JP7207901B2 - Impact noise reduction structure and impact noise reduction method - Google Patents

Description

The present invention relates to technology for reducing impact noise. In particular, in structures with an air layer such as dry double floors and double floors, it is a technology that reduces the transmission of floor impact noise to the rooms on the lower floors, which is generated when heavy objects fall on the floor. .

One of the impact noises generated in collective housing is the floor impact sound insulation performance. Floor impact sounds include light floor impact sounds and heavy floor impact sounds. Heavy floor impact sound is one of the "floor impact sounds" transmitted from the upper floor to the lower floor through the floor. It's a low tone. On the other hand, the sound of dropping a light object such as a spoon and the sound of footsteps made by slippers are "lightweight floor impact sounds".
Weight impact noise is difficult to reduce with floor coverings and ceiling coverings.
The dry double floor is a floor finish structure (Patent Document 1: Japanese Patent Application Laid-Open No. 2011-074694) in which the floor panel is supported by support legs with anti-vibration rubber, etc., and is used in many buildings such as collective housing. there is
The problem with the dry double floor is that it tends to amplify rather than reduce in the frequency band (63 Hz band) that is important for heavy floor impact noise. The reason for this is that the dry double floor system amplifies the vibration by forming a resonant system with the plate material as the mass and the rubber at the bottom of the support leg as the spring. It is also believed that the air in the bosom of the dry double floor is also involved in the spring of the resonance system. It is considered that the resonance frequency of the resonance system due to them exists in the frequency band that is important for the heavy floor impact sound.
As a conventional technique to solve this problem, the plate material of the dry double floor is thickened and the mass is increased (Non-Patent Document 1) to lower the resonance frequency of the resonance system and reduce the frequency band that is important for heavy floor impact noise. Measures are taken to prevent inclusion.
In addition, in order to reduce the effect of the spring due to air, measures are taken to provide a gap between the surroundings of the dry double floor and the wall of the room so that air can escape at the time of impact (Patent Document 2: Japanese Patent Laid-Open No. 2015-17392).
In addition, a sound absorbing material such as glass wool is widely laid in the pocket of the dry double floor (Non-Patent Document 1), or a resonator-type sound absorbing body (Helmholtz resonator structure) provided with a communicating pipe (Non-Patent Document 2, Patent Document 3: JP-A-2015-52260) is installed (see FIG. 14), and an attempt is made to reduce the floor impact noise by their sound absorbing effect.

また、二重天井の懐内では二次元的な音響共鳴も生じる（以降、二次元共鳴と記す）。一般の居室の平面寸法の場合、低次の二次元共鳴がちょうど重量床衝撃音で重要となる周波数帯域に存在してしまう。
このうち、バネ・マス共振による増幅を軽減するための従来の技術として、二重天井の板材を厚くして質量を増して共振系の共振周波数を下げ、重量床衝撃音で重要となる周波数帯域に含まれないようにする対策が、よく知られた軽減方法として行われる。
しかし、上記の二重天井の質量を増す方法では、式１からも分かるように板の重さを２倍にした場合でも共振周波数は０．７倍（１／√２）までしか下がらず、大幅に板を重くする必要がある。
また、バネ・マス共振による増幅を軽減するための別の技術として、質量ではなく空気の特性を変化させることにより、共振系の共振周波数を下げ、重量床衝撃音で重要となる周波数帯域に含まれないようにする技術が提案されている（特許文献４：特開２００６－３１６４５９号公報）。これは、天井内空間を全て埋めるように多孔質材を充填させることにより、懐空間内の音速を空気中のそれよりも遅くすることによって共振周波数を下げるものである。
上記の天井内空間全てに多孔質材を充填する方法は共振周波数f₀を著しく小さくすることが可能である。しかし、天井内空気の音速を変化させるためには、特許文献４によれば、多孔質材を空間の９０％以上充填させる必要があり、例えば３２ｋｇ／ｍ³のグラスウールを用いて充填した場合、天井懐高さが１５０ｍｍならば天井板には約５ｋｇ／ｍ²と大きな荷重がかかってしまう。また、天井には下地があり、例えば天井懐１５０ｍｍ、下地の高さ４５ｍｍの場合を想定すると、下地間の隙間空間は天井内空間のおよそ３０％をも占めるため、多孔質材を９０％以上充填させるためには下地を避けるように隙間なく設置する必要がある。
また、二重天井懐内に吸音材を敷設（二重天井の上にグラスウールを敷く）して床衝撃音を低減しようとすることもある。しかし、非特許文献３に示されるように、この方法は中高周波数域で性能が決定される軽量床衝撃音には低減効果が得られる場合があるが、重量床衝撃音のように低い周波数の音に対しては、敷設された吸音材による低減効果は認められず、むしろ、性能が低下する場合が多い。
特許文献５（特開2017-89307号公報）にあるように天井の板材や下地材にダイナミックダンパーを多数設置し、天井の振動を低減することで床衝撃音の低減を図る試みもある。この場合、多数のダンパーやそれを設置するための多くの部材が必要となる。また、一般的な天井施工に加えて専門の技術を要する工事が必要となってしまう。 In a suspended ceiling (double ceiling), the double ceiling uses a plate material as a mass and becomes a resonance system using the air in the bosom as a spring, amplifying vibrations. This resonance frequency exists in the frequency band that is important for heavy floor impact noise. The resonance frequency f ₀ is related to the density of air ρ ₀ , the speed of sound in air c ₀ , the height of the air space h, and the surface density m of the plate, as shown by the following equation.

