JP2024053114A - Sound absorbing body - Google Patents

Abstract

[Problem] To provide a sound absorber that exhibits an excellent sound absorbing effect in the range of sound generated by daily life noises and has an excellent reverberation suppression effect in the low frequency range. [Solution] The sound absorber comprises a pair of base fabrics arranged apart from each other, sheet-like first and second three-dimensional knitted fabrics knitted with a connecting yarn that travels back and forth between the base fabrics to connect them, and a support plate arranged between the first and second three-dimensional knitted fabrics and supporting the first and second three-dimensional knitted fabrics on the front and back, respectively. The first three-dimensional knitted fabric has an air permeability of 20 to 30 cm3/cm2/sec, the second three-dimensional knitted fabric has an air permeability of 10 to 20 cm3/cm2/sec, the support plate is air permeable at least in the thickness direction, and forms an air layer between the first and second three-dimensional knitted fabrics, and the connecting yarn is composed of a synthetic fiber monofilament and a synthetic fiber processed yarn. [Selected Figure] Figure 1

Description

The present invention relates to a sound absorber that is installed indoors to absorb sound within the room, and in particular to a sound absorber formed into a panel shape by combining two types of sheet-like three-dimensional knitted fabric.

Conventionally, noise control measures have been implemented by installing sound-absorbing materials on the walls and ceilings of concert halls, music rooms, etc. For example, Patent Document 1 discloses a sound-absorbing material that exhibits a sound-absorbing effect against sounds in a wide frequency range, including low frequencies, and a sound-absorbing device that uses this sound-absorbing material.

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

JP 2009-299332 A

The sound-absorbing material in Patent Document 1 has a certain sound-absorbing effect on sounds in a relatively wide frequency range, including the low frequency range, but the sound-absorbing effect is not sufficient in the range of everyday noise (600 to 2000 Hz), and there is a demand for the development of a sound-absorbing body (i.e., a sound-absorbing material or sound-absorbing device) with even better sound-absorbing effects.

In recent years, sound-absorbing devices and panels have been installed on the walls and corners of rooms in ordinary homes and conference rooms to improve acoustics (i.e., to reduce reverberation). For such applications, it is necessary to reduce reverberation in the low-frequency range (100 to 1000 Hz), and there is a demand for the development of sound absorbers that are excellent at reducing reverberation in the low-frequency range.

The present invention was made in consideration of the above circumstances, and aims to provide a sound absorber that exhibits excellent sound absorption effects in the range of everyday noise and has excellent reverberation suppression effects in the low frequency range.

In order to achieve the above-mentioned object, the inventors conducted intensive research and discovered that a sheet-like three-dimensional knitted fabric having a predetermined breathability is effective in absorbing sounds in the range of everyday noise (600 to 2000 Hz).
Furthermore, the inventors discovered that by combining two types of sheet-like three-dimensional knitted fabrics with different breathability to form a panel and forming an air layer between them (i.e., between the two types of three-dimensional knitted fabrics), it is possible to create a sound absorber that has extremely high sound absorption properties in at least the 300 to 10,000 Hz frequency range and also exhibits excellent reverberation suppression effects in the low frequency range (100 to 1,000 Hz), thereby completing the present invention.

That is, the sound absorber of the present invention comprises first and second three-dimensional knitted fabrics in a sheet shape woven from a pair of base fabrics arranged at a distance from each other and a connecting yarn that passes back and forth between the base fabrics to connect them, and a support plate arranged between the first and second three-dimensional knitted fabrics and supporting the first and second three-dimensional knitted fabrics on the front and back, respectively, wherein the first three-dimensional knitted fabric has an air permeability of 20 to 30 cm ³ /cm ² /sec and the second three-dimensional knitted fabric has an air permeability of 10 to 20 cm ³ /cm ² /sec, the support plate is air permeable at least in the thickness direction, forms an air layer between the first and second three-dimensional knitted fabrics, and the connecting yarn is composed of a synthetic fiber monofilament and a synthetic fiber processed yarn.

