JP4832245B2 - Sound absorber - Google Patents

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JP4832245B2
JP4832245B2 JP2006280314A JP2006280314A JP4832245B2 JP 4832245 B2 JP4832245 B2 JP 4832245B2 JP 2006280314 A JP2006280314 A JP 2006280314A JP 2006280314 A JP2006280314 A JP 2006280314A JP 4832245 B2 JP4832245 B2 JP 4832245B2
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長則 増渕
雅夫 住田
修一 赤坂
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Riken Technos Corp
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Description

本発明は吸音体に関する。   The present invention relates to a sound absorber.

騒音は、振動とともに身近な問題であり、吸音体への要求は依然として高い。また、用途や目的に応じて要求特性も多岐にわたり、最近では、低周波領域での吸音性能が高い材料が望まれている。
従来より用いられている吸音材料として、例えば、グラスウール、ロックウールのように繊維を綿状またはボード状に成型した材料や、ポリウレタンフォームのように高分子材料を発泡させた材料などの多孔質材料が用いられる。これらの多孔質材料に音波が入射すると、音波が材料内の隙間の空気を振動させるため、空気自身の粘性および周囲との摩擦によって、振動エネルギーの一部が熱エネルギーに変換、散逸されて吸音効果が得られる。 Noise is a familiar problem with vibration, and the demand for sound absorbers is still high. In addition, there are a wide variety of required characteristics depending on the application and purpose, and recently, a material having high sound absorption performance in a low frequency region is desired.
Conventionally used as a sound absorbing material, for example, a porous material such as a material obtained by molding fibers into a cotton or board shape such as glass wool or rock wool, or a material obtained by foaming a polymer material such as polyurethane foam Is used. When sound waves are incident on these porous materials, the sound waves vibrate the air in the gaps in the materials, so some of the vibration energy is converted into heat energy and dissipated by the viscosity of the air itself and the friction with the surroundings. An effect is obtained.

低周波領域における吸音性能の向上を目的とした吸音体として、例えば下記特許文献１には、音響的に透明な２枚のシートの間の空間に粉体を充填してなる粉体含有シート状物を断熱材層に積層一体化した構成が開示されており、この構成においては、粉体粒子の縦振動により低周波領域での吸音が得られる旨が記載されている。
下記特許文献２には、可撓性を有するベースフィルム上にバインダー接着剤により微細な粒子を接着してなる吸音層と、弾性層とを面接着してなる吸音体が開示されている。この吸音体において、ベースフィルムの厚さ、粒子の重さや大きさ、およびバインダー接着剤の粘性によって、吸音効果が得られる音域を変えることができる旨が記載されている。
下記特許文献３には、通気性材料の一面に通気止めフィルムを積層するとともに、該通気性材料の一面に凹部を設けるなどして、通気性材料と通気止めフィルムとが接触していない部分を形成することにより、共振効果による膜振動を利用して、広い周波数領域で吸音効果が得られるようにした吸音体が記載されている。
特開平９−１７０２７６号公報 特開平７−１４０９８５号公報 特開２００４−１３０７３１号公報 As a sound absorber for the purpose of improving the sound absorption performance in the low frequency region, for example, in Patent Document 1 below, a powder-containing sheet shape in which powder is filled in a space between two acoustically transparent sheets. A structure in which an object is laminated and integrated with a heat insulating material layer is disclosed, and in this structure, it is described that sound absorption in a low frequency region can be obtained by longitudinal vibration of powder particles.
Patent Document 2 below discloses a sound absorber formed by surface-bonding a sound absorbing layer formed by bonding fine particles with a binder adhesive onto a flexible base film and an elastic layer. In this sound absorbing body, it is described that the sound range in which the sound absorbing effect can be obtained can be changed by the thickness of the base film, the weight and size of the particles, and the viscosity of the binder adhesive.
In Patent Document 3 below, a portion where the air-permeable material and the air-blocking film are not in contact with each other is formed by laminating a gas-permeable film on one surface of the air-permeable material and providing a recess on one surface of the air-permeable material. There is described a sound absorber that is formed so that a sound absorption effect can be obtained in a wide frequency range by utilizing membrane vibration due to a resonance effect.
JP-A-9-170276 Japanese Patent Laid-Open No. 7-140985 JP 2004-130731 A

しかしながら、上記特許文献１〜３に記載されている吸音体では、５００Ｈｚ以下の低周波数領域において、吸音率が０．５以上となるような高度な吸音効果を達成することは難しい。
図７は、発泡ウレタン（厚さ１０、２０、５０ｍｍ）、フェルト（厚さ１０、５０ｍｍ）、エチレン−酢酸ビニル共重合体の発泡体（発泡ＥＶＡ、厚さ１０ｍｍ）について、吸音率の周波数特性を測定した結果を示すグラフである。横軸は周波数（単位：Ｈｚ）、縦軸は吸音率を示す。
従来の多孔質材料にあっては、例えば図７に示すように、厚みを増大させれば低周波領域での吸音率が向上し、例えば発泡ウレタンの厚さを５０ｍｍにすれば４５０〜５００Ｈｚの周波数領域において、０．５〜０．６程度の吸音率を達成することが可能である。
しかしながら、多孔質材料の厚みを増大させると、吸音体が大型化するため好ましくない。
本発明は前記事情に鑑みてなされたもので、吸音体の大型化を招くことなく、低周波領域において高度な吸音効果を達成することができる吸音体を提供することを目的とする。 However, in the sound absorbers described in Patent Documents 1 to 3, it is difficult to achieve a high sound absorption effect such that the sound absorption coefficient is 0.5 or more in a low frequency region of 500 Hz or less.
FIG. 7 shows frequency characteristics of sound absorption coefficient for foamed urethane (thickness 10, 20, 50 mm), felt (thickness 10, 50 mm), and ethylene-vinyl acetate copolymer foam (foamed EVA, thickness 10 mm). It is a graph which shows the result of having measured. The horizontal axis represents frequency (unit: Hz), and the vertical axis represents sound absorption rate.
In the conventional porous material, for example, as shown in FIG. 7, if the thickness is increased, the sound absorption coefficient in the low frequency region is improved. For example, if the thickness of the urethane foam is 50 mm, it is 450 to 500 Hz. In the frequency domain, it is possible to achieve a sound absorption coefficient of about 0.5 to 0.6.
However, increasing the thickness of the porous material is not preferable because the sound absorber increases in size.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sound absorber that can achieve an advanced sound absorbing effect in a low frequency region without causing an increase in the size of the sound absorber.

