JP7637530B2 - Sound absorbing structure - Google Patents

Description

The present invention relates to a sound-absorbing structure installed inside a building.

Conventionally, sound-absorbing panel materials have been widely used as interior wall and ceiling materials for buildings such as houses and office buildings. For example, Patent Document 1 discloses a soundproof interior material made of a panel material composed of a surface layer material in which multiple sound-absorbing holes are formed and a backing material laminated on the back surface of the surface layer material. In this soundproof interior material, each sound-absorbing hole is composed of a small diameter hole portion on the surface side and a large diameter hole portion on the back side that is larger than the small diameter hole portion, and adjacent large diameter holes are connected by a groove-shaped space portion formed on the back surface of the surface layer material. With this configuration, the soundproof interior material exhibits a sound-absorbing effect that utilizes the principle of the Helmholtz resonator.

JP 2006-342565 A

However, panel materials that utilize the principle of the Helmholtz resonator to achieve sound absorption have the problem that, although they exhibit excellent sound absorption performance near the resonant frequency, the frequency band in which they exhibit excellent sound absorption performance is narrow.

The present invention was made in consideration of these points, and its purpose is to provide a sound absorbing structure that can exhibit excellent sound absorbing performance over a wide frequency range.

To achieve the above objective, the present invention provides a method of attaching multiple louver materials to the surface of a sound-absorbing panel on which multiple Helmholtz resonators are formed.

Specifically, the first invention is a sound-absorbing structure installed inside a building, characterized in that it comprises a sound-absorbing panel having multiple Helmholtz resonators formed therein, each having a cavity that opens on the surface, and multiple louver materials attached at predetermined intervals on the surface of the sound-absorbing panel.

In the first invention, sound waves that reach the vicinity of the sound-absorbing structure are absorbed by multiple Helmholtz resonators formed in the sound-absorbing panel. Specifically, in the above-mentioned sound-absorbing panel, sound waves near the resonant frequency (natural frequency) enter the multiple Helmholtz resonators, causing the air inside (inside the cavity) of each Helmholtz resonator to resonate and vibrate violently at the opening (neck). The violently vibrating air in the opening generates friction with the inner wall of the opening, and sound energy (vibration energy) is converted into thermal energy. According to the first invention, of the sound waves that reach the vicinity of the sound-absorbing structure in this way, sound waves near the resonant frequency of the multiple Helmholtz resonators can be significantly attenuated.

In addition, in the first invention, multiple louver materials are attached to the surface of the sound-absorbing panel. Therefore, some of the sound waves that reach the vicinity of the sound-absorbing structure are reflected by the multiple louver materials and change their traveling direction in various ways. In this way, in the first invention, by reflecting the sound waves in various directions by the multiple louver materials, the sound waves are incident on the multiple Helmholtz resonators of the sound-absorbing panel from various angles.

In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (the length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. However, even in a Helmholtz resonator of the same shape, if the angle of incidence of the sound waves changes, the cross-sectional area and length of the opening change artificially, and the resonant frequency changes. Therefore, as described above, by attaching multiple louver materials to the surface of the sound-absorbing panel and configuring multiple Helmholtz resonators so that sound waves are incident at various angles, the frequency band of sound waves that can be absorbed (sound waves that can be attenuated) by the sound-absorbing panel can be expanded compared to the case where no louver materials are provided. Therefore, according to the first invention, it is possible to provide a sound-absorbing structure that can exhibit excellent sound-absorbing performance over a wide frequency band.

The second invention is the first invention, characterized in that the sound-absorbing panel has a decorative plate provided on the front side and having a plurality of through holes formed therein that serve as openings for the Helmholtz resonator, and a plate-shaped sound-absorbing base material made of a porous sound-absorbing material, superimposed on the back side of the decorative plate, and having a plurality of recesses formed on the surface between the decorative plate and the back side of the decorative plate that define the cavity of the Helmholtz resonator.

In the second invention, a sound-absorbing panel with multiple Helmholtz resonators can be easily formed by simply stacking a decorative panel with multiple through holes and a sound-absorbing base material with multiple recesses on its surface.

In the second invention, the sound-absorbing base material is made of a porous sound-absorbing material. Therefore, according to the second invention, the sound energy is converted into thermal energy and the sound waves are attenuated by the vibration of the air contained in the porous sound-absorbing material that constitutes the sound-absorbing base material as the air inside the Helmholtz resonator formed in the sound-absorbing panel resonates. In other words, according to the second invention, it is possible to provide a sound-absorbing structure with superior sound-absorbing performance.

Furthermore, in the second invention, multiple recesses that define the cavity of the Helmholtz resonator are formed in the sound-absorbing base material made of a porous sound-absorbing material, so that most of the peripheral wall of the cavity of the Helmholtz resonator is formed of the porous sound-absorbing material. Therefore, according to the second invention, the sound absorption effect due to the vibration of the air contained in the porous sound-absorbing material can be improved compared to when the cavity of the Helmholtz resonator is formed in a decorative panel.

Normally, a plate-shaped body made of a porous sound-absorbing material is lighter and softer than a decorative board, which requires a certain degree of rigidity. Therefore, as in the above-mentioned sound-absorbing structure, by forming the recesses that define the cavity of the Helmholtz resonator not in the decorative board but in the sound-absorbing base material made of a porous sound-absorbing material, the recesses can be easily processed. In addition, since the recesses are easy to process, it is also easy to form multiple types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed in the sound-absorbing panel by changing the shapes of some of the multiple recesses formed in the sound-absorbing base material. And, according to the sound-absorbing structure using a sound-absorbing panel in which multiple types of Helmholtz resonators are formed in this way, the frequency band in which excellent sound absorption performance is demonstrated can be further expanded.

The third invention is the second invention, characterized in that the plurality of through holes includes a first through hole having a first inner diameter and a second through hole having a second inner diameter larger than the first inner diameter.

In the third invention, the multiple through holes that function as openings for the Helmholtz resonators in the sound-absorbing panel include two types of through holes (first and second through holes) with different inner diameters. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, by forming two types of through holes with different inner diameters in the decorative panel, two types of Helmholtz resonators are formed that have different opening shapes and therefore different frequency bands of sound waves that can be absorbed. Therefore, according to the third invention, it is possible to provide a sound-absorbing structure that can exhibit excellent sound-absorbing performance over a wide frequency band.

The fourth invention is the second or third invention, characterized in that the decorative panel and the sound-absorbing base material are made of a material having non-flammable properties.

In the fourth invention, the decorative board and sound-absorbing base material are made of a material that has non-combustible properties, thereby imparting non-combustible properties to the sound-absorbing panel.

The fifth invention is any one of the second to fourth inventions, characterized in that the sound-absorbing base material is made of a rock wool board.

In the fifth invention, the sound-absorbing base material is made of rock wool board, which has excellent sound-absorbing and non-flammable properties, so that the sound-absorbing panel can be endowed with not only high sound-absorbing properties but also non-flammable properties.

The sixth invention is any one of the first to fifth inventions, in which the louver material has multiple Helmholtz resonators formed therein, each having a cavity that opens on the side.

In the sixth invention, multiple Helmholtz resonators are formed not only in the sound-absorbing panel but also in the louver material attached to the sound-absorbing panel. Therefore, sound waves that reach the vicinity of the sound-absorbing structure are absorbed not only by the sound-absorbing panel but also by each louver material. Specifically, in each louver material, sound waves near the resonant frequency (natural frequency) enter the multiple Helmholtz resonators, causing the air inside the Helmholtz resonator (inside the cavity) to resonate and vibrate violently at the opening. The violently vibrating air at the opening generates friction with the inner wall of the opening, and sound energy (vibration energy) is converted into thermal energy. According to the sixth invention, among the sound waves that reach the vicinity of the sound-absorbing structure in this way, sound waves near the resonant frequency of the multiple Helmholtz resonators formed in the louver material can be significantly attenuated. In other words, according to the sixth invention, the sound-absorbing performance of the sound-absorbing structure can be further improved by imparting a sound-absorbing function to each louver material.