With this configuration, two types of sheet-like three-dimensional knitted fabrics with different breathability are combined into a panel shape, and an air layer is formed between them (i.e., between the two types of three-dimensional knitted fabrics), resulting in a sound absorber that exhibits excellent sound absorption effects in the range of everyday noise and has excellent reverberation suppression effects in the low-frequency range.

It is also preferable that the connecting yarn has a viscosity of 150 to 220 decibels.
It is also preferable that the connecting thread is made of polyester.
It is also preferable that the ground yarn forming the pair of base fabrics is made of spun yarn. In this case, it is also preferable that the ground yarn forming the pair of base fabrics has a density of 150 to 220 decibels.
Moreover, it is preferable that the ground yarns forming the pair of base fabrics are made of cotton or polyester.

It is also desirable that the thickness of the first and second three-dimensional knitted fabrics be 10 to 20 mm.

The support plate can also be configured to have multiple circular openings that are densely arranged two-dimensionally when viewed in a plan view.

The support plate can also be configured to have a number of corrugated openings that are densely arranged two-dimensionally when viewed in a plane.

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

It is also desirable for the thickness of the support plate to be 30 to 50 mm.

It is also desirable for the sound absorbing material to be positioned so that it is approximately parallel to the vertical direction.

It is also desirable for the sound absorber to have an absorption band in the range of at least 300 to 10,000 Hz.

It is also desirable for the sound absorber to suppress reverberation in the range of at least 250 to 1000 Hz.

As described above, the present invention provides a sound absorbing body that exhibits excellent sound absorbing effects in the range of everyday noise and has excellent reverberation suppression effects in the low frequency range.

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

The following describes in detail an embodiment of the present invention with reference to the drawings. However, unless otherwise specified, the components, types, combinations, materials, shapes, and relative positions described in the embodiment are merely illustrative examples and do not intend to limit the scope of the invention thereto. In addition, the same or corresponding parts in the drawings are given the same reference numerals and their descriptions will not be repeated.

(Configuration of sound absorbing body 1)
1 and 2 are diagrams showing the configuration of a sound absorber 1 according to an embodiment of the present invention, in which FIG. 1 is a perspective view of the sound absorber 1, and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. As shown in FIG. 1, the sound absorber 1 according to this embodiment has a rectangular plate shape (for example, width: 600 mm, height: 1300 mm, thickness: 70 mm), and is used, for example, by standing perpendicular to a floor surface (that is, arranged so as to be approximately parallel to the vertical direction (up and down direction in FIG. 1)). The sound absorber 1 is formed of a support plate 10, and a three-dimensional knit 20 (first three-dimensional knit) and a three-dimensional knit 30 (second three-dimensional knit) bonded to the front and back surfaces of the support plate 10, respectively. The support plate 10 has a plurality of openings 15 arranged two-dimensionally in a hexagonal close-packed manner, and has air permeability at least in the plate thickness direction (details will be described later), so that an air layer is formed between the three-dimensional knit 20 and the three-dimensional knit 30.

With such a sound absorber 1, when sound passes through each of the three-dimensional knits 20, 30, heat is generated due to friction between the air and the fibers inside the three-dimensional knits 20, 30 and friction between the fibers, and part of the sound energy is converted into thermal energy, thereby reducing the sound energy (i.e., a sound absorption effect is achieved).
In addition, any sound that is not completely absorbed by each three-dimensional knitted fabric 20, 30 propagates into the air within the opening 15 of the support plate 10, and some of the sound is canceled out within the opening 15 due to the resonance effect (i.e., a sound absorption effect is achieved).

(Configuration of Support Plate 10)
Fig. 3 is a plan view of the support plate 10 of the present embodiment. Fig. 4 is a photograph of one side of the support plate 10 of the present embodiment taken from an oblique direction. As shown in Figs. 3 and 4, the support plate 10 of the present embodiment is a rectangular plate-like member (e.g., width: 600 mm, height: 1300 mm, thickness: 40 mm) formed by bonding a plurality of paperboards, in which approximately cylindrical partition walls 12 having a diameter of about 15 mm and a height of about 40 mm are arranged two-dimensionally, and a plurality of circular openings 15 are arranged two-dimensionally in a hexagonal close-packed manner in a plan view.
The support plate 10 is formed, for example, by bonding together pieces of paperboard of a given width (for example, 40 mm) that are curved into an eight-shape and then joined (bonded) onto a flat surface (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 board structure, so it has very high rigidity in the thickness direction (the direction perpendicular to the paper surface in FIG. 3) of the support plate 10. In addition, since a plurality of circular openings 15 are formed in the thickness direction, the air flow is not blocked at least in the thickness direction, and the support plate 10 has sufficient breathability.