前記課題を解決するために、本発明の吸音体は、貫通孔が形成された枠体と、該貫通孔の一方の開口を覆う吸音材を有し、前記吸音材の下記数式（１）で求められる第１の貯蔵弾性率Ｅ１が９．７×１０６以上であり、下記数式（２）で求められる第２の貯蔵弾性率Ｅ２が３４６以下であることを特徴とする。 In order to solve the above-mentioned problem, the sound absorber of the present invention has a frame body in which a through hole is formed and a sound absorbing material that covers one opening of the through hole. The obtained first storage elastic modulus E1 is 9.7 × 10 6 or more, and the second storage elastic modulus E2 obtained by the following formula (2) is 346 or less.

Figure 0004832245
Figure 0004832245

（式中、Ｅ’は貯蔵弾性率の測定値（単位：Ｐａ）を表し、Ｔ１は吸音材の厚み（単位：ｍｍ）を表し、Ｔ２は枠体の厚み（単位：ｍｍ）を表し、Ｇは吸音材の密度（単位：ｇ／ｃｍ３）を表し、Ｄは枠体の貫通孔の直径（単位：ｍｍ）を表す。） (In the formula, E ′ represents a measured value of storage elastic modulus (unit: Pa), T 1 represents the thickness of the sound absorbing material (unit: mm), and T 2 represents the thickness of the frame (unit: mm)). G represents the density of the sound absorbing material (unit: g / cm 3 ), and D represents the diameter of the through hole of the frame (unit: mm).

本発明によれば、吸音体の大型化を招くことなく、低周波領域において高度な吸音効果を達成することができる吸音体が得られる。   ADVANTAGE OF THE INVENTION According to this invention, the sound absorber which can achieve a high-quality sound absorption effect in a low frequency area | region without causing the enlargement of a sound absorber is obtained.

まず、上記数式（１）、（２）について説明する。
板状または膜状の吸音材と、背後空気層とで構成される吸音体にあっては、特定の周波数（共鳴周波数）の音波が吸音体に入射すると、共振が生じて吸音されると考えられており、該共鳴周波数を与える理論式として、下記数式（３）が知られている。該数式（３）では吸音材自身の曲げに対する剛性と、背後空気層の弾性が考慮されているが、該数式（３）で求められる共振周波数と、実際の吸音体において吸音が生じる周波数とが必ずしも一致しないことも知られており、一般的には下記数式（４）が用いられている（「吸音材料」子安勝著、技報堂出版、１９７６年、第２０〜２１頁）。 First, the mathematical formulas (1) and (2) will be described.
In a sound absorbing body composed of a plate-like or film-like sound absorbing material and a back air layer, when a sound wave having a specific frequency (resonance frequency) is incident on the sound absorbing body, resonance is generated and the sound is absorbed. As a theoretical formula that gives the resonance frequency, the following formula (3) is known. The mathematical formula (3) takes into account the bending rigidity of the sound absorbing material itself and the elasticity of the back air layer, but the resonance frequency obtained by the mathematical formula (3) and the frequency at which sound is absorbed in the actual sound absorbing body are obtained. It is known that they do not always match, and generally, the following formula (4) is used ("Sound absorbing material" by Koyasu Koyasu, Gihodo Publishing, 1976, pp. 20-21).

Figure 0004832245
Figure 0004832245

上記数式（３）において、ｌ、ｍは任意の自然数であり、共鳴周波数ｆ０（ｌ、ｍ）はｌ、ｍの値によっていくつかの値をとり得るが、実際にはｌ＝ｍ＝１、すなわち吸音材の基本振動に対応する共鳴周波数が最も重要であるとされている。
上記数式（３）、（４）において、ｃは空気中の音速度（m／ｓ）、Ｍは吸音材の面密度（ｋｇ／ｍ２）、ρは空気の密度（ｋｇ／ｍ３）、Ｌは背後空気層の厚さ（ｍ）、Ｅは吸音材のヤング率（Ｎ／ｍ２）、ｔは吸音材の厚さ（ｍ）、σはポアソン比、ａ、ｂは長方形の吸音材の縦、横の長さ（ｍ）を示す。
上記数式（４）におけるＫは、共振周波数の実測値から求められる値であり、数式（３）におけるルート内の第２項に対応する値である。なお該数式（４）におけるＫは、吸音材の周囲の支持条件により大きく変化するため、吸音材の剛性を示すＥの値からＫを計算により求めることはできない。 In the above equation (3), l and m are arbitrary natural numbers, and the resonance frequency f 0 (l, m) can take several values depending on the values of l and m, but actually, l = m = 1. That is, the resonance frequency corresponding to the fundamental vibration of the sound absorbing material is considered to be the most important.
In the above formulas (3) and (4), c is the speed of sound in the air (m / s), M is the surface density (kg / m 2 ) of the sound absorbing material, ρ is the density of air (kg / m 3 ), L is the thickness of the back air layer (m), E is the Young's modulus (N / m 2 ) of the sound absorbing material, t is the thickness (m) of the sound absorbing material, σ is the Poisson's ratio, and a and b are rectangular sound absorbing materials The vertical and horizontal length (m) is shown.
K in the above equation (4) is a value obtained from the actually measured value of the resonance frequency, and is a value corresponding to the second term in the route in the equation (3). Since K in Equation (4) varies greatly depending on the support conditions around the sound absorbing material, K cannot be calculated from the value of E indicating the rigidity of the sound absorbing material.