In addition, two-dimensional acoustic resonance also occurs in the bosom of the double ceiling (hereafter referred to as two-dimensional resonance). In the case of the plane dimensions of a general living room, low-order two-dimensional resonance exists in the frequency band that is important for heavy floor impact sound.
Among these, as a conventional technology to reduce the amplification due to spring-mass resonance, the thickness of the plate material of the double ceiling is increased to increase the mass, lowering the resonance frequency of the resonance system, and the frequency band that is important for heavy floor impact noise. A well-known mitigation is taking measures to prevent inclusion in
However, in the above method of increasing the mass of the double ceiling, as can be seen from Equation 1, even if the weight of the plate is doubled, the resonance frequency only drops by 0.7 times (1/√2). The board needs to be significantly heavier.
In addition, as another technology to reduce the amplification due to spring-mass resonance, by changing the characteristics of air rather than mass, the resonance frequency of the resonance system is lowered, and it is included in the frequency band that is important for heavy floor impact noise. A technique has been proposed to prevent this from occurring (Patent Document 4: Japanese Unexamined Patent Application Publication No. 2006-316459). This lowers the resonance frequency by filling the entire space in the ceiling with a porous material so that the speed of sound in the space is slower than that in the air.
The method of filling the entire space in the ceiling with a porous material can significantly reduce the resonance frequency f ₀ . However, in order to change the sound velocity of the air in the ceiling, according to Patent Document ⁴ , it is necessary to fill 90% or more of the space with a porous material. If the ceiling height is 150 mm, a large load of about 5 kg/m ² is applied to the ceiling board. In addition, the ceiling has a foundation, and assuming that the ceiling is 150 mm high and the foundation is 45 mm high, the space between the foundations occupies about 30% of the space in the ceiling, so 90% or more of the porous material is used. In order to fill it, it is necessary to install it without gaps so as to avoid the base.
In some cases, sound absorbing material is laid in the double ceiling pocket (glass wool is laid over the double ceiling) to reduce floor impact noise. However, as shown in Non-Patent Document 3, this method may provide a reduction effect for light weight floor impact noise whose performance is determined in the mid-high frequency range, but it may provide a reduction effect for low frequency floor impact noise such as heavy floor impact noise. With respect to sound, the installed sound-absorbing material does not have the effect of reducing sound, and in many cases, rather, the performance is lowered.
As described in Patent Document 5 (Japanese Patent Application Laid-Open No. 2017-89307), there is an attempt to reduce floor impact noise by installing a large number of dynamic dampers on ceiling plate materials and base materials to reduce ceiling vibration. In this case, many dampers and many members for installing them are required. Moreover, in addition to general ceiling construction, construction work that requires specialized techniques is required.

https://bankyo.co.jp/product/mansions/ype_g2.html (Bankyo floor, catalog) Yabushita et al., "Development of a high-performance sound insulation double floor (Part 2: Overview of measurements in a full-scale laboratory building)", Summaries of technical papers of Annual Meeting of Architectural Institute of Japan, September 2012. Katsuo Yoshida, et al., "Prevention effect of floor impact noise by gypsum board ceiling", Noise Control, Vol. 14, No. 4, 1990

JP 2011-074694 A JP 2015-17392 A JP 2015-052260 A JP 2006-316459 A JP 2017-89307 A

An object of the present invention is to develop a new means for reducing impact noise.

The present invention has a flat plate structure arranged with an air layer interposed therebetween, and arranges an air-permeable material so as to partition the air layer to make it difficult for a two-dimensional resonance phenomenon to occur. To reduce impact noise transmitted through a flat plate.
The dry double floor has a resonance system with the plate material of the dry double floor as mass and the rubber at the bottom of the support leg as a spring. The amplification of the heavy floor is not only due to the resonance due to the spring and mass, but also greatly influenced by the two-dimensional resonance phenomenon inside the bosom. The present invention is based on the technical idea of identifying this resonance phenomenon and suppressing the resonance phenomenon to reduce floor impact noise.
This phenomenon applies equally to double ceilings such as suspended ceilings. An air-permeable material is installed in the pocket of the double ceiling so as to partition the pocket, and the two-dimensional resonance phenomenon in the pocket is made difficult to occur, thereby reducing floor impact noise. In addition, in the present invention, as a structure for supporting the ceiling plate, the ceiling plate and the ceiling slab (upper floor floor) are configured to support the base material such as the joist on the wall, or to support the joist (including the joist holder) with a hanging tool. A ceiling structure in which an air layer is formed between slabs is called a double ceiling.
Furthermore, it can also be applied to a wall structure in which a plurality of plate materials are installed with an air layer.

1. An impact sound reduction structure characterized by an architectural structure in which two flat members are formed with an air layer sandwiched between them, and a breathable material is installed in a place where the sound particle velocity is high when the air layer resonates. .
2. The building structure is a dry double floor, double ceiling or wall, and in the air layer formed in these double floors, double ceilings, walls, the line that divides the side into two or four, or 1. A breathable material is installed so as to partition the air layer every 2.5 m to 3.5 m. The described impact sound reduction structure.
3. The placement of the air-permeable material is characterized by the location where the sound particle velocity is high when the air layer resonates.1. or 2. The described impact sound reduction structure.
4. The air-permeable material has a flow resistance of 100 Pa·s/m to 10,000 Pa·s/m and mainly reduces impact noise in the 63 Hz band.1. ~3. The impact noise reduction structure according to any one of .
5. 1. The air-permeable material is any one of membrane, cloth, net, mat, punching metal, perforated plate, honeycomb plate, fibrous material, and porous board. ~ 4. The impact noise reduction structure according to any one of .
6. In an impact sound transmission structure in which two flat plate members are formed with an air layer in between, and the impact sound generated by the impact given to one flat plate member is transmitted through the other flat plate member, when the air layer resonates A method of reducing impact noise by installing breathable materials in places where sound particles speed up.
7. In a building with a dry double floor or double ceiling as an impact sound transmission structure, air-permeable materials are installed on the line that divides the side of the air layer into two or four, and the floor impact noise is mainly in the 63 Hz band. 6. is characterized by reducing A method for reducing the described impulsive sound.
8. 7. The method of installing the breathable material is to install it on a dry double floor board, attach it to the legs of a dry double floor, or install it on a concrete floor.7. A method for reducing the described impulsive sound.
9. 7. The method of installing the breathable material in the double ceiling is characterized in that the breathable material is installed by hooking it to the joists of the ceiling or attached to the concrete ceiling slab. A method for reducing the described impulsive sound.