(Configuration of the three-dimensional knitted fabric 20 and the 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 a rectangular sheet-like (e.g., width: 600 mm, height: 1300 mm, thickness: 10 mm) double raschel three-dimensional base fabric knitted from the front base fabrics 22, 32 and the rear base fabrics 24, 34 arranged at a distance from each other, and the connecting yarns 26, 36 that connect the front base fabrics 22, 32 and the rear base fabrics 24, 34 by reciprocating between them. In this embodiment, the three-dimensional knitted fabric 20 is configured to have an air permeability of about 20 to 30 ^cm3 / ^cm2 /sec, and the three-dimensional knitted fabric 30 is configured to have an air permeability of about 10 to 20 ^cm3 / ^cm2 /sec.

The knitting structure of the ground yarns 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, it is preferable that the knitting structure of the rear base fabrics 24, 34 has a flat knit 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 to maintain the distance between the front base fabrics 22, 32 and the rear base fabrics 24, 34, and are a part that contributes greatly to adjusting the breathability of the three-dimensional knitted fabrics 20 and 30, as well as providing cushioning properties. Therefore, it is preferable that the structure formed by the connecting yarns 26, 36 has a large underlap and is thick.

The yarn materials for knitting the front base fabrics 22, 32 and the rear base fabrics 24, 34 of the three-dimensional knitted fabrics 20, 30 are preferably spun yarns (short fibers) made of natural fibers (cotton) or synthetic fibers (polyester, acrylic, nylon, rayon, etc.) from the standpoints of flexibility, durability, weather resistance, and abrasion resistance.

In addition, the materials for the connecting yarns 26, 36 of the three-dimensional knits 20, 30 are preferably made of synthetic fiber processed yarns such as polyester or nylon and synthetic fiber monofilament yarns, respectively, in order to ensure appropriate breathability and thickness of the three-dimensional knits 20, 30.
In addition, by using synthetic fiber processed yarn, it is possible to reduce the air permeability of the three-dimensional knitted fabrics 20, 30. On the other hand, by using synthetic fiber monofilament yarn, it is possible to ensure the thickness of the three-dimensional knitted fabrics 20, 30.

The thickness of the connecting yarns 26, 36 is preferably thicker in order to ensure the appropriate breathability and thickness of the three-dimensional knitted fabrics 20, 30 and to obtain high shape stability, and is actually determined by the specifications of the knitting machine used. For example, when using a Karl Mayer double raschel machine RD6DPLM/8 or RD6DPLM/12-3 (22 gauge/2.54 cm) as the knitting machine, the limit value of the thickness that can be placed on one needle is 529 denier/588 dtex for long fibers and 310 denier/345 dtex for short fibers. For this reason, it is desirable for each yarn to be around 150 to 220 dtex.

The thickness of the three-dimensional knitted fabrics 20, 30 is preferably thicker in order to ensure sufficient cushioning and resilience while maintaining a suitable degree of breathability. However, if the thickness of the three-dimensional knitted fabrics 20, 30 is increased, post-processing of the three-dimensional knitted fabrics 20, 30 becomes difficult and the amount of yarn consumed increases, so the thickness is preferably about 10 to 20 mm, and more preferably about 12 to 18 mm.

