JP2022191503A - Sound absorbing body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorbing body which exhibits excellent sound-absorption effect in a sound range of daily life noise and has excellent reverberation suppression effect in a low sound range.

SOLUTION: A sound absorbing body comprises: sheet-like first and second solid knittings knitted from a pair of base fabrics which are disposed apart from each other and connecting threads connecting the base fabrics by reciprocating between them; and supporting plates which are arranged between the first solid knitting and the second solid knitting and support the first solid knitting and the second solid knitting at a surface and a rear face. The first solid knitting has first permeability and the second solid knitting has second permeability different from the first permeability, and the supporting plates have permeability in at least a plate thickness direction and form air layers between the first solid knitting and the second solid knitting.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing body that is installed indoors and absorbs indoor sound, and more particularly to a sound absorbing body that is formed in a panel shape by combining two types of sheet-shaped three-dimensional knitted fabrics.

2. Description of the Related Art Conventionally, sound absorbing materials have been installed on the walls and ceilings of concert halls, music rooms, and the like to take measures against noise. For example, Patent Literature 1 discloses a sound absorbing material that exerts a sound absorbing effect on sound in a wide frequency band including a low frequency range, and a sound absorbing device using this sound absorbing material.

The sound absorbing material of Patent Document 1 includes a first layer made of porous urethane foam impregnated with activated carbon, and a second layer made of a honeycomb three-dimensional knitted fabric laminated on the first layer. is constructed by packing this sound absorbing material into a hollow container.

JP 2009-299332 A

The sound absorbing material of Patent Document 1 has a certain sound absorbing effect for sound in a relatively wide frequency band including low frequency regions, but in the sound range of daily noise (600 to 2000 Hz), the sound absorbing effect is It cannot be said that it is sufficient, and the development of a sound absorbing body (that is, a sound absorbing material or a sound absorbing device) that has an even better sound absorbing effect is desired.

In addition, in recent years, in order to improve the acoustic effect (that is, to suppress reverberation) in ordinary homes and conference rooms, etc., sound absorbing devices and sound absorbing panels have been placed on the walls and corners of the room. In such applications, it is necessary to suppress reverberation in the low frequency range (100 to 1000 Hz), and there is a demand for the development of sound absorbers that are excellent in the effect of suppressing reverberation in the low frequency range.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a sound absorber that exhibits an excellent sound absorbing effect in the sound range of everyday noise and has an excellent reverberation suppressing effect in the low sound range.

In order to achieve the above object, the inventors of the present invention conducted extensive studies and found that a sheet-like three-dimensional knitted fabric having a predetermined air permeability is effective in absorbing sound in the sound range of daily life noise (600 to 2000 Hz). I found out.
Furthermore, the present inventors combined two types of sheet-like three-dimensional knitted fabrics with different air permeability to form a panel, and formed an air layer between them (that is, between two types of three-dimensional knitted fabrics). As a result, it has been found that a sound absorber that has very high sound absorption characteristics in the sound range of at least 300 to 10000 Hz and exhibits an excellent reverberation suppression effect in the low sound range (100 to 1000 Hz) can be obtained, and the present invention has been completed. rice field.

That is, the sound absorbing body of the present invention comprises first and second sheet-shaped first and second sheets knitted from a pair of base fabrics spaced apart from each other and connecting yarns reciprocating between the base fabrics and connecting them. a three-dimensional knitted fabric, and a support plate disposed between the first three-dimensional knitted fabric and the second three-dimensional knitted fabric and supporting the first three-dimensional knitted fabric and the second three-dimensional knitted fabric on the front and back sides, respectively, the first three-dimensional knitted fabric has a first air permeability, the second three-dimensional knitted fabric has a second air permeability different from the first air permeability, the support plate has air permeability at least in the plate thickness direction, An air layer is formed between the first three-dimensional knitted fabric and the second three-dimensional knitted fabric.

According to such a configuration, two types of sheet-like three-dimensional knitted fabrics having different air permeability are combined to form a panel, and an air layer is formed between them (that is, between the two types of three-dimensional knitted fabrics). Therefore, it is possible to realize a sound absorber that exhibits an excellent sound absorbing effect in the sound range of daily noises and an excellent reverberation suppressing effect in the low sound range.

Also, the support plate can be configured to have a plurality of circular openings densely arranged two-dimensionally in plan view.

Further, the support plate can be configured to have a plurality of wavy openings densely arranged two-dimensionally in a plan view.

It is also desirable that the support plate is made of paperboard.

Moreover, it is desirable that the first air permeability is 20 to 30 cm ³ /cm ² /sec and the second air permeability is 10 to 20 cm ³ /cm ² /sec.

Moreover, it is desirable that the thickness of the first and second three-dimensional knitted fabrics is 10 to 20 mm.