In addition, according to the sixth invention, by changing the shape of the Helmholtz resonator formed in the sound-absorbing panel and the louver material, sound waves in a frequency band that are not absorbed by the sound-absorbing panel can be absorbed by the louver material. With this configuration, it is possible to provide a sound-absorbing structure that exhibits excellent sound-absorbing performance over an even wider frequency band.

The seventh invention is the sixth invention, in which the louver material has a core material formed of a porous sound-absorbing material, and a surface material with a U-shaped cross section that has two side portions covering the two side surfaces of the core material and a front portion connecting the two side portions and is fitted onto the core material, and at least one of the side portions of the surface material is formed with a plurality of through holes that become the openings of the Helmholtz resonator, and the side of the core material corresponding to the through holes has a plurality of recesses formed between the inner surface of the surface material that faces it, defining the cavity of the Helmholtz resonator.

In the seventh invention, a louver material with multiple Helmholtz resonators can be easily formed by simply fitting a surface material with a U-shaped cross section, which has multiple through holes formed in at least one side portion, onto a core material, which has multiple recesses formed in the side portion.

In the seventh invention, the core material is made of a porous sound-absorbing material. Therefore, according to the seventh invention, as the air inside the Helmholtz resonators formed in each louver material resonates, the air contained in the porous sound-absorbing material that makes up the core material vibrates, converting sound energy into thermal energy and attenuating the sound waves. In other words, according to the seventh invention, it is possible to provide a sound-absorbing structure with superior sound-absorbing performance.

Furthermore, in the seventh invention, multiple recesses that define the cavity of the Helmholtz resonator are formed in the core material made of a porous sound-absorbing material, so that most of the peripheral wall of the cavity of the Helmholtz resonator is formed of the porous sound-absorbing material. Therefore, according to the seventh invention, the sound absorption effect due to the vibration of the air contained in the porous sound-absorbing material can be improved compared to when the cavity of the Helmholtz resonator is formed in the surface material.

Normally, a plate-shaped body made of a porous sound-absorbing material is lighter and softer than a surface material that requires a certain degree of rigidity. Therefore, as in the above-mentioned sound-absorbing structure, by forming the recesses that define the cavity of the Helmholtz resonator in the core material made of a porous sound-absorbing material rather than in the surface material, the recesses can be easily processed. In addition, since the recesses are easy to process, it is also easy to form multiple types of Helmholtz resonators in the louver material that have different frequency bands of sound waves that can be absorbed by changing the shapes of some of the multiple recesses formed in the core material. And, according to the sound-absorbing structure using the louver material in which multiple types of Helmholtz resonators are formed in this way, the frequency band in which excellent sound absorption performance is demonstrated can be further expanded.

The eighth invention is the seventh invention, characterized in that the multiple through holes are formed on both of the two side portions of the surface material, and the core material is composed of two plate-like members with multiple recesses formed on the surface and with the back surfaces overlapping each other.

In the eighth invention, sound waves can be absorbed from both sides of the louver material, so a sound absorbing structure with better sound absorbing performance can be provided. In addition, according to the eighth invention, by using a core material made by overlapping two plate-like members with processing only on the surface, without processing recesses on both sides of the core material, it is possible to easily form a louver material that can absorb sound waves from both sides.

The ninth invention is the seventh or eighth invention, characterized in that the plurality of recesses formed on the side surface of the core material include a first recess having a first volume and a second recess having a second volume larger than the first volume.

In the ninth invention, the multiple recesses that define the cavity of the Helmholtz resonator in the louver material include two types of recesses (first and second recesses) with different volumes. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, by forming two types of recesses with different volumes in the core material, two types of Helmholtz resonators are formed in the louver material with different cavity volumes, and therefore with different frequency bands of sound waves that can be absorbed. Therefore, according to the ninth invention, it is possible to provide a sound absorbing structure that can exhibit excellent sound absorbing performance over a wide frequency band.

The tenth invention is any one of the seventh to ninth inventions, characterized in that the core material and the surface material are made of a material having non-flammable properties.

In the tenth aspect of the invention, the core material and surface material are made of a material having non-flammable properties, thereby imparting non-flammable properties to the louver material.

The eleventh invention is any one of the seventh to tenth inventions, characterized in that the core material is made of a rock wool board.

In the eleventh invention, the core material is made of rock wool board, which has excellent sound absorption and fire resistance, so that the louver material can be endowed with not only high sound absorption but also fire resistance.

As described above, according to the present invention, by attaching multiple louver materials to the surface of a sound-absorbing panel on which multiple Helmholtz resonators are formed, it is possible to provide a sound-absorbing structure that can exhibit excellent sound-absorbing performance over a wide frequency range.

FIG. 1 is a perspective view showing a sound absorbing structure according to a first embodiment, with a part cut away. FIG. 2 is an exploded perspective view of the sound-absorbing panel according to the first embodiment. FIG. 3 is a cross-sectional view of a portion of the sound-absorbing panel according to the first embodiment. FIG. 4 is a cross-sectional view of the louver material according to the first embodiment. FIG. 5 is a diagram showing the results of a sound absorption coefficient test carried out in the first embodiment. FIG. 6 is a perspective view showing a sound absorbing structure according to the second embodiment, with a part cut away. FIG. 7 is a cross-sectional view of a louver material according to the second embodiment. FIG. 8 is a diagram showing the results of a sound absorption coefficient test carried out in the second embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings. The following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

First Embodiment of the Invention
As shown in FIG. 1, in the first embodiment, an example of a sound absorbing structure according to the present invention that is provided in a building and that is applied to a ceiling of an indoor space will be described.

- Sound-absorbing structure -
As shown in Fig. 1, the sound absorbing structure 1 includes a sound absorbing panel 10 and a louver 20. The sound absorbing panel 10 is attached to a ceiling underlayment 2, and the louver 20 is attached to the surface of the sound absorbing panel 10. In Fig. 1, only some of the sound absorbing panels 10 attached to the ceiling underlayment 2 made of plywood or the like are shown by solid lines, and the rest (the upper part in Fig. 1) are shown by virtual lines (two-dot chain lines). In Fig. 1, only some of the louvers 20 (the lower part in Fig. 1) are shown by solid lines, and the other parts are not shown, but the louvers 20 are provided over the entire area where the sound absorbing panels 10 are provided.

In this embodiment 1, an example in which the sound absorbing structure 1 includes multiple sound absorbing panels 10 is described, but the sound absorbing structure 1 may include only one sound absorbing panel 10.

[Sound absorbing panel]
2 and 3, the sound-absorbing panel 10 has a decorative board 11 having a plurality of through holes 13, 13 formed from the front surface to the back surface, and a sound-absorbing base material 12 having a plurality of grooves 14, 14 formed on the front surface. The decorative board 11 is provided on the front side of the sound-absorbing panel 10, and the sound-absorbing base material 12 is overlaid on the back surface of the decorative board 11 and bonded thereto with, for example, a vinyl acetate resin-based emulsion-type adhesive.

The decorative board 11 is composed of a rectangular plate having a certain thickness (6 mm in this embodiment 1). In this embodiment 1, the decorative board 11 is composed of a volcanic glassy laminate (product name: Dailite, manufactured by Daiken Corporation) formed from volcanic glass and mineral fibers.

As the decorative board 11, in addition to volcanic glassy laminate boards, calcium silicate boards, melamine laminate boards, plywood, wood fiber boards such as MDF and particle boards, inorganic fiber boards such as glass wool boards, gypsum boards, etc. can be used. From the viewpoint of sound absorption, it is preferable to use fiber boards with a porous structure such as wood fiber boards and inorganic fiber boards as the decorative board 11. In fiber boards, sound waves that enter between the fibers are attenuated by friction with the fibers, so if the decorative board 11 is made of fiber boards, the sound absorption performance can be improved. From the viewpoint of non-flammability, it is preferable to use volcanic glassy laminate boards, inorganic fiber boards, calcium silicate boards, melamine laminate boards, gypsum boards, etc. as the decorative board 11.