5 is a graph showing the sound absorption characteristics of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30, with the vertical axis representing sound absorption coefficient (%) and the horizontal axis representing frequency (Hz). The graph in FIG. 5 shows the results obtained by a normal incidence sound absorption coefficient test (based on JIS A 1405-2 and ISO 10534-2:1998).
5, the sound absorption coefficient of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of this embodiment gradually increases from about 300 Hz, then increases sharply from about 800 Hz, and reaches about 100% at 4000 to 6300 Hz. In this way, the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of this embodiment can absorb sounds in the range of everyday noise (600 to 2000 Hz).
6 and 7 are photographs showing the appearance of the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 of the present 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 by an adhesive.
Examples of adhesives that can be used include acrylic resin adhesives, α-olefin adhesives, urethane resin adhesives, hot melt adhesives, etc. Among these, hot melt adhesives are preferred because they can be bonded in a short time, have excellent processability, and do not use solvents.
The hot melt adhesive may be in the form of, for example, a powder, liquid, gel, or the like, with the powder being particularly preferred from the viewpoint of ease of handling.

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, the "Hibon" (registered trademark) series manufactured by Hitachi Chemical Polymer Co., Ltd., the "Takemelt" (registered trademark) MA series manufactured by Mitsui Takeda Chemical Co., Ltd., the "Aronmelt" (registered trademark) R series manufactured by Toa Gosei Co., Ltd., the "Nitite" (registered trademark) ARX series manufactured by Nitta Gelatin Co., Ltd., and the "Bond" (registered trademark) KUM series manufactured by Konishi Co., Ltd.

(Method of manufacturing sound absorber 1)
Next, a method for manufacturing the sound absorber 1 of this embodiment will be described.
Fig. 8 is a flow chart for explaining the method for manufacturing the sound absorber 1 of this embodiment. The diagrams on the right side of Fig. 8 show the state of the sound absorber 1 in each process.
To give an overview of the manufacturing method, first, the base material of the three-dimensional knit fabric 20 (hereinafter referred to as "three-dimensional knit fabric X") and the base material of the three-dimensional knit fabric 30 (hereinafter referred to as "three-dimensional knit fabric Y") are manufactured, and then the three-dimensional knit fabric X and the three-dimensional knit fabric Y are cut to a predetermined size, respectively, to obtain the three-dimensional knit fabric 20 and the three-dimensional knit fabric 30. Then, adhesive is applied to the rear base fabric 24 of the three-dimensional knit fabric 20 and the rear base fabric 34 of the three-dimensional knit fabric 30, and the three-dimensional knit fabric 20 and the three-dimensional knit fabric 30 are adhered to the front and back surfaces of the support plate 10, respectively.

(Production of three-dimensional knitted fabric X)
In the manufacturing process of the three-dimensional knitted fabric X, a knitting machine (double raschel machine) is used to manufacture the three-dimensional knitted fabric X. Fig. 9 is a diagram showing the configuration of a knitting machine 100 having a double row of knitting needles used to knit a three-dimensional double raschel fabric. Here, symbols L1 to L6 indicate guides (reeds) that introduce the knitting yarn, symbol 103 indicates a trick plate on the front needle bed, and symbol 104 indicates a trick plate on the back needle bed. Also, symbol 101 indicates a front needle, symbol 102 indicates a back needle, and symbol 105 indicates a shuttle.

The ground yarns SX1 and SX2 are threaded through the guides L1 and L2, and the ground yarns SX1 and SX2 form the front base fabric X2 (22). The ground yarns SX5 and SX6 are threaded through the guides L5 and L6, and the ground yarns SX5 and SX6 form the rear base fabric X4 (24). The ground yarns SX3 and SX4 of the connecting yarn X6 (26) that connects the front base fabric X2 and the rear base fabric X4 are threaded through the guides L3 and L4, and the ground yarns SX3 and SX4 form a gap between the front base fabric X2 and the rear base fabric X4.

Figure 10 is a diagram showing an example of the knitting structure of each constituent yarn used to knit three-dimensional knitted fabric X. In Figure 10, "." (black dot) indicates the position of the front needle 101 and the back needle 103, with the front side knitting needle row indicated by "F" and the back side knitting needle row indicated by "B". The numbers below the knitting of each knitting structure indicate the knitting needle position number.

As shown in FIG. 10, the position of the ground yarn SX1 of the outermost knitting structure of the front base fabric X2 is swung in from needle position number 3 relative to the front needle 101 by the guide L1, overlaps to needle position number 4, then swings out, underlaps to needle position number 1, swings in from needle position number 1, overlaps to needle position number 0, then swings out, and underlaps to needle position number 3, forming one cycle of closure.