本発明者等は、吸音体の構造と共鳴周波数との関係をさらに明らかにすべく、数式（３）におけるルート内の第２項に着目して鋭意研究を行った。その結果、該第２項の中でも、特に「Ｅｔ３／Ｍ」の１／２乗の値と、吸音が生じる周波数（以下、吸音周波数ということもある。）との相関が高いことを知見した。また該Ｅ（吸音材のヤング率）に代えて、共振曲線に基づく曲げ振動法により測定された貯蔵弾性率（Ｅ’）の値を用いることにより、「Ｅ’ｔ３／Ｍ」の１／２乗の値と吸音周波数との相関が得られることを見出した。さらに、理論式ではｔの3乗であるが、ｔの2乗、つまり 「Ｅ’ｔ２／Ｍ」の１／２乗の値と、吸音周波数とのより高い相関が得られることを見出した。
数式（３）では、板の共鳴周波数を決める為に、板自身の曲げに対する剛性を考慮して、板の曲げモーメントを用いた式になっている。それに対して、本発明では、ｔの3乗でなく、ｔの2乗で高い相関が得られていることから、単純な曲げではない振動が起きているものと考える。
この「Ｅ’ｔ２／Ｍ」は、Ｍ＝Ｇ×ｔ（Ｇは吸音材の密度）よりＧを用いて表すと「Ｅ’ｔ／Ｇ」となり、吸音材の厚みｔをＴ１に置き換えると「（Ｅ’×Ｔ１）／Ｇ」となる。これは本発明にかかる数式（１）、（２）におけるルート内の項である。
ここで、本発明における粘弾貯蔵率Ｅ’の測定値は ＪＩＳ Ｋ７２４４−３（曲げ振動）に準処する測定方法により、サンプルサイズを長さ２０ｍｍ、幅５ｍｍ、厚み２ｍｍとし、測定条件を歪振幅６μｍ、２５℃、２０Ｈｚとして得られる値（単位：Ｐａ）である。該粘弾貯蔵率Ｅ’の測定周波数は、一般的に測定可能な範囲（０．２〜５０Ｈｚ）の中で、実際の吸音周波数により近いという理由で２０Ｈｚを採用した。（なお、５０Ｈｚではデータのばらつきが多い為、２０Ｈｚとした。） In order to further clarify the relationship between the structure of the sound absorber and the resonance frequency, the present inventors have conducted intensive research focusing on the second term in the route in Equation (3). As a result, it has been found that the correlation between the value of 1/2 of “Et 3 / M” and the frequency at which sound absorption occurs (hereinafter also referred to as sound absorption frequency) is high among the second term. . Further, instead of the E (Young's modulus of the sound absorbing material), by using the value of the storage elastic modulus (E ′) measured by the bending vibration method based on the resonance curve, 1 / “E′t 3 / M” is obtained. It has been found that a correlation between the square value and the sound absorption frequency can be obtained. Furthermore, although it is the cube of t in the theoretical formula, it has been found that a higher correlation can be obtained between the square of t, that is, the value of 1/2 of “E't 2 / M”, and the sound absorption frequency. .
In formula (3), in order to determine the resonance frequency of the plate, the equation using the bending moment of the plate in consideration of the rigidity with respect to the bending of the plate itself. On the other hand, in the present invention, since a high correlation is obtained not by the cube of t but by the square of t, it is considered that vibration that is not simple bending occurs.
This “E′t 2 / M” becomes “E′t / G” when expressed by G from M = G × t (G is the density of the sound absorbing material), and the thickness t of the sound absorbing material is replaced with T 1 . And “(E ′ × T 1 ) / G”. This is a term in the route in the equations (1) and (2) according to the present invention.
Here, the measured value of the viscoelastic storage rate E ′ in the present invention is measured according to JIS K7244-3 (bending vibration), the sample size is 20 mm long, 5 mm wide, 2 mm thick, and the measurement conditions are strain amplitude. It is a value (unit: Pa) obtained as 6 μm, 25 ° C., and 20 Hz. The measurement frequency of the viscoelastic storage rate E ′ is 20 Hz because it is closer to the actual sound absorption frequency within a generally measurable range (0.2 to 50 Hz). (In addition, since there was much variation in data at 50 Hz, it was set to 20 Hz.)

また吸音周波数は、背後空気層の厚さ、すなわち枠体の厚み（Ｔ２）、および枠体の貫通孔の直径（Ｄ）とも相関があり、該Ｔ２が大きいほど吸音周波数は低下し、該Ｄが大きいほど吸音周波数は低下する。したがって、前記「（Ｅ’×Ｔ１）／Ｇ」の１／２乗の値を、Ｔ２で割り、さらにＤで割った値（下記数式（５）で表されるＥ２）は、吸音周波数と良好な相関を示す。 The sound absorption frequency is also correlated with the thickness of the back air layer, that is, the thickness of the frame (T 2 ), and the diameter of the through hole of the frame (D), and the sound absorption frequency decreases as T 2 increases. The greater the D, the lower the sound absorption frequency. Therefore, the 1/2 square of the value of "(E '× T 1) / G " divided by T 2, (E2 expressed by the following equation (5)) further divided by the D is sound-absorption frequency And a good correlation.

Figure 0004832245
Figure 0004832245

さらに、後述の参考例１に示すように、背後空気層の厚さ、すなわち枠体の厚み（Ｔ２）と吸音周波数との関係を詳細に検討した結果、両者の間には図５のグラフで示される関係があることが判明した。この関係に基づいて上記数式（５）におけるＴ２を補正することにより上記数式（２）が得られる。 Furthermore, as shown in Reference Example 1 described later, the relationship between the thickness of the back air layer, that is, the thickness of the frame (T 2 ) and the sound absorption frequency was examined in detail. It was found that there is a relationship indicated by. The equation (2) is obtained by correcting the T 2 in the above equation (5) on the basis of this relationship.

