JP2007194768A - Acoustic resistance measurement apparatus for acoustic resistance member, and measurement method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of accurately measuring the acoustic resistance of an object to be measured, even if the acoustic resistance member that is an object to be measured is a soft material, such as sponge. <P>SOLUTION: An acoustic resistance measurement apparatus disclosed herein includes a hollow housing 10 on an upper side 11 of which has an opening 12; a speaker 21 for emitting a sound wave to one face of the acoustic resistance member AR; a microphone 22 arranged to the other side of the acoustic resistance member AR and for picking up the sound wave transmitting through the acoustic resistance member AR; a measurement unit 23 for measuring the magnitude of picked-up sound; and an exhaust fan 14 for exhausting air inside the housing, and the acoustic resistance member AR is placed on the upper side 11 of the housing 10 in a way of covering the opening 12, the sound wave is emitted from the speaker 21 toward one side of the acoustic resistance member AR, the microphone 22 picks up the sound waves transmitted through the acoustic resistance member AR; and when the measurement unit 23 measures the acoustic resistance of the acoustic resistance member AR, the exhaust fan 14 exhausts the air inside the housing 10 and the circumferential edge part of the acoustic resistance member AR is adhered closely and fixed to the upper side 11 of the housing 10 under atmospheric pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acoustic resistance measuring device for an acoustic resistance material used for a microphone and a measurement method thereof, and more specifically, the acoustic resistance of a sheet-like acoustic resistance material alone is accurately measured without applying an extra load. It relates to the technology to measure.

  The microphone is provided with several acoustic resistance members in the sound wave path from the sound source to the acoustic-electric converter built in the microphone unit. In general, this type of acoustic resistance material is a fine mesh mesh, felt material, or open-cell sponge material, which adjusts the acoustic conditions of the microphone unit and prevents wind noise. This also applies to windscreens.

  As described in Non-Patent Document 1, a method of measuring acoustic impedance includes a proximity method, a reflection method, and the like. However, in order to measure only acoustic resistance, the sound transmitted through the acoustic resistance material is measured. A method of measuring the magnitude (sound pressure) is common. In this specification, this measurement method is called a transmission method for convenience, and an example thereof will be described with reference to the schematic diagrams of FIGS.

  First, as shown in FIG. 3, in the transmission method, a hollow housing 10 having a flat upper surface 11 is used. The upper surface 11 is a mounting surface on which a sheet-like acoustic resistance material AR, which is an object to be measured, is detachably mounted. The upper surface (mounting surface) 11 has an opening 12 covered with the acoustic resistance material AR. Is formed.

  A speaker 21 serving as a sound emitting unit is disposed outside the housing 10 and directly above the opening 12. On the other hand, a microphone 22 serving as a sound collecting unit is disposed inside the housing 10. Arranged directly below. The microphone 22 is connected to a measuring instrument 23 such as a level meter.

  According to this configuration, in a state where the acoustic resistance material AR is placed on the upper surface 11 of the housing 10 so as to cover the opening 12, sound waves are emitted from the speaker 21 with a substantially constant sound pressure, and the acoustic resistance material The sound wave transmitted through the AR is picked up by the microphone 22, and the microphone output is measured by the measuring device 23, so that the sound pressure emitted from the speaker 21 and the sound pressure picked up by the microphone 22 are Based on the ratio, the acoustic resistance of the acoustic resistance material AR can be measured. The unit of acoustic resistance is usually expressed in g (grams) / sec (seconds).

Masaaki Nishimaki, “Revised Electroacoustic Vibration”, published by Corona, April 24, 1982, 24th edition (see p228-230)

  Incidentally, as shown exaggeratedly in FIG. 3, the sheet-like acoustic resistance material AR is somewhat undulated, and even if it is flat, the acoustic resistance material AR is simply the upper surface of the housing 10. 11, a part of the sound wave emitted from the speaker 21 enters the housing 10 through the opening 12 from between the acoustic resistance material AR and the upper surface 11 of the housing 10. Therefore, the reliability of measurement is impaired.

  Therefore, conventionally, as shown in FIG. 4, for example, a cylindrical weight W is placed on the peripheral portion of the acoustic resistance material AR around the opening 12, and the acoustic resistance material AR is placed on the upper surface 11 of the housing 10. It is trying to press against it.