1. In structures such as dry double floors and double ceilings such as suspended ceilings, where plate-like bodies pass through an air layer, the impact given to one plate-like body resonates in the air layer and impacts from the other plate-like body. A phenomenon that is emitted as sound occurs. According to the present invention, by installing the air-permeable material so as to partition the air layer, it is possible to reduce the impact noise emitted from the other plate-like body. The present invention is mainly effective in reducing floor impact noise. The impact sound applied to the floor of the upper floor is reduced by installing a breathable material in the pocket of the dry double floor, double ceiling, etc.
The invention is also applicable to wall structures. For example, in an office or conference room adjacent to the exercise area of a gymnasium, the impact noise given to the walls can be reduced. Further, the present invention is expected to be effective not only for impact noise but also for transmission of air-borne sound. For example, by applying it to a window using a double sash, it can be expected to improve the performance of blocking noise transmitted from the outside to the inside of the room.
2. We have developed a method to reduce floor impact noise by installing air-permeable materials so as to partition the air layers of dry double floors or double ceilings. The present invention reduces floor impact noise by installing a breathable material so as to partition the interior of a dry double floor or double ceiling and making it difficult for the two-dimensional resonance phenomenon that occurs in the interior to occur. By arranging the air-permeable material at the point where the sound particle velocity is the highest (air particles are vibrating) in the pocket of the dry double floor or double ceiling, the vibration of the air is converted into heat energy, and the floor Impact noise is reduced. In particular, heavy floor impact noise represented by the 63 Hz frequency band can be reduced. A guideline for the location is the line that divides the floor into 2 or 4 parts, and in a large room, it should be installed every 2.5m to 3.5m. It should be noted that the "guideline" includes the vicinity of the 2-division and the 4-division since it may be difficult to install it accurately in the center depending on the situation of the mounting location. Even if the position of the air-permeable material deviates to some extent, the reduction effect is not greatly impaired.
Breathable materials include membranes, cloths, nets, mats, punching metals, perforated plates, honeycomb plates, fiber materials such as glass wool, porous boards, etc., which are easy to install and have good flexibility and shape. Since changes can be flexibly accommodated, there are no restrictions on the arrangement of wiring, piping, etc. in a double-floor or double-ceiling space.
In addition, it can be easily installed without requiring special skills for construction.
3. Conventional floor impact sound reduction methods require complex equipment in dry double floors or double ceilings and add to the mass of the floor or ceiling. In addition, in the case of a dry double floor, it is necessary to secure a gap for underfloor piping, so there are restrictions on equipment installed under the floor. There is a high degree of freedom in designing heavy floors.
4. In the case of increasing the mass of the floor material among the impact noise reduction methods, the floor becomes thicker and the underfloor space is lowered accordingly. If the pocket height is lowered, it will affect the piping. If the height is not changed to avoid this, the height of the ceiling will be lowered and the feeling of living will be deteriorated.
5. In the method of providing a gap between the perimeter of the dry double floor and the wall of the room, it is desirable to provide a large gap. cannot be established. In addition, depending on the specifications specified by the client, there are cases in which gaps must be closed with a baseboard with rubber fins attached to the bottom, which is called a baseboard with fins.
In the method of laying sound-absorbing materials and sound-absorbing bodies widely in the pocket of a dry double floor, simply laying sound-absorbing materials such as glass wool in the pocket may reduce light weight floor impact noise, but heavy floor impact noise may be reduced. A reduction effect cannot be obtained for the sound. Moreover, when a resonator-type sound absorber is installed, it is difficult to adjust the resonator, and the cost increases.
6. The present invention can apply the same theory and mechanism as the double floor to the double ceiling. In particular, in a double ceiling such as a suspended ceiling, it is not preferable to load the plate material of the ceiling with weight. In addition, it is necessary to place the sound absorbing material while avoiding air conditioning ducts and wiring. Breathable materials that are lightweight and easy to work with are ideal for installation in double ceilings.
In addition, in the ceiling, the air-permeable material can be locked by using a base material such as a coffer for fixing the plate material. The air-permeable material can be provided with a notch in the cross-sectional shape of the ceiling joist, and the notch can be fitted into and locked to the ceiling joist. Alternatively, fasteners attached to the joists can be used to place the breathable material parallel to the joists. Ceiling concrete or a ceiling hanger can also be used to install the air-permeable material.

Figures showing installation examples of breathable materials, (a) double floor structure, (b) double ceiling structure, and (c) wall structure. A diagram showing an example of an arrangement pattern of air-permeable materials Illustration showing an example of installing breathable materials Example of installing with a gap in breathable material A diagram showing the sound pressure distribution in the bosom Conditions at the end of a dry double floor in an experiment conducted on the effect of floor impact noise of the air in the bosom of a dry double floor Floor impact sound level reduction by experiment Experimental sound pressure level in the bosom of a dry double floor Sound pressure level (relative level) in a dry double floor space by numerical calculation Sound pressure level distribution in a dry double floor under the condition of "no gap" by numerical calculation Experimental equipment for confirming the reduction effect of air-permeable materials (one-dimensional sound field) Results of experiments to confirm the reduction effect of breathable materials (conditions where no breathable materials are installed) Results of experiments to confirm the reduction effect of breathable materials (conditions where breathable materials are installed) FIG. 3 shows a conventional example described in FIG. 3 of Patent Document 3 Schematic showing installation of breathable material in double ceiling pocket A diagram showing an example of an arrangement pattern of breathable materials installed in a double ceiling pocket Example of installing breathable materials with gaps in a double ceiling A diagram showing the sound pressure distribution in the bosom Experimental equipment for confirming the reduction effect of air-permeable materials (one-dimensional sound field) Results of experiments to confirm the reduction effect of breathable materials (conditions where no breathable materials are installed) Results of experiments to confirm the reduction effect of breathable materials (installation conditions for breathable materials) A diagram showing the results of investigating how the effect changes when the air-permeable material is installed with a gap (a) using the experimental apparatus of FIG. A diagram showing an example of a base material used for a double ceiling A diagram showing an example of installing a breathable material on the base material (roofing) in a double ceiling. A diagram showing an example of using a breathable material with notches in the base material (roofing) in a double ceiling. Diagram showing an example of breathable materials installed parallel to the base material (roofing) in a double ceiling