また吸音率に関しては、従来これを導く理論式は知られていない。本発明者等は、前記「（Ｅ’×Ｔ１）／Ｇ」の１／２乗の値と吸音率との関係に着目して、各種の吸音体について実測を行った.結果、該「（Ｅ’×Ｔ１）／Ｇ」の１／２乗の値と吸音率とは相関があることを知見した。
さらに、吸音率は、背後空気層の厚さ、すなわち枠体の厚み（Ｔ２）、および枠体の貫通孔の直径（Ｄ）とも相関があり、該Ｔ２が大きいほど吸音率は増加し、該Ｄが大きいほど吸音率は増加することから、前記「（Ｅ’×Ｔ１）／Ｇ」の１／２乗の値に、Ｔ２を乗じ、さらにＤを乗じた値（上記数式（１）で表されるＥ１）が、吸音率と良好な相関を示すことを見出した。 As for the sound absorption coefficient, there is no known theoretical formula that leads to this. The present inventors have made various measurements on various sound absorbers by paying attention to the relationship between the value of the half power of “(E ′ × T 1 ) / G” and the sound absorption coefficient. It has been found that there is a correlation between the value of 1/2 of (E ′ × T 1 ) / G ”and the sound absorption coefficient.
Furthermore, the sound absorption coefficient is also correlated with the thickness of the back air layer, that is, the thickness of the frame body (T 2 ) and the diameter of the through hole of the frame body (D), and the sound absorption coefficient increases as T 2 increases. Since the sound absorption rate increases as D increases, a value obtained by multiplying the value of 1/2 of “(E ′ × T 1 ) / G” by T 2 and further by D (the above formula ( It was found that E1) represented by 1) shows a good correlation with the sound absorption coefficient.

ここで本明細書における吸音率は「垂直入射吸音率」の意味であり、ＪＩＳ Ａ １４０５−２に準処する方法で、直径１００ｍｍのインピーダンス管内にサンプルをセットして測定される値である。サンプル直径は１００ｍｍ弱とし、スペーサーを介して、インピーダンス管内に固定する。背後空気層厚（すなわち、枠体の厚みＴ２）の変更は、サンプルの背後にある剛体（ピストン）の位置を調整することによって行うことができる。またサンプル径（すなわち、枠体の貫通孔の直径Ｄ）の変更は、スペーサーの内径を調整することによって行うことができる。 Here, the sound absorption coefficient in this specification means “normal incidence sound absorption coefficient”, and is a value measured by setting a sample in an impedance tube having a diameter of 100 mm by a method according to JIS A 1405-2. The sample diameter is a little less than 100 mm, and it is fixed in the impedance tube through a spacer. The change of the back air layer thickness (that is, the frame thickness T 2 ) can be performed by adjusting the position of the rigid body (piston) behind the sample. The sample diameter (that is, the diameter D of the through hole of the frame) can be changed by adjusting the inner diameter of the spacer.

次に、本発明の吸音体について説明する。
図１は本発明の吸音体の一実施形態を示したもので、図１（ａ）は平面図、（ｂ）は（ａ）中のＢ−Ｂ線に沿う断面図である。図中符号１は吸音体、２は枠体、３は吸音材、４は吸音体が取り付けられている施工面を示している。吸音体１は、貫通孔２ａを有する枠体２の表面２ｂ上に、吸音材３が積層され、固定されている。
本実施形態の吸音体１は枠体２の裏面２ｃが施工面４に接着固定されており、吸音材３と施工面４との間に背後空気層５が形成された状態で使用される。すなわち枠体２の表面２ｂおよび裏面２ｃそれぞれにおける貫通孔２ａの開口のうち、表面における開口が吸音材３で覆われており、裏面における開口が施工面４によって閉じられている。 Next, the sound absorber of the present invention will be described.
1A and 1B show an embodiment of a sound absorber according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line BB in FIG. In the figure, reference numeral 1 denotes a sound absorbing body, 2 denotes a frame body, 3 denotes a sound absorbing material, and 4 denotes a construction surface to which the sound absorbing body is attached. In the sound absorber 1, the sound absorbing material 3 is laminated and fixed on the surface 2b of the frame 2 having the through hole 2a.
The sound absorber 1 of this embodiment is used in a state in which the back surface 2 c of the frame 2 is bonded and fixed to the construction surface 4 and a back air layer 5 is formed between the sound absorbing material 3 and the construction surface 4. That is, among the openings of the through holes 2 a on the front surface 2 b and the back surface 2 c of the frame body 2, the opening on the front surface is covered with the sound absorbing material 3, and the opening on the back surface is closed by the construction surface 4.

本実施形態の枠体２は、外形形状が円形で、同心円状の貫通孔２ａが設けられている。枠体２は貫通孔２ａを有していればよく、外形形状は任意とすることができる。枠体２自身は、吸音性能を有していてもよく、有していなくてもよい。枠体２の材質は特に制限されないが、軽量化の点からは樹脂などの比重の低い材料が好ましい。
枠体２の厚さＴ２によって吸音材３の施工面４側に形成される背後空気層５の厚さが決まる。該厚さＴ２は上記数式（１）および（２）を満たせばよいが、吸音性能の点からは３ｍｍ以上が好ましい。また全体のサイズを抑える点からは、５０ｍｍ以下が好ましい。
枠体２の厚さが不均一である場合は、Ｔ２として中央値を用いる。 The frame body 2 of the present embodiment has a circular outer shape and is provided with concentric through holes 2a. The frame 2 only needs to have the through hole 2a, and the outer shape can be arbitrary. The frame 2 itself may or may not have sound absorbing performance. The material of the frame 2 is not particularly limited, but a material having a low specific gravity such as a resin is preferable from the viewpoint of weight reduction.
The thickness T 2 of the frame body 2 determines the thickness of the back air layer 5 formed on the construction surface 4 side of the sound absorbing material 3. It said thickness T 2 are should satisfy the above equation (1) and (2), preferably not less than 3mm in terms of sound absorbing performance. Moreover, from the point which suppresses the whole size, 50 mm or less is preferable.
When the thickness of the frame 2 is not uniform, using a central value as T 2.

貫通孔２ａの形状（枠体２の表面２ｂにおける開口の形状）は円形に限らず、多角形など任意の形状とすることができる。特に、吸音率がピークとなるピーク周波数がより低くなる点、および該ピーク周波数における吸音率がより高くなる点からは、円形であることが好ましい。
貫通孔２ａの直径Ｄは上記数式（１）および（２）を満たせばよいが、吸音性能の点から２０ｍｍ以上が好ましい。
本発明において貫通孔２ａが円形でない場合、数式（１）および（２）における「Ｄ」の値は、該貫通孔２ａの面積（枠体２の表面２ｂにおける開口の面積）と同面積の円の直径の値を用いるものとする。 The shape of the through hole 2a (the shape of the opening in the surface 2b of the frame 2) is not limited to a circle, and may be an arbitrary shape such as a polygon. In particular, a circular shape is preferable from the viewpoint that the peak frequency at which the sound absorption coefficient reaches a peak is lower and the sound absorption coefficient at the peak frequency is higher.
Although the diameter D of the through-hole 2a should just satisfy | fill said Numerical formula (1) and (2), 20 mm or more is preferable from the point of sound absorption performance.
In the present invention, when the through hole 2a is not circular, the value of “D” in the formulas (1) and (2) is a circle having the same area as the area of the through hole 2a (the area of the opening in the surface 2b of the frame 2). The value of the diameter is used.