The multiple through holes 13, ..., 13 are provided at equal pitches (25 mm in this embodiment 1) vertically and horizontally in the decorative board 11. In this embodiment 1, the multiple through holes 13, ..., 13 include a first through hole 13a having a first inner diameter D1 (3 mm in this embodiment 1) and a second through hole 13b having a second inner diameter D2 (5 mm in this embodiment 1) larger than the inner diameter of the first through hole 13a. In other words, the decorative board 11 has two types of through holes 13a, 13b with different inner diameters.

The first through holes 13a and the second through holes 13b are arranged in the decorative board 11 so that the same types of holes are arranged vertically and different types of holes are arranged horizontally, i.e., the first through holes 13a and the second through holes 13b are arranged alternately. In other words, a first through hole row consisting of a plurality of first through holes 13a and a second through hole row consisting of a plurality of second through holes 13b are formed alternately on the decorative board 11.

The sound-absorbing base material 12 is made of a rectangular plate with a certain thickness (9 mm in this embodiment). In this embodiment, the sound-absorbing base material 12 is made of a rock wool plate (product name: Dairoton, manufactured by Daiken Corporation).

The sound-absorbing base material 12 may be any porous sound-absorbing material, and inorganic fiberboards other than rock wool boards (such as glass wool boards) may be used. However, from the standpoint of being able to withstand lamination and cutting (grooving), it is preferable to use rock wool boards as the sound-absorbing base material 12.

The multiple grooves 14, ..., 14 are provided on the surface of the sound-absorbing base material 12 in parallel with each other at the same pitch (25 mm in this embodiment) as the multiple through holes 13, ..., 13 of the decorative board 11. In this embodiment, the multiple grooves 14, ..., 14 are formed in the same way. Each groove 14 is formed in a U-shape in cross section, has a constant groove width (12 mm in this embodiment) and a constant depth (5 mm in this embodiment), and is formed from one end to the other end of the surface of the sound-absorbing base material 12 (from one to the other of the two opposing sides).

The decorative board 11 and the sound-absorbing base material 12 are overlapped and bonded together so that the same type of multiple through holes 13, ..., 13 in each through hole row (first through hole row, second through hole row) of the decorative board 11 correspond to the same groove 14 in the sound-absorbing base material 12 (the multiple through holes in each through hole row are connected to the same groove 14). By overlapping the decorative board 11 and the sound-absorbing base material 12 in this way, multiple Helmholtz resonators are formed in the sound-absorbing panel 10.

Specifically, as shown in FIG. 3, multiple elongated cavities are formed between the decorative panel 11 and the sound-absorbing base material 12 by each groove 14 (recess) formed on the surface of the sound-absorbing base material 12. Each cavity opens to the outside through a corresponding number of through holes 13, ..., 13. A Helmholtz resonator is formed by the peripheral wall portion that defines each of these cavities and the through holes 13 corresponding to the cavity. In other words, the sound-absorbing panel 10 has as many Helmholtz resonators as there are through holes 13, ..., 13.

In addition, in this embodiment 1, the multiple through holes 13, ..., 13 include two types of through holes (first through hole 13a, second through hole 13b) with different inner diameters. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening (cross-sectional area of the through hole 13), the length of the opening (length of the through hole 13), and the volume of the cavity, and the frequency of sound waves that can be absorbed (attenuated) varies. Therefore, in the sound-absorbing panel 10 of this embodiment 1, in which two types of through holes 13a, 13b with different inner diameters are formed in the decorative plate 11, two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed are formed due to the different shapes of the openings.

[louver]
As shown in Fig. 1, the louver 20 is composed of a plurality of louver materials 21, ..., 21 attached to the surface of the sound-absorbing panel 10. The plurality of louver materials 21, ..., 21 are fixed to the surface of the sound-absorbing panel 10 at a predetermined pitch (125 mm in the present embodiment 1) and are arranged parallel to one another. Note that in Fig. 1, only a portion of the louver 20 is shown by a solid line, and the illustration of the other portions is omitted, but in reality, the plurality of louver materials 21, ..., 21 are arranged parallel to one another over the entire portion where the plurality of sound-absorbing panels 10, ..., 10 are provided.

As shown in FIG. 4, the louver material 21 has a core material 22, a surface material 23, and an end grain material (not shown).

The core material 22 has a thick bottom 22a and a pair of plate-like side walls 22b, 22b that extend parallel to each other by the same dimension from both ends of the width direction (left and right direction in FIG. 4) of the bottom 22a, and is formed as a long member with a U-shaped cross section. The bottom 22a is formed, for example, from plywood of a constant thickness (21 mm in this embodiment 1) that is laminated in its thickness direction, and each side wall 22b is made of plywood of a constant thickness (2.4 mm in this embodiment 1) and is integrally bonded to the width direction end face of the bottom 22a. The bottom 22a of the core material 22 is fixed by screws or the like that penetrate the bottom 22a in the thickness direction with the back surface abutting against the front surface of the sound-absorbing panel 10.

The surface material 23 has a plate-shaped front portion 23a and a pair of plate-shaped side portions 23b, 23b that extend in the same direction and in parallel from both widthwise ends of the front portion 23a, and is formed with a U-shaped cross section. The surface material 23 is composed of a volcanic glass composite plate similar to the decorative plate 11 of the sound-absorbing panel 10. Specifically, the surface material 23 is formed with multiple notches extending in the lengthwise direction in the middle of the widthwise direction of a long volcanic glass composite plate, and is bent at right angles at the notches to form a U-shaped cross section.

As with the decorative board 11, the surface material 23 can be a volcanic glass laminate, calcium silicate board, melamine decorative board, plywood, wood fiber board such as MDF or particle board, inorganic fiber board such as glass wool board, gypsum board, etc.

The surface material 23 is fitted over the core material 22 so as to cover the bottom 22a and both side walls 22b, 22b of the core material 22 from the opening side of the core material 22, with the opening of the surface material 23 facing the opening of the core material 22. The core material 22 and the surface material 23 are fixed with adhesive and pin nails (not shown). The end of the core material 22 on the butt side is covered with an butt member (not shown). The core material 22 and the butt member are fixed with adhesive and pin nails (not shown).

- Sound absorbing effect of sound absorbing structure 1 -
As described above, in the sound absorbing structure 1, a plurality of Helmholtz resonators are formed in the sound absorbing panel 10. Therefore, sound waves that reach the vicinity of the ceiling on which the sound absorbing structure 1 is provided are absorbed by the plurality of Helmholtz resonators formed in the sound absorbing panel 10. Specifically, in the sound absorbing panel 10, sound waves near the resonant frequency (1000 Hz in the first embodiment) enter the plurality of Helmholtz resonators, causing the air inside each Helmholtz resonator (in the groove 14) to resonate, and the air vibrates violently in each through hole 13 formed in the decorative panel 11. The violently vibrating air in each through hole 13 generates friction with the peripheral wall of each through hole 13, and sound energy (vibration energy) is converted into heat energy. In the sound absorbing structure 1, sound waves near the resonant frequency of the plurality of Helmholtz resonators are significantly attenuated among the sound waves that reach the vicinity of the ceiling on which the sound absorbing structure 1 is provided in this way.

As described above, the sound-absorbing panel 10 of this embodiment 1 has a decorative plate 11 in which two types of through holes 13a, 13b with different inner diameters are formed, and therefore two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed are formed because the shapes of the openings (through holes 13) are different. Therefore, in the above sound-absorbing structure 1, sound waves in different frequency bands are absorbed by the sound-absorbing panel 10.

In addition, in the above-mentioned sound-absorbing structure 1, since the sound-absorbing base material 12 is composed of a porous sound-absorbing material, the sound energy is converted into thermal energy and the sound waves are attenuated by the vibration of the air contained in the porous sound-absorbing material that composes the sound-absorbing base material 12 as the air inside the Helmholtz resonator formed in the sound-absorbing panel 10 resonates.