The present invention provides a structure in which two plate-shaped bodies sandwich an air layer, and when an impact applied to one plate-shaped body is released from the other plate-shaped body through the air layer, the air The impact noise is reduced by installing air-permeable materials so as to divide the layers.
Such impulsive sounds include, for example, impulsive sounds that impact the floors of upper floors to the lower floors. The air layer is formed as a floor space and a ceiling space by a dry double floor and a double ceiling. Alternatively, an outer wall or a wall between adjacent rooms may have a structure in which the wall is made of double plates and an air layer is provided between them. In the gymnasium, it is necessary to provide a sound insulation structure that reduces the sound generated in the exercise space in the adjacent offices and conference rooms. Furthermore, there is a double sash window as a structure in which plate-like bodies face each other with an air layer interposed therebetween. Applying the structure of dividing the air layer with this breathable material and arranging the breathable material that converts the sound energy into heat to the double sash can reduce the sound outside the building, thereby reducing the noise level inside the building. can do.
The present invention reduces impact noise by arranging a breathable material at the location where air particles vibrate the most due to the resonance phenomenon that occurs in the air layer, and converting air vibration into heat energy. The present invention does not require air isolation, is not intended to absorb sound, and does not enclose the sound source. In particular, the present invention can reduce heavy floor impact noise represented by the 63 Hz frequency band.
A representative example is shown in FIG. (a) is an example of a double floor, (b) is a double ceiling composed of a double floor, and (c) is a wall structure with an air layer.
FIG. 1(a) shows a dry double floor in which a floor panel 4 is formed on a concrete slab 5 with support legs 6 interposed therebetween. A floor cavity 2 serving as an air layer is formed between the concrete slab 5 and the floor panel 4. - 特許庁A breathable material 3 is arranged so as to partition the floor pocket 2. - 特許庁FIG. 1(b) shows a double ceiling in which an air layer is provided under a concrete slab 25 and a ceiling plate is installed. Although the ceiling board is attached to the joists that are passed between the walls or hung by the hanging members, the illustration is omitted. A breathable material 23 is arranged so as to partition a ceiling pocket 22 formed as an air layer between the ceiling plate 24 and the concrete slab 25 . FIG. 1(c) shows a wall structure 31 in which a wall plate material 34 is provided on a concrete wall body 35 via an air layer 32 formed by a wall base material or the like. A breathable material 33 is arranged so as to partition the air layer 32 . In this figure the breathable material is arranged horizontally, but it can also be provided vertically.

<Embodiment for dry double bed>
The present invention, as shown in FIG. 1(a), is a dry double floor 1 in which support legs 6 are erected on a concrete slab 5 and floor panels 4 are placed thereon with a floor 2 (height h) provided. Applies to As shown in FIG. 1(a), a breathable material 3 is installed in the bottom pocket 2 of a dry double floor 1 so as to partition the bottom wall, thereby making it difficult for the resonance phenomenon in the bottom pocket 2 to occur. to reduce the floor impact sound transmitted to the lower floor through the concrete slab 5. In particular, it reduces heavy floor impact noise typified by the 63 Hz frequency band. On the line that divides the floor side of the target room into two or four as a measure to improve the floor impact sound insulation performance of a building using a dry double floor, or as a sound insulation measure for the floor when renovating to a dry double floor. , or placing a breathable material every 2.5m to 3.5m.
The present invention reduces heavy floor impact noise by arranging a breathable material at the location where air particles vibrate the most due to the resonance phenomenon in the bosom of the dry double floor and converting air vibration into thermal energy. . In particular, heavy floor impact noise represented by the 63 Hz frequency band can be reduced.
Since the present invention takes measures to partition the underfloor with a lightweight, flexible and breathable material, there is no need to change the underfloor height and there is no effect on the piping.

The object is the dry double floor, and it can be applied to the dry double floor to be newly constructed or renovated. For example, it applies to double floors in newly constructed office buildings, double floors in collective housing, or when these existing buildings are refurbished to have double floors.
It is installed on the floor panel 4, on the support leg 6 of the dry double floor 1, on the concrete slab 5, or the like.
As a guideline, the mounting point should be the central part or 1/4 part of the side of the floor of the room.
The "reference" includes the vicinity of the center and the vicinity of 1/4, because it may be difficult to install the sensor exactly in the center depending on the condition of the mounting location. These installation locations are locations where the sound particle velocity is high.
FIG. 2 shows an example of an arrangement pattern of air-permeable materials. In FIG. 2(a), when the short side width W and the long side width D of the floor are less than 4 m, the respective sides are divided into two at positions D*1/2 and W*1/2. In FIG. 2B, when the long side width D of the floor is 4 m or more and the short side width W is less than 4 m, the positions are W*1/2 and D*1/4. In FIG. 2(c), when the short side width W of the floor is 4 m or more and the long side width D is 4 m or more, the positions are W*1/4 and D*1/4. In addition, in the case of a large-sized floor where the side of the room exceeds 8m, install it every 2.5m to 3.5m.

Breathable materials include membranes, cloths, nets, mats, punching metals, perforated plates, honeycomb plates, fibrous materials such as glass wool, and porous boards. Materials that can flexibly and flexibly adapt to changes in shape are not subject to restrictions on the arrangement of wiring, piping, etc. in the space of the double floor. Since the plate-like object stands on its own, it is suitable for fixing to the floor slab.
Air flow resistance of 100 Pa·s/m to 10,000 Pa·s/m is suitable for air permeability.
The flow resistance, r _f [Pa·s/m], is expressed by Equation 2 below.