吸音材３は、その材質によって、数式（１）および（２）における密度Ｇおよび粘弾貯蔵率Ｅ’が変わるため、これらの値が上記の式を満たすように材質を選択する。
吸音材３の密度Ｇは特に制限されないが、例えば０．８６〜１．６５が好ましい。
吸音材３の粘弾貯蔵率Ｅ’は特に制限されないが、例えば１×１０７〜１×１０１０Ｐａが好ましく、５×１０７〜５×１０９Ｐａがより好ましい。 Since the sound absorbing material 3 changes the density G and the viscoelastic storage rate E ′ in the formulas (1) and (2) depending on the material, the material is selected so that these values satisfy the above formula.
The density G of the sound absorbing material 3 is not particularly limited, but is preferably 0.86 to 1.65, for example.
Although the viscoelastic storage rate E ′ of the sound absorbing material 3 is not particularly limited, for example, 1 × 10 7 to 1 × 10 10 Pa is preferable, and 5 × 10 7 to 5 × 10 9 Pa is more preferable.

吸音材３は、単一の材料からなっていてもよく、２種以上の材料の組み合わせであってもよい。
吸音材３の構成材料としては、例えば、熱可塑性樹脂を用いることができ、具体的にはＥＥＡ（エチレンエチルアクリレート）、ＥＶＡ（酢酸ビニル共重合体）、ＰＥ（ポリエチレン）、ＣＰＥ（塩素化ポリエチレン）、ＰＶＣ（ポリ塩化ビニル）、ＰＰ（ポリプロピレン）、ＳＥＢＳ（スチレンエチレンブチレンスチレンブロック共重合体）、ＳＩＳ（スチレンイソプレンスチレンブロック共重合体），ＳＥＰＳ（スチレンエチレンプロピレンスチレンブロック共重合体）、ＰＥＴ（ポリエチレンテレフタレート）、アクリル樹脂、ポリメチルペンテン、ポリブテン、ＰＥＥＫ（ポリエーテルエーテルケトン）、環状オレフィン、ポリ乳酸等から選ばれる１種または２種以上の樹脂、またはこれらの樹脂をベース樹脂とし、これに無機フィラー及び又は有機フィラーを適宜添加した混合物等が挙げられる。
上記に挙げた樹脂の中でも、ＰＥ、ＰＶＣ、ＥＥＡまたはこれらの混合樹脂が好ましい。 The sound absorbing material 3 may be made of a single material or a combination of two or more materials.
As a constituent material of the sound absorbing material 3, for example, a thermoplastic resin can be used. Specifically, EEA (ethylene ethyl acrylate), EVA (vinyl acetate copolymer), PE (polyethylene), CPE (chlorinated polyethylene). ), PVC (polyvinyl chloride), PP (polypropylene), SEBS (styrene ethylene butylene styrene block copolymer), SIS (styrene isoprene styrene block copolymer), SEPS (styrene ethylene propylene styrene block copolymer), PET (Polyethylene terephthalate), acrylic resin, polymethylpentene, polybutene, PEEK (polyetheretherketone), cyclic olefin, polylactic acid, etc. Inorganic film Over and or mixture of organic filler appropriately added, and the like.
Among the resins listed above, PE, PVC, EEA or a mixed resin thereof is preferable.

無機フィラーの例としては、マイカ、タルク、炭酸カルシウム、水酸化マグネシウム、等が挙げられる。
無機フィラーを配合する場合、その配合量は特に限定されず、数式（１）および（２）における密度Ｇおよび粘弾貯蔵率Ｅ’を満たす範囲であればよいが、機械強度の点からは、吸音材３の構成材料中８０質量％以下が好ましく、６０質量％以下がより好ましい。
有機フィラーの例としては、３，３’，３’’，５，５’，５’’−ヘキサ−ｔｅｒｔ−ブチル−ａ，ａ’，ａ’’−（メシチレン−２，４，６−トリイル）トリ−ｐ−クレゾール（例えば、製品名：アデカスタブ ＡＯ−３３０、ＡＤＥＫＡ社製）、トリス（２，４ジ−ｔｅｒｔ−ブチルフェニル）フォスファイト（例えば、製品名：Ｉｒｇ１６８、チバ・スペシャルティ・ケミカルズ社製）が好ましい。
有機フィラーを配合する場合、その配合量は特に限定されず、数式（１）および（２）における密度Ｇおよび粘弾貯蔵率Ｅ’を満たす範囲であればよいが、機械強度の点からは、吸音材３の構成材料中８０質量％以下が好ましく、６０質量％以下がより好ましい。 Examples of the inorganic filler include mica, talc, calcium carbonate, magnesium hydroxide, and the like.
When the inorganic filler is blended, the blending amount is not particularly limited as long as it satisfies the density G and the viscoelastic storage rate E ′ in the formulas (1) and (2), but from the point of mechanical strength, 80 mass% or less is preferable in the constituent material of the sound-absorbing material 3, and 60 mass% or less is more preferable.
Examples of organic fillers include 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl ) Tri-p-cresol (for example, product name: ADK STAB AO-330, manufactured by ADEKA), tris (2,4 di-tert-butylphenyl) phosphite (for example, product name: Irg168, Ciba Specialty Chemicals) Product).
When blending the organic filler, the blending amount is not particularly limited as long as the density G and the viscoelastic storage rate E ′ in the formulas (1) and (2) are satisfied, but from the viewpoint of mechanical strength, 80 mass% or less is preferable in the constituent material of the sound-absorbing material 3, and 60 mass% or less is more preferable.

