JP2005328347A - Acoustic resistance measuring device of acoustic resistance material and adjusting method of same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure acoustic resistance with high precision without destroying an acoustic resistance material, and to match the resistance of an acoustic resistance material to a reference value with high precision. <P>SOLUTION: The acoustic resistance measuring device comprises first piping 10 having one end connected with a compressed air supply C and the other end 11 arranged with a reference acoustic resistance material 40S and provided with an air throttle section 12 in the way; second piping 20 of identical arrangement having one end connected with the compressed air supply C and the other end 21 arranged with a acoustic resistance material 40X to be measured and provided with an air throttle section 22 in the way; and a bridge pipe 30 having a differential pressure gage 31 and coupled between the first piping 10 and the second piping 20 on the downstream side of the air throttle sections 12 and 22. An equivalent circuit of Wheatstone bridge is constituted and acoustic resistance of the acoustic resistance material 40X is measured. Acoustic resistance of the acoustic resistance material 40X to be measured can be matched to the acoustic resistance of the reference acoustic resistance material 40S. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acoustic resistance measuring device for an acoustic resistance material used for a microphone and an acoustic resistance adjusting method for an acoustic resistance material, and more specifically, a technique that enables highly accurate measurement and adjustment without damaging the acoustic resistance material. It is about.

  The primary sound pressure gradient condenser microphone has a rear acoustic terminal, and an acoustic resistance material such as a nylon mesh or a sponge having open cells is arranged in a sound wave path extending from the rear acoustic terminal to the back surface of the diaphragm (for example, Patent Document 1).

  Usually, the acoustic resistance material on the rear acoustic terminal side is attached to the back side of the fixed pole support pedestal having a sound hole (sound wave introduction hole) via an adjustment nut, for example, and a predetermined sound is obtained by adjusting the tightening force of the adjustment nut. Although it is adjusted to the resistance value, individual differences in acoustic resistance values cause large variations in directivity.

  Therefore, when assembling the microphone unit, the resistance value of the acoustic resistance material is measured in advance to match the reference value. As a method for measuring the resistance value of an acoustic resistance material, for example, a method of checking the transmittance of sound waves and the transmittance of compressed air is known.

  However, in a narrow directivity microphone unit used for a line microphone (gun microphone) or the like, the acoustic resistance on the rear acoustic terminal side is extremely high. Therefore, in the method for measuring the transmittance of the sound wave or the compressed air, a large sound wave or compressed air must be applied to the sound resistance material, which may destroy the sound resistance material.

JP 2000-50386 A

  Therefore, the problem to be solved by the present invention is to measure the acoustic resistance value with high accuracy without destroying the acoustic resistance material, and to adjust the resistance value of the acoustic resistance material to the reference value with high accuracy. There is to be able to do it.

  In order to solve the above-mentioned problem, the first invention of the present application is an acoustic resistance measuring device for an acoustic resistance material, in which compressed air is blown to an acoustic resistance material used for a microphone and the acoustic resistance is measured. A reference acoustic resistance material that is connected to the other end of the pipe and has a reference acoustic resistance material disposed at the other end and an air throttle part in the middle thereof, and one end connected to the compressed air supply source and the other end of the pipe end The acoustic resistance material to be measured is disposed on the air pipe, and has an air throttle portion in the middle thereof, the second pipe having the same configuration as the first pipe including the air resistance value of the air throttle section, and the differential pressure gauge. A bridge pipe connected between the first pipe and the second pipe is provided downstream of each air restrictor.

  In the first aspect of the invention, it is preferable that the air resistance value of each air restrictor is set to a value substantially equal to the acoustic resistance value of the reference acoustic resistance material. In addition, a throttle valve or the like can be used for each of the air restrictors, but from the viewpoint of cost, each of the air restrictors is a pipe having a smaller diameter than the other parts of the first and second pipes. It is preferable.

  In order to solve the above-mentioned problem, the second invention of the present application is substantially equal to the acoustic resistance value of the reference acoustic resistance material used as a reference based on the acoustic resistance value of the acoustic resistance material (adjusted acoustic resistance material) used in the microphone. In the acoustic resistance adjustment method of the acoustic resistance material to be adjusted as described above, a first end having one end connected to a compressed air supply source, the reference acoustic resistance material disposed at the other end side of the tube end, and an air throttle portion in the middle thereof. The pipe and one end are connected to the compressed air supply source, the adjusted acoustic resistance material is arranged at the other end of the pipe, and the air restrictor is included in the middle, including the air resistance value of the air restrictor A second pipe having the same configuration as that of the first pipe, and a bridge pipe having a differential pressure gauge and connected between the first pipe and the second pipe on the downstream side of each air restrictor, Fixed pole support with sound hole The differential pressure gauge is disposed at the pipe end of the second pipe in a state of being mounted on the pedestal via the pressing force varying means, and the compressed air is supplied from the compressed air supply source to the first and second pipes. The pressing force of the pressing force varying means with respect to the to-be-adjusted acoustic resistance material is adjusted so that the read value becomes zero.

  The acoustic resistance measuring device for acoustic resistance material according to the first aspect of the invention can be regarded as a Wheatstone bridge circuit. That is, the pipe part including each air throttle part of the first pipe and the second pipe corresponds to the fixed side, and the pipe part where the reference acoustic resistance material is arranged downstream of the air throttle part of the first pipe is the reference side. Correspondingly, the pipe portion where the acoustic resistance material to be measured is arranged on the downstream side of the air throttle portion of the second pipe corresponds to the side to be measured, and the differential pressure gauge corresponds to the galvanometer. Therefore, the acoustic resistance value of the acoustic resistance material to be measured with respect to the reference acoustic resistance material can be measured based on the indication value of the differential pressure gauge.

  According to the second aspect of the present invention, when adjusting the acoustic resistance value of the adjusted acoustic resistance material by the pressing force variable means (for example, an adjusting nut), the pressing force variable means is adjusted so that the reading of the differential pressure gauge becomes zero. By adjusting the pressing force, the acoustic resistance value of the adjusted acoustic resistance material can be adjusted to the reference acoustic resistance value of the reference acoustic resistance material.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2, but the present invention is not limited to this. FIG. 1 is a schematic diagram showing an acoustic resistance measuring apparatus for acoustic resistance material according to the present invention, and FIG. 2 is an equivalent circuit diagram thereof.

  Referring to FIG. 1, the acoustic resistance measuring apparatus for acoustic resistance material according to the present invention includes a first pipe 10 and a second pipe 20 that are both connected to a compressed air supply source C at one end side. An air compressor can be used as the compressed air supply source C. It is preferable that the first pipe 10 and the second pipe 20 have the same length and inner diameter.

  The pipe end 11 on the other end side of the first pipe 10 is formed in a tray shape, and a reference acoustic resistance material 40S having a known acoustic resistance value is disposed therein. An air throttle 12 is provided in the middle of the first pipe 10. Although the air throttle part 12 may be comprised from a throttle valve, in this example, the thin pipe material 12a whose diameter is smaller than the main pipe internal diameter of the 1st piping 10 is used as the air throttle part 12. FIG. That is, only the air throttle part 12 in the air passage in the first pipe 10 is made narrower than the other parts. According to this, the cost concerning the air throttle part 12 can be made cheap.

  The pipe end 21 on the other end side of the second pipe 20 is also formed in a tray shape, and a measured (adjusted) acoustic resistance material 40X having an unknown acoustic resistance value is disposed therein. An air restrictor 22 is also provided in the middle of the second pipe 20. As the air throttle portion 22 on the first pipe 10 side, a pipe material 22a having a smaller diameter than the main pipe inner diameter of the second pipe 20 is used for the air throttle portion 22.

  The air resistance values of the air throttle unit 12 and the air throttle unit 22 are the same. Note that, for example, one of the air throttling portions 12 and 22 may be a throttling valve capable of adjusting the flow rate, and the air resistance value may be matched with the air resistance value of the air throttling portion made of the other pipe material.

  A bridge pipe 30 having a differential pressure gauge 31 is connected between the first pipe 10 and the second pipe 20 on the downstream side (pipe end side) of the air restrictors 12 and 22. The differential pressure gauge 31 is preferably provided approximately at the center of the bridge tube 30. In this example, the differential pressure gauge 31 includes an analog indicator instrument 32 having a pointer 32a. However, for example, a digital indicator instrument may be used.

  The reference acoustic resistance material 40S is arranged at the pipe end 11 of the first pipe 10, and the measured acoustic resistance material 40X is arranged at the pipe end 21 of the second pipe 20 so that the compressed air is supplied from the compressed air supply source C at a predetermined pressure. Supply. Here, when the pressure in the first pipe 10 is P1, the pressure in the second pipe 20 is P2, and P1 = P2, the pointer 32a indicates “0”, and if P1> P2, the pointer 32a is, for example, “+ ”(Clockwise in FIG. 1), and if P1 <P2, the pointer 32a swings in the“ − ”direction (counterclockwise in FIG. 1), for example.

  Since the pressure P1 in the first pipe 10 reflects the acoustic resistance value of the reference acoustic resistance material 40S, and the pressure P2 in the second pipe 20 reflects the acoustic resistance value of the acoustic resistance material 40X to be measured, By observing how the pointer 32a swings, it can be determined whether the acoustic resistance value of the acoustic resistance material to be measured 40X is equal to, smaller or larger than the acoustic resistance value of the reference acoustic resistance material 40S. That is, if the pointer 32a swings in the “+” direction, the acoustic resistance value is higher in the reference acoustic resistance material 40S, and conversely, if the pointer 32a swings in the “−” direction, the measured acoustic resistance material 40X is higher. .

  In the present invention, the acoustic resistance measuring device having the above configuration is used as it is, and the acoustic resistance value of the acoustic resistance material to be measured (in this case, the acoustic resistance material to be adjusted) 40X is matched with the acoustic resistance value of the reference acoustic resistance material 40S. Can be adjusted. Therefore, the acoustic resistance value of the to-be-adjusted acoustic resistance material 40 </ b> X is made adjustable and arranged at the pipe end 21 of the second pipe 20.

  In this example, the acoustic resistance material 40X to be adjusted is mounted on the support base 42 of the fixed pole 41 and is actually incorporated into the microphone unit. The support pedestal 42 is provided with a plurality of sound holes (sound wave introduction holes) 42a. Although not shown, the fixed pole 41 is also provided with a plurality of sound holes. It is guided through the sound hole to the back surface of a diaphragm (not shown) disposed opposite to the fixed pole 41.

  The to-be-adjusted acoustic resistance material 40X is disposed on the back side of the support base 42 so as to cover all the sound holes 42a. The adjusted acoustic resistance material 40X is made of nylon mesh or open-cell sponge (for example, Bridgestone Sponge HR-50), and the acoustic resistance value changes depending on the compression ratio.

  A cylindrical boss 42b having a male screw protrudes from the back side of the support pedestal 42, and an adjustment nut (pressing force varying means) 43 that applies a pressing force to the adjusted acoustic resistance material 40X to the boss 42b. The acoustic resistance value of the to-be-adjusted acoustic resistance material 40X is changed by screwing in and out.

  Reference numeral 44 denotes an electrode rod fitted to the boss 42b for taking out an electric signal generated in the fixed pole 41, and is connected to an impedance converter (for example, FET: field effect transistor) not shown.

  Further, in this example, the reference acoustic resistance material 40S has the same conditions as the adjusted acoustic resistance material 40X, and therefore the pipe end 11 of the first pipe 10 is disposed on the back side of the support base 42 that supports the fixed pole 41. Placed in.

  As described above, after the adjusted acoustic resistance material 40X and the reference acoustic resistance material 40S are mounted on the support pedestal 42 and arranged on the tube ends 11 and 21 of the acoustic resistance measuring device having the above-described configuration, the compressed air supply source C Compressed air is supplied to the first pipe 10 and the second pipe 20 at a predetermined pressure. Then, by adjusting the tightening force (pressing force) of the adjustment nut 43 against the adjusted acoustic resistance material 40X so that the pointer 32a of the indicating instrument 32 of the differential pressure gauge 31 indicates “0”, the adjusted acoustic resistance material 40X is adjusted. The acoustic resistance value can be accurately adjusted to the acoustic resistance value of the reference acoustic resistance material 40S.

  In this case, in order to achieve a more accurate adjustment of the acoustic resistance value, the air resistance values of the air restrictors 12 and 22 of the first pipe 10 and the second pipe 20 are close to the acoustic resistance value of the reference acoustic resistance material 40S. It is preferable to use a value.

  The acoustic resistance measuring device can be regarded as a Wheatstone bridge circuit shown in FIG. That is, the pipe portion including the air throttle parts 12 and 22 of the first pipe 10 and the second pipe 20 corresponds to the fixed resistances R1 and R2 of the fixed side, and is the reference on the downstream side of the air throttle part 12 of the first pipe 10. The piping portion where the acoustic resistance material 40S is arranged corresponds to the reference resistance R3 of the reference side, and the piping portion where the adjusted acoustic resistance material 40X is arranged on the downstream side of the air throttle portion 22 of the second piping 20 is the measured side. The differential pressure gauge 31 corresponds to the galvanometer G.

  In this way, a Wheatstone bridge is configured with each ventilation resistance of the first pipe 10 and the second pipe 20 (including each acoustic resistance of the reference acoustic resistance material 40S and the adjusted acoustic resistance material 40X), and the differential pressure is measured. By doing so, highly accurate acoustic resistance measurement and acoustic resistance adjustment can be performed.

When the acoustic resistance on the rear acoustic terminal side is particularly high, such as a line microphone (gun microphone), by increasing the air resistance value of each of the air throttling portions 12 and 22, accurate acoustic resistance measurement and sound Resistance adjustment is possible. Moreover, since the pressure of compressed air may be a low value of about 1000 mmH ₂ O, for example, there is no possibility of destroying the acoustic resistance materials 40S and 40X.

The schematic diagram which shows the acoustic resistance measuring apparatus of the acoustic resistance material by this invention. The equivalent circuit diagram of the said acoustic resistance measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st piping 11 Pipe end 12 Air throttle part 12a Pipe material 20 2nd piping 21 Pipe end 22 Air throttle part 22a Pipe material 30 Bridge pipe 31 Differential pressure gauge 32 Indicator instrument 40S Reference | standard acoustic resistance material 40X Measured (adjusted) sound Resistance material 41 Fixed pole 42 Support base 43 Adjustment nut

Claims (4)

In the acoustic resistance measuring device of the acoustic resistance material for measuring the acoustic resistance by blowing compressed air on the acoustic resistance material used for the microphone,
One end is connected to a compressed air supply source, a reference acoustic resistance material serving as a reference is disposed at the other end of the tube, and a first pipe having an air restrictor in the middle, and one end connected to a compressed air supply source. A second pipe having the same configuration as the first pipe, the acoustic resistance material to be measured being disposed at the pipe end on the other end side and having an air throttle part in the middle thereof, including the air resistance value of the air throttle part; An acoustic resistance measuring device for an acoustic resistance material, comprising a differential pressure gauge and a bridge pipe connected between the first pipe and the second pipe on the downstream side of each air restrictor. .   2. The acoustic resistance measurement device for an acoustic resistance material according to claim 1, wherein an air resistance value of each of the air restriction portions is set to a value substantially equal to an acoustic resistance value of the reference acoustic resistance material.   The acoustic resistance measuring device for an acoustic resistance material according to claim 1, wherein each of the air restricting portions is a pipe having a smaller diameter than other portions of the first and second pipes. In the acoustic resistance adjustment method of the acoustic resistance material, the acoustic resistance value of the acoustic resistance material (adjusted acoustic resistance material) used for the microphone is adjusted to be substantially equal to the acoustic resistance value of the reference acoustic resistance material as a reference.
A first pipe having one end connected to a compressed air supply source and the reference acoustic resistance material disposed at the other end of the pipe and having an air constriction in the middle, and one end connected to the compressed air supply source and the other end A second pipe having the same configuration as that of the first pipe, including the air-throttle part in the middle thereof, including the air resistance value of the air-throttle part, and the adjusted acoustic resistance material disposed at the pipe end on the side A bridge pipe that has a pressure gauge and is connected between the first pipe and the second pipe on the downstream side of each air restrictor;
The adjusted acoustic resistance material is disposed at the pipe end of the second pipe in a state of being attached to a fixed pole support base having a sound hole via a pressing force varying means, and the first and second from the compressed air supply source. Compressed air is supplied to the pipe, and the pressing force of the pressing force varying means on the adjusted acoustic resistance material is adjusted so that the reading of the differential pressure gauge at that time becomes 0. Acoustic resistance adjustment method.

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