JP7170512B2 - Acoustic characteristic measurement system and acoustic characteristic measurement method - Google Patents

Description

The present invention relates to an acoustic property measuring system and an acoustic property measuring method.

2. Description of the Related Art In buildings, vehicles, etc., sound-absorbing materials that block or reduce the transmission of sound are used mainly in order to suppress the intrusion of noise from the outside. One of the indices indicating the sound absorbing effect of a sound absorbing material is the reverberation room method sound absorption coefficient described in Patent Document 1. When measuring the reverberation room method sound absorption coefficient, sound is generated in the reverberation room with the sound absorbing material placed on the floor of the reverberation room, and the reverberation time is measured. The sound absorbing effect of the sound absorbing material can be obtained by calculating the difference between the reverberation time thus obtained and the reverberation time measured after the sound is produced in the reverberation room without the sound absorbing material.

In order to further improve the sound absorbing effect at the target frequency, a space may be provided behind the sound absorbing material when the sound absorbing material is installed, and the air layer existing in this space may be utilized. In this way, when the sound absorbing material is used with an air layer behind it, even when obtaining the reverberation room method sound absorption coefficient, the presence of an air layer behind the sound absorbing material makes it possible to obtain the actual use. It is preferable to obtain a sound absorbing effect suitable for the state. When an exterior material that encloses a sound absorbing material and an air layer (space) is provided as in Patent Document 1, the sound absorption is obtained by placing the exterior material on the floor surface of the reverberation room and performing measurement. It is possible to obtain the sound absorption effect between the material and the air layer. However, in the case of a simple structure in which the sound absorbing material is installed so that there is a space behind the sound absorbing material without such an exterior material, the sound absorbing material is placed on the floor of the reverberation room. When the measurement is performed, the measurement result does not reflect the sound absorption effect of the air layer that exists during actual use. Therefore, by measuring the reverberation room method sound absorption coefficient with the sound absorbing material suspended from the floor of the reverberation room, the sound absorption effect of the air layer located between the sound absorbing material and the floor of the reverberation room was taken into account. It is possible to obtain a sound absorbing effect suitable for the usage condition of the

JP-A-11-247322

In order to create an air layer behind the sound-absorbing material when obtaining the reverberation room method sound absorption coefficient, multiple spacers are placed on the floor of the reverberation room, and the sound-absorbing material is placed on top of the spacers. A space can be provided between the surface and the sound absorbing material. However, when the sound absorbing material is soft and has low rigidity, the sound absorbing material hangs down between the spacers due to gravity, making it difficult to form a space with a constant thickness between the floor surface and the sound absorbing material. In that case, the same air layer as in actual use cannot exist behind the sound absorbing material, and the sound absorbing effect cannot be obtained accurately.

Therefore, an object of the present invention is to provide an acoustic characteristic measuring system and an acoustic characteristic measuring method that can easily determine the sound absorbing effect of the sound absorbing material and the air layer behind it in a state suitable for actual use.

The acoustic characteristic measurement system of the present invention is an acoustic characteristic measurement system in which an object to be measured is a sound absorbing material which is not provided with an exterior material and is used so as to create a space behind it. a plurality of spacers arranged on the floor of the apparatus; and a mesh material for supporting the object to be measured placed on the plurality of spacers.

The method of measuring acoustic characteristics of the present invention is a method of measuring acoustic characteristics in which an object to be measured is a sound absorbing material that is installed so as to create a space behind it without an exterior material. A plurality of spacers are arranged in the space, a mesh material is arranged on the plurality of spacers, and the acoustic characteristics are measured in a state in which an object to be measured is placed on the mesh material.

According to the present invention, it is possible to easily obtain the sound absorbing effect of the sound absorbing material and the air layer behind it in a state suitable for actual use.