吸音材３の厚さＴ１は、上記数式（１）および（２）を満たせばよく特に制限されない。
本発明の吸音体１は、吸音材３の厚さＴ１が薄くても、低周波領域において高度な吸音効果を達成できる。吸音材３の厚さＴ１は制限されないが、軽量化の点から５ｍｍ以下が好ましく、３ｍｍ以下がより好ましい。また吸音材３の厚さＴ１の下限値は０．０５ｍｍ以上が好ましく、０．１ｍｍ以上がより好ましい。吸音材３の厚さが不均一である場合は、Ｔ１として中央値を用いる。 The thickness T 1 of the sound-absorbing material 3 is not particularly limited as long as the above mathematical expressions (1) and (2) are satisfied.
Sound absorber 1 of the present invention, even if small thickness T 1 of the sound absorbing material 3 can be achieved a high degree of sound absorption effect in the low frequency region. The thickness T 1 of the sound absorbing material 3 is not limited but is preferably 5mm or less from the viewpoint of weight reduction, more preferably at most 3 mm. The lower limit of the thickness T 1 of the sound absorbing material 3 is preferably at least 0.05 mm, more preferably at least 0.1 mm. If the thickness of the sound absorbing material 3 is not uniform, using a central value as T 1.

枠体２に吸音材３を固定する手段としては、接着剤、両面テープ等の接着手段を用いてもよく、圧着、溶融圧着により固定してもよい。   As a means for fixing the sound absorbing material 3 to the frame body 2, an adhesive means such as an adhesive or a double-sided tape may be used, and it may be fixed by pressure bonding or melt pressure bonding.

さらに吸音材３の表面上（枠体２側とは反対側）に、他の吸音層（図示せず）を積層してもよい。かかる他の吸音層の材質は特に制限されず、従来の吸音材として公知の材料を適宜使用できる。例えば、吸音材３により吸音効果が得られる周波数領域よりも、高周波数領域において吸音効果を奏する吸音層を吸音材３上に積層して設けることにより、吸音体１全体として、吸音効果が得られる周波数領域をより広くすることができる。かかる他の吸音層の材質としては、例えば、発泡樹脂、フェルト、繊維材料、グラスウール、ロックウール、木粉セメント等が挙げられる。特に発泡樹脂、フェルト、繊維材料、グラスウールが好ましい。   Further, another sound absorbing layer (not shown) may be laminated on the surface of the sound absorbing material 3 (on the side opposite to the frame 2 side). The material of the other sound absorbing layer is not particularly limited, and a known material can be appropriately used as a conventional sound absorbing material. For example, a sound absorbing effect can be obtained as a whole of the sound absorber 1 by providing a sound absorbing layer on the sound absorbing material 3 so as to have a sound absorbing effect in a higher frequency region than in a frequency region where the sound absorbing effect can be obtained by the sound absorbing material 3. The frequency region can be made wider. Examples of the material of the other sound absorbing layer include foamed resin, felt, fiber material, glass wool, rock wool, and wood powder cement. Particularly preferred are foamed resin, felt, fiber material, and glass wool.

吸音体１は、上記数式（１），（２）を満たすように、吸音材３の材質、吸音材３の厚さ、枠体２の厚さ、貫通孔２ａの形状および大きさを選択することにより、吸音率のピーク周波数が５００Ｈｚ以下であり、かつ該ピーク周波数における吸音率が０．５以上であるような、低周波領域における高度な吸音効果が得られる。
すなわち、上記数式（１）で求められるＥ１と吸音率のピーク値とは、後述の実施例における図３のグラフに示されるような相関関係があり、このＥ１の値が９．７×１０６（グラフでは９．７Ｅ＋６と記載する。以下、同様。）以上であれば、吸音率のピーク値が０．５以上となる。
また、上記式（２）で求められるＥ２と吸音率のピーク周波数とは、後述の実施例における図４のグラフに示されるような相関関係があり、このＥ２の値が３４６以下であれば、吸音率のピーク周波数が５００Ｈｚ以下となる。 The sound absorber 1 selects the material of the sound absorbing material 3, the thickness of the sound absorbing material 3, the thickness of the frame 2, and the shape and size of the through hole 2 a so as to satisfy the above formulas (1) and (2). As a result, it is possible to obtain a high sound absorption effect in a low frequency region such that the peak frequency of the sound absorption coefficient is 500 Hz or less and the sound absorption coefficient at the peak frequency is 0.5 or more.
That is, E1 obtained by the above formula (1) and the peak value of the sound absorption coefficient have a correlation as shown in the graph of FIG. 3 in an example described later, and the value of E1 is 9.7 × 10 6. (In the graph, it is described as 9.7E + 6. The same shall apply hereinafter.) If so, the peak value of the sound absorption coefficient is 0.5 or more.
Moreover, E2 calculated | required by said Formula (2) and the peak frequency of a sound absorption rate have a correlation as shown by the graph of FIG. 4 in the below-mentioned Example, and if the value of this E2 is 346 or less, The peak frequency of the sound absorption coefficient is 500 Hz or less.

また吸音体１は、薄型でも低周波領域において高度な吸音効果を達成できるものであり、Ｔ１とＴ２の合計の厚さが例えば５５ｍｍ以下、好ましくは２５ｍｍ以下でありながら、５００Ｈｚ以下の低周波領域において、吸音率が０．５以上の高度な吸音効果を達成できる吸音体が得られる。
このように、従来は達成することが難しかった、薄い吸音材３で低周波領域における高度な吸音効果を得ることができる。 The sound absorber 1 can achieve a high level of sound absorbing effect even in a low frequency region even when it is thin, and the total thickness of T 1 and T 2 is, for example, 55 mm or less, preferably 25 mm or less, and a low frequency of 500 Hz or less. In the frequency domain, a sound absorber that can achieve an advanced sound absorbing effect with a sound absorption coefficient of 0.5 or more is obtained.
As described above, it is possible to obtain an advanced sound absorbing effect in the low frequency region with the thin sound absorbing material 3 that has been difficult to achieve in the past.