  However, in the case where the acoustic resistance material AR is a relatively hard material, there is no particular problem even if the weight W is placed, and the change in acoustic resistance is not particularly problematic. However, when the acoustic resistance material AR is a soft material such as a sponge. Is still problematic in terms of measurement reliability, since the acoustic resistance changes greatly due to compression.

  Accordingly, an object of the present invention is to apply a sound wave having a predetermined sound pressure to one surface side of the acoustic resistance material, collect the sound wave transmitted through the acoustic resistance material, and measure the acoustic resistance of the acoustic resistance material. The object is to enable accurate measurement of acoustic resistance even if the acoustic resistance material is a soft material such as sponge.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a sheet-like acoustic resistance material disposed in a sound wave path from a sound source to an acoustic-electric converter included in a microphone, and the acoustic resistance is reduced. In the acoustic resistance measurement apparatus for an acoustic resistance material to be measured, a hollow housing having an opening having a size covered by the acoustic resistance material on an upper surface on which the acoustic resistance material is detachably mounted, and the acoustic resistance A sound emitting means for emitting sound waves toward one surface of the material; a sound collecting means for collecting sound waves that are disposed on the other surface side of the acoustic resistance material; Measuring means for measuring the volume of sound collected by the means, and exhaust means for exhausting the air in the housing.

  According to a second aspect of the present invention, in the first aspect, the sound emitting means is a speaker and is disposed on the outside of the casing and directly above the opening, and the sound collecting means is a microphone. It is arrange | positioned just under the said opening part inside.

  According to a third aspect of the present invention, in the first or second aspect, an exhaust fan is used as the exhaust means.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a bar-like or lattice-like support body that flatly supports the acoustic resistance material is provided in the opening. It is characterized by.

  In order to solve the above-mentioned problem, the invention according to claim 5 is characterized in that a sheet-like acoustic resistance material disposed in a sound wave path from a sound source to an acoustic-electric converter included in a microphone is used as a single unit. In the acoustic resistance measurement method of an acoustic resistance material for measuring resistance, a hollow housing having an opening having a size covered by the acoustic resistance material on an upper surface on which the acoustic resistance material is detachably mounted; and A sound emitting means for emitting sound waves toward one surface of the acoustic resistance material; a sound collection means for collecting sound waves that are disposed on the other surface side of the acoustic resistance material and that pass through the acoustic resistance material; and Measuring means for measuring the volume of sound collected by the sound collecting means, and exhaust means for exhausting air in the housing, and the acoustic resistance so as to cover the opening on the upper surface of the housing A material is placed and the acoustic resistance is A sound wave is emitted toward one surface of the material, and a sound wave transmitted through the acoustic resistance material is collected by the sound collecting means disposed on the other surface side of the acoustic resistance material, and the measurement is performed. When the acoustic resistance of the acoustic resistance material is measured by the means, the air inside the casing is exhausted by the exhaust means so that the peripheral portion of the acoustic resistance material is brought into close contact with the upper surface of the casing at atmospheric pressure. It is characterized by fixing.

  According to the first or fifth aspect of the invention, a hollow housing having an opening having a size covered by the acoustic resistance material on an upper surface on which the acoustic resistance material formed in a sheet shape is detachably mounted. A sound collecting means for emitting a sound wave toward one surface of the body, the sound resistance material, and a sound collecting device disposed on the other surface side of the sound resistance material and collecting the sound wave transmitted through the sound resistance material Means, measuring means for measuring the volume of sound collected by the sound collecting means, and exhaust means for exhausting air in the casing, and covering the opening on the upper surface of the casing The sound collecting means is placed on the other surface side of the acoustic resistance material while the acoustic resistance material is placed on the acoustic resistance material and the sound emitting means emits a sound wave toward one surface of the acoustic resistance material. The sound wave that passes through the acoustic resistance material is collected at When measuring the acoustic resistance of the acoustic resistance material, the air in the housing is exhausted by the exhaust means, and the peripheral portion of the acoustic resistance material is brought into close contact with the upper surface of the housing at atmospheric pressure and fixed. Thus, even if the acoustic resistance material is an acoustic resistance material whose acoustic resistance changes when compressed, for example, like a sponge material, the acoustic resistance can be accurately measured. In addition, since an additional fixing means such as a weight for pressing and fixing the acoustic resistance material is unnecessary, stable measurement can be easily performed.