1A and 1B are a cross-sectional view and a plan view showing a main part of an acoustic characteristic measurement system of the present invention; FIG. 2A and 2B are a plan view showing an arrangement of spacers in the acoustic characteristic measurement system shown in FIG. 1 and a perspective view showing an example of the shape of the spacers; FIG. FIG. 2 is a cross-sectional view showing a main part of a conventional acoustic characteristic measurement system; 4 is a graph showing measurement results of reverberation chamber method sound absorption coefficients of objects to be measured having low rigidity in Examples of the present invention and Reference Examples 1 and 2. FIG. 5 is a graph showing measurement results of reverberation chamber method sound absorption coefficients of objects to be measured having high rigidity in the example of the present invention and reference example 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The acoustic property measurement system of this embodiment is shown in FIGS. 1 and 2. FIG. FIG. 1(a) is a cross-sectional view of the main part of this acoustic characteristic measurement system, taken along line AA of FIG. 1(b). FIG. 1(b) is a plan view thereof. FIG. 2 is a plan view showing the arrangement of spacers in the acoustic characteristic measurement system. A plurality of spacers 2 are provided on the floor 1a of the reverberation chamber 1, and a mesh material 3 for supporting the object to be measured is placed on the spacers 2. As shown in FIG. The mesh material 3 has a flat plate-like outer shape and is not a flexible member. The height of the spacer 2 is obtained by subtracting the thickness of the mesh material 3 from the predetermined thickness of the air layer. That is, the height of the spacers 2 is adjusted so that the sum of the thickness of the mesh material 3 and the height of the spacers 2 matches the thickness of the air layer existing behind the object 4 to be measured when the object 4 is actually used. is determined. According to this configuration, it is possible to obtain the sound absorbing effect in a state where there is an air layer with a predetermined thickness behind the object 4 to be measured, that is, the same thickness as in actual use. A metal frame 5 , for example, is arranged at a position in contact with the outer periphery of the net material 3 . Further, as schematically shown in FIG. 1(a), at least one sounding body (speaker 6) for acoustic characteristic measurement and a plurality of sound collectors (microphones 7) are arranged in the reverberation chamber 1. ing.

To explain the technical significance of the acoustic characteristic measurement system shown in FIGS. 1 and 2, conventionally, as shown in FIG. The object to be measured 4 was placed directly on the . However, when using an object 4 to be measured that is soft and has low rigidity, such as sound-absorbing non-woven fabric, the object 4 hangs down between the spacers 2, so the air behind the object 4 is The layer becomes partially thin, and the same air layer as in actual use is not formed. If an extremely large number of spacers 2 are arranged, it is conceivable that the hanging of the object 4 to be measured can be suppressed. However, in order to arrange the spacers 2 to such an extent that the object 4 to be measured hardly hangs down, an extremely large number of spacers 2 are required, which increases the cost and makes the work of arranging the spacers 2 extremely complicated. Become.

In contrast, in the present embodiment shown in FIGS. 1 and 2, it is not necessary to increase the number of spaces 2 as compared with the prior art, and it is only necessary to place a net material 3 such as a wire net on the spacer 2, thus reducing the cost. Elevation and work complexity are kept small. Even if the object 4 to be measured is a soft, low-rigidity member such as a sound-absorbing non-woven fabric, the mesh material 3 can easily suppress the sagging of the object 4 to be measured. Since the mesh material 3 has a large number of small meshes (openings), it hardly impairs the sound absorbing effect of the object 4 to be measured. Therefore, according to this configuration, an air layer with a substantially constant thickness exists behind the object 4 to be measured, and acoustic characteristics (sound absorption effect) suitable for actual usage conditions can be easily obtained.

A detailed embodiment of the acoustic characteristic measurement system described above will be described. In the present invention, an object 4 to be measured having a planar area of 1 m ² or more is measured for acoustic characteristics such as a reverberation room method sound absorption coefficient. The measured object 4 of this embodiment is a sound-absorbing nonwoven fabric having a square planar shape with an area of 1 m ² and a thickness of 4.5 mm. As shown in FIG. 2(a), the spacer 2 is placed 17 in a square area R corresponding to the planar shape of the object 4 to be measured (area where the object 4 to be measured is placed) on the floor 1a of the reverberation chamber 1. are arranged individually. Specifically, along each side of the square region R, five spacers 2 are arranged at equal intervals. Since the spacers 2 at both ends of each side also serve as the spacers 2 at the ends of the sides perpendicular to that side, there are 16 spacers 2 along the perimeter of the square. Furthermore, one spacer 2 is arranged at the center position of this square region R. As shown in FIG. In this way, a total of 17 spacers 2 are arranged in this embodiment. The spacer 2 is preferably made of a material having a vibration-damping effect, such as urethane or elastomer. The spacer 2 may have various shapes such as the columnar shape shown in ^FIG . 2(b) and the polygonal columnar shape shown in FIG. ² (c). If the planar area of the spacer 2 is too small, it will be difficult to hold the net material 3 horizontally when placed. Moreover, if the area of the planar shape is too large, there is a possibility that a sufficient volume of the air layer located behind the object 4 to be measured cannot be ensured. The height of the spacer 2 varies from the thickness of the space (air layer) behind the object 4 (eg, 10 mm) to the thickness of the mesh material 3 (eg, 3.5 mm) when the object 4 is actually used. ) is subtracted (6.5 mm in this case).