FIG. 3 shows an installation example of the breathable material 3 .
FIG. 3A shows an example in which the floor panel 4 is provided with a floor panel fixing portion 11 and the breathable material 3 is attached. The floor panel fixing part 11 is a means such as a rail, a mounting base or an adhesive. It can also be provided separately or continuously. In the case of dividing and providing, it is possible to install the floor panel by attaching it to each corresponding floor panel. In this example, it is easy to construct flexible materials such as hanging type and cloth.
FIG. 3(b) attaches the breathable material 3 between the support legs 6,6. Since it is attached using the supporting legs 6, it is possible to stretch a long air-permeable material and support the intermediate supporting legs 6 with fasteners. After installing the support legs 6 on the concrete slab 5, the ventilation material 3 can be installed while laying the floor panel 4, so the degree of freedom is high.
In FIG. 3(c), a concrete slab 5 is provided with a slab fixing portion 12 of the air-permeable material 3. FIG. Since it does not depend on floor panels or supporting legs, the position of installing the breathable material on the floor is free. In this example, self-supporting breathable materials such as boards are easy to construct.
The air-permeable material is basically installed continuously, but it is not limited to this, and may be installed with a gap for reasons such as to avoid supporting legs as shown in FIG. 4 . FIG. 4(a) shows a case in which a gap is provided next to the leg. In FIG. 4(b), a space is provided between the floor panel.
In addition, it is not necessary to install the floor panel 4 and the concrete slab 5 so as to completely separate them from above and below, but they can be installed with a certain amount of clearance. For example, as shown in FIG. 4(b), the air-permeable material is raised from the concrete slab 5 so as not to come into contact with the floor panel even if it is deformed (bent). If the floor panel is in contact with the floor panel, the perforated board or the like, which is not flexible, may be bent, and the upper end of the perforated board or the like may rub against the floor panel, generating a squeak sound. By providing a gap, it is possible to prevent damage to perforated plates and the like.
The technology of the present invention transmits the vibrational energy of the air to the air-permeable material and converts it into thermal energy to attenuate the sound. No need.

FIG. 5 shows a sound pressure distribution model when two-dimensional resonance occurs in the bosom of the dry double floor.
A light color indicates high sound pressure, and a dark color indicates low sound pressure. For example, if the floor dimension in FIG. 5 is 3 m (short side width W)×4 m (long side width D), the 1,0 mode is 43 Hz, the 0,1 mode is 57 Hz, and the 1,1 mode is 72 Hz.
In a typical sized room, these modes fall within the 63 Hz band (octave) that is important for heavy floor impact sounds.
In the 1,0 mode of FIG. 5(a), the sound pressure is shown near the center of the long side width D, and in the 0,1 mode of FIG. 5(b), the sound pressure is near the center of the short side width W. In the 1,1 mode of 5(c), low-frequency pressure is shown near the center of the width W of the short side and the center of the width D of the long side.
When such resonance occurs, the sound particle velocity is high where the sound pressure is low. That is, air particles vibrate violently. Therefore, if the air-permeable material is installed in a place where the air vibrates violently, it receives resistance, the vibration energy of the air is converted into heat, and resonance is suppressed, thereby reducing the sound pressure of the whole pocket. Fig. 5 also shows that in a dry double floor of a room of normal size, it is suitable to arrange the breathable material on the line dividing each side into two shown in Fig. 2(a). .
Note that for large rooms, the frequencies corresponding to these modes are contained in bands lower than the 63 Hz band, in which higher order modes are contained. In that case, it would be appropriate to install the breathable material at the position shown in FIG. 2(b) or FIG. 2(c).

<Experiment to investigate how the air in the pocket of a dry double floor affects the floor impact sound>
An experiment was conducted to investigate how the air in the pocket of a dry double floor affects floor impact noise. In this experiment, a frame was installed on the concrete floor of the laboratory as a substitute for a wall, and a dry double floor with a plane dimension of 3.8m x 4.7m was constructed under the following conditions. A detail of the end of the dry double bed is shown in FIG. In the experiment, an impact source with impact force characteristics (1) conforming to JIS A 1418-2 was used, and heavy floor impact noise was measured under the conditions of a dry double floor and a bare concrete floor, respectively.
1. The planar dimensions of the dry double floor were 3.8m x 4.7m. In this case, if internal resonance occurs, the 1,0 mode occurs at 37 Hz, the 0,1 mode at 45 Hz, and the 1,1 mode at 58 Hz.
There are three conditions for the end of the dry double bed.
(1) Create a gap of 2 mm between the frame and the dry double floor (Fig. 6(a) there is a gap)
(2) The gap between the frame and the dry double floor was covered with curing tape (Fig. 6(b) no gap).
(3) The frame was removed so that the bosom of the dry double floor was open to the outside (Figure 6(c) no frame).

2. Measurement results (1) Floor impact noise reduction: The value obtained by subtracting the floor impact sound level measured under the condition of each dry double floor from the result measured under the condition of the bare concrete slab without the dry double floor. FIG. 7 shows the amount of floor impact noise reduction.
The lower portion of the vertical axis (negative amount) indicates amplification. If there is resonance or the phenomenon of resonance, there will be a sharp drop in the amount of reduction. In other words, it can be seen that the frequency band is greatly amplified.
The resonance system described above (the resonance system with the mass of the floor panel plate material of the dry double floor and the rubber at the bottom of the support leg as the spring) is assumed to be around 50 Hz to 60 Hz in this test specimen, but "there is a gap ' and 'no gap' results show a distinct dip in the 40 Hz band of frequencies. On the other hand, no 40 Hz drop is observed in the "no frame" result.