The position of the ground yarn SX2 of the second knitting structure from the outside of the front base fabric X2 is a closed loop in which the guide L2 swings in from needle position number 1 relative to the front needle 101, overlaps to needle position number 0, then swings out, underlaps to needle position number 1, swings in from needle position number 1, overlaps to needle position number 2, swings out, and underlaps to needle position number 1, completing one cycle.

The position of the ground yarn SX3 of the knitted structure on the front base fabric X2 side of the connecting yarn X6 is swung in from knitting needle position number 1 with respect to the front needle 101 by the guide L3, overlaps to knitting needle position number 0 and then swings out, underlaps to knitting needle position number 3 with respect to the back needle 102, swings in from knitting needle position number 3, overlaps to knitting needle position number 2 and then swings out, underlaps to knitting needle position number 4 with respect to the front needle 101, swings in from knitting needle position number 4, overlaps to knitting needle position number 5 and then swings out, and underlaps to knitting needle position number 2 with respect to the back needle 102. The back needle 102 is then underlapped to needle position number 1, swung in from needle position number 1, overlapped to needle position number 0, swung out, underlapped to needle position number 1, swung in from needle position number 1, overlapped to needle position number 2, swung out, and underlapped to needle position number 1. This cycle is repeated three times, making one closed stitch.

The position of the ground yarn SX4 of the knitted structure on the rear base fabric X4 side of the connecting yarn X6 is swung in from knitting needle position number 5 with respect to the front needle 101 by the guide L4, overlaps to knitting needle position number 4 and then swings out, underlaps to knitting needle position number 3 with respect to the back needle 102, swings in from knitting needle position number 3, overlaps to knitting needle position number 2 and then swings out, underlaps to knitting needle position number 0 with respect to the front needle 101, swings in from knitting needle position number 0, overlaps to knitting needle position number 1 and then swings out, underlaps to knitting needle position number 2 with respect to the back needle 102, One cycle consists of three cycles of wrapping, swinging in from needle position number 2, overlapping to needle position number 3, swinging out, and underlapping to needle position number 5, then underlapping to needle position number 1 for the front needle 101, swinging in from needle position number 1, overlapping to needle position number 0, swinging out, underlapping to needle position number 1, swinging in from needle position number 1, overlapping to needle position number 2, swinging out, and underlapping to needle position number 1.

The position of the ground yarn SX5 of the second knitting structure from the outside of the rear base fabric X4 is a closed loop in which the guide L5 underlaps the back needle 102 to needle position number 1, swings in from needle position number 1, overlaps to needle position number 0, then swings out, underlaps to needle position number 1, swings in from needle position number 1, overlaps to needle position number 2, then swings out, completing one cycle.

The position of the ground yarn SX6 of the outermost knitted structure of the rear base fabric X4 is a closed loop in which the guide L6 underlaps the back needle 102 up to needle position number 2, swings in from needle position number 2, overlaps up to needle position number 3, then swings out, underlaps up to needle position number 1, swings in from needle position number 1, overlaps up to needle position number 0, then swings out, completing one cycle.

(Production of 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, ground yarns SY1 and SY2 are threaded through the guides L1 and L2, and the ground yarns SY1 and SY2 form a front base fabric Y2 (32). Ground yarns SY5 and SY6 are threaded through the guides L5 and L6, and the ground yarns SY5 and SY6 form a rear base fabric Y4 (34). Ground yarns SY3 and SY4 of a connecting yarn Y6 (36) that connects the front base fabric Y2 and the rear base fabric Y4 are threaded through the guides L3 and L4, and a gap is formed between the front base fabric Y2 and the rear base fabric Y4 by the ground yarns SY3 and SY4.

Figure 11 is a diagram showing an example of the knitting structure of each constituent yarn used to knit the three-dimensional knitted fabric Y. In Figure 11, "." (black dot) indicates the position of the front needle 101 and the back needle 103, with the front side knitting needle row indicated by "F" and the back side knitting needle row indicated by "B". The numbers below the knitting of each knitting structure indicate the knitting needle position number.