  Preferably, a speaker is used as the sound emitting means, and a microphone is used as the sound collecting means. The speaker may be disposed inside the housing and the microphone may be disposed outside the housing. However, as in the invention according to claim 2, the speaker is disposed outside the housing and directly above the opening. By placing the microphone inside the housing and directly under the opening, the microphone is isolated from the outside by the housing, so only the sound from the speaker can be collected, increasing the measurement reliability. It is done.

  The exhaust means may be a negative pressure source such as a vacuum pump. However, as in the invention described in claim 3, by using an exhaust fan as the exhaust means, the apparatus can be simplified and the equipment cost can be reduced. Can be planned.

  According to the invention described in claim 4, wherein the opening is provided with a cross-shaped or grid-like support that flatly supports the acoustic resistance material. In fixing the resistance material, it is possible to prevent a partial dent of the acoustic resistance material corresponding to the opening.

  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 sectional view showing an acoustic resistance measuring device for an acoustic resistance material according to the present invention, and FIG. 2 is a perspective view showing a configuration of a support according to claim 4. In the description of this embodiment, the same reference numerals are assigned to components that do not require any change from the conventional example described in FIGS.

  As shown in FIG. 1, the acoustic resistance measuring apparatus for acoustic resistance material according to the present invention includes a housing 10 whose inside is hollow. The upper surface 11 of the housing 10 is formed as a flat mounting surface on which a sheet-like acoustic resistance material AR, which is an object to be measured, is detachably mounted. The upper surface 11 is covered with the acoustic resistance material AR. An opening 12 that is covered, that is, smaller than the acoustic resistance material AR is formed.

  The acoustic resistance material AR used for measurement is a mother acoustic resistance material made of a fine mesh mesh, felt material, open-cell sponge material, etc., and determined to have an appropriate acoustic resistance. An acoustic resistance material having an individual size is cut out from the mother acoustic resistance material AR for each microphone unit.

  The measurement system includes a speaker 21 as sound emitting means, a microphone 22 as sound collecting means, and a measuring device 23 such as a level meter connected to the microphone 22. The speaker 21 and the microphone 22 are disposed on opposite sides of the acoustic resistance material AR, respectively, and the microphone 22 collects a sound wave transmitted through the acoustic resistance material AR among sound waves emitted from the speaker 21.

  When measuring in an anechoic room or the like where there is no sound source other than the speaker 21, the speaker 21 may be disposed inside the housing 10 and the microphone 22 may be disposed outside the housing 10. In order to cut off the microphone 22 from the outside world, the microphone 22 is disposed directly below the opening 12 in the housing 10, whereas the speaker 21 is disposed outside the housing 10 and directly above the opening 12. Is preferred.

  The acoustic measuring device includes an exhaust unit that exhausts air in the housing 10 in order to fix the acoustic resistance material AR to the upper surface 11 of the housing 10 during measurement. The exhaust means may be a negative pressure source such as a vacuum pump, but from the viewpoint of simplification of the apparatus and reduction of equipment costs, as shown in FIG. And an exhaust fan 14 made of, for example, a propeller fan is disposed in the exhaust cylinder 13.

  In order to measure the acoustic resistance of the acoustic resistance material AR with this acoustic measurement device, the acoustic resistance material AR is placed on the housing 10 and the exhaust fan 14 is driven to exhaust the air in the housing 10. . Thereby, since the inside of the housing | casing 10 becomes a negative pressure, the acoustic resistance material AR is fixed so that it may closely_contact | adhere to the upper surface of the housing | casing 10 at atmospheric pressure.

  Next, sound waves are emitted from the speaker 21 with a substantially constant sound pressure, and sound waves transmitted through the acoustic resistance material AR are picked up by the microphone 22, and the sound pressure level of the picked-up sound waves is measured by the measuring device 23. And the acoustic resistance of the acoustic resistance material AR is measured (calculated) based on the sound pressure level and the output sound pressure of the speaker 21. After the measurement, the exhaust fan 14 is stopped and the acoustic resistance material AR is removed. This is repeated for each acoustic resistance material AR.