Moreover, it is desirable that the thickness of the support plate is 30 to 50 mm.

In addition, it is desirable that the sound absorbers are arranged and used so as to be substantially parallel to the vertical direction.

Also, it is desirable that the sound absorber has an absorption band in the sound range of at least 300 to 10000 Hz.

It is also desirable that the sound absorber suppresses reverberation in at least the 250-1000 Hz sound range.

As described above, according to the present invention, it is possible to realize a sound absorber that exhibits an excellent sound absorbing effect in the sound range of daily noises and exhibits an excellent reverberation suppressing effect in the low sound range.

FIG. 1 is a perspective view showing the configuration of a sound absorbing body according to an embodiment of the invention. FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a plan view of the support plate of the sound absorber according to the embodiment of the present invention. FIG. 4 is a photograph of the appearance of the support plate of the sound absorber according to the embodiment of the present invention. FIG. 5 is a graph showing the sound absorption characteristics of the first and second three-dimensional knitted fabrics of the sound absorbing body according to the embodiment of the present invention. FIG. 6 is a photograph of the appearance of the first three-dimensional knitted fabric of the sound absorbing body according to the embodiment of the present invention. FIG. 7 is a photograph of the appearance of the second three-dimensional knitted fabric of the sound absorbing body according to the embodiment of the present invention. FIG. 8 is a flow chart explaining a method for manufacturing a sound absorbing body according to an embodiment of the invention. FIG. 9 is a diagram showing the configuration of a knitting machine used for knitting the three-dimensional knitted fabric of the sound absorbing body according to the embodiment of the present invention. FIG. 10 is a diagram showing an example of a knitting structure of each component yarn used for knitting the first three-dimensional knitted fabric of the sound absorbing body according to the embodiment of the present invention. FIG. 11 is a diagram showing an example of a knitting structure of each component yarn used for knitting the second three-dimensional knitted fabric of the sound absorbing body according to the embodiment of the present invention. FIG. 12 is a graph showing the results of measuring the sound absorption coefficient of the sound absorber according to the embodiment of the present invention. FIG. 13 is a graph showing the results of measuring the reverberation time of the sound absorber according to the embodiment of the invention. FIG. 14 is a plan view showing a modification of the support plate of the sound absorber according to the embodiment of the invention. FIG. 15 is a photograph showing a modified example of the support plate of the sound absorber according to the embodiment of the present invention. FIG. 16 is a graph showing the results of measuring the sound absorption coefficient of the sound absorber provided with the support plate shown in FIGS. 14 and 15. FIG. FIG. 17 is a graph showing the results of measuring the reverberation time of the sound absorber provided with the support plate shown in FIGS. 14 and 15. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, unless there is a specific description, the components, types, combinations, materials, shapes, relative arrangements, etc. described in this embodiment are not the gist of limiting the scope of this invention only, but are merely illustrative examples. Not too much. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

(Structure of Sound Absorber 1)
1 and 2 are diagrams showing the configuration of a sound absorber 1 according to an embodiment of the present invention, FIG. 1 is a perspective view of the sound absorber 1, and FIG. 2 is a cross section taken along line AA of FIG. It is a diagram. As shown in FIG. 1, the sound absorber 1 of this embodiment has a rectangular plate shape (for example, width: 600 mm, height: 1300 mm, thickness: 70 mm). (that is, arranged so as to be substantially parallel to the vertical direction (vertical direction in FIG. 1)). The sound absorbing body 1 is formed of a support plate 10, and a three-dimensional knitted fabric 20 (first three-dimensional knitted fabric) and a three-dimensional knitted fabric 30 (second three-dimensional knitted fabric) respectively adhered to the front and back surfaces of the support plate 10. . Since the support plate 10 has a plurality of openings 15 two-dimensionally arranged in a hexagonally dense manner and has air permeability at least in the plate thickness direction (details will be described later), an air layer is formed between the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30. It is formed.

According to such a sound absorbing body 1, when sound passes through each three-dimensional knitted fabric 20, 30, heat is generated due to friction between the air inside the three-dimensional knitted fabric 20, 30 and the fibers, and friction between the fibers. A part of the energy is converted into heat energy, so the energy of the sound is reduced (that is, the sound absorption effect is exhibited).
In addition, since the sound that cannot be completely absorbed by the three-dimensional knitted fabrics 20 and 30 propagates to the air in the opening 15 of the support plate 10, part of it is canceled in the opening 15 by the resonance effect (that is, sound absorbing effect).