As shown in FIG. 11, the position of the ground yarn SY1 of the outermost knitted structure of the front base fabric Y2, the position of the ground yarn SY2 of the second knitted structure from the outside of the front base fabric Y2, the position of the ground yarn SY5 of the second knitted structure from the outside of the rear base fabric Y4, and the position of the ground yarn SY6 of the outermost knitted structure of the rear base fabric Y4 are each a closed loop that has one cycle of movement similar to that of the ground yarns SX1, SX2, SX5, and SX6 of the three-dimensional knit fabric X.

The position of the ground yarn SY3 of the knitted structure on the front base fabric Y2 side of the connecting yarn Y6 is swung in from needle position number 1 with respect to the front needle 101 by the guide L3, overlaps to needle position number 0 and then swings out, underlaps to needle position number 3 with respect to the back needle 102, swings in from needle position number 3, overlaps to needle position number 2 and then swings out, underlaps to needle position number 4 with respect to the front needle 101, swings in from needle position number 4, overlaps to needle position number 5 and then swings out, underlaps to needle position number 2 with respect to the back needle 102, swings in from needle position number 2, overlaps to needle position number 3 and then swings out, and underlaps to needle position number 1 with respect to the back needle 102, swings in from needle position number 2, overlaps to needle position number 3 and then swings out, forming one cycle of closed stitches.

The position of the ground yarn SY4 of the knitted structure on the rear base fabric Y4 side of the connecting yarn Y6 is an opening stitch that swings in from needle position number 5 with respect to the front needle 101 by the guide L4, overlaps to needle position number 4, then swings out, underlaps to needle position number 3 with respect to the back needle 102, swings in from needle position number 3, overlaps to needle position number 2, then swings out, underlaps to needle position number 0 with respect to the front needle 101, swings in from needle position number 0, overlaps to needle position number 1, then swings out, underlaps to needle position number 2 with respect to the back needle 102, swings in from needle position number 2, overlaps to needle position number 3, then swings out, and underlaps to needle position number 5, completing one cycle.

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

(Adhesion of the support plate 10 and the three-dimensional knitted fabrics 20, 30)
In the bonding process, 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 hot melt resin is applied in a scattered manner to the ends of the partition walls 12 using a heated gravure coater. Then, the three-dimensional knitted fabric 20 is bonded to the front surface of the support plate 10, the three-dimensional knitted fabric 30 is bonded to the back surface of the support plate 10, and the adhesive is allowed to harden by leaving it at room temperature for about 48 hours.

In this embodiment, the sound absorber 1 is obtained by laminating the three-dimensional knitted fabrics 20 and 30 with different air permeabilities on the front and back of the support plate 10. Therefore, with 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 and the fibers inside the three-dimensional knitted fabrics 20 and 30 and friction between the fibers, and part of the sound energy is converted into thermal energy, so that the sound energy is reduced (i.e., a sound absorbing effect is achieved). As a result, at least sounds of 300 to 6300 Hz are absorbed.
Furthermore, the sound that is not completely absorbed by the three-dimensional knitted fabrics 20, 30 propagates to the air in the opening 15 of the support plate 10, and a part of the sound is cancelled out in the opening 15 by the resonance effect (i.e., a sound absorbing effect is exerted). As a result, sound in the low frequency range (100 to 1000 Hz) is absorbed.
In the configuration of this embodiment, the knitting structure of the connecting yarn 26 of the three-dimensional knitted fabric 20 is different from the knitting structure of the connecting yarn X6 of the three-dimensional knitted fabric 30, and the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30 have different air permeabilities, and therefore the air flows (i.e., vibration propagation of acoustic particles) are different between the three-dimensional knitted fabric 20 and the three-dimensional knitted fabric 30, and the wavelengths of the sounds absorbed by each of them are slightly different. Thus, in this embodiment, 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 are appropriately set to absorb sounds of different frequency bands, thereby efficiently absorbing sounds of a wide frequency band.

Next, a specific example of the sound absorber 1 is shown. Note that the sound absorber of the present invention is not limited to this example.

1. Production of Three-Dimensional Knit Fabrics The following three-dimensional knit fabrics X and Y were produced using a double raschel machine RD6DPLM/8 and RD6DPLM/12-3 (22 gauge/2.54 cm, hook distance 10 mm) manufactured by Karl Mayer.
The three-dimensional knitted fabrics X and Y had a finished thickness of 10 mm±1.0 mm.