(2) Fig. 8 shows the results of measuring the sound pressure inside the bosom of the dry double floor for a more detailed study.
The 1,0 mode in the bosom is 37 Hz, the 0,1 mode is 45 Hz, and the 1,1 mode is 58 Hz, which are marked in FIGS. 8(a), (b), and (c), respectively. "no gap""withgap"
In , the values near these frequencies are large, whereas in "no frame", they are significantly smaller.

It is clear from the measurement results in FIG. 8 that the drop in the amount of reduction at 40 Hz seen in the experimental results of FIG. In order to investigate whether this is due to the resonance of two-dimensional sound in the bosom, a separate study was conducted using numerical calculations based on FEM analysis.
In the numerical calculation, we focused on the air in the bosom of the dry double floor, so we modeled only the board part and the air of the dry double floor, and did the calculation without including the supporting legs in the model.
The dimensions of the dry double bed were 3.8m x 4.7m as in the experiment, and the sound pressure level inside the body was obtained by vibrating the dry double bed.
Calculation was performed under the following three conditions for the dry double bed.
(a) When setting the side surface corresponding to the frame by simulating "no gap" and setting the damping of the side surface to be small (b) By simulating "with a gap", setting the side surface corresponding to the frame and setting the side surface When the damping is set to be large (c) When the side is opened without providing a side that corresponds to the frame, simulating "no frame"

FIG. 9 shows the calculation result of the sound pressure level inside the bosom. Since the excitation force was assumed to be the same for all frequencies in the calculation, the sound pressure is shown as a relative level. In addition, although the slope of the entire frequency band cannot be compared with experimental values due to the difference in excitation force characteristics, the characteristics of the frequency range in which the low-order mode around 40 Hz occurs will be compared.
Similar to the experiment, the calculation results show a sound pressure peak under the condition (a) with no gap. When the sound pressure distribution in the bosom is drawn at the frequencies at which these peaks occur, distributions of 1,0 mode, 0,1 mode, and 1,1 mode can be seen as shown in FIG. Therefore, it can be confirmed that the increase in sound pressure in the vicinity of these frequencies is due to the two-dimensional resonance in the bosom, which reduces the amount of reduction.
In addition, under the condition (b) with a gap in FIG. 9, these peaks are difficult to see and the sound pressure level is low. Under the condition (c) with no frame, the sound pressure level in this vicinity is low.
The results of these calculations show trends consistent with the experimental results.
In other words, two-dimensional resonance occurs in the dry double floor, and if it can be eliminated, the amount of reduction in floor impact noise can be improved.

<Experiment on a tubular test piece cut out from a two-dimensional part>
Then, by installing a breathable material in the place where the particle speed of sound in the pocket of the dry double floor is high, which is the technology of the present invention, the resonance phenomenon in the pocket is suppressed and the sound pressure level of the whole pocket is reduced. In order to confirm this, another experiment was conducted.
In this experiment, in order to simplify the phenomenon, we replaced the actual two-dimensional dry double floor space with a one-dimensional sound field. In other words, the experiment was carried out on a tubular specimen obtained by cutting out a part of the two-dimensional specimen.
Sound (random noise) was generated by a speaker inside the acoustic tube. A permeable material was installed so as to partition the center of this acoustic tube, and the sound pressure inside the tube was compared with and without installation. Glass wool (density 32 kg/m ³ , thickness 50 mm, flow resistance 300 to 14,000 Pa·s/m) was used as the air-permeable material.

First, FIG. 12 shows the sound pressure level measurement results when no breathable material is installed. Looking at the frequency characteristics shown in the lower part of the figure, resonance occurs in the acoustic tube and the sound pressure rises at those frequencies. The primary mode is the mode aiming at reduction and occurs at 60 Hz. Drawing the sound pressure distribution at this frequency shows that the sound pressure is low in the center of the tube. This means that the particle velocities are very high here. By the way, when the sound pressure distributions of the 2nd mode and the 4th mode generated at frequencies higher than the 63 Hz band are drawn in the same way, it can be seen that the particle velocity in the 4th mode is high in the center as in the 1st mode.

Next, FIG. 13 shows the results of the conditions in which the air-permeable material was installed. When installed in the center (Fig. left), the primary sound pressure is greatly reduced. A reduction due to the air-permeable material was confirmed. Incidentally, the 4th order mode occurring at frequencies higher than the 63 Hz band is also reduced. As with the first mode, the quaternary mode also has a high particle velocity in the central part of the tube, so if a breathable material is placed here, the sound will be reduced. If the size of the room (the length of the tube in this experiment) is large, the 4th mode will be included in the 63 Hz band. It can be seen that it is effective for

By the way, in order to show that the above-mentioned reduction by the air-permeable material is not simply the effect of installing the sound-absorbing material, an experiment was also conducted under the condition that the air-permeable material was installed at the end of the acoustic tube. As the results are shown on the right side of FIG. 13, the end installation cannot reduce the sound pressure rise due to the primary resonance. Since the particle velocity is not high at the edges, even if a breathable material is installed there, the energy of air vibration caused by sound cannot be converted into heat and cannot be reduced.

In addition to the glass wool density of 32 kg/m ³ and the thickness of 50 mm, similar experiments were conducted with various breathable materials. /m ³ with a thickness of 50 mm, although the effect is small, a certain reduction (approximately 5 dB) was obtained. In the case of the air-permeable material having a flow resistance of 700 to 5,000 Pa·s/m, a reduction equal to or greater than that obtained with a glass wool density of 32 kg/m ³ and a thickness of 50 mm was obtained.

From these results, the floor impact noise is amplified by the resonance phenomenon in the bosom of the dry double floor, so it can be reduced by suppressing this. That is, it is effective to install the breathable material above the line that divides the floor into two or four.