Furthermore, in the sound absorbing structure 1, multiple louver materials 21, ..., 21 are attached to the surface of the sound absorbing panel 10. Therefore, some of the sound waves that reach the vicinity of the ceiling where the sound absorbing structure 1 is installed are reflected by the multiple louver materials 21, ..., 21 and change their traveling direction. In the sound absorbing structure 1, the sound waves are reflected by the multiple louver materials 21, ..., 21 and travel in various directions, so that the sound waves enter the interior of the multiple Helmholtz resonators formed in the sound absorbing panel 10 at various angles.

In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (the length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. However, even in a Helmholtz resonator of the same shape, if the angle of incidence of the sound waves changes, the cross-sectional area and length of the opening change in a pseudo manner, and the resonant frequency changes. Therefore, according to the above sound absorbing structure 1 in which multiple louver materials 21, ..., 21 are attached to the surface of the sound absorbing panel 10, the frequency band of sound waves that can be absorbed (sound waves that can be attenuated) is expanded compared to a conventional sound absorbing structure consisting only of a sound absorbing panel. In other words, according to the above sound absorbing structure 1, the frequency band in which excellent sound absorbing performance is exhibited is wider than that of a conventional sound absorbing structure equipped only with a sound absorbing panel. To verify this effect, the following sound absorption coefficient test (reverberation chamber method sound absorption coefficient test) was conducted.

[Sound absorption test]
The sound absorption coefficient of the sound absorbing structure 1A of Example 1 and the sound absorbing structure 1B of Comparative Example 1 was measured in a reverberation room at a temperature of 23.4° C. and a humidity of 55% RH in accordance with the "Test method for sound absorption coefficient in a reverberation room" specified in JIS A 1409: 1998. The measurement was performed for each ⅓ octave band with a center frequency of 100 Hz to 4 kHz.

Example 1
A decorative panel 11 was produced in which a volcanic glass laminate (product name: Dailite, manufactured by Daiken Corporation) measuring 606 mm x 2,420 mm x 6 mm had first through holes 13a with an inner diameter of 3 mm and second through holes 13b with an inner diameter of 5 mm formed at a pitch of 25 mm in both the vertical and horizontal directions, with the same types of holes lined up vertically and different types lined up horizontally.

A sound-absorbing base material 12 was also produced by forming multiple grooves 14, ..., 14 parallel to each other at a 25 mm pitch on the surface of a 606 mm x 2420 mm x 9 mm rock wool board (product name: Dairoton, manufactured by Daiken Corporation).

The decorative board 11 and the sound-absorbing base material 12 were overlapped and glued together so that the same type of multiple through holes 13, ..., 13 in each through hole row (first through hole row, second through hole row) of the decorative board 11 correspond to the same grooves 14 in the sound-absorbing base material 12 (the multiple through holes in each through hole row are connected to the same grooves 14), and a sound-absorbing panel 10 measuring 606 mm x 2420 mm x 15 mm was produced.

The louver material 21, 30 mm wide, 100 mm high and 2420 mm long, was made from the core material 22 made of plywood as described in the first embodiment and the surface material 23 made of volcanic glass laminate, and fixed at a pitch of 125 mm to the surface of the sound-absorbing panel 10, measuring 606 mm x 2420 mm x 15 mm, to create the sound-absorbing structure 1A.

<Comparative Example 1>
A sound absorbing structure 1B consisting of only the sound absorbing panel 10 of Example 1 measuring 606 mm x 2420 mm x 15 mm was produced.

<Measurement results>
The sound absorption coefficients of the sound absorbing structure 1A of Example 1 and the sound absorbing structure 1B of Comparative Example 1 were measured using a reverberation room method, and the results are shown in Fig. 5. In Fig. 5, the sound absorption coefficient of the sound absorbing structure 1A is shown by a solid line, and the sound absorption coefficient of the sound absorbing structure 1B is shown by a dashed line.

As shown in Figure 5, the sound absorbing structure 1B of Comparative Example 1 has a reverberation room method sound absorption coefficient of 0.6 or more in the center frequency range of 630 to 2000 Hz, while the sound absorbing structure 1A has a reverberation room method sound absorption coefficient of 0.6 or more in the center frequency range of 400 to 2000 Hz. This result shows that the sound absorbing structure 1 (sound absorbing structure 1A) in which multiple louver materials 21, 21, 21 are attached to the surface of the sound absorbing panel 10 exhibits superior sound absorbing performance in a wide frequency range compared to the conventional sound absorbing structure (sound absorbing structure 1B) consisting only of the sound absorbing panel 10.

The average reverberation room sound absorption coefficient (N.R.C.) measured in the center frequency range of 250 to 2000 Hz was 0.72 for sound absorbing structure 1A and 0.58 for sound absorbing structure 1B. These results show that the sound absorbing performance of the sound absorbing structure 1 according to the present invention (sound absorbing structure 1A) is superior to that of the conventional sound absorbing structure (sound absorbing structure 1B).

--Effects of the First Embodiment--
As described above, in the sound absorbing structure 1 of the first embodiment, sound waves that reach the vicinity of the sound absorbing structure 1 are absorbed by the multiple Helmholtz resonators formed in the sound absorbing panel 10. Specifically, in the sound absorbing panel 10, sound waves near the resonant frequency (natural frequency) are incident on the multiple Helmholtz resonators, causing the air inside each Helmholtz resonator (in the groove 14) to resonate and vibrate violently in the through hole 13. The violently vibrating air in the through hole 13 generates friction with the peripheral wall of the through hole 13, so that sound energy (vibration energy) is converted into thermal energy. According to the sound absorbing structure 1, among the sound waves that reach the vicinity of the sound absorbing structure 1 in this way, sound waves near the resonant frequency of the multiple Helmholtz resonators formed in the sound absorbing panel 10 can be significantly attenuated.

In addition, in the sound absorbing structure 1 of this embodiment 1, multiple louver materials 21, ..., 21 are attached to the surface of the sound absorbing panel 10. Therefore, some of the sound waves that reach the vicinity of the sound absorbing structure 1 are reflected by the multiple louver materials 21, ..., 21 and their traveling direction changes in various ways. In the above sound absorbing structure 1, by reflecting the sound waves in various directions by the multiple louver materials 21, ..., 21 in this way, the sound waves are incident on the multiple Helmholtz resonators of the sound absorbing panel 10 from various angles.

In the Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (the length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. However, even in a Helmholtz resonator of the same shape, when the angle of incidence of the sound waves changes, the cross-sectional area and length of the opening change in a pseudo manner, and the resonant frequency changes. Therefore, as described above, by attaching multiple louver materials 21, ..., 21 to the surface of the sound-absorbing panel 10 and configuring the multiple Helmholtz resonators so that sound waves are incident at various angles, the frequency band of sound waves that can be absorbed (sound waves that can be attenuated) by the sound-absorbing panel 10 can be expanded compared to conventional sound-absorbing structures that do not have louver materials 21. Therefore, according to this embodiment 1, it is possible to provide a sound-absorbing structure 1 that can exhibit excellent sound-absorbing performance in a wide frequency band.

In addition, in this embodiment 1, the sound-absorbing panel 10 is formed by superimposing a plate-shaped sound-absorbing base material 12, which is made of a porous sound-absorbing material and has a plurality of grooves (recesses) 14 formed on its surface that define the cavities of the Helmholtz resonators between the back surface of the decorative board 11 and the back surface of the decorative board 11, on the back surface of the decorative board 11, on which a plurality of through holes 13, ..., 13 that serve as openings for the Helmholtz resonators are formed. In this embodiment 1, this configuration makes it easy to form the sound-absorbing panel 10 on which a plurality of Helmholtz resonators are formed, simply by superimposing the sound-absorbing base material 12 on the back surface of the decorative board 11.

In addition, in this embodiment 1, the sound-absorbing base material 12 is made of a porous sound-absorbing material. Therefore, according to this embodiment 1, as the air inside the Helmholtz resonator formed in the sound-absorbing panel 10 resonates, the air contained in the porous sound-absorbing material that makes up the sound-absorbing base material 12 vibrates, converting sound energy into thermal energy and attenuating the sound waves. In other words, according to this embodiment 1, it is possible to provide a sound-absorbing structure with superior sound-absorbing performance.