(Production of three-dimensional knitted fabric X)
Using the following ground yarns SX1 to SX6, a three-dimensional knitted fabric X was produced according to the knitting method described above.
SX1: Cotton (spun yarn: 30 count)
SX2: Cotton (spun yarn: 30 count)
SX3: Polyester monofilament yarn (220 decitex)
SX4: Polyester textured yarn (167 decitex, 48 filament count)
SX5: Cotton (spun yarn: 30 count)
SX6: Cotton (spun yarn: 30 count)

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

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

The air permeability of the resulting three-dimensional knitted fabric Y was measured in the same manner as above, and the result was that the air permeability of the three-dimensional knitted fabric Y was 15 cm ³ /cm ² /sec.

2. Manufacturing of sound absorber The obtained three-dimensional knitted fabrics X and Y were cut to produce three-dimensional knitted fabrics 20 and 30 with a width of 600 mm, a height of 1300 mm, and a thickness of 10 mm. The three-dimensional knitted fabrics 20 and 30 were adhered to the front and back surfaces, respectively, of a support plate 10 with a width of 600 mm, a height of 1300 mm, and a thickness of 40 mm to obtain a rectangular plate-shaped sound absorber 1 with a width of 600 mm, a height of 1300 mm, and a thickness of 60 mm.

3. Measurement of sound absorption coefficient by reverberation room method The sound absorption coefficient and reverberation time of the sound absorber 1 of this example were measured in a reverberation room at a temperature of 11.1° C. and a humidity of 57% RH in accordance with the “Test method for sound absorption coefficient by reverberation room method” specified in JIS A 1409:1998.
Fig. 12 is a graph showing the results of measuring the sound absorption coefficient when one sound absorber 1 is placed independently on the floor of a reverberation room. Also, Fig. 13 is a graph showing the results of measuring the reverberation time when one sound absorber 1 is placed independently on the floor of a reverberation room. Note that Fig. 13 also shows the measurement results when there is no sound absorber in the reverberation room in order to clarify the effect of the sound absorber 1.

As shown in FIG. 12, it was found that the sound absorber 1 of this example, while being lightweight, has extremely high sound absorbing properties at least in the frequency band of 300 to 10,000 Hz.
13, it was found that the sound absorber 1 of this embodiment can reduce the reverberation time over the entire frequency range (100 to 10,000 Hz) (i.e., the reverberation of sound can be suppressed regardless of the pitch of the sound). Furthermore, since this effect is particularly noticeable in the low-frequency range of daily noise, 250 to 1,000 Hz, it was found that the sound absorber 1 is effective when adjusting the reverberation of sound indoors, such as in a house.
Furthermore, since the sound absorber 1 of this embodiment is made of paperboard, cotton, and polyester, it does not produce toxic gases even when burned, making it environmentally friendly.

The above is an explanation of the embodiment and examples of the present invention, but the present invention is not limited to the above configuration, and various modifications are possible within the scope of the technical concept of the present invention.

For example, the sound absorber 1 of this embodiment has been described as being used by standing perpendicular to the floor surface (i.e., arranged so as to be approximately parallel to the vertical direction (up and down direction in FIG. 1)) and absorbing sound from both sides, but it is also possible to arrange it parallel to the floor surface (i.e., so that either the three-dimensional knitted fabric 20 or the three-dimensional knitted fabric 30 is in contact with the floor surface) or parallel to a wall surface (i.e., so that either the three-dimensional knitted fabric 20 or the three-dimensional knitted fabric 30 is in contact with the wall surface) and configure it to absorb sound from either the three-dimensional knitted fabric 20 or the three-dimensional knitted fabric 30. Note that when the sound absorber 1 is arranged perpendicular to the floor surface (i.e., when arranged so as to absorb sound from both sides), the sound absorbing area is doubled compared to the case of single-sided sound absorption, and sound absorption performance is dramatically improved.
In addition, the sound absorber 1 of this embodiment has been described as having a rectangular plate shape, but multiple sound absorbers 1 can be combined in an L-shape or a cross shape using stays, etc. In this way, using multiple sound absorbers 1 further increases the sound absorbing area, thereby further improving the sound absorbing performance.

