JPS596070Y2 - microphone - Google Patents

Description

[Detailed description of the invention] This invention has independent cavities on each side of two diaphragms, and each cavity is provided with a sound hole to create a gradient in the pressure of sound waves applied to both sides of the diaphragms. This invention relates to a microphone that can eliminate output due to mechanical vibrations and obtain unidirectionality.

A conventional noise canceling type microphone using a vibrating membrane formed by providing electrodes on both sides of a polymeric piezoelectric film was constructed as shown in FIG.

That is, a first diaphragm 3 and a second diaphragm 4 are attached to both openings of a conductive back cavity case 2 that houses a sound absorbing material 1, and a conductive spacer 5 is attached to the outer peripheral edge of the diaphragms 3 and 4. . Outer case 10 made of conductor
A sound hole 11 on the diaphragm 3 side is provided on the ceiling surface of the outer case 10, and the outer case 10, the insulating case 7, and the spacer 6
A sound hole 12 is provided on the peripheral side of the diaphragm 4, and one electrode of the diaphragm 3 is connected to the outer case 10 through a spacer 5.
and further connected to the source terminal of the field effect transistor 8 through the pattern of the terminal plate 9.

Further, one electrode of the vibrating membrane 4 is connected to a gate terminal of a field effect transistor 8 via a spacer 6.

Further, the other electrodes of both vibrating membranes 3 and 4 are electrically connected to each other via the back cavity case 2.

The source terminal of the field effect transistor 8 is on the ground side of the microphone, and the drain terminal is on the hot side.

In such a structured microphone, the diaphragms 3, 4
The polarities of will be connected as shown in Figure 2a,
When external pressure P is applied to the surfaces of the diaphragms 3 and 4 through the sound holes 11 and 12, a displacement as shown in FIG. 2b occurs, and a summed voltage E is generated at the output terminal.

However, due to external vibrations, for example, mechanical vibrations such as vibration noise of a motor of a recorder, etc., a displacement as shown in FIG. q becomes the same potential at each output terminal, making it impossible to obtain an output voltage.

As described above, the above-mentioned conventional microphone has the characteristic that it does not output mechanical vibration sound, but it has the disadvantage that it becomes omnidirectional because the diaphragms 3 and 4 are displaced in response to pressure from any direction. there were.

The present invention eliminates the above-mentioned drawbacks of the prior art.

Hereinafter, an embodiment of the present invention will be explained with reference to FIG. 3 of the drawing.

Reference numeral 13 denotes an outer case made of a conductive material such as metal, which has a sound hole 14 on the upper surface and an opening on the lower surface.The inner bottom opening of this outer case 13 has a terminal plate incorporating a field effect transistor 15 for impedance matching. 16 are connected, and this terminal board 1
6 is also formed with a sound hole 17, and is provided with a cylindrical portion 19 having a sound hole 18 formed in the middle part of the upper surface.

A back cavity case 20 is arranged on this cylindrical portion 19, and a side wall of this back cavity case 20 is provided with a sound hole 21, and a sound absorbing material 22 is housed inside.

A first diaphragm 23 made of a polymer piezoelectric film with electrodes provided on both sides is disposed at the upper end of the back cavity case 20, and a front cavity case having sound holes 24 on the upper surface is disposed on the diaphragm 23. The vibrating membrane 23 is supported by a back cavity case 20 and a front cavity case 25.

Further, on this front cavity case 25, a front cavity case 28 having sound holes 27 on the lower surface is arranged at regular intervals by spacers 26, and in the opening on the upper surface of this front cavity case 28, a second cavity similar to that described above is provided. A diaphragm 29 is disposed on the diaphragm 29, and a back cavity case 32 having a sound hole 30 in the side wall and housing a sound absorbing material 31 inside is disposed on the diaphragm 29.
The peripheral edge of is held between the front cavity case 28 and the back cavity case 32.

A spacer 33 is arranged between the back cavity case 32 and the ceiling surface of the outer case 13 so as to have a certain space.

Further, the dimensions are such that a sound path is formed between the inner wall of the outer case 13, the cylindrical portion 19 of the terminal plate 16, and the peripheral walls of the back cavity case 20, 32 and front cavity case 25, 28. and front cavity case 25
This sound path is divided into two by the upper surface, forming a front sound path 34 and a back sound path 35.
is connected to the sound hole 30 of the back cavity case 32 on the side of the diaphragm 29 by a sound tube 36.

The first diaphragm 23 and the second diaphragm 29 are connected to have polarities like the first diaphragm 3 and the second diaphragm 4 in FIG. 2a, and one output terminal is The gate terminal of the field effect transistor 15 is connected to the other output terminal, and the other output terminal is connected to the source terminal of the field effect transistor 15 and the outer case 13 .

The sound waves pass through the sound path 34 from the sound hole 14 of the outer case 13 to the sound hole 2 of both front cavity cases 25 and 28.
4, 27 to one side of the diaphragm 23, 29, the sound path 35 passes through the sound holes 17, 18 of the terminal plate 16, and the sound path 35 passes from the sound hole 21 of the back cavity case 20 to the other side of the diaphragm 23. 35, the acoustic sound 36 passes through the sound hole 30 of the back cavity case 32 and reaches the other surface of the vibrating membrane 29, where it is converted into an electrical signal.

When mechanical vibration is applied to this structure, the two vibrating membranes 23.
29 acts in the same manner as in FIG. 2C, and no electrical output is generated at the output terminal.

However, the sound waves displace the vibrating membrane 23, 29 from the above-mentioned path and a predetermined output signal is obtained.

Note that the vibrating membrane 23. Since the sound pressure caused by the sound waves on the front side and the back side of 29 has a slope depending on the length of the path, the size of the sound hole, and the presence or absence of the sound absorbing material 22.31, as in the case shown in Fig. 2b, Electrical output can be obtained according to the sound pressure gradient.

In addition, by configuring the sound hole and sound tube so that the sound pressure gradient is close to O for sound waves from the back side, a unidirectional microphone can be obtained. By arranging the sound holes and acoustic tubes so that they are equal, you can obtain bidirectional microns.

As mentioned above, since the microphone of the present invention is disadvantageous,
Even in a structure with two diaphragms, output is produced in response to mechanical vibrations, but depending on the dimensions of the sound hole, sound path, sound absorbing material, and sound tube that connects the sound path and sound hole, unidirectionality, It has the advantage of being able to freely design things such as interactivity, and is of great practical value.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional microphone, FIGS. 2A-2C are diagrams illustrating the wiring structure and operation of the same microphone, and FIG. 3 is a sectional view showing an embodiment of the microphone of the present invention. 13... Outer case, 14... Sound hole, 1
5... Field effect transistor, 16...
...Terminal board, 17...Sound hole, 18...
Sound hole, 19...Cylindrical part, 20.32...
・Back cavity case, 21, 30... Sound hole, 22.31... Sound absorbing material, 23, 29...
... Vibration membrane, 24.27 ... Sound hole, 25.
28...Front cavity case, 26,3
3...Spacer, 34.35...Sound path, 36...Sound tube.

Claims (1)

[Scope of utility model registration request] The opening of the outer case has a sound hole on the top and an opening on the bottom.
A terminal board having a cylindrical part with a sound hole on the top surface is attached, and a back cavity case with a sound hole on the side and a sound absorbing material housed inside is placed on the cylindrical part of the terminal board. A first vibrating membrane made of a polymer piezoelectric film with electrodes on both sides is placed on the back cavity case, a front cavity case having sound holes on the upper surface is placed on the first vibrating membrane, and the front cavity case is placed on the first vibrating membrane. A front cavity case having a sound hole on the bottom surface is placed on the cavity case via a spacer, and a second vibrating membrane made of a polymer film with electrodes provided on both sides is placed in the opening on the top surface of the front cavity case. A back cavity case having a sound hole on the side surface and containing a sound absorbing material inside is arranged on this second diaphragm, and a certain space is left between the top surface of this back cavity case and the ceiling surface of the outer case. Moreover, a sound path is formed between the inner wall of the outer case, the terminal plate, the cylindrical part, the peripheral wall of each back cavity case, and the front cavity case, and the upper surface of the front cavity case of the first diaphragm is the boundary. A microphone in which the sound path is divided into two, and the sound path on the first diaphragm side is connected to the sound hole of the back cavity case on the second diaphragm side with an acoustic tube.