In addition, in this embodiment 1, multiple grooves (recesses) 14, ..., 14 that define the cavity of the Helmholtz resonator are formed in the sound-absorbing base material 12 made of a porous sound-absorbing material, so that most of the peripheral wall of the cavity of the Helmholtz resonator is formed of the porous sound-absorbing material. Therefore, according to this embodiment 1, the sound absorption effect due to the vibration of the air contained in the porous sound-absorbing material can be improved compared to when the cavity of the Helmholtz resonator is formed in the decorative panel 11.

By the way, a plate-like body made of a porous sound-absorbing material is usually lighter and softer than the decorative board 11, which requires a certain degree of rigidity. Therefore, as in the sound-absorbing structure 1 of the present embodiment 1, by forming the recess (groove 14 in the present embodiment 1) that divides the cavity of the Helmholtz resonator not in the decorative board 11 but in the sound-absorbing base material 12 made of a porous sound-absorbing material, the recess can be easily processed. In addition, since the recess is easy to process, in the present embodiment 1, a plurality of grooves 14, ..., 14 having the same cross-sectional shape are formed as the plurality of recesses, but by changing the shape of some of these recesses (grooves 14), it is also easy to form a plurality of types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed in the sound-absorbing panel 10. And, according to the sound-absorbing structure 1 using the sound-absorbing panel 10 in which a plurality of types of Helmholtz resonators are formed in this way, the frequency band in which excellent sound absorption performance is exhibited can be further expanded.

In addition, in this embodiment 1, the multiple through holes 13, ..., 13 that function as openings of the Helmholtz resonator in the sound-absorbing panel 10 include two types of through holes (first and second through holes 13a, 13b) with different inner diameters. In the Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening (cross-sectional area of the through hole 13), the length of the opening (length of the through hole 13), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, by forming two types of through holes 13a, 13b with different inner diameters in the decorative panel 11, two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed due to the different shapes of the openings (through holes 13) are formed. Therefore, according to this embodiment 1, it is possible to provide a sound-absorbing structure 1 that can exhibit excellent sound-absorbing performance in a wider frequency band.

In addition, in this embodiment 1, the decorative panel 11 and the sound-absorbing base material 12 are made of a material that has non-flammable properties. This configuration gives the sound-absorbing panel 10 non-flammable properties.

In particular, in this embodiment 1, the sound-absorbing base material 12 is made of rock wool board, which has excellent sound-absorbing and non-flammable properties. This gives the sound-absorbing panel 10 not only high sound-absorbing properties but also non-flammable properties.

Second Embodiment of the Invention
The second embodiment is a modification of a part of the configuration of the sound absorbing structure 1 of the first embodiment. In the second embodiment, the louver material 21 constituting the louver 20 is configured to have a plurality of Helmholtz resonators.

[louver]
As shown in Fig. 6, in the second embodiment as well, the louver 20 is composed of a plurality of louver materials 21, ..., 21 attached to the surface of the sound-absorbing panel 10. The plurality of louver materials 21, ..., 21 are fixed to the surface of the sound-absorbing panel 10 at a predetermined pitch (125 mm in the second embodiment) and are provided parallel to one another. Note that, although Fig. 6 shows only a portion of the louver 20 with a solid line, in reality, the plurality of louver materials 21, ..., 21 are provided parallel to one another over the entire portion where the plurality of sound-absorbing panels 10, ..., 10 are provided.

As shown in FIG. 7, the louver material 21 has a core material 22, a surface material 23, a sealing material 24, and an end piece material (not shown), and is fixed to the sound-absorbing panel 10 via a support material 25.

The core material 22 is composed of two plate-like members 22A and 22B. The two plate-like members 22A and 22B are each composed of a long (2420 mm in this embodiment) rock wool plate (product name: Dairoton, manufactured by Daiken Corporation) having a constant thickness (9 mm in this embodiment) and a constant width (59 mm in this embodiment). In this embodiment, the two plate-like members 22A and 22B are formed in a plane-symmetrical shape.

A plurality of grooves (recesses) 26, ..., 26 extending in the length direction are formed on the surface of each plate-like member 22A, 22B. In this embodiment 2, three grooves 26 are formed, and are arranged parallel to each other at an equal pitch (20 mm in this embodiment 2) on the surface of each plate-like member 22A, 22B. Each groove 26 is formed in a U-shape in cross section, has a constant groove width and a constant depth (5 mm in this embodiment 2), and is formed from one end to the other end in the length direction of each plate-like member 22A, 22B. In this embodiment 2, the three grooves 26, 26, 26 are composed of two types of first grooves (first recesses) 26a and second grooves (second recesses) 26b with different groove widths (different volumes). The groove 26 located at one end of the width direction (vertical direction in FIG. 4) of the plate-like members 22A and 22B is configured as a first groove 26a having a first volume and a groove width shorter than the other two, and the remaining two are configured as second grooves 26b having a second volume larger than the first volume and a groove width wider than the first groove 26a.

When the back surfaces (surfaces behind the front surface on which the grooves 26 are formed) of the two plate-like members 22A and 22B are overlapped with each other, the two plate-like members 22A and 22B are formed in a shape that is plane-symmetrical with respect to each other's back surfaces. In the second embodiment, the core material 22 is formed by overlapping the back surfaces of the two plate-like members 22A and 22B having such plane-symmetrical shapes. Furthermore, by configuring the core material 22 in this way, multiple grooves (recesses) 26 (three on each side) that define the cavity of the Helmholtz resonator are formed between the two sides of the core material 22 and the inner surface of the facing surface material 23.

The two plate-like members 22A and 22B that make up the core material 22 may be any porous sound-absorbing material, and inorganic fiberboards other than rock wool boards (such as glass wool boards) may be used, but it is preferable to use rock wool boards because they can withstand stacking and cutting.

The surface material 23 has a plate-shaped front portion 23a and a pair of plate-shaped side portions 23b, 23b that extend in the same direction and in parallel from both widthwise ends of the front portion 23a by the same distance, and is formed with a U-shaped cross section. The surface material 23 is fitted onto the core material 22, with the front portion 23a covering one end face of the core material 22 in the width direction (the vertical direction in Figure 4), and the two side portions 23b, 23b covering the two side faces of the core material 22.

The surface material 23 is made of a volcanic glass laminate (product name: Dailite, manufactured by Daiken Corporation) having a constant thickness (6 mm in this embodiment 2) similar to that of the decorative panel 11 of the sound-absorbing panel 10. Specifically, the surface material 23 is formed with multiple notches extending in the length direction in the middle of the width direction of a long volcanic glass laminate, and is bent at right angles at the notches to form a U-shaped cross section.

As with the decorative board 11, the surface material 23 can be a volcanic glass laminate, calcium silicate board, melamine decorative board, plywood, wood fiber board such as MDF or particle board, inorganic fiber board such as glass wool board, gypsum board, etc.

The two side portions 23b, 23b of the surface material 23 have a plurality of through holes 27, ..., 27 formed from the outer surface to the inner surface. The plurality of through holes 27, ..., 27 are provided at equal pitches in the length direction and width direction in each side portion 23b. In this embodiment 2, the plurality of through holes 27, ..., 27 are provided in the length direction of each side portion 23b (direction perpendicular to the paper surface in FIG. 4) at the same pitch (25 mm in this embodiment 2) as the plurality of through holes 13, ..., 13 of the decorative plate 11 of the sound-absorbing panel 10, and in the width direction (vertical direction in FIG. 4) of each side portion 23b, three through holes are provided at the same pitch (20 mm in this embodiment 2) as the three grooves 26, 26, 26 of the core material 22. In this embodiment 2, the plurality of through holes 27, ..., 27 are all formed in the same shape (in this embodiment 2, a circular cross section with an inner diameter of 5 mm).

In addition, a fitting groove 28 into which the side end of the blocking material 24 fits is formed on each inner surface of the two side portions 23b, 23b of the surface material 23. The fitting groove 28 is formed in a U-shape in cross section, has a constant groove width (12 mm in this embodiment 2) and a constant depth (1 mm in this embodiment 2), and is formed from one end of the surface material 23 in the longitudinal direction to the other end so that the blocking material 24 can be inserted from one end to the other end of the surface material 23 in the longitudinal direction.

