JPH06339192A - Microphone unit - Google Patents

Abstract

(57) [Abstract] [Purpose] In an omnidirectional electric condenser microphone, variations in individual acoustic impedance characteristics can be easily adjusted to predetermined characteristics. [Structure] In a microphone unit 1 in which a diaphragm 5, a back plate 6, a cover plate 9 and the like are housed in a unit case 2, a passage 12 that connects the back portion of the back plate 6 and the outside is formed, and this passage 12 is provided with this passage 12. Passage 12
Is provided with an adjusting mechanism for changing the acoustic impedance of the. As an example of the adjusting mechanism, the cover plate 9 is provided with a passage.
12 was provided, and a bolt 14 was screwed into this passage 12. Bolt 14
The acoustic impedance of the passage 12 is changed by changing the screwing degree of the.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone unit applied to an omnidirectional electric condenser microphone.

[0002]

2. Description of the Related Art In the case of an omnidirectional electric condenser microphone, it is not necessary to send a sound wave to the rear surface of the diaphragm, so that a cavity is provided in the rear portion of the diaphragm for sealing. However, in reality, when completely sealed, the air in the rear air chamber expands and contracts due to changes in temperature and atmospheric pressure, which affects performance.Therefore, it is common to make this rear air chamber slightly communicate with the outside. Has been done. As this communication means, a groove is often provided in a part of the fitting portion of the component or the like.

FIG. 5 shows this. In this figure, 1 is a microphone unit, and 2 is a unit case. A small hole 3 is provided on the front surface of the unit case 2 so that sound waves can enter. Unit case 2
A vibration plate 5 is stretched inside the inside of the back plate 6 with a spacer 4 interposed between the back plate 6 and the back plate 6 with a minute gap.
Is located. The back plate 6 has a plurality of small holes 7
Is provided.

The lower edge of the unit case 2 is bent inward, and the peripheral edge of the printed circuit board 8 is held at this portion. A cylindrical cover plate 9 is interposed between the printed circuit board 8 and the back plate 6, and positions and supports the printed circuit board 8 and the back plate 6.
The printed circuit board 8 has an F as an impedance converter.
An ET (Field Effect Transistor) 10 is attached and connected to the back plate 6 and the printed circuit board 8.

In the case of the microphone unit 1 of this structure, the notch 9a is provided in a part of the cover plate 9 and the notch 2a is also provided in the unit case 2 so that the back plate 6 as shown by an arrow A in the figure is formed. The rear air chamber 11 located at the back is in communication with the outside.

When a sound wave from the outside enters the small hole 3 of the unit case 2 and vibrates the vibrating plate 5, the gap between the vibrating plate 5 and the back plate 6 changes,
During this period, the capacitance changes, and a voice current corresponding to this change can be obtained. This voice current is impedance-converted by the FET 10 and is input to the amplifier (not shown) through the printed board 8.

In the case of the conventional microphone unit 1 which operates in this way, it is sufficient if the acoustic impedance of the passage communicating the rear air chamber 11 and the outside can be made uniform, but notches are provided in a plurality of parts, Because of the structure in which these are communicated with each other, when manufactured in large quantities, it is not possible to make the same effective aperture area for each one, and each has an individual phase difference.

[0008]

Even if the phase difference is generated individually as described above, since the difference is not as large as the left side from the left, no problem occurs in the normal use method. However, in the case where the microphone units are combined and the outputs of these microphone units are added / subtracted to shift the phase difference, the individual phase differences greatly affect the overall characteristics. become.

The present invention has been made in view of this point, and makes it possible to make individual characteristics of the microphone units uniform so as to be suitable for use in combination with a plurality of microphone units as described above. It was done.

[0010]

As a means for solving the above-mentioned problems, the present invention provides a microphone unit in which a diaphragm, a back plate, a cover plate, etc. are housed in a unit case. A communication passage is formed and an adjustment mechanism for changing the acoustic impedance of the passage is provided in the passage.