(Configuration of support plate 10)
FIG. 3 is a plan view of the support plate 10 of this embodiment. FIG. 4 is a photograph of one surface of the support plate 10 of the present embodiment taken obliquely. As shown in FIGS. 3 and 4, the support plate 10 of this embodiment is a rectangular plate-shaped member (for example, width: 600 mm, height: 1300 mm, thickness: 40 mm) formed by bonding a plurality of paperboards. , substantially cylindrical partition walls 12 having a diameter of about 15 mm and a height of about 40 mm are arranged two-dimensionally, and in plan view, a plurality of circular openings 15 are arranged two-dimensionally in a hexagonally dense manner.
The support plate 10 is formed, for example, by connecting (adhering) on a plane a member obtained by bonding a paperboard of a predetermined width (eg, 40 mm) while bending it into a figure 8 (FIG. 4).
As described above, the support plate 10 of the present embodiment is very light because it is made of paperboard, and has a so-called corrugated cardboard structure. It has a very high rigidity in In addition, since a plurality of circular openings 15 are formed in the plate thickness direction, at least air flow in the plate thickness direction is not interrupted and sufficient air permeability is provided.

(Structure of three-dimensional knitted fabric 20 and three-dimensional knitted fabric 30)
As shown in FIG. 2, the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 are respectively arranged with front base fabrics 22, 32 and rear base fabrics 24, 34 spaced apart from each other, and front base fabrics 22, 32 and the rear base fabrics. A double raschel three-dimensional rectangular sheet (for example, width: 600 mm, height: 1300 mm, thickness: 10 mm) knitted from connecting yarns 26, 36 that reciprocate between the base fabrics 24, 34 and bind them together. It is the base fabric. In this embodiment, the three-dimensional knitted fabric 20 has an air permeability of approximately 20 to 30 cm ³ /cm ² /sec, and the three-dimensional knitted fabric 30 has an air permeability of approximately 10 to 20 cm ³ /cm ² /sec. It is configured.

The knitting structure of the base threads of the front base fabrics 22, 32 and the rear base fabrics 24, 34 is not particularly limited, but from the viewpoint of adhesion to the support plate 10, the back base fabrics 24, 34 The knitted structure preferably has a flat knitted fabric structure that is continuous in both the wale direction and the course direction.

The connecting yarns 26, 36 are woven between the front base fabrics 22, 32 and the rear base fabrics 24, 34 so as to maintain the spacing between the front base fabrics 22, 32 and the rear base fabrics 24, 34. It is a portion that greatly contributes to the adjustment of air permeability of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30, and is also a portion that imparts cushioning properties. Therefore, it is preferable that the structure formed by the connecting threads 26 and 36 has a large underlap and a large thickness.

Natural fibers ( Spun yarns (short fibers) of cotton) and synthetic fibers (polyester, acrylic, nylon, rayon, etc.) are suitable.

In addition, as the material of the connecting yarns 26 and 36 of the three-dimensional knitted fabrics 20 and 30, from the viewpoint of ensuring appropriate air permeability and thickness of the three-dimensional knitted fabrics 20 and 30, respectively, synthetic fiber processed yarn such as polyester and nylon and synthetic fibers are used. It is preferably constituted by a textile monofilament thread.
By using the synthetic fiber textured yarn, the air permeability of the three-dimensional knitted fabrics 20 and 30 can be lowered. On the other hand, the thickness of the three-dimensional knitted fabrics 20 and 30 can be ensured by using the synthetic fiber monofilament yarn.

The thickness of the connecting yarns 26, 36 is preferably thicker in order to secure appropriate air permeability and thickness of the three-dimensional knitted fabrics 20, 30 and to obtain high shape stability thereof. Determined by machine specifications. For example, when using a double raschel machine RD6DPLM/8, RD6DPLM/12-3 (22 gauge/2.54 cm) manufactured by Karl Mayer as a knitting machine, the limit value of the thickness applied to one needle is long fiber 529 denier/588 dtex in the staple fiber and 310 denier/345 dtex in the staple fiber. Therefore, it is desirable that each thread has a thickness of about 150 to 220 decitex.

In addition, the three-dimensional knitted fabrics 20 and 30 are preferably thicker from the viewpoint of sufficiently securing cushioning properties and resilience while maintaining appropriate air permeability. However, if the thickness of the three-dimensional knitted fabrics 20, 30 is increased, the post-processing of the three-dimensional knitted fabrics 20, 30 becomes difficult and the amount of yarn consumption increases, so the thickness is preferably about 10 to 20 mm. , 12 to 18 mm.

FIG. 5 is a graph showing the sound absorption characteristics of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30, where the vertical axis represents the sound absorption coefficient (%) and the horizontal axis represents the frequency (Hz). The graph of FIG. 5 is the result obtained by normal incident sound absorption coefficient test (JIS A 1405-2, ISO 10534-2: 1998 compliant).
As shown in FIG. 5, the sound absorption coefficients of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of the present embodiment gradually increase from around 300 Hz, rise sharply from around 800 Hz, and reach about 100% at 4000 to 6300 Hz. It has a sound absorption coefficient. Thus, the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of the present embodiment can absorb sound in the sound range of daily noises (600 to 2000 Hz).
6 and 7 are photographs of the external appearance of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of this embodiment, respectively.