In addition, the support plate 10 of the sound absorber 1 of this embodiment has substantially cylindrical partitions 12 arranged two-dimensionally, and a plurality of circular openings 15 arranged two-dimensionally in a hexagonal close-packed manner in a plan view, but is not limited to this shape. As long as 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, the shape of the partitions 12 of the support plate 10 can be changed to another shape.

[Modifications of the support plate 10]
14 and 15 are diagrams showing modified examples 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 the support plate 10A of this modified example, and FIG. 15 is a photograph of one side of the support plate 10A taken from an oblique direction. As shown in FIG. 14 and FIG. 15, the support plate 10A is a rectangular plate-shaped member (e.g., width: 600 mm, height: 1300 mm, thickness: 40 mm) formed by bonding multiple pieces of paperboard, and is composed of multiple partition walls 13 arranged in a straight line and multiple corrugated partition walls 14 arranged between the partition walls 13 so as to connect a pair of the partition walls 13. In addition, the support plate 10A has multiple corrugated openings 15A densely arranged two-dimensionally in a plan view.

Figure 16 is a graph showing the results of measuring the sound absorption coefficient when sound absorber 1A equipped with support plate 10A of this modified example is placed freestanding on the floor of a reverberation chamber. Also, Figure 17 is a graph showing the results of measuring the reverberation time when sound absorber 1A equipped with support plate 10A of this modified example is placed freestanding on the floor of a reverberation chamber. Note that in Figure 17, in order to clarify the effect of sound absorber 1A, the measurement results when there is no sound absorber in the reverberation chamber are also shown.

As shown in FIG. 16, the sound absorber 1A having the support plate 10A of this modified example also has very high sound absorbing properties in at least the frequency band of 300 to 10,000 Hz, similar to the sound absorber 1 described above.
17, it can be seen that the sound absorber 1A equipped with the support plate 10A of this modified example can also reduce the reverberation time over the entire frequency range (100 to 10,000 Hz) (i.e., it can suppress the reverberation of sounds regardless of their pitch) in the same way as the sound absorber 1. This effect is particularly noticeable in the low-frequency range of daily noise, 250 to 1,000 Hz, so it can be seen that the sound absorber 1A is also effective when adjusting the reverberation of sounds indoors, such as in a house.

Furthermore, the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and 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 knit fabric 22, 32 Front base fabric 24, 34 Rear base fabric 26, 36 Connecting thread 50 Adhesive X, Y Three-dimensional knit fabric X2, Y2 Front base fabric X4, Y4 Rear base fabric X6, Y6 Connecting thread 100 Knitting machine 101 Front needle 102 Back needle 103, 104 Trick plate 105 Hook space L1, L2, L3, L4, L5, L6 Guide SX1, SX2, SX3, SX4, SX5, SX6 Ground thread SY1, SY2, SY3, SY4, SY5, SY6 Ground thread

Claims (14)

A pair of base fabrics arranged apart from each other, and a sheet-like first and second three-dimensional knitted fabrics knitted from a connecting yarn that travels back and forth between the base fabrics to connect the two,
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;
Equipped with
The first three-dimensional knitted fabric has an air permeability of 20 to 30 cm ³ /cm ² /sec,
The second three-dimensional knitted fabric has an air permeability of 10 to 20 cm ³ /cm ² /sec,
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;
A sound absorber characterized in that the connecting thread is composed of a synthetic fiber monofilament and a synthetic fiber textured thread. The sound absorber according to claim 1, characterized in that the connecting thread is 150 to 220 dex. The sound absorber according to claim 1 or 2, characterized in that the connecting thread is made of polyester. A sound absorber according to any one of claims 1 to 3, characterized in that the ground yarns forming the pair of base fabrics are made of spun yarn. The sound absorber according to claim 4, characterized in that the ground yarn forming the pair of base fabrics is 150 to 220 decibels. The sound absorber according to claim 4 or 5, characterized in that the ground yarns forming the pair of base fabrics are made of cotton or polyester. The sound absