JP2607002Y2 - Sound pressure gradient microphone - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a sound pressure gradient type microphone, and more specifically, to improve sensitivity, S / N ratio and frequency response characteristics by providing a baffle between front and rear sound terminals. The present invention relates to a sound pressure gradient microphone.

[0002]

2. Description of the Related Art A sound pressure gradient type microphone has two or more sound terminals, takes in the sound pressure difference between these sound terminals, gives a pressure difference between the front and rear of the diaphragm, and performs sound-to-mechanical conversion by the pressure difference. It is. In order to increase the sensitivity of such a sound pressure gradient microphone, a large driving force is required for the diaphragm, and a large driving force can be obtained by increasing the distance between the acoustic terminals. Unnecessarily increasing the distance between the acoustic terminals reduces the high frequency limit of the frequency response, for example, the driving force becomes 0 at a high frequency where the half wavelength of the sound wave is the same as the distance between the acoustic terminals. Would.

Therefore, it has been proposed that a leaky baffle plate made of an acoustic resistance material is provided between acoustic terminals to increase the frequency response in the middle and low frequencies, thereby increasing the driving force on the diaphragm. An example of such a sound pressure gradient type microphone will be described with reference to FIGS. FIG. 4 is a cross-sectional view of a conventional sound pressure gradient microphone, and FIG. 5 is a front view. In these figures, a microphone unit 1 of a sound pressure gradient type microphone includes a case 4 having a diaphragm 2 and a back electrode plate 3 provided on the rear side thereof, and a donut shape stretched on the front surface of the case 4. For example # 200
It is mainly composed of an acoustic resistance material 5 which is a baffle plate made of a nylon mesh of a certain degree, and electrode pins 6 connected to the back electrode plate 3 and connected to an impedance converter (not shown).

A large number of ventilation holes 7 are provided on the outer peripheral side of the case 4, and an opening 8 for introducing a sound wave is formed in a case front portion 9 on the inner peripheral side. The acoustic resistance member 5 is located on the inlet side of each ventilation hole 7. The diaphragm 2 is disposed behind the case front part 9 and in parallel with the case front part 9 via a diaphragm support ring 10, and a spacer 11 is provided between the diaphragm 2 and the back electrode plate 3. The outer peripheral side behind the back electrode plate 3 is fixed to the case 4 by a lock ring 12. Further, the electrode pin 6 is fixed to the insulating seat 18 by a lock nut 19. 13 is an adjuster 14
Is an acoustic resistance material whose acoustic resistance is adjustable. Thus, the front side of the case 4 functions as the front acoustic terminal 15 and the rear side functions as the rear acoustic terminal 16.

[0005]

By providing the acoustic resistance material 5 which is a leaky baffle plate made of an acoustic resistance material in the opening 7, the frequency response in the middle and low frequency range is increased to some extent. Although it is possible, increasing the acoustic resistance of the baffle will also lower the high frequency response limit.

[0006] The present invention has been made in view of such circumstances of the prior art, and has as its object the purpose of improving sound pressure, S / N ratio and frequency response characteristics with a simple configuration. An object of the present invention is to provide a gradient microphone.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method in which a diaphragm and a back plate are provided at a predetermined distance.
And the above case
A front acoustic terminal for the diaphragm is located on the front side of
The rear acoustic terminal is located on the rear side of the case.
And the front acoustic terminal side on the outer peripheral side of the case.
And a ventilation hole communicating between the rear acoustic terminal side and
Cage, sound capture sound pressure difference between the both acoustic terminal - in sound pressure gradient type microphone for performing mechanical conversion, the through
The pores have no air leakage and vibrate by sound waves
A baffle plate made of a flexible film .

According to the above configuration, not the baffle plate is acoustically leakage, because it is constructed as a vibrating plate that vibrates in response to the input vibration, because it has a high impedance at medium low range, It operates as a large baffle and has a low impedance in the high-frequency range, so that sound waves can easily pass through, and a frequency at which the driving force becomes zero is less likely to occur. Therefore, the frequency response characteristics are improved.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of the present invention.

FIG. 1 is a sectional view of a sound pressure gradient type microphone according to this embodiment, and FIG. 2 is a rear view thereof. This embodiment is characterized in that a diaphragm made of a plastic film is stretched as a baffle 17 on the opening end surface of the ventilation hole 7 on the rear acoustic terminal 16 side, and the other components are shown in FIGS. This is exactly the same as the conventional example. Therefore, the same components are denoted by the same reference numerals, and overlapping description will be omitted.

Since the baffle 17 is composed of a diaphragm, it operates as a large baffle having a high impedance in the middle and low tone ranges, and has a low impedance in the high tone range, so that sound waves can easily pass through. Therefore, it becomes difficult to generate a frequency at which the driving force becomes zero. In this embodiment, the plastic film stretched as the baffle 17 is 1
The baffle 1 is a PET film having a thickness of 2 μm.
FIG. 3 is a characteristic diagram showing a measured frequency response when the above-described configuration is applied to the unidirectional electret condenser microphone as the sound pressure gradient microphone using the No. 7 microphone.

As a result, in the sensitivity comparison at the same frequency response, the baffle having only the acoustic resistance increases the sensitivity by 2 to 3 dB as compared with the case without the baffle, and the vibration increases as compared with the baffle having only the acoustic resistance. In the case of a baffle using a plate, the sensitivity is further increased by 1 to 1.5 dB.

Incidentally, according to the measured characteristic diagram, the sensitivity at the reference frequency is -30.5 dB / Pa,
N is 79 dB.

[0014]

[Effects of the Invention] As described above, according to the invention,
For example, in a sound pressure gradient type microphone,
Air leaks through the ventilation holes provided in the
Baffle plate made of film vibrating by waves
As a result, the frequency at which the driving force becomes 0 can be reduced, so that the frequency response characteristics can be improved, and the sensitivity can be improved as compared with the case without a baffle having the same frequency response. Also, the S / N ratio can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a sound pressure gradient type microphone according to an embodiment of the present invention.

FIG. 2 is a rear view of the sound pressure gradient type microphone shown in FIG. 1;

FIG. 3 is a measurement diagram showing a frequency characteristic of the sound pressure gradient type microphone according to the embodiment.

FIG. 4 is a cross-sectional view showing an example of a conventional sound pressure gradient microphone.

FIG. 5 is a front view of the sound pressure gradient type microphone shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microphone unit 2 Diaphragm 3 Back electrode plate 4 Case 5 Acoustic resistance material 7 Vent hole 8 Opening 9 Case front part 10 Diaphragm support ring 15 Front acoustic terminal 16 Rear acoustic terminal 17 Baffle

Claims (1)

(57) [Scope of request for utility model registration] (1) A predetermined interval is provided between a diaphragm and a back electrode plate.
Including the case that is opposed to
A front acoustic terminal for the diaphragm is arranged on the front side,
If the rear acoustic terminal is located on the rear side of the case
In both cases, the front acoustic terminal side and the upper
There is a ventilation hole that communicates with the rear acoustic terminal side.
Ri, captures sound pressure acoustic between upper Symbol both acoustic terminal - in sound pressure gradient type microphone for performing mechanical conversion, the above-mentioned ventilation hole, there is no air leakage and, depending on the wave
Baffle plate made of vibrating film
Sound pressure gradient type microphone, characterized in that that.