As shown in FIGS. 1 and 2, the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of this embodiment are fixed to the support plate 10 with an adhesive.
Examples of adhesives that can be used include acrylic resin adhesives, α-olefin adhesives, urethane resin adhesives, hot melt adhesives, and the like. Among these, hot-melt adhesives are preferable from the viewpoints of being able to adhere in a short time, being excellent in workability, and not using a solvent.
Examples of the form of the hot-melt adhesive include powder, liquid, gel, etc. From the viewpoint of excellent handleability, powder is particularly preferred.

Commercially available hot melt adhesives include the "Tyforce" (registered trademark) series manufactured by DIC Corporation, the "Scotch-Weld" (registered trademark) series manufactured by 3M Company, and the "Hibon" (registered trademark) series, "Takemelt" (registered trademark) MA series manufactured by Mitsui Takeda Chemicals Co., Ltd., "Aron Melt" (registered trademark) R series manufactured by Toagosei Co., Ltd., Nitta Gelatin Co., Ltd. " Nittai" (registered trademark) ARX series and "Bond" (registered trademark) KUM series manufactured by Konishi Co., Ltd. can be mentioned.

(Manufacturing method of sound absorber 1)
Next, a method for manufacturing the sound absorbing body 1 of this embodiment will be described.
FIG. 8 is a flowchart for explaining the method for manufacturing the sound absorbing body 1 of this embodiment. The diagrams on the right side of FIG. 8 show the state of the sound absorber 1 in each step.
To explain the outline of the manufacturing method, first, a base material for the three-dimensional knitted fabric 20 (hereinafter referred to as “three-dimensional knitted fabric X”) and a base material for the three-dimensional knitted fabric 30 (hereinafter referred to as “three-dimensional knitted fabric Y”) are manufactured, and then Next, the three-dimensional knitted fabric X and the three-dimensional knitted fabric Y are each cut into a predetermined size to obtain a three-dimensional knitted fabric 20 and a three-dimensional knitted fabric 30 . Then, an adhesive is applied to the back base fabric 24 of the three-dimensional knitted fabric 20 and the back side base fabric 34 of the three-dimensional knitted fabric 30 to bond the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 to the front and back surfaces of the support plate 10, respectively.

(Manufacturing three-dimensional knitted fabric X)
In the manufacturing process of the three-dimensional knitted fabric X, the three-dimensional knitted fabric X is manufactured using a knitting machine (double Raschel machine). FIG. 9 is a diagram showing the configuration of a knitting machine 100 having double rows of knitting needles, which is used for knitting a double raschel fabric of three-dimensional knitted fabric. Here, reference numerals L1 to L6 denote guides (reeds) for guiding knitting yarns, reference numeral 103 denotes a trick plate on the front side needle bed, and reference numeral 104 denotes a trick plate on the back side needle bed. there is Reference numeral 101 denotes a front needle, reference numeral 102 denotes a back needle, and reference numeral 105 denotes a distance between hooks.

Ground threads SX1 and SX2 are passed through the guides L1 and L2, and the front side base fabric X2 (22) is formed by the ground threads SX1 and SX2. Ground threads SX5 and SX6 are passed through the guides L5 and L6, and the back side base fabric X4 (24) is formed by the ground threads SX5 and SX6. The base threads SX3 and SX4 of the connecting threads X6 (26) connecting the front base fabric X2 and the back base fabric X4 are passed through the guides L3 and L4. and the rear base cloth X4.

FIG. 10 is a diagram showing an example of a knitting structure of each component yarn used for knitting the three-dimensional knitted fabric X. As shown in FIG. In FIG. 10, "·" (black dots) indicates the positions of the front needles 101 and the back needles 103, with "F" indicating the row of knitting needles on the front side and "B" indicating the row of knitting needles on the back side. there is Also, the numbers below the knitting of each knitting structure indicate the knitting needle position number.

As shown in FIG. 10, the position of the base yarn SX1 of the outermost knitting structure of the front base fabric X2 swings in from the knitting needle position number 3 with respect to the front needle 101 by the guide L1, and over to the knitting needle position number 4. After wrapping, swing out, underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 0, swing out, and underlap to knitting needle position number 3. It is a closed eye that makes one cycle.

The position of the base yarn SX2 of the second knitting structure from the outside of the front side base fabric X2 swings in from the knitting needle position number 1 with respect to the front needle 101 by the guide L2, overlaps to the knitting needle position number 0, and then swings out. , underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 2, swing out, and underwrap to knitting needle position number 1. are the eyes.