なお、本発明の吸音体は、貫通孔を有する枠体と、該貫通孔の一方の開口を覆う吸音材を備えた構成であればよく、図１に示す形態に限らず、各種の構成とすることができる。例えば図６に示すように、板状の枠体２２に複数の貫通孔２２ａが設けられており、該枠体２２の一面上に、該複数の貫通孔２２ａを一括的に覆うように吸音材２３が積層、固定された構成を有する吸音体２１であってもよい。図６は吸音体２１を枠体２２側から見た斜視図である。
このように、枠体２２に複数の貫通孔２２ａが設けられている場合、該複数の貫通孔２２ａの形状および大きさは均一でもよく、異なっていてもよい。
また該複数の貫通孔２２ａの配置は任意であるが、隣り合う貫通孔２２ａどうしの距離ｄが小さいほど吸音体２１における吸音の効率が高くなる。
このような構成の吸音体２１においても、上記数式（１），（２）を満たすように、吸音材２３の材質、吸音材２３の厚さ、枠体２２の厚さ、貫通孔２２ａの形状および大きさを選択することにより、吸音率のピーク周波数が５００Ｈｚ以下であり、かつ該ピーク周波数における吸音率が０．５以上であるような、低周波領域における高度な吸音効果が得られる。 Note that the sound absorber of the present invention is not limited to the form shown in FIG. 1 and various configurations, as long as the sound absorber has a frame having a through hole and a sound absorbing material that covers one opening of the through hole. can do. For example, as shown in FIG. 6, a plurality of through holes 22 a are provided in the plate-like frame body 22, and a sound absorbing material is provided on one surface of the frame body 22 so as to cover the plurality of through holes 22 a collectively. The sound absorber 21 may have a configuration in which 23 is stacked and fixed. FIG. 6 is a perspective view of the sound absorber 21 viewed from the frame body 22 side.
Thus, when the frame body 22 is provided with a plurality of through holes 22a, the shapes and sizes of the plurality of through holes 22a may be uniform or different.
The arrangement of the plurality of through holes 22a is arbitrary, but the sound absorption efficiency of the sound absorber 21 increases as the distance d between the adjacent through holes 22a decreases.
Also in the sound absorber 21 having such a configuration, the material of the sound absorbing material 23, the thickness of the sound absorbing material 23, the thickness of the frame body 22, and the shape of the through hole 22a are satisfied so as to satisfy the above formulas (1) and (2). By selecting the size and the magnitude, it is possible to obtain a high sound absorption effect in a low frequency region in which the peak frequency of the sound absorption coefficient is 500 Hz or less and the sound absorption coefficient at the peak frequency is 0.5 or more.

以下に実施例を用いて本発明をさらに詳しく説明するが、本発明はこれら実施例に限定されるものではない。
（例１〜２７）
表１に示す配合の材料（樹脂または樹脂とフィラーの混合物）を用いて膜状の吸音材３を作製した。使用した樹脂およびフィラー等は表２の通りである。表１における「部」は「質質部」である。
吸音材３の厚みＴ１は表３に示す値とした。吸音材３を構成する材料の粘弾貯蔵率Ｅ’および密度Ｇを測定した結果を表３に示す。
得られた膜状の吸音材３を用いて図１に示す構成の吸音体１を作製した。枠体２の材質はアクリル樹脂であり、貫通孔２ａは円形とした。枠体の厚みＴ２および貫通孔２ａの直径Ｄは表３に示す値とした。
作製した吸音体１について、上記数式（１）で求められる第１の貯蔵弾性率Ｅ１および上記数式（２）で求められる第２の貯蔵弾性率Ｅ２の値を計算により求めた。結果を表３に示す。
また作製した吸音体１について、上述した測定方法により吸音率を測定し、ピーク周波数と該ピーク周波数における吸音率の値（ピーク値）を求めた。図２は例１６で得られた吸音体について上述した測定方法により吸音率を測定して得られた周波数と吸音率の関係を示すグラフである。このグラフより例１６における吸音率ピーク値は０．９５、ピーク周波数は３５２Ｈｚであることがわかる。
例１〜２７についての測定結果を表３に示すとともに、図３、４のグラフに示す。
図３は、第１の貯蔵弾性率Ｅ１を横軸、ピーク周波数における吸音率の値を縦軸とし、各例の結果をプロットしたグラフである。グラフ中のＲ２は相関係数を示す（以下、同様。）。
図４は、第２の貯蔵弾性率Ｅ２を横軸、ピーク周波数の値を縦軸とし、各例の結果をプロットしたグラフである。 Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
(Examples 1-27)
Using a material (resin or a mixture of resin and filler) having the composition shown in Table 1, a film-like sound absorbing material 3 was produced. The resins and fillers used are as shown in Table 2. “Part” in Table 1 is “quality part”.
The thickness T 1 of the sound absorbing material 3 was set to the values shown in Table 3. Table 3 shows the results of measuring the viscoelastic storage rate E ′ and density G of the material constituting the sound absorbing material 3.
Using the obtained film-like sound absorbing material 3, a sound absorbing body 1 having the configuration shown in FIG. 1 was produced. The material of the frame 2 was acrylic resin, and the through hole 2a was circular. The diameter D of the thickness T 2 and the through hole 2a of the frame body is set to a value shown in Table 3.
About the produced sound-absorbing body 1, the value of the 1st storage elastic modulus E1 calculated | required by the said Numerical formula (1) and the 2nd storage elastic modulus E2 calculated | required by the said Numerical formula (2) was calculated | required. The results are shown in Table 3.
Further, the sound absorption coefficient of the produced sound absorber 1 was measured by the measurement method described above, and the peak frequency and the value of the sound absorption coefficient (peak value) at the peak frequency were obtained. FIG. 2 is a graph showing the relationship between the frequency and the sound absorption coefficient obtained by measuring the sound absorption coefficient of the sound absorber obtained in Example 16 by the measurement method described above. From this graph, it can be seen that the peak value of the sound absorption coefficient in Example 16 is 0.95 and the peak frequency is 352 Hz.
The measurement results for Examples 1 to 27 are shown in Table 3 and shown in the graphs of FIGS.
FIG. 3 is a graph in which the results of each example are plotted with the first storage elastic modulus E1 as the horizontal axis and the sound absorption coefficient value at the peak frequency as the vertical axis. R 2 in the graph represents a correlation coefficient (the same applies hereinafter).
FIG. 4 is a graph in which the results of each example are plotted with the second storage elastic modulus E2 as the horizontal axis and the peak frequency value as the vertical axis.