<Embodiment for Double Ceiling>
This embodiment reduces the floor impact noise by installing a breathable material in the pocket of the double ceiling to make it difficult for the two-dimensional resonance phenomenon in the pocket to occur.
The air-permeable material is installed so as to partition the interior of the ceiling as shown in the schematic structure of FIG. 15 .
Place the breathable material so that it divides the plane of the room equally. If the side of the room is less than 4m, divide the side into two.
It should be noted that the "guideline" includes the vicinity of the 2-division and the 4-division since it may be difficult to install it accurately in the center depending on the situation of the mounting location. Even if the position of the air-permeable material deviates to some extent, the reduction effect is not greatly impaired.

Examples of air-permeable materials include membranes, cloths, nets, porous boards or mats such as glass wool, perforated plates such as punching metals, and honeycomb plates.

Breathable materials should have adequate flow resistance. The flow resistance r _f [Pa·s/m] is expressed by the following formula. A suitable flow resistance is in the range of 100 Pa·s/m to 10,000 Pa·s/m.

Ventilation materials may be installed by hanging from concrete ceiling slabs, or by clamping or simply resting on double ceiling boards or planks.
The air-permeable material may be installed continuously in the horizontal direction, or may be installed with a gap therebetween for reasons such as avoiding the substrate. FIG. 17 shows an example in which the breathable material is installed with a gap in the double ceiling. Fig. 17(a) shows an example in which a gap is provided in a plane, and Fig. 17(b) shows an example in which the device is attached to a concrete ceiling and a gap is provided between it and a ceiling plate such as a gypsum board.

ここで
ｆは共振周波数、Ｌ_xは二重天井のｘ方向の辺の長さ、Ｌ_yは二重天井のｙ方向の辺の長さ、ｎ_xはｘ方向の次数、ｎ_yはｙ方向の次数。 (Principle of Invention)
As mentioned above, the double ceiling has a resonance system with the plate material as the mass and the air in the ceiling as the spring, and the resonance frequency is considered to be the main cause of the amplification. However, the cause of the amplification is not only the resonance due to the spring mass, but also the two-dimensional resonance phenomenon inside the bosom greatly affects the amplification.
The resonance frequency f differs depending on the planar dimension of the double ceiling. For example, if it is 3 m×4 m, the 0,1 mode inside the bosom is 57 Hz, the 1,0 mode is 43 Hz, and the 1,1 mode is 72 Hz. Floor impact sounds are likely to be amplified in the vicinity of these frequencies. f can be calculated by Equation 4.

where f is the resonance frequency, L _x is the x-direction side length of the double ceiling, Ly is the _y -direction side length of the double ceiling, n _x is the order in the x direction, and ny is the _y direction. order of .

The sound pressure distribution in the bosom is as shown in FIG. 18, and air particles vibrate violently where the sound pressure is low. At this time, if an air-permeable material is installed at the place where the vibration is violently vibrating, that is, the position indicated by the dotted line in FIG. In addition, since the 0,1 mode, 1,0 mode, and 1,1 mode in the ceiling pocket are included in the important 63 Hz band (octave) for heavy floor impact sound in a room of general size, the sound as shown in Fig. 18 A pressure distribution is obtained, and the installation position of the air-permeable material is the position shown in FIG. 16(a). If the room is large, the frequencies corresponding to these modes are contained in lower bands than the 63 Hz band, which contains higher order modes. In that case, the breathable material is installed at the position indicated by the dotted line in FIG. 16(b) or (c).

(confirmation test)
Regarding the question of whether the resonance phenomenon in the interior of the interior of the interior can be suppressed and the sound pressure level of the entire interior of the interior of the interior can be reduced by installing a breathable material in the location where the particle velocity of sound in the interior of the interior of the double ceiling is high. An experiment was conducted to confirm.
In this experiment, in order to simplify the phenomenon, we replaced the two-dimensional double-ceiling space with a one-dimensional sound field. In other words, the experiment was carried out on a tubular specimen obtained by cutting out a part of the two-dimensional specimen. A test model is shown in FIG.
Sound (random noise) was generated by a speaker inside the acoustic tube. A permeable material was installed so as to partition the center of this acoustic tube, and the sound pressure inside the tube was compared with and without installation. Glass wool (density 32 kg/m ³ , thickness 50 mm, flow resistance 300 to 14,000 Pa·s/m) was used as the air-permeable material.

First, FIG. 20 shows the sound pressure level measurement results when no breathable material is installed. Looking at the frequency characteristics shown in the lower part of the figure, resonance occurs in the acoustic tube and the sound pressure rises at those frequencies. The primary mode is the mode aiming at reduction and occurs at 60 Hz. Drawing the sound pressure distribution at this frequency shows that the sound pressure is low in the center of the tube. This means that the particle velocities are very high here. By the way, when the sound pressure distributions of the 2nd mode and the 4th mode generated at frequencies higher than the 63 Hz band are drawn in the same way, it can be seen that the particle velocity in the 4th mode is high in the center as in the 1st mode.

Next, FIG. 21 shows the results of the conditions in which the air-permeable material was installed. When installed in the center (Fig. left), the primary sound pressure is greatly reduced. A reduction due to the air-permeable material was confirmed. Incidentally, the 4th order mode occurring at frequencies higher than the 63 Hz band is also reduced. As with the first mode, the quaternary mode also has a high particle velocity in the central part of the tube, so if a breathable material is placed here, the sound will be reduced. If the size of the room (the length of the tube in this experiment) is large, the 4th mode will be included in the 63 Hz band. It can be seen that it is effective for

By the way, in order to show that the above-mentioned reduction by the air-permeable material is not simply the effect of installing the sound-absorbing material, an experiment was also conducted under the condition that the air-permeable material was installed at the end of the acoustic tube. As the results are shown on the right side of FIG. 21, the end installation cannot reduce the sound pressure rise due to the primary resonance. Since the particle velocity is not high at the edges, even if a breathable material is installed there, the energy of air vibration caused by sound cannot be converted into heat and cannot be reduced.