The position of the base yarn SX3 of the knitting structure on the front side base fabric X2 side of the connecting yarn X6 is swung in from the knitting needle position number 1 with respect to the front needle 101 by the guide L3, overlapped to the knitting needle position number 0, and then swung out. , underlaps the back needle 102 to the knitting needle position number 3, swings in from the knitting needle position number 3, overlaps to the knitting needle position number 2, swings out, and swings out to the front needle 101 to the knitting needle position number 4. Perform underlap, swing in from knitting needle position number 4, overlap to knitting needle position number 5, swing out, perform underlap on the back needle 102 to knitting needle position number 2, and swing in from knitting needle position number 2. Then, after overlapping up to knitting needle position number 3, swinging out, and performing underlap to knitting needle position number 1, the cycle is performed three times. Swing in from number 1, overlap to knitting needle position number 0, swing out, perform underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 2, and then swing out. This is a closed stitch in which three cycles of underlap to knitting needle position number 1 are performed as one cycle.

The position of the base yarn SX4 of the knitting structure on the back side base fabric X4 side of the connecting yarn X6 is swung in from the knitting needle position number 5 with respect to the front needle 101 by the guide L4, overlapped to the knitting needle position number 4, and then swung out. Then, it underlaps the back needle 102 to the knitting needle position number 3, swings in from the knitting needle position number 3, overlaps to the knitting needle position number 2, swings out, and then swings out to the front needle 101 at the knitting needle position number 0. swing-in from the knitting needle position number 0, overlap to the knitting needle position number 1, swing out, underlap the back needle 102 to the knitting needle position number 2, and swing from the knitting needle position number 2. After performing a cycle of going in, overlapping to knitting needle position number 3, swinging out, and underlap to knitting needle position number 5, the cycle is performed three times, and then underlap is performed to knitting needle position number 1 on the front needle 101, and the knitting needle is underwound to knitting needle position number 1. Swing in from position number 1, overlap to knitting needle position number 0, swing out, perform underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 2, and then swing. One cycle is to perform three cycles of out and underlap to knitting needle position number 1.

The position of the base yarn SX5 of the second knitting structure from the outside of the back side base fabric X4 is underlapped to the knitting needle position number 1 with respect to the back needle 102 by the guide L5, swinging in from the knitting needle position number 1, One cycle is to overlap to knitting needle position number 0 and then swing out, perform underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 2 and then swing out. eyes closed.

The position of the base yarn SX6 of the outermost knitting structure of the back side base fabric X4 underlaps the back needle 102 to the knitting needle position number 2 by the guide L6, swings in from the knitting needle position number 2, and reaches the knitting needle position. One cycle is to swing out after overlapping up to number 3, underlap to knitting needle position number 1, swing in from knitting needle position number 1, overlap to knitting needle position number 0 and swing out. is.

(Manufacturing three-dimensional knitted fabric Y)
In the manufacturing process of the three-dimensional knitted fabric Y, the three-dimensional knitted fabric Y is manufactured using a knitting machine similar to the knitting machine (double Raschel machine) shown in FIG.
When manufacturing the three-dimensional knitted fabric Y, base yarns SY1 and SY2 are passed through the guides L1 and L2, and the front base fabric Y2 (32) is formed by the base yarns SY1 and SY2. Ground threads SY5 and SY6 are passed through the guides L5 and L6, and the back side base fabric Y4 (34) is formed by the ground threads SY5 and SY6. Ground threads SY3 and SY4 of connecting threads Y6 (36) that connect the front side base fabric Y2 and the back side base fabric Y4 are passed through the guides L3 and L4. and the rear base fabric Y4.

FIG. 11 is a diagram showing an example of a knitting structure of each component yarn used for knitting the three-dimensional knitted fabric Y. As shown in FIG. In FIG. 11, "·" (black dots) indicates the positions of the front needles 101 and the back needles 103, the front side knitting needle row is indicated by "F", and the back side knitting needle row is indicated by "B". there is Also, the numbers below the knitting of each knitting structure indicate the knitting needle position number.

As shown in FIG. 11, the position of the base yarn SY1 of the outermost knitting structure of the front base fabric Y2, the position of the base yarn SY2 of the second knitting structure from the outside of the front base fabric Y2, and the position of the back base fabric Y4. The position of the base yarn SY5 of the second knitting structure from the outside and the position of the base yarn SY6 of the outermost knitting structure of the rear base fabric Y4 are the base yarns SX1, SX2, SX5 and SX6 of the three-dimensional knitted fabric X, respectively. It is a closed eye that makes the same movement one cycle.