[0011]

With this structure, the characteristics of the individual microphone units can be made uniform by operating the adjusting mechanism to change the acoustic impedance of the passage.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 and FIG. 2 which is a bottom view thereof, wherein the same members as those described with reference to FIG. Reference numeral 1 is a microphone unit, and 2 is a unit case. A small hole 3 is provided on the front surface of the unit case 2 so that sound waves can enter. A diaphragm 5 is stretched inside the unit case 2 via a spacer 4, and a back plate 6 is located behind the diaphragm 5 with a minute gap. The back plate 6 is provided with a plurality of small holes 7.

The lower edge of the unit case 2 is bent inward, and the peripheral edge of the printed circuit board 8 is held at this portion. A cover plate 9 is interposed between the printed board 8 and the back plate 6, and positions and supports the printed board 8 and the back plate 6. The printed circuit board 8 has an FET as an impedance converter.
A (field effect transistor) 10 is attached and connected to the back plate 6 and the printed circuit board 8.

In the case of the present invention, the cover plate 9 is not cylindrical, but has a shape that fills the space between the back plate 6 and the printed circuit board 8.
A passage 12 that connects the back of the back plate 6 and the outside is formed. This passage 12 is provided on the printed circuit board 8.
The hole 12 is communicated with a hole 13 (see FIG. 2) that is eccentrically provided. A female screw is engraved in the passage 12, and a bolt 14 is screwed into the female screw.

As shown in the drawing, a driver groove 14a is provided at the base end of the bolt 14, and if the cutting edge of the driver is fitted into this driver groove 14a, the bolt is inserted into the passage 12.
You can move 14 forwards and backwards.

In the microphone unit thus constructed, the blade tip of a driver (not shown) is fitted into the driver groove 14a provided at the base end of the bolt 14 to move the bolt 14 forward and backward. The engagement length between 14 and the female screw will change. As a result, the passage formed by the gap between the female screw and the male screw of the bolt 14 is formed.
The acoustic impedance of 12 will change. This acoustic impedance is adjusted by moving the bolt 14 back and forth. After adjusting the acoustic impedance in this way,
The printed board 8 and the bolt 14 are fixed with an adhesive.

FIG. 3 shows another embodiment of the present invention. In this case, the cover plate 9 has a U-shaped cross section, and a small hole 15 is formed at the bottom of the cover plate 9.
A narrow groove 16 communicating with the small hole 15 is provided. A hole 17 is provided near the small hole 15, and a bolt 18 protruding from the center of the back surface of the back plate 6 is passed through the hole 17. The bolt 18 is a buffer material made of silicon rubber applied to the outside of the bottom of the cover plate 9.
19 and the metal plate 20 also pass through, and a nut 21 is screwed onto the tip thereof.

In the microphone unit having this structure, the buffer material is changed by changing the tightening amount of the nut 21.
By changing the pressing amount of the back surface of the back plate 6 by 19, the effective cross-sectional area of the groove 16 can be changed, so that the acoustic impedance can be adjusted.

FIG. 4 shows still another embodiment of the present invention. In this embodiment, a hole 22 is provided at the bottom of the cover plate 9, and a tube 23 is tightly fitted in the hole 22. Since the tube 23 functions as an acoustic resistance due to its small hole, the direction in which the acoustic resistance is reduced can be adjusted by appropriately cutting the tube 23 to shorten it.

[0020]

Since the present invention is the microphone unit constructed as described above, the acoustic impedance can be adjusted by a simple operation. This allows you to combine multiple identical microphone units,
Even when the output of these multiple microphone units is added or subtracted and the phase difference is shifted and used,
Since there is no phase difference between the microphone units, good overall characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a bottom view of that of FIG.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a sectional view of still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional microphone unit.

[Explanation of symbols]

 1 Microphone Unit 2 Unit Case 5 Vibration Plate 6 Back Plate 8 Printed Circuit Board 9 Cover Plate 11 Rear Air Chamber 12 Passage 14 Bolt

Claims (1)

[Claims] 1. In a microphone unit in which a diaphragm, a back plate, a cover plate, etc. are housed in a unit case, a passage communicating between the back portion of the back plate and the outside is formed, and the acoustic impedance of the passage is changed to the passage. A microphone unit with an adjustment mechanism.