In addition to the glass wool density of 32 kg/m ³ and the thickness of 50 mm, similar experiments were conducted with various breathable materials. Some reduction (approximately 5 dB) was obtained, although the effect was small when compared to a thickness of 50 mm/m ³ . In the case of air-permeable materials with a flow resistance of 700 to 5,000, a reduction equal to or greater than that of a glass wool density of 32 kg/m ³ and a thickness of 50 mm was obtained.

From these results, the floor impact sound is amplified by the two-dimensional resonance phenomenon in the bosom of the double ceiling, so it can be reduced by suppressing this. It turns out that it is effective to install the breathable material on the part where the double ceiling is formed, that is, above the line that divides the side of the double ceiling into two or four.

As mentioned above, the air-permeable material is effective even if there is some gap at the top or bottom. FIG. 22 shows the result of investigating how the effect changes when the air-permeable material is installed with a gap (FIG. 22(a)) using the experimental apparatus of FIG. (a) is a model with a gap, (b) shows the results with a gap of 10 mm, (c) with a gap of 20 mm, and (d) with a gap of 30 mm. As can be seen from this figure, even when there is a gap, the noise is reduced compared to when there is no breathable material. However, the reduction effect is small compared to the case of installing without gaps.

(Consideration of installing breathable materials in the double ceiling)
(Example of installing a breathable material on top of the ceiling base material)
In a double ceiling that is actually constructed in a house, a base material as shown in FIG. 23 is used, and a plate material for the ceiling is installed under this base material. If the air-permeable material is installed while avoiding the base, a gap that is large compared to the pocket height is generated as shown in FIG. 24 .

(Example of installing a breathable material with notches in the joists)
In order to avoid the occurrence of gaps corresponding to the height of the ceiling joists, it is advisable to treat the breathable material in advance so as to avoid the base. For example, the air-permeable material that is perpendicular to the joists is provided with notched recesses as shown in FIG. In particular, when the breathable material is made of a material that has a certain degree of flexibility, such as a porous board, if the dimensions of the breathable material are slightly larger than the pocket size, it can be easily assembled without using jigs, screws, or the like. , it is possible to complete the installation simply by pushing it between the base and the ceiling.

(Example of installing breathable materials parallel to the joists)
Also, regarding the breathable material installed in the direction parallel to the ceiling joist, if it is installed between the double ceiling and the ceiling slab while avoiding the ceiling joists, there will be no gap. It is also possible to install the ventilation material by pushing it in while attaching the double ceiling, but as shown in FIG. The ventilation material can be installed at the same time, and the workability is improved. At this time, if the air-permeable material is a material having a certain degree of flexibility, such as a porous board, it is only necessary to make a cut at the position where the jig is passed, and it is not necessary to process the recess.

1 Dry double floor 2 Floor pocket (pocket height h)
3 Breathable material 4 Floor panel 5 Concrete slab 6 Support leg 11 Floor panel fixing part 12 Slab fixing part 21 Double ceiling (suspended ceiling)
22 Ceiling pocket 23 Breathable material 31 Wall structure 32 Air layer 33 Breathable material 34 Wall plate material 35 Concrete wall body

Claims (7)

In a building structure in which two flat plate members are formed with an air layer in between,
An impact sound reduction structure in which a film-like or thin-plate-like air-permeable material is installed in a place where the particle speed of sound is high when an air layer resonates,
The breathable material has a flow resistance of 100 Pa·s/m to 10,000 Pa·s/m ,
The building structure is a dry double floor, and in the air layer formed in this double floor, above the line that divides the side into two or four, or at every 2.5m to 3.5m breathable material is installed so as to partition the air layer. In a building structure in which two flat plate members are formed with an air layer in between,
An impact sound reduction structure in which a film-like or thin-plate-like air-permeable material is installed in a place where the particle speed of sound is high when an air layer resonates,
The breathable material has a flow resistance of 100 Pa·s/m to 10,000 Pa·s/m,
The building structure is a double ceiling, and in the air layer formed in this double ceiling, above the line that divides the side into two or four, or every 2.5 m to 3.5 m, the double ceiling An impact noise reduction structure characterized in that an air-permeable material is installed so as to partition an air layer with a gap provided therein. 3. The impact sound according to claim 1 or 2, wherein the air-permeable material is any one of membrane, cloth, net, mat, punching metal, perforated plate, honeycomb plate, fibrous material, and porous board. Reduced structure. In an impact sound transmission structure in which two flat plate members are formed with an air layer sandwiched therebetween, and an impact sound generated by an impact applied to one flat plate member is transmitted through the other flat plate member,
A method of reducing impact noise by installing a breathable material with a flow resistance of 100 Pa·s/m to 10,000 Pa·s/m at locations where the sound particle velocity is high when the air layer resonates. There is
In a building with a dry double floor as an impact sound transmission structure, air-permeable materials are installed on the line that divides the side of the air layer into two or four to reduce floor impact noise mainly in the 63 Hz band. A method of reducing impact noise, characterized by: In an impact sound transmission structure in which two flat plate members are formed with an air layer sandwiched therebetween, and an impact sound generated by an impact applied to one flat plate member is transmitted through the other flat plate member,
A method of reducing impact noise by installing a breathable material with a flow resistance of 100 Pa·s/m to 10,000 Pa·s/m at locations where the sound particle velocity is high when the air layer resonates. There is
A building with a double ceiling as an impact sound transmission structure, and a breathable material is installed on the line dividing the side of the air layer into two or four with a gap in the double ceiling, and the main A method for reducing impact noise, characterized by reducing floor impact noise in the 63 Hz band. 5. The method for reducing impact noise according to claim 4 , wherein the permeable material is installed on a dry double floor board, attached to the legs of a dry double floor, or installed on a concrete floor. . As a method for installing a breathable material in a double ceiling, the part that contacts the ceiling joist is cut out to install the breathable material in the joist with a recess, or between the adjacent joists of the ceiling. 6. A method for reducing impact noise according to claim 5, characterized by locking and installing the air-permeable material through a jig .

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