The position of the base yarn SY3 of the knitting structure on the front side base fabric Y2 side of the connecting yarn Y6 swings in from the knitting needle position number 1 with respect to the front needle 101 by the guide L3, overlaps to the knitting needle position number 0, and then swings out. , underlaps the back needle 102 to the knitting needle position number 3, swings in from the knitting needle position number 3, overlaps to the knitting needle position number 2, swings out, and swings out to the front needle 101 to the knitting needle position number 4. Perform underlap, swing in from knitting needle position number 4, overlap to knitting needle position number 5, swing out, perform underlap on the back needle 102 to knitting needle position number 2, and swing in from knitting needle position number 2. One cycle is a closed stitch in which the stitch overlaps to the knitting needle position number 3, swings out, and underlaps to the knitting needle position number 1.

The position of the base yarn SY4 of the knitting structure on the back side base fabric Y4 side of the connecting yarn Y6 swings in from the knitting needle position number 5 with respect to the front needle 101 by the guide L4, overlaps to the knitting needle position number 4, and then swings out. Then, it underlaps the back needle 102 to the knitting needle position number 3, swings in from the knitting needle position number 3, overlaps to the knitting needle position number 2, swings out, and then swings out to the front needle 101 at the knitting needle position number 0. swing-in from the knitting needle position number 0, overlap to the knitting needle position number 1, swing out, underlap the back needle 102 to the knitting needle position number 2, and swing from the knitting needle position number 2. It is an open stitch in which one cycle is to go in, overlap to knitting needle position number 3, swing out, and underlap to knitting needle position number 5.

(cutting)
Returning to FIG. 8, in the cutting step, the three-dimensional knitted fabric X and the three-dimensional knitted fabric Y are cut to obtain the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of a predetermined size (for example, width: 600 mm, height: 1300 mm).

(Adhesion of support plate 10 and three-dimensional knitted fabrics 20, 30)
In the bonding step, an adhesive is applied to the ends of the partition walls 12 facing the front and back surfaces of the support plate 10 . Specifically, for example, a heated gravure coater is used to apply a hot-melt resin to the ends of the partition walls 12 in scattered dots. Then, the three-dimensional knitted fabric 20 is adhered to the front surface of the support plate 10, the three-dimensional knitted fabric 30 is adhered to the back surface, and the adhesive is hardened by being left at room temperature for about 48 hours.

Thus, in the present embodiment, the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 having different air permeability are laminated on the front and back sides of the support plate 10 to obtain the sound absorber 1 . Therefore, according to such a sound absorber 1, when sound passes through the three-dimensional knitted fabrics 20 and 30, heat is generated due to friction between the air inside the three-dimensional knitted fabrics 20 and 30 and the fibers, and friction between the fibers. A part of the sound energy is converted into heat energy, so the sound energy is reduced (that is, the sound absorption effect is exhibited). And, as a result, at least sounds of 300-6300 Hz are absorbed.
In addition, since the sound that cannot be completely absorbed by the three-dimensional knitted fabrics 20 and 30 propagates to the air in the opening 15 of the support plate 10, part of it is canceled in the opening 15 by the resonance effect (that is, sound absorbing effect). As a result, sounds in the low frequency range (100 to 1000 Hz) are absorbed.
In the configuration of the present embodiment, the knitting structure of the connecting yarn 26 of the three-dimensional knitted fabric 20 and the knitting structure of the connecting yarn X6 of the three-dimensional knitted fabric 30 are different, and the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 have different air permeability. Since the knitted fabric 20 and the three-dimensional knitted fabric 30 have different air flows (that is, vibrational propagation of acoustic particles), the wavelengths of sound absorbed by them are slightly different. As described above, in the present embodiment, by appropriately setting the air permeability (first air permeability) of the three-dimensional knitted fabric 20 and the air permeability (second air permeability) of the three-dimensional knitted fabric 30, sounds of different frequency bands can be generated. It is configured to absorb, thereby efficiently absorbing sound in a wide frequency band.

Next, specific examples of the sound absorber 1 will be shown. It should be noted that the sound absorbing body of the present invention is not limited to this example.

1. Manufacture of three-dimensional knitted fabric As a knitting machine, a double Raschel machine RD6DPLM / 8 / RD6DPLM / 12-3 manufactured by Karl Mayer (22 gauge / 2.54 cm, distance between hooks 10 mm) is used, and the following three-dimensional knitted fabrics X and Y manufactured.
The three-dimensional knitted fabrics X and Y have a finished thickness of 10 mm±1.0 mm.

(Manufacturing three-dimensional knitted fabric X)
Using the ground yarns SX1 to SX6 below, a three-dimensional knitted fabric X was produced according to the knitting method described above.
SX1: Cotton (Spun yarn: No. 30)
SX2: Cotton (Spun yarn: No. 30)
SX3: Polyester monofilament thread (220 decitex)
SX4: Polyester processed yarn (167 decitex, filament count 48)
SX5: Cotton (Spun yarn: No. 30)
SX6: Cotton (Spun yarn: No. 30)

The air permeability of the obtained three-dimensional knitted fabric X was measured at an air pressure of 125 Pa according to JIS L 1096 A method. As a result, the air permeability of the three-dimensional knitted fabric X was 24.8 cm ³ /cm ² /sec.

(Manufacturing three-dimensional knitted fabric Y)
Using the ground yarns SY1 to SY6 below, a three-dimensional knitted fabric Y was produced according to the knitting method described above.
SY1: Polyester processed yarn (220 decitex, filament count 72)
SY2: Polyester processed yarn (220 decitex, filament count 72)
SY3: Polyester monofilament yarn (220 decitex)
SY4: Polyester processed yarn (167 decitex, filament count 48)
SY5: Polyester regular thread (167 decitex, filament count 48)
SY6: Polyester regular thread (167 decitex, filament count 48)

The air permeability of the obtained three-dimensional knitted fabric Y was measured in the same manner as described above. As a result, the air permeability of the three-dimensional knitted fabric Y was 15 cm ³ /cm ² /sec.

2. Manufacture of sound absorbing body The three-dimensional knitted fabric X and the three-dimensional knitted fabric Y thus obtained are cut to produce a three-dimensional knitted fabric 20 and a three-dimensional knitted fabric 30 having a width of 600 mm, a height of 1300 mm, and a thickness of 10 mm. A knitted fabric 30 is adhered to the front and rear surfaces of a support plate 10 having a width of 600 mm, a height of 1300 mm, and a thickness of 40 mm, to form a sound absorbing rectangular plate having a width of 600 mm, a height of 1300 mm, and a thickness of 60 mm. Got 1 body.

3. Measurement of reverberation room method sound absorption coefficient For the sound absorber 1 of this example, in a reverberation room with a temperature of 11.1 ° C. and a humidity of 57% RH, "Reverberation room method sound absorption coefficient test" specified in JIS A 1409: 1998 The sound absorption coefficient and reverberation time were measured according to "Method".
FIG. 12 is a graph showing the results of measuring the sound absorption coefficient with one sound absorber 1 standing on the floor of a reverberation room. Moreover, FIG. 13 is a graph showing the result of measuring the reverberation time with one sound absorber 1 standing on the floor of the reverberation room. In order to clarify the effect of the sound absorber 1, FIG. 13 also shows the measurement results in the case where there is no sound absorber in the reverberation room.

As shown in FIG. 12, it was found that the sound absorber 1 of this example is lightweight and has very high sound absorption characteristics at least in the frequency band of 300 to 10000 Hz.
Further, as shown in FIG. 13, according to the sound absorber 1 of the present embodiment, the reverberation time can be reduced in the entire frequency band (100 to 10000 Hz) (that is, the reverberation of sound can be suppressed regardless of the pitch of the sound). I found out. In addition, since this effect is particularly remarkable in the low-frequency noise band of 250 to 1000 Hz, it was found that the sound absorber 1 is effective when it is desired to adjust the resonance of sound indoors such as a house. .
Since the sound absorber 1 of this embodiment is made of paperboard, cotton, and polyester, it does not generate toxic gas even if it burns, and is environmentally friendly.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above configurations, and various modifications are possible within the scope of the technical idea of the present invention. .

For example, the sound absorber 1 of the present embodiment is used while being erected so as to be perpendicular to the floor surface (that is, arranged so as to be substantially parallel to the vertical direction (vertical direction in FIG. 1)), Although it has been described as being able to absorb sound from both sides, it can be arranged parallel to the floor surface (that is, either the three-dimensional knitted fabric 20 or the three-dimensional knitted fabric 30 is in contact with the floor surface), or parallel to the wall surface ( That is, it is also possible to arrange so that either one of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 is in contact with the wall surface, and to absorb sound from either one of the three-dimensional knitted fabric 20 or the three-dimensional knitted fabric 30 . When the sound absorbing body 1 is arranged so as to be perpendicular to the floor surface (that is, when arranged so that sound can be absorbed on both sides), the sound absorbing area is doubled compared to the case of one-sided sound absorption. Dramatically improves sound absorption performance.
Further, although the sound absorber 1 of the present embodiment has been described as having a rectangular plate shape, a plurality of sound absorbers 1 can be combined in an L shape or a cross shape using a stay or the like. . Using a plurality of sound absorbing bodies 1 in this manner further increases the sound absorbing area, thereby further improving the sound absorbing performance.

Further, in the support plate 10 of the sound absorber 1 of the present embodiment, the substantially cylindrical partition walls 12 are arranged two-dimensionally, and in plan view, a plurality of circular openings 15 are arranged two-dimensionally in a hexagonally dense manner. However, it is not limited to such a shape. A space is formed inside the support plate 10 and an air layer is formed between the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30, and the shape of the partition wall 12 of the support plate 10 can be changed to another shape.