Figure 0004832245
Figure 0004832245

Figure 0004832245
Figure 0004832245

Figure 0004832245
Figure 0004832245

表３および図３に示されるように、第１の貯蔵弾性率Ｅ１が９．７×１０６〜３．３×１０７の範囲において、吸音率のピーク値は０．５〜１．０であった。また表３および図４に示されるように、第２の貯蔵弾性率Ｅ２が１３３〜３４６の範囲において、ピーク周波数は２９０〜５００Ｈｚであった。
したがって、Ｅ１が９．７×１０６以上、かつＥ２が３４６以下である例１〜２０の吸音体において、５００Ｈｚ以下の低周波領域において、吸音率０．５以上の高度な吸音効果が得られる。 As shown in Table 3 and FIG. 3, when the first storage elastic modulus E1 is in the range of 9.7 × 10 6 to 3.3 × 10 7 , the peak value of the sound absorption coefficient is 0.5 to 1.0. there were. In addition, as shown in Table 3 and FIG. 4, the peak frequency was 290 to 500 Hz when the second storage elastic modulus E2 was in the range of 133 to 346.
Therefore, in the sound absorbers of Examples 1 to 20 where E1 is 9.7 × 10 6 or more and E2 is 346 or less, a high sound absorption effect with a sound absorption coefficient of 0.5 or more is obtained in a low frequency region of 500 Hz or less. .

（参考例１）
吸音周波数に対する背後空気層の関係を調べた。
表４に示す４種類の配合の材料（樹脂または樹脂とフィラーの混合物）Ａ〜Ｄを用いて膜状の吸音材３を作製した。使用した樹脂およびフィラーは前記表２の通りである。表４における「部」は「質質部」である。 (Reference Example 1)
The relationship of the back air layer to the sound absorption frequency was investigated.
A film-like sound-absorbing material 3 was prepared using materials (resin or a mixture of resin and filler) A to D having four kinds of blends shown in Table 4. The resins and fillers used are as shown in Table 2 above. “Part” in Table 4 is “quality part”.

Figure 0004832245
Figure 0004832245

吸音材３の厚みＴ１は、Ａ〜Ｃについては１ｍｍ、Ｄは０．７ｍｍとした。背後空気層の厚さを表５に示すように変化させ、それぞれ吸音周波数（ピーク周波数）を測定した。その結果を表５に示す。またＡ〜Ｄのそれぞれにおいて、背後空気層の厚さが９ｍｍのときの吸音周波数を１として、各吸音周波数の測定値を規格化した値を求めた。その結果を表５に示すとともに、該規格化した吸音周波数の値と背後空気層の厚さとの関係を図５のグラフに示す。 The thickness T 1 of the sound absorbing material 3 was 1 mm for A to C, and 0.7 mm for D. The thickness of the back air layer was changed as shown in Table 5, and the sound absorption frequency (peak frequency) was measured. The results are shown in Table 5. In each of A to D, the sound absorption frequency when the thickness of the back air layer was 9 mm was set to 1, and the value obtained by standardizing the measured value of each sound absorption frequency was obtained. The results are shown in Table 5, and the relationship between the normalized sound absorption frequency value and the thickness of the back air layer is shown in the graph of FIG.

Figure 0004832245
Figure 0004832245

本発明の吸音体は、例えば、壁、床などの建材、自動車用の吸音材、電気製品の吸音材など、広い範囲に適用できる。   The sound absorber of the present invention can be applied to a wide range, for example, building materials such as walls and floors, sound absorbing materials for automobiles, and sound absorbing materials for electric products.

本発明の吸音体の一実施形態を示すもので（ａ）は平面図、（ｂ）は（ａ）中のＢ−Ｂ線に沿う断面図である。An embodiment of the sound absorber of the present invention is shown, in which (a) is a plan view and (b) is a cross-sectional view taken along line BB in (a). 実施例にかかる吸音率測定結果の例を示すグラフである。It is a graph which shows the example of the sound absorption coefficient measurement result concerning an Example. 実施例の結果を示すグラフである。It is a graph which shows the result of an Example. 実施例の結果を示すグラフである。It is a graph which shows the result of an Example. 参考例の結果を示すグラフである。It is a graph which shows the result of a reference example. 本発明の吸音体の他の実施形態を示す斜視図である。It is a perspective view which shows other embodiment of the sound-absorbing body of this invention. 従来の吸音材料における吸音特性を示すグラフである。It is a graph which shows the sound absorption characteristic in the conventional sound-absorbing material.

符号の説明Explanation of symbols

１、２１…吸音体、
２、２２…枠体、
２ａ、２２ａ…貫通孔、
３、１３、２３…吸音材、
５、１５…背後空気層。 1, 21 ... Sound absorber,
2, 22 ... Frame,
2a, 22a ... through hole,
3, 13, 23 ... sound absorbing material,
5, 15 ... Air layer behind.

Claims (1)

貫通孔が形成された枠体と、該貫通孔の一方の開口を覆う吸音材を有し、
前記吸音材の下記数式（１）で求められる第１の貯蔵弾性率Ｅ１が９．７×１０６以上であり、下記数式（２）で求められる第２の貯蔵弾性率Ｅ２が３４６以下であることを特徴とする吸音体。
Figure 0004832245
 （式中、Ｅ’は貯蔵弾性率の測定値（単位：Ｐａ）を表し、Ｔ１は吸音材の厚み（単位：ｍｍ）を表し、Ｔ２は枠体の厚み（単位：ｍｍ）を表し、Ｇは吸音材の密度（単位：ｇ／ｃｍ３）を表し、Ｄは枠体の貫通孔の直径（単位：ｍｍ）を表す。） A frame body having a through hole and a sound absorbing material covering one opening of the through hole;
The first storage elastic modulus E1 obtained by the following mathematical formula (1) of the sound absorbing material is 9.7 × 10 6 or more, and the second storage elastic modulus E2 obtained by the following mathematical formula (2) is 346 or less. A sound absorber characterized by that.
Figure 0004832245
 (In the formula, E ′ represents a measured value of storage elastic modulus (unit: Pa), T 1 represents the thickness of the sound absorbing material (unit: mm), and T 2 represents the thickness of the frame (unit: mm)). G represents the density of the sound absorbing material (unit: g / cm 3 ), and D represents the diameter of the through hole of the frame (unit: mm).
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