10L and 10R with their directivity axes (sound collecting axes) X and X in the same direction and parallel to each other. Arranged as symmetrical. Each directivity axis X, X is also parallel to the plate surface of the baffle plate 10.

  In this embodiment, each of the microphone units 20L and 20R is a capacitor type (electrostatic type), but a dynamic type (electrodynamic type) may be adopted depending on circumstances.

  The unit covers 30 and 30 (30L and 30R) are made of an acoustic resistance material (for example, non-woven fabric JH-1007 manufactured by Japan Vilene Co., Ltd.), and an acoustic tube-like through hole in which the microphone units 20L and 20R are housed. 31 is provided.

  The through hole 31 may be a hole that is hollowed out in a perfect circle shape. However, in this embodiment, the through hole 31 has a slit 32 formed in a portion in contact with the baffle plate 10 as shown in FIG. It consists of a hole with a C-shaped cross section. The slit 32 is formed over the entire length along the axial direction of the through hole 31.

  The unit covers 30L and 30R cover the rear space portion 11 including the rear end portion 10E of the baffle plate 10 in a state where the microphone units 20L and 20R are accommodated in the respective through holes 31 and 31. Are attached symmetrically to each surface 10L, 10R via an adhesive or the like.

  As a result, in the portions extending rearward from the rear end portion 10E of the unit covers 30L and 30R, the slits 32 and 32 of the respective through holes 31 and 31 are baffle plates as shown by chain lines in FIG. 10 communicate with each other via the rear space portion 11.

  Since each microphone unit 20L, 20R is unidirectional, it has its own front acoustic terminal and rear acoustic terminal. According to this stereo microphone 1, as shown in FIG. The central portion of the front surface 31F of the through hole 31 on the unit cover 30L side is the left front acoustic terminal PL as the stereo microphone 1, and the central portion of the front surface 31F of the through hole 31 on the unit cover 30R side is the stereo microphone 1. It becomes the right front acoustic terminal PR.

  On the other hand, between the rear surface 31E of the through hole 31 on the unit cover 30L side and the rear surface 31E of the through hole 31 on the unit cover 30R side, each microphone unit 20L, 20R is on the extension line of the baffle plate 10 with respect to each microphone unit 20L, 20R. A rear acoustic terminal PB is provided as a common stereo microphone 1.

  Therefore, as shown in FIG. 3, the line connecting the rear acoustic terminal PB and the right front acoustic terminal PR is the right sound pickup axis (right directing axis) RX, and the line connecting the rear acoustic terminal PB and the left front acoustic terminal PL. The left sound-collecting axis (left-handed directing axis) LX, and by adjusting the distance between the rear acoustic terminal PB and the front acoustic terminals PR and PL, the plane including the baffle plate 10 is set to the 0 ° direction so that the image of the camcorder The opening angle ± θ of the sound collection axis can be easily set according to the angle. In addition, the collection of sound waves from the 180 ° direction can be reduced.

  In this embodiment, the left and right sound pickup axes are set to ± 12 °. For reference, the polar pattern of the right microphone unit 20R is shown in FIG. 5A, and the directivity frequency response is shown in FIG. 5B. . FIG. 6A shows the polar pattern of the left microphone unit 20L, and FIG. 6B shows the directivity frequency response.

  In the above-described embodiment, the slits 32 are provided in the respective through holes 31 and 31 of the unit covers 30L and 30R over the entire length in the axial direction. The units 20L and 20R are perfectly circular with no slits, and the slits 32 are provided only in the portions covering the rear space portion 11 including the rear end portion 10E of the baffle plate 10 so that the insides of the through holes 31 and 31 are mutually connected. You may make it communicate.

DESCRIPTION OF SYMBOLS 1 Stereo microphone 10 Baffle board 10F Front end part of baffle board 10E Rear end part of baffle board 11 Rear part of baffle board 20 (20L, 20R) Microphone unit 30 (30L, 30R) Unit cover 31 Through hole 31F Front of through hole 31E Rear surface of through-hole 32 Slit PR Right front acoustic terminal PL Left front acoustic terminal PB Rear acoustic terminal RX Right sound collection axis LX Left sound collection axis

Claims (1)

A stereo microphone including first and second two microphone units each having directivity that is unidirectional,
A baffle plate formed in a flat plate shape, each microphone unit having a directivity axis parallel to each other, the first microphone unit arranged on one surface side of the baffle plate, and the second microphone unit being the baffle plate It is arranged symmetrically with the first microphone unit on the other surface side of the plate,
On each surface of the baffle plate, a unit cover made of an acoustic resistance material having a through hole formed coaxially with the directivity axis of the microphone unit is provided.
Each of the microphone units is housed in the through hole of each of the unit covers, and the right front acoustic terminal and the left front acoustic terminal are configured on the front end side of each through hole by the baffle plate and the unit cover.
The rear end portion of each unit cover extends rearward from the rear end portion of the baffle plate, and the internal spaces of the through holes communicate with each other at the rear end portion of the unit cover, and the baffle plate A stereo microphone common to each of the microphone units is provided between the rear ends of the unit covers on the extension line.

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