[Modified example of support plate 10]
14 and 15 are diagrams showing modifications of the support plate 10 of the sound absorber 1 according to the embodiment of the present invention. FIG. 14 is a plan view of a support plate 10A of this modified example, and FIG. 15 is a photograph of one surface of the support plate 10A taken from an oblique direction. As shown in FIGS. 14 and 15, the support plate 10A is a rectangular plate-shaped member (for example, width: 600 mm, height: 1300 mm, thickness: 40 mm) formed by bonding a plurality of paperboards. and a plurality of corrugated partitions 14 arranged between the partitions 13 so as to connect the pair of partitions 13 . The support plate 10A has a plurality of wave-shaped openings 15A densely arranged two-dimensionally in plan view.

FIG. 16 is a graph showing the result of measuring the sound absorption coefficient of the sound absorber 1A provided with the support plate 10A of this modified example, which was allowed to stand on the floor of the reverberation room. FIG. 17 is a graph showing the results of measuring the reverberation time when the sound absorber 1A provided with the support plate 10A of this modified example is allowed to stand on the floor of the reverberation room. In order to clarify the effect of the sound absorber 1A, FIG. 17 also shows the measurement results in the case where there is no sound absorber in the reverberation room.

As shown in FIG. 16, the sound absorber 1A including the support plate 10A of this modified example also has very high sound absorption characteristics in the frequency band of at least 300 to 10000 Hz, like the sound absorber 1 described above.
Further, as shown in FIG. 17, the sound absorber 1A including the support plate 10A of the present modified example can also reduce the reverberation time in the entire frequency band (100 to 10000 Hz) as in the sound absorber 1 (that is, the sound It can be seen that the resonance of the sound can be suppressed regardless of the pitch). Moreover, since this effect is particularly remarkable in the low-frequency noise band of 250 to 1000 Hz, it can be seen that the sound absorber 1A is also effective when it is desired to adjust the resonance of sound indoors such as a house.

In addition, the embodiments disclosed this time should be considered as examples in all respects and not as restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

Reference Signs List 1, 1A sound absorber 10, 10A support plate 12, 13, 14 partition wall 15, 15A opening 20, 30 three-dimensional knitted fabric 22, 32 front base fabric 24, 34 rear base fabric 26, 36 connecting thread 50 adhesive X, Y Three-dimensional knitted fabric X2, Y2 Front base fabric X4, Y4 Back base fabric X6, Y6 Connecting thread 100 Knitting machine 101 Front needle 102 Back needle 103, 104 Trick plate 105 Between hooks L1, L2, L3, L4, L5, L6 Guide SX1 , SX2, SX3, SX4, SX5, SX6 ground thread SY1, SY2, SY3, SY4, SY5, SY6 ground thread

Claims (10)

sheet-like first and second three-dimensional knitted fabrics knitted from a pair of base fabrics spaced apart from each other and connecting yarns that reciprocate between the base fabrics and connect them;
a support plate disposed between the first three-dimensional knitted fabric and the second three-dimensional knitted fabric and supporting the first three-dimensional knitted fabric and the second three-dimensional knitted fabric on the front and back sides, respectively;
with
The first three-dimensional knitted fabric has a first air permeability,
The second three-dimensional knitted fabric has a second air permeability different from the first air permeability,
A sound absorbing body, wherein the support plate has air permeability at least in a plate thickness direction and forms an air layer between the first three-dimensional knitted fabric and the second three-dimensional knitted fabric. 2. The sound absorber according to claim 1, wherein the support plate has a plurality of circular openings densely arranged two-dimensionally in plan view. 2. The sound absorber according to claim 1, wherein the support plate has a plurality of wavy openings densely arranged two-dimensionally in plan view. 4. The sound absorber according to any one of claims 1 to 3, wherein the support plate is made of paperboard. According to any of claims 1 to 4, the first air permeability is 20 to 30 cm ³ /cm ² /sec, and the second air permeability is 10 to 20 cm ³ /cm ² /sec. A sound absorber according to any one of claims 1 to 3. The sound absorbing body according to any one of claims 1 to 5, wherein the first and second three-dimensional knitted fabrics have a thickness of 10 to 20 mm. 7. The sound absorber according to any one of claims 1 to 6, wherein the support plate has a thickness of 30 to 50 mm. The sound absorber according to any one of claims 1 to 7, wherein the sound absorber is arranged and used so as to be substantially parallel to the vertical direction. The sound absorber according to any one of claims 1 to 8, wherein the sound absorber has an absorption band in at least a sound range of 300 to 10,000 Hz. 10. The sound absorber according to any one of claims 1 to 9, wherein the sound absorber suppresses reverberation in a sound range of at least 250 to 1000 Hz.

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