The mesh material 3 placed on the plurality of spacers 2 in the square region R described above is made of metal (generally stainless steel wire, hard steel wire, galvanized iron wire, etc.) or resin (polypropylene, polyethylene, polyester, nylon (trademark), etc.). A preferable form of the mesh material 3 is a wire mesh such as a flat top woven wire mesh (smooth wire mesh), a plain woven wire mesh, a crimp woven wire mesh, a lock crimp woven wire mesh, a toncap woven wire mesh (long wire mesh), or a resin material as described above. It is an integrally molded net-like molded product. In this embodiment, the mesh material 3 is a flat top woven wire mesh (smooth surface type wire mesh) made of stainless steel wire. The preferred dimensions and characteristics of the mesh material 3 are as follows.

ここで、厚さは網材３の最大厚さである。線径は網材３を構成する線（例えばステンレス鋼線）の太さである。メッシュは、網材３の網目の数を表す単位であり、一つの方向に沿って見た時に長さ２５．４ｍｍ（１インチ）の範囲に存在する網目（開口部分）の数である。開き目は、網材３を構成する線と線の間の空間の長さ、すなわち、隣り合う線の近接縁部同士の間の間隔であって、線自体の太さを含まない寸法である。開き目＝（２５．４ｍｍ／メッシュ数）－線径である。空間率（open area）は、網目における空間（開口部分）の面積の割合であり、空間率＝｛（開き目）²／（開き目＋線径）²｝×１００である。本実施例の網材３は、空間率が５８％で、厚さが３．５ｍｍ、線径が１．２ｍｍ、メッシュ数が５個／インチ、開き目が３．８８ｍｍである。

Here, the thickness is the maximum thickness of the mesh material 3 . The wire diameter is the thickness of the wire (for example, stainless steel wire) forming the mesh material 3 . The mesh is a unit representing the number of meshes of the mesh material 3, and is the number of meshes (openings) present in a range of 25.4 mm (1 inch) in length when viewed along one direction. The opening is the length of the space between the lines forming the mesh material 3, that is, the distance between the adjacent edges of adjacent lines, and is a dimension that does not include the thickness of the lines themselves. . Open mesh = (25.4 mm/number of meshes) - wire diameter. The open area is the ratio of the area of the spaces (openings) in the mesh, and is expressed as {(opening) ² /(opening + wire diameter) ² }×100. The mesh material 3 of this embodiment has a void ratio of 58%, a thickness of 3.5 mm, a wire diameter of 1.2 mm, a mesh number of 5 per inch, and an opening of 3.88 mm.

Here, when the thickness of the net material 3 is 0.2 mm or less, when the wire diameter of the net material 3 is 0.05 mm or less, or when the number of meshes of the net material 3 is less than 2/inch, the net When the object 4 to be measured is placed on the material 3, the mesh material 3 is distorted, making it difficult to form a space with a constant thickness between the floor surface 1a and the object to be measured (sound absorbing material) 4. tend to become Moreover, when the thickness of the net material 3 is 10 mm or more, or when the wire diameter of the net material 3 is 8 mm or more, a predetermined thickness is provided between the floor surface 1a and the object to be measured (sound absorbing material) 4. space tends to be difficult to form. In these cases, the acoustic characteristics cannot be obtained with high accuracy when there is an air layer behind the object 4 to be measured. Also, when the number of meshes of the net material 3 is 15 or more per inch, the air permeability of the net material 3 is low. It tends to be difficult to accurately obtain the acoustic characteristics of the device under test 4 with layers added.

Furthermore, in the present embodiment, a reflective frame 5 made of metal such as aluminum is arranged outside the above-described square region R so as to be in contact with the outer periphery of the mesh material 3 (see FIG. 1). ). The frame 5 substantially covers the side end surfaces of the object 4 to be measured. As a result, the sound absorbing effect on the side end faces of the object 4 to be measured is suppressed. In general, it is thought that the sound absorbing material is not often used with the side end faces of the sound absorbing material open. easy to obtain.

At least one speaker 6 and a plurality of microphones 7 are arranged in the reverberation chamber 1. - 特許庁Although schematically shown in FIG. 1(a), the plurality of microphones 7 are arranged according to the method described in JIS A1409.

FIG. 4 shows the result of measuring the reverberation chamber method sound absorption coefficient, which is one of the acoustic characteristics of a soft, low-rigidity sound-absorbing nonwoven fabric as the object 4 to be measured, using the acoustic characteristic measurement system of the present embodiment described above. shown in In FIG. 4, as Reference Example 1, a spacer 2 is placed in a reverberation chamber 1, and an object 4 to be measured is placed directly on the spacer 2 without using a net material 3. The results of calculating the ratio are also shown. Further, as Reference Example 2, neither the spacer 2 nor the mesh material 3 is placed in the reverberation chamber 1, and the reverberation chamber method sound absorption coefficient is obtained in a state in which the object 4 to be measured is placed directly on the floor surface 1a of the reverberation chamber 1. The results are shown. The measurement results of the reverberation room method sound absorption coefficient in Reference Example 1 are not significantly different from the measurement results of the reverberation chamber method sound absorption coefficient in Reference Example 2. That is, in Reference Example 1, although the spacer 2 is used, the sound absorption effect of the air layer behind the object 4 to be measured does not act much. On the other hand, in the present embodiment, compared with Reference Examples 1 and 2, the reverberation room method sound absorption coefficient for sound in the frequency band from 630 Hz to 4 kHz is particularly high. This result includes the sound absorbing effect of the air layer located behind the object 4 to be measured, and indicates the sound absorbing effect that matches the actual use condition of the object 4 to be measured. In addition, in the present embodiment, the peak of the reverberating room method sound absorption coefficient is shifted to the low frequency side as compared with the first and second reference examples. It is considered that this is based on the sound absorbing effect of the air layer located behind the object 4 to be measured.

The nonwoven fabric used in the above examples is a nonwoven fabric produced by processing polypropylene by a meltblown method, and has a water absorption rate of 16%, a bulk density of 31 kg/m ³ , and a surface area of 4000 mm ² . It is formed, and the compressive stress (25% compressive stress) for compressing the dimension in the compression direction of the nonwoven fabric is less than the lower limit of measurement (cannot be measured), and the compression for compressing it until it is reduced by 50% It consists of a material with a stress of 0.09 N/cm ² . Measurement of water absorption is performed as follows. That is, a non-woven fabric having a surface area of 4000 mm ² was evacuated to -635 mmHg at a position 50 mm below the water surface and held for 3 minutes. Subsequently, after returning to the atmospheric pressure for 3 minutes, the weight of the water-absorbed test piece was measured, and the water absorption rate of the test piece was calculated from the following formula.
Water absorption [%]={(W2−W1)/W1}×100
W1: Weight of test piece before immersion (g)
W2: Weight of test piece after immersion (g)

In addition, using the acoustic property measurement system of this example, a sound absorbing porous material sheet (Calmflex manufactured by INOAC Corporation) having higher rigidity than non-woven fabric was used as the measurement object 4, and the reverberation chamber method sound absorption coefficient is shown in FIG. In FIG. 5, as Reference Example 1, a spacer 2 is placed in a reverberation chamber 1, and an object 4 to be measured is placed directly on the spacer 2 without using a net material 3. The results of calculating the ratio are also shown. Looking at the experimental results shown in FIG. 5, substantially the same reverberation room method sound absorption coefficient is obtained for Reference Example 1 and this embodiment. In the case of the object to be measured 4 having high rigidity, the object to be measured 4 does not easily hang down between the spacers 2 even without using the net material 3 . Therefore, an air layer having a substantially constant thickness corresponding to the sum of the height of the spacer 2 and the thickness of the mesh material 3 is formed behind the object 4 to be measured in the reverberation chamber 1 . Therefore, as described above, the reverberation chamber method sound absorption coefficient of this embodiment, in which the object to be measured 4 is supported using the net material 3 and measured, and the sound absorption coefficient in which the object to be measured 4 is supported only by the spacer 2 without using the net material 3 are obtained. The difference from the reverberation room method sound absorption coefficient of Reference Example 1 measured by