The surface material 23 is fitted so that each side portion 23b, 23b covers two side surfaces of the core material 22 in which the three grooves 26, 26, 26 are formed. More specifically, the surface material 23 is fitted to the core material 22 so that all of the multiple through holes 27, ..., 27 formed in each side portion 23b correspond to any one of the three grooves 26, 26, 26 formed in the side surface of the core material 22. By fitting the surface material 23 to the core material 22 in this manner, multiple Helmholtz resonators are formed in the louver material 21.

Specifically, as shown in FIG. 7, grooves 26 (recesses) formed on both side surfaces of the core material 22 form multiple elongated cavities between each side surface portion 23b of the surface material 23 and each side surface of the core material 22. Each cavity opens to the outside through a corresponding number of through holes 27, ..., 27. A Helmholtz resonator is formed by the peripheral wall portion that defines each of these cavities and the through holes 27 corresponding to the cavity. In other words, the louver material 21 has as many Helmholtz resonators as there are through holes 27, ..., 27.

In addition, in this embodiment 2, one of the three grooves 26, 26, 26 formed on the surface of each of the two plate-like members 22A, 22B constituting the core material 22, the first groove 26a, has a shorter groove width and a smaller volume than the other two second grooves 26b, 26b. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening (cross-sectional area of the through hole 27), the length of the opening (length of the through hole 27), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, in the louver material 21 of this embodiment 2 in which two types of first grooves 26a and second grooves 26b with different groove widths (different volumes) are formed in the core material 22, two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed are formed due to the different volumes of the cavities.

The blocking material 24 is made of a long plywood (2420 mm in this embodiment 2) having a certain thickness (12 mm in this embodiment 2) and a certain width (20 mm in this embodiment 2). The blocking material 24 is fitted into the surface material 23 by being inserted from one end side in the length direction of the surface material 23 fitted onto the core material 22 into two corresponding fitting grooves 28, 28 formed on the two side portions 23b, 23b. The blocking material 24 is restricted from moving in the thickness direction (the width direction of the louver material 21, the up-down direction in this embodiment 2) by fitting both ends in the width direction into the two fitting grooves 28, 28 of the surface material 23. Such a blocking material 24 restricts the core material 22 provided between the blocking material 24 and the front portion 23a of the surface material 23 from moving in the width direction (the thickness direction of the blocking material 24) and coming out of the surface material 23.

The core material 22 and the surface material 23, and the surface material 23 and the sealing material 24 are fixed with an adhesive (not shown). The end of the core material 22 on the butt side is covered with an butt material (not shown). The core material 22 and the butt material are fixed with an adhesive and pin nails (not shown).

The louver material 21 thus constructed from the core material 22, surface material 23, blocking material 24, and end grain material (not shown) is fixed to the sound-absorbing panel 10 via the receiving material 25, as shown in FIG. 7. The receiving material 25 is formed to a size that fits into the groove formed by the blocking material 24 and the portions of the two side portions 23b, 23b of the surface material 23 that are closer to the opening than the blocking material 24, and is formed from, for example, plywood.

Specifically, as shown in FIG. 7, the receiving material 25 is fixed in advance with a pin nail or the like so that it spans the multiple sound-absorbing panels 10, ..., 10. Then, the louver material 21 is positioned so that the receiving material 25 fixed to the multiple sound-absorbing panels 10, ..., 10 fits into the above-mentioned groove of the louver material 21, and the louver material 21 is fixed to the receiving material 25 by driving a pin nail into the side of the louver material 21 so that it reaches the receiving material 25. Each louver material 21 is fixed to the multiple sound-absorbing panels 10, ..., 10 in this manner.

- Sound absorbing effect of sound absorbing structure 1 -
In the sound absorbing structure 1 of the second embodiment, a plurality of Helmholtz resonators are also formed in the sound absorbing panel 10. Therefore, sound waves that reach the vicinity of the ceiling on which the sound absorbing structure 1 is provided are absorbed by the plurality of Helmholtz resonators formed in the sound absorbing panel 10. Specifically, in the sound absorbing panel 10, sound waves near the resonant frequency (1000 Hz in the first embodiment) enter the plurality of Helmholtz resonators, causing the air inside each Helmholtz resonator (in the groove 14) to resonate, and the air vibrates violently in each through hole 13 formed in the decorative panel 11. The violently vibrating air in each through hole 13 generates friction with the peripheral wall of each through hole 13, and sound energy (vibration energy) is converted into heat energy. In the sound absorbing structure 1, sound waves near the resonant frequency of the plurality of Helmholtz resonators are significantly attenuated among the sound waves that reach the vicinity of the ceiling on which the sound absorbing structure 1 is provided in this way.

Also, in the second embodiment, by forming two types of through holes 13a, 13b with different inner diameters in the decorative panel 11, two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed due to the different shapes of the openings (through holes 13) are formed in the sound-absorbing panel 10, and sound waves of different frequency bands are absorbed by the sound-absorbing panel 10.

Also, in the second embodiment, the sound-absorbing base material 12 is made of a porous sound-absorbing material, so that as the air inside the Helmholtz resonator formed in the sound-absorbing panel 10 resonates, the air contained in the porous sound-absorbing material that makes up the sound-absorbing base material 12 vibrates, converting sound energy into thermal energy and attenuating the sound waves.

Furthermore, in the sound absorbing structure 1 of the second embodiment, similarly to the first embodiment, a plurality of louver materials 21, ..., 21 are attached to the surface of the sound absorbing panel 10, and a Helmholtz resonator is formed in each louver material 21. Therefore, sound waves that reach the vicinity of the sound absorbing structure 1 are absorbed not only by the sound absorbing panel 10 but also by each louver material 21. Specifically, in each louver material 21, sound waves near the resonant frequency are incident on the plurality of Helmholtz resonators, causing the air inside each Helmholtz resonator (in the groove 26) to resonate, and the air vibrates violently in each through hole 27 formed in the surface material 23. The violently vibrating air in each through hole 27 generates friction with the peripheral wall of each through hole 27, and sound energy (vibration energy) is converted into heat energy. In the above sound absorbing structure 1, sound waves that reach the vicinity of the ceiling on which the sound absorbing structure 1 is provided are attenuated by the Helmholtz resonators formed not only in the sound absorbing panel 10 but also in each louver material 21.

In addition, in embodiment 2, two types of first grooves (first recesses) 26a and second grooves (second recesses) 26b with different groove widths (different volumes) are formed in the core material 22, so that each louver material 21 has two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed due to the different cavity volumes. Therefore, in embodiment 2, sound waves of different frequency bands are absorbed by each louver material 21.

In addition, in the second embodiment, the core material 22 is made of a porous sound-absorbing material, so that the air contained in the porous sound-absorbing material that constitutes the core material 22 vibrates as the air inside the Helmholtz resonators formed in each louver material 21 resonates, converting sound energy into thermal energy and attenuating the sound waves.

Furthermore, in the second embodiment, by attaching multiple louver materials 21, ..., 21 to the surface of the sound-absorbing panel 10 and configuring it so that sound waves are incident at various angles on the multiple Helmholtz resonators formed on the sound-absorbing panel 10, the frequency band of sound waves that can be absorbed (sound waves that can be attenuated) by the sound-absorbing panel 10 formed with multiple Helmholtz resonators is expanded compared to the case where the louver materials 21 are not provided.

Due to the above-mentioned sound absorbing action, the sound absorbing structure 1 of embodiment 2 exhibits better sound absorbing performance than the sound absorbing structure 1 of embodiment 1. Furthermore, according to the sound absorbing structure 1 of embodiment 2, the frequency band in which the excellent sound absorbing performance is exhibited is wider than that of a sound absorbing structure equipped only with a conventional sound absorbing panel. To verify this effect, the following sound absorption coefficient test (reverberation chamber method sound absorption coefficient test) was conducted.

