JPH1127781A - Sound pressure microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce dispersion of a phase characteristic in a low frequency range, without the need for high machining accuracy by venting the rear pole part space of a condenser type sound pressure microphone and the outside through an acoustic resistor that is formed with a porous sintered metal, and maintaining equally static pressure inside and outside a diaphragm film even if there is fluctuation of atmospheric pressure. SOLUTION: A diaphragm film 2 is attached to an open end of a cylindrically peripheral wall 1, a rear pole 3 is arranged in the wall 1 to face the film 2, an output terminal 4 is connected to the pole 3, an insulator 6 which has a penetration hole 6a at its center as a barrier plate to form a rear pole part space 5 is attached to the wall 1 and further, a gap 7 which is formed by the hole 6a of the insulator 6 and the terminal 4 that is inserted loosely into the hole 6a is closed by a sintered metallic body 8 as an acoustic resistor. The body 8 is a porous member that has many continuous air holes consisting of metallic powder such as stainless powder and bronze powder and has little dispersion in the viscosity resistance of average air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound pressure microphone used for a sound intensity probe to which a two-microphone method is applied.

[0002]

2. Description of the Related Art In a sound intensity probe to which the two-microphone method is applied, a difference in phase characteristics between two microphones particularly in a low frequency region greatly affects the measurement accuracy of the sound intensity. For this reason, when manufacturing an acoustic intensity probe, the processing accuracy of each microphone is increased to make the phase characteristics uniform, or a number of microphones are made, and two microphones having the same phase characteristics are selected from among them. I have.

As shown in FIG. 5, a conventional condenser-type sound pressure microphone is designed to maintain the same static pressure inside and outside the diaphragm 100 so that a correct sound pressure can be obtained even when the atmospheric pressure fluctuates. Inside of microphone (back space) 1
A very narrow pressure balance passage 103 that ventilates the outside (outside) from the outside is formed in an insulator 104 serving as a partition. In addition, 105 is a back pole, 106 is an output terminal, and 107 is an outer peripheral wall.

[0004]

However, since the pressure balancing passage 103 is very thin and has a large viscous resistance to the air and acts as an acoustic resistance, the inside of the diaphragm 100 passes through the pressure balancing passage 103 at a high frequency. , But at a low frequency, the inside of the diaphragm 100 is affected. Therefore, when measuring the sound pressure, the provision of the pressure equilibrium passage 103 makes it possible to directly
In addition to the sound pressure applied to the diaphragm 100 from the outside of 0, the sound pressure is also applied to the diaphragm 100 from the inside of the diaphragm 100 through the pressure equilibrium passage 103, which causes the phase characteristic to be disturbed.

[0005] Since the frequency range and the degree of influence are determined by the shape of the pressure balance passage 103, in order to reduce the difference in phase characteristics between the microphones, the pressure balance passage 103 of the paired microphones must be reduced. It is necessary to reduce the variation in the processing accuracy so as to have the same shape. However, in the case of a low frequency, the pressure equilibrium passage 10 is sufficient to satisfy the desired phase characteristic.
It is not easy to machine 3 because it requires a high machining accuracy, and it is difficult to machine the pressure balancing passage 103 into the same shape for the paired microphones.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to reduce the variation in the phase characteristics of the low-frequency band of a microphone and achieve a special processing accuracy. It is intended to propose a sound pressure microphone that does not require a microphone.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to ventilate the space between the back pole and the outside through an acoustic resistor.

[0008] The acoustic resistor may be formed of a porous sintered metal.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a schematic sectional view of a sound pressure microphone according to the present invention, FIG. 2 is a sectional view showing a mounted state of a sintered metal body, FIG. 3 is an exploded perspective view of a female member of an output terminal, and FIG. It is sectional drawing which shows the other attachment states of a binding metal body.

As shown in FIG. 1, the sound pressure microphone according to the present invention is a condenser type microphone, in which a diaphragm 2 is attached to an open end of a cylindrical outer peripheral wall 1 so as to face the diaphragm 2. A back electrode 3 is disposed in the outer peripheral wall 1, an output terminal 4 is connected to the back electrode 3, and an insulator 6 provided with a through hole 6 a at the center as a partition to form a back electrode space 5 is formed on the outer peripheral wall 1.
And a gap 7 formed between the through-hole 6a of the insulator 6 and the output terminal 4 loosely mounted in the through-hole 6a is closed by a sintered metal body 8 as an acoustic resistor.

The sintered metal body 8 is cylindrical and has a through hole 8a formed in the axis thereof, and the output terminal 4 is fitted into the through hole 8a and abuts on the insulator 6 to close the gap 7. . A DC voltage source for bias connected to the output terminal 4 and the like and a case connected to the outer peripheral wall 1 are not shown.

The sintered metal body 8 is made of a porous material having a large number of continuous ventilation holes in place of the pressure equilibrium passage 103 used in the conventional sound pressure microphone in order to ventilate the back electrode space 5 and the outside world. It is a quality member. For the sintered metal body 8, a metal powder such as a stainless steel powder or a bronze powder is used as a raw material powder.

A large number of air holes 1 in the sintered metal body 8
Although the size and shape of each sintered metal body 8 are different from each other, the average viscous resistance of air when the entire sintered metal body 8 is considered as a pressure equilibrium passage is substantially equal between the plurality of sintered metal bodies 8.

As a result, variations in the phase characteristics of the sound pressure microphone at low frequencies are reduced. Further, holes and grooves as pressure equalizing passages are not required, and no special processing accuracy is required.

As the acoustic resistor, a sintered metal body 8 is used.
A ceramic sintered member having the same structure as described above, a polymer material, a sheet of a continuous porous body of ethylene tetrafluoride, or the like may be used.

As shown in FIG. 2, a male member 4a of the output terminal 4 formed integrally with the back electrode 3 is inserted into a through hole 8a of the sintered metal body 8, as shown in FIG. Next, the male member 4a is screwed into the female member 4b of the output terminal 4, and the sintered metal body 8 is sandwiched between the locking portion 4c formed on the outer periphery of the male member 4a and the insulator 6.

The female member 4b of the output terminal 4 is fixed in contact with the insulator 6 by screwing the male member 4a. The outer diameter of the sintered metal body 8 is larger than the inner diameter of the through hole 6a of the insulator 6.

The female member 4b is, as shown in FIG.
A fitting member 4e formed from below to form a through hole 4d and fits into the through hole 6a of the insulator 6, a press ring 4g formed with a through hole 4f, and a blind thread formed on the inner peripheral surface of the through hole 4h. And a tube terminal member 4i.

By screwing the male member 4a of the output terminal 4 into the female member 4b of the output terminal 4, the sintered metal body 8
And functions as a pressure equilibrium passage between the back pole space 5 and the outside world, and can electrically connect the back pole 3 to the female member 4b.

As described above, since the sintered metal body 8 is fixed by sandwiching it between the locking portion 4c and the insulator 6, no adhesive is required.
The ventilation holes of the sintered metal body 8 are not closed by the adhesive, and as a result, it is possible to prevent the variation in acoustic resistance of the sintered metal body 8 from occurring.

As another mounting method of the sintered metal body, as shown in FIG. 4, a cylindrical output terminal 10 is formed integrally with the back electrode 3, and a circular portion 11 is formed in the hollow portion 11 of the output terminal 10. After the columnar sintered metal body 12 is fitted, the output terminal 10 can be fitted into the through-hole 6 a of the insulator 6. Reference numeral 13 denotes an electrode screwed to the tip of the output terminal 10.

The wall 10a of the output terminal 10 has a plurality of through-holes 10b communicating the back electrode space 5 and the hollow portion 11, a step portion 10c for bringing the sintered metal body 12 into contact with and positioning, and a hollow portion 11a. And a plurality of through-holes 10d communicating with the outside world.

The cylindrical sintered metal body 12 is formed by sintering at a predetermined temperature in a state where a metal cylindrical member is filled with metal particles. When the sintered metal body 12 is fitted into the hollow portion 11 of the output terminal 10, an unnecessary gap is not formed between the outer peripheral surface of the sintered metal body 12 and the inner peripheral surface of the output terminal 10. This part is sealed with an adhesive or the like.

By inserting the output terminal 10 with the sintered metal body 12 fitted therein into the through-hole 6a of the insulator 6, the through-hole 10b and the hollow space are formed between the back electrode space 5 and the outside world. Part 11, sintered metal body 12, hollow part 11, and through hole 10d
Thus, a desired ventilation state is maintained.

According to the method of mounting the sintered metal body 12 shown in FIG. 4, compared to the method of mounting the sintered metal body 8 shown in FIG.
It becomes easy to apply to a smaller microphone.

[0026]

As described above, according to the present invention, the space between the back pole portion and the outside world is ventilated through the acoustic resistor, thereby replacing the pressure equilibrium passage and requiring no special processing accuracy. In addition, variations in the phase characteristics of the microphone in the low frequency region can be reduced.

Further, by using a sintered metal body having a large number of continuous ventilation holes as the acoustic resistor, it is possible to further reduce the variation in the phase characteristics of the microphone in the low frequency region.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a sound pressure microphone according to the present invention.

FIG. 2 is a cross-sectional view showing a mounted state of a sintered metal body.

FIG. 3 is an exploded perspective view of a female member of the output terminal.

FIG. 4 is a sectional view showing another mounting state of the sintered metal body.

FIG. 5 is a schematic sectional view of a conventional sound pressure microphone.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer peripheral wall, 2 ... Vibration film, 3 ... Back electrode, 4, 10 ... Output terminal, 5 ... Back electrode space, 6 ... Insulator, 7 ... Gap, 8, 12
... Sintered metal body (acoustic resistor).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Hayashi 3-4-2-21 Owada-cho, Hachioji-shi, Tokyo Inside the National Acoustic Research Institute

Claims (2)

[Claims] 1. A sound pressure microphone wherein the back pole space and the outside world are ventilated through an acoustic resistor. 2. The sound pressure microphone according to claim 1, wherein said acoustic resistor is formed of a porous sintered metal.