As described above, according to the present embodiment using the net material 3, the reverberation room method sound absorption coefficient does not always increase as compared with the reference example 1 which does not use the net material 3. If the reverberation room method sound absorption coefficient can be measured with relatively high accuracy in Reference Example 1, the present example will also yield substantially the same results as in Reference Example 1. To explain this point, even when measurement results in which the reverberation room method sound absorption coefficient is always higher than that of Reference Example 1 are obtained, it is not always possible to obtain good measurement accuracy. That is, depending on the rigidity of the object to be measured 4, the object to be measured 4 does not sag much between the spacers 2 and 2 even in the reference example 1, and the measurement results are relatively accurate considering the sound absorbing effect of the air layer. may be obtained. In such a case, if a reverberation chamber method sound absorption coefficient higher than that of Reference Example 1 is required, it can be said that the measurement accuracy is rather poor. On the other hand, in the present embodiment, as shown in FIG. 5, when the rigidity of the object 4 to be measured is high and the reverberation room method sound absorption coefficient can be obtained with high accuracy even in Reference Example 1, the measurement results are about the same as in Reference Example 1. is obtained. That is, in FIG. 5, the fact that the measurement result close to that of Reference Example 1 is obtained in this embodiment indicates that the measurement of the reverberation room method sound absorption coefficient in this embodiment is rather highly reliable. As shown in FIG. 4, when the rigidity of the object to be measured is low and the reverberation chamber method sound absorption coefficient cannot be obtained with high accuracy in Reference Example 1, according to the present embodiment, it is higher than Reference Example 1 (air layer The reverberation room method sound absorption coefficient can be obtained with high accuracy. As described above, from the experimental results shown in FIGS. 4 and 5, it can be seen that according to this embodiment, the acoustic characteristics can be measured satisfactorily regardless of the rigidity of the object to be measured.

As described above, in Reference Example 1, depending on the rigidity of the object 4 to be measured, it is possible to obtain the reverberation room method sound absorption coefficient that matches the actual usage conditions (case of FIG. 5). There is a difficult case (case of FIG. 4). However, according to this embodiment, it is possible to appropriately reproduce the actual usage conditions and obtain the acoustic characteristics (for example, the reverberation chamber method sound absorption coefficient) with high accuracy without being affected by the rigidity of the object 4 to be measured. Excellent effect is obtained.

The acoustic characteristic measurement according to the present invention described above can be carried out under the environment and conditions that do not rely on JIS A 1409, as long as the acoustic characteristics can be evaluated. For example, the present invention can be applied not only in a reverberant room but also indoors or outdoors in other buildings as long as the environment and conditions allow acoustic characteristics to be evaluated. Also, the number of microphones and speakers, installation positions, installation directions, etc. can be arbitrarily set and changed as long as the acoustic characteristics can be evaluated.

1 reverberation chamber 1a floor 2 spacer 3 mesh 4 object to be measured 5 frame 6 speaker (sounding body)
7 Microphone (sound collector)
R area

Claims (9)

An acoustic characteristic measurement system in which an object to be measured is a sound absorbing material that is not provided with an exterior material and is used so as to create a space behind it,
A reverberation chamber, a plurality of spacers arranged on the floor surface of the reverberation chamber, and a mesh material for supporting the object to be measured, which is placed on the plurality of spacers. and an acoustic characteristic measurement system. 2. The acoustic characteristic measuring system according to claim 1, wherein said mesh material is made of metal or resin. 3. The acoustic property measuring system according to claim 2, wherein the mesh material is made of stainless steel wire, hard steel wire or galvanized iron wire. 4. The acoustic characteristic measuring system according to any one of claims 1 to 3, wherein the net material has a void ratio of 40% or more and 70% or less. 5. The acoustic characteristic measuring system according to any one of claims 1 to 4, wherein the mesh material has a thickness of 2 mm or more and 5 mm or less. The wire diameter of the wire constituting the net material is 0.5 mm or more and 2 mm or less, the mesh of the net material is 2 or more and 11 or less, and the mesh size is 0.3 mm or more and 12.2 mm or less. The acoustic property measurement system according to any one of claims 1 to 5. A method for measuring acoustic characteristics in which an object to be measured is a sound-absorbing material that is installed so that a space is created behind it without an exterior material,
Arranging a plurality of spacers on the floor of a reverberation chamber, arranging a mesh material on the plurality of spacers, and measuring the acoustic characteristics in a state where the object to be measured is placed on the mesh material. A method for measuring acoustic characteristics, characterized by: 8. The acoustic characteristic measuring method according to claim 7, wherein a reverberation room method sound absorption coefficient is obtained as the acoustic characteristic. 8. The reverberation time is obtained by generating sound from at least one sounding body arranged inside the reverberation room and collecting the sound with a plurality of sound collectors arranged inside the reverberation room. Or the acoustic characteristic measuring method according to 8.

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