[Sound absorption test]
In addition to the sound absorbing structures 1A and 1B shown in the first embodiment, the sound absorbing structure 1C of the following example 2 was measured for sound absorption coefficient in a reverberation room at a temperature of 23.4° C. and a humidity of 55% RH in accordance with the “Test method for sound absorption coefficient in a reverberation room” specified in JIS A 1409: 1998. The measurement was performed for each ⅓ octave band with a center frequency of 100 Hz to 4 kHz.

Example 2
A sound absorbing panel 10 of 606 mm × 2420 mm × 15 mm similar to that of Example 1 was produced by the same procedure as in Example 1. Also, louver materials 21 of 30 mm × 100 mm × 2420 mm with a length of 2420 mm as described in the second embodiment were produced and attached at a pitch of 125 mm to the surface of the sound absorbing panel 10 of 606 mm × 2420 mm × 15 mm to produce a sound absorbing structure 1C.

<Measurement results>
When the sound absorption coefficient of the sound absorbing structure 1C of Example 2 was measured in a reverberation room, the results were as shown in Fig. 8. In Fig. 8, the sound absorption coefficient of the sound absorbing structure 1C is shown by a solid line, and for comparison with the first embodiment, the sound absorption coefficient of the sound absorbing structure 1A of Example 1 is shown by a dashed line, and the sound absorption coefficient of the sound absorbing structure 1B of Comparative Example 1 is shown by a dashed line.

From the results shown in Figure 8, the average reverberation chamber sound absorption coefficient (N.R.C.) measured for sound absorbing structure 1C in the center frequency range of 250 to 2000 Hz was found to be 0.83. This result shows that the sound absorbing performance of sound absorbing structure 1 according to embodiment 2 (sound absorbing structure 1C) is even better than that of sound absorbing structure 1 according to embodiment 1 (sound absorbing structure 1A).

As shown in FIG. 8, in the sound absorbing structure 1A of Example 1, the reverberation room method sound absorption coefficient was 0.6 or more in the center frequency range of 400 to 2000 Hz, whereas in the sound absorbing structure 1C, the reverberation room method sound absorption coefficient was 0.6 or more in the center frequency range of 400 to 2500 Hz. From this result, it can be seen that the sound absorbing structure 1 of embodiment 2 (sound absorbing structure 1C) in which the louvers 20 of the sound absorbing structure 1 are formed from the louver material 21 of embodiment 2 having a sound absorbing function exhibits excellent sound absorbing performance in a wider frequency band than the sound absorbing structure 1 of embodiment 1 (sound absorbing structure 1A) in which the louvers 20 are formed from the normal louver material 21 of embodiment 1 not having a sound absorbing function.

--Effects of the second embodiment--
The sound absorbing structure 1 of the second embodiment can also achieve the same effects as the sound absorbing structure 1 of the first embodiment.

In addition, in the sound absorbing structure 1 of the second embodiment, multiple Helmholtz resonators are formed not only in the sound absorbing panel 10 but also in the louver material 21 attached to the sound absorbing panel 10. Therefore, sound waves that reach the vicinity of the sound absorbing structure 1 are absorbed not only by the sound absorbing panel 10 but also by each louver material 21. Specifically, in each louver material 21, sound waves near the resonant frequency (natural frequency) are incident on the multiple Helmholtz resonators, causing the air inside the Helmholtz resonator (in the groove 26) to resonate, and the air vibrates violently in each through hole 27. The violently vibrating air in each through hole 27 generates friction with the peripheral wall of each through hole 27, and sound energy (vibration energy) is converted into heat energy. According to the second embodiment, among the sound waves that reach the vicinity of the sound absorbing structure in this way, sound waves near the resonant frequency of the multiple Helmholtz resonators formed in the louver material can be significantly attenuated by the Helmholtz resonators formed in each louver material 21. In other words, according to the second embodiment, the sound absorbing performance of the sound absorbing structure 1 can be further improved by imparting sound absorbing functionality to each louver material 21.

Furthermore, according to the second embodiment, by changing the shape of the Helmholtz resonator formed in the sound-absorbing panel 10 and the louver material 21, sound waves in a frequency band that is not absorbed by the sound-absorbing panel 10 can be absorbed by the louver material 21. With this configuration, it is possible to provide a sound-absorbing structure 1 that exhibits excellent sound-absorbing performance over an even wider frequency band.

In addition, in the sound absorbing structure 1 of embodiment 2, a louver material 21 having multiple Helmholtz resonators can be easily formed by simply fitting a surface material 23 having a U-shaped cross section and multiple through holes 27, ..., 27 formed in at least one side portion 23b onto a core material 22 having multiple grooves (recesses) 26, ..., 26 formed on the side.

In addition, in the second embodiment, the core material 22 is made of a porous sound-absorbing material. Therefore, according to the second embodiment, the air contained in the porous sound-absorbing material that constitutes the core material 22 vibrates as the air inside the Helmholtz resonators formed in each louver material 21 resonates, and sound energy is converted into thermal energy, causing the sound waves to attenuate. In other words, according to the second embodiment, it is possible to provide a sound-absorbing structure 1 with superior sound-absorbing performance.

In addition, in the second embodiment, since a plurality of grooves (recesses) 26, ..., 26 that divide the cavity of the Helmholtz resonator are formed in the core material 22 made of a porous sound-absorbing material, most of the peripheral wall of the cavity of the Helmholtz resonator is formed of the porous sound-absorbing material. Therefore, according to the second embodiment, the sound absorption effect due to the vibration of the air contained in the porous sound-absorbing material can be improved compared to the case where the cavity of the Helmholtz resonator is formed in the surface material 23.

Normally, a plate-shaped body made of a porous sound-absorbing material is lighter and softer than the surface material 23, which requires a certain degree of rigidity. Therefore, as in the sound-absorbing structure 1 of embodiment 2, the recess (groove 26 in embodiment 2) that defines the cavity of the Helmholtz resonator is formed on the side of the core material 22 made of a porous sound-absorbing material, rather than on the surface material 23, making it easier to process the groove (recess) 26. In addition, since the groove (recess) 26 is easy to process, it is also easy to form multiple types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed in the louver material 21 by changing the shapes of some of the multiple grooves (recesses) 26, ..., 26 formed in the core material 22.

In the sound absorbing structure 1 of the second embodiment, the grooves (recesses) 26, 26, 26 formed on the surfaces of the plate-like members 22A and 22B include two types of recesses (first groove 26a and second groove 26b) with different volumes. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (the length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, by forming two types of recesses with different volumes in the core material 22, two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed due to the different volumes of the cavities in the louver material 21 are formed. According to the second embodiment, by using such a louver material 21, it is possible to provide a sound absorbing structure 1 that can exhibit excellent sound absorbing performance in an even wider frequency band than the sound absorbing structure 1 of the first embodiment.

In the sound absorbing structure 1 of the second embodiment, a plurality of through holes 27, ..., 27 are formed on both of the two side portions 23b, 23b of the surface material 23, a plurality of grooves (recesses) 26, ..., 26 are formed on the surface, and the core material 22 is formed by two plate-like members 22A, 22B with their back surfaces overlapped. In the second embodiment, by configuring the louver material 21 in this way, sound waves can be absorbed from both sides of the louver material 21, so that a sound absorbing structure 1 with better sound absorbing performance can be provided. In the sound absorbing structure 1 of the second embodiment, the core material 22 is made of two overlapping plate-like members 22A, 22B with only the surface processed, without processing the grooves 26 on both sides of the core material 22, and the louver material 21 capable of absorbing sound waves from both sides can be easily formed.

In addition, in the sound absorbing structure 1 of embodiment 2, the core material 22 and the surface material 23 are formed from a material that has non-flammable properties, so that the louver material 21 can be given non-flammable properties.

In addition, in the sound absorbing structure 1 of embodiment 2, the core material 22 is made of a rock wool board, which gives the louver material 21 not only high sound absorbing performance but also non-flammable performance.

Other Embodiments
In the above embodiments, the sound absorbing structure according to the present invention is applied to a ceiling of an indoor space as an example of a sound absorbing structure provided in a building, but the location to which the sound absorbing structure according to the present invention can be applied is not limited to the ceiling. The sound absorbing structure according to the present invention may be applied to a wall constituting an indoor space, or may be applied to a partition member such as a partition wall or a screen.

In addition, in each of the above embodiments, a sound-absorbing structure 1 including a sound-absorbing panel 10 made of a decorative panel 11 and a sound-absorbing base material 12 has been described, but the sound-absorbing panel used in the sound-absorbing structure according to the present invention may be any panel in which multiple Helmholtz resonators are formed.

In addition, in each of the above embodiments, two types of through holes 13a, 13b with different inner diameters are formed in the sound-absorbing panel 10, thereby forming two types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed. However, the sound-absorbing panel according to the present invention may be configured such that the inner diameters of the multiple through holes 13, ..., 13 formed are all the same. Furthermore, the sound-absorbing panel 10 may be configured such that three or more types of through holes with different inner diameters are formed.

In addition, in each of the above embodiments, the recess formed on the surface of the sound-absorbing base material 12 in the sound-absorbing panel 10 to partition the cavity of the Helmholtz resonator is configured as a groove 14 extending from one end to the other end of the sound-absorbing base material 12, and each groove 14 corresponds to a plurality of through holes 13, ..., 13. However, the recess according to the present invention is not limited to being configured as a groove 14 corresponding to a plurality of through holes 13, ..., 13 as described above, but may correspond one-to-one to the through holes 13.

In addition, in each of the above embodiments, the multiple grooves 14, ..., 14 formed on the surface of the sound-absorbing base material 12 have the same configuration, but the multiple grooves (recesses) 14, ..., 14 may have different cross-sectional shapes and cross-sectional dimensions. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the opening (the length of the neck), and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, when multiple types of grooves (recesses) 14, ..., 14 with different cross-sectional shapes and cross-sectional dimensions are formed on the surface of the sound-absorbing base material 12, multiple types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed are formed on the sound-absorbing panel 10. In other words, it is possible to provide a sound-absorbing structure 1 that can exhibit excellent sound-absorbing performance in a wide frequency band by simply forming multiple types of grooves (recesses) 14, ..., 14 with different cross-sectional shapes and cross-sectional dimensions on the surface of the sound-absorbing base material 12.

In addition, in each of the above embodiments, the various dimensions of the sound-absorbing panel 10 and the louver material 21 are shown as examples, and the dimensions of the sound-absorbing panel and louver material according to the present invention are not limited to those described above. Therefore, the sound-absorbing structure 1 may be constructed by attaching multiple louver materials 21, ..., 21 to a single huge sound-absorbing panel 10.

In addition, in the above embodiment 2, a sound absorbing structure 1 was described that includes multiple louver materials 21, ..., 21 each having a core material 22 and a surface material 23. However, the louver material used in the sound absorbing structure according to the present invention may be any material that has multiple Helmholtz resonators formed therein, each having a cavity that opens on the side, and that can form a louver.

In addition, in the above-mentioned second embodiment, the recesses formed on the surfaces of the two plate-like members 22A, 22B made of a porous sound-absorbing material in the louver material 21 to partition the cavity of the Helmholtz resonator are configured as grooves 26 extending from one end to the other in the longitudinal direction, and each groove 26 corresponds to a plurality of through holes 27, ..., 27. However, the recesses according to the present invention are not limited to those configured by grooves 26 corresponding to a plurality of through holes 27, ..., 27 as described above, but may correspond one-to-one to the through holes 27.

In the above embodiment 2, the multiple through holes 27, ..., 27 formed in the side portion 23b of the surface material 23 have the same configuration, but the multiple through holes 27, ..., 27 may have different cross-sectional shapes and cross-sectional dimensions. In a Helmholtz resonator, the resonant frequency varies depending on the cross-sectional area of the opening, the length of the neck, and the volume of the cavity, and the frequency of the sound waves that can be absorbed (attenuated) varies. Therefore, when multiple types of through holes 27, ..., 27 with different cross-sectional shapes and cross-sectional dimensions are formed in the side portion 23b of the surface material 23, multiple types of Helmholtz resonators with different frequency bands of sound waves that can be absorbed are formed in the louver material 21. In other words, it is possible to provide a sound absorbing structure 1 that can exhibit excellent sound absorbing performance in a wide frequency band by simply forming multiple types of through holes 27, ..., 27 with different cross-sectional shapes and cross-sectional dimensions in the side portion 23b of the surface material 23.

As explained above, the present invention is useful for sound absorbing structures installed indoors in buildings.

1. Sound-absorbing structure
10. Sound-absorbing panels
11 Decorative panels
12. Sound-absorbing base material
13 Through hole
13a First through hole
13b Second through hole
14 Groove (recess)
20 Louver
21 Louver material
22 Core material
22A, 22B Plate-shaped members
23 Surface material
23a Front part
23b Side portion
26 Groove (recess)
26a First groove (first recess)
26b Second groove (second recess)
27 Through hole
D1 First inner diameter
D2 Second inner diameter

Claims (10)

A sound absorbing structure installed in a building,
a sound-absorbing panel having a plurality of Helmholtz resonators formed therein, each having a cavity that opens on a surface thereof;
a plurality of louver members attached at predetermined intervals on the surface of the sound-absorbing panel ;
The sound absorbing structure is characterized in that the louver material has a core material and a surface material having a U-shaped cross section and no through hole, which is fitted onto the outside of the core material . The sound absorbing structure according to claim 1,
The sound-absorbing panel is
a decorative plate provided on a front surface side and having a plurality of through holes formed therein to serve as openings for the Helmholtz resonator;
A sound-absorbing structure comprising: a plate-shaped sound-absorbing base material formed of a porous sound-absorbing material, layered on the back surface of the decorative panel, and having a plurality of recesses on its surface that define a cavity for the Helmholtz resonator between the back surface of the decorative panel and the plate-shaped sound-absorbing base material. The sound absorbing structure according to claim 2,
A sound-absorbing structure characterized in that the plurality of through holes include a first through hole having a first inner diameter and a second through hole having a second inner diameter larger than the first inner diameter. The sound absorbing structure according to claim 2 or 3,
A sound-absorbing structure, characterized in that the decorative panel and the sound-absorbing base material are formed from a material having non-flammable properties. The sound absorbing structure according to any one of claims 2 to 4,
The sound-absorbing structure is characterized in that the sound-absorbing base material is made of a rock wool board. A sound absorbing structure installed in a building,
a sound-absorbing panel having a plurality of Helmholtz resonators formed therein, each having a cavity that opens on a surface thereof;
a plurality of louver members attached at predetermined intervals on the surface of the sound-absorbing panel;
The louver material has a plurality of Helmholtz resonators formed therein, each having a cavity that opens at a side surface,
The louver material has a core material formed of a porous sound absorbing material, and a surface material having a U-shaped cross section, the surface material having two side portions covering two side surfaces of the core material and a front portion connecting the two side portions, and is fitted onto the core material;
a plurality of through holes serving as openings of the Helmholtz resonator are formed in at least one of the side surfaces of the surface material;
A sound-absorbing structure characterized in that a plurality of recesses are formed on the side of the core material corresponding to the through hole, defining a cavity of the Helmholtz resonator between the side and the opposing inner surface of the surface material. 7. The sound absorbing structure according to claim 6 ,
The plurality of through holes are formed in both of the two side portions of the surface material,
The sound absorbing structure is characterized in that the core material is composed of two plate-like members having a plurality of the recesses formed on the surface and overlapping each other with their back surfaces facing each other. In the sound absorbing structure according to claim 6 or 7 ,
A sound-absorbing structure characterized in that the multiple recesses formed on the side of the core material include a first recess having a first volume and a second recess having a second volume larger than the first volume. The sound absorbing structure according to any one of claims 6 to 8 ,
A sound-absorbing structure, characterized in that the core material and the surface material are formed from a material having non-flammable properties. 10. The sound absorbing structure according to claim 6 ,
A sound-absorbing structure characterized in that the core material is made of rock wool board.

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