  As described above, according to the present invention, since the acoustic resistance material AR is fixed to the upper surface of the housing 10 by atmospheric pressure, the acoustic resistance material AR whose acoustic resistance changes when compressed like a sponge material, for example. Even if it exists, the acoustic resistance can be measured accurately. In addition, since a fixing weight as described in the conventional example is unnecessary, stable measurement can be easily performed.

  For example, when the opening 12 is relatively large or the acoustic resistance material AR is rich in flexibility, the central portion of the acoustic resistance material AR is directed toward the opening 12 as the inside of the housing 10 is exhausted. May dent. In order to prevent this, as shown in FIG. 2, it is preferable to provide a support 15 that supports the acoustic resistance material AR flatly in the opening 12. In this example, the support 15 is formed in a lattice shape, but it may be formed in a cross shape. In some cases, a mesh body with a coarse mesh may be used.

The typical sectional view showing the sound resistance measuring device of the sound resistance material by the present invention. The perspective view which shows the structure of the support body provided in an opening part. Typical sectional drawing which shows the acoustic resistance measuring apparatus of the conventional acoustic resistance material. The typical sectional view showing the acoustic resistance measuring device of the conventional acoustic resistance material using the weight for fixation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing | casing 11 Upper surface 12 Opening part 13 Exhaust pipe 14 Exhaust fan 15 Support body 21 Speaker (sound emission means)
22 Microphone (Sound collecting means)
23 Measuring instrument AR Acoustic resistance material

Claims (5)

In the acoustic resistance measurement device for an acoustic resistance material for measuring the acoustic resistance as a single unit, a sheet-like acoustic resistance material disposed in a sound wave path from a sound source to an acoustic-electric converter included in the microphone,
A hollow housing having an opening of a size covered with the acoustic resistance material on the top surface on which the acoustic resistance material is detachably mounted, and emitting sound waves toward one surface of the acoustic resistance material A sound emitting means, a sound collecting means disposed on the other surface side of the acoustic resistance material, for collecting a sound wave transmitted through the acoustic resistance material, and a volume of sound collected by the sound collection means. An acoustic resistance measurement apparatus for an acoustic resistance material, comprising: measurement means for measuring; and exhaust means for exhausting air in the casing.   The sound emitting means is a speaker and is arranged directly above the opening on the outside of the casing, and the sound collecting means is arranged on the inside of the casing and directly below the opening with a microphone. The acoustic resistance measuring device for an acoustic resistance material according to claim 1.   The acoustic resistance measurement apparatus for an acoustic resistance material according to claim 1, wherein an exhaust fan is used as the exhaust means.   The sound of the acoustic resistance material according to any one of claims 1 to 3, wherein a support in the form of a bar or a grid that flatly supports the acoustic resistance material is provided in the opening. Resistance measuring device. In the acoustic resistance measurement method for an acoustic resistance material, the acoustic resistance material is measured as a single piece of a sheet-like acoustic resistance material disposed in a sound wave path from a sound source to an acoustic-electric converter included in the microphone.
A hollow housing having an opening of a size covered with the acoustic resistance material on the top surface on which the acoustic resistance material is detachably mounted, and emitting sound waves toward one surface of the acoustic resistance material A sound emitting means, a sound collecting means disposed on the other surface side of the acoustic resistance material, for collecting a sound wave transmitted through the acoustic resistance material, and a volume of sound collected by the sound collection means. Measuring means for measuring, and exhaust means for exhausting the air in the housing,
The acoustic resistance material is placed on the upper surface of the housing so as to cover the opening, and the sound emitting means emits a sound wave toward one surface of the acoustic resistance material, and the other of the acoustic resistance material. In collecting the sound wave transmitted through the acoustic resistance material by the sound collection means arranged on the surface side of the acoustic resistance material, and measuring the acoustic resistance of the acoustic resistance material by the measurement means,
The acoustic resistance measurement of the acoustic resistance material characterized in that the air in the housing is exhausted by the exhaust means, and the peripheral portion of the acoustic resistance material is brought into close contact with the upper surface of the housing at atmospheric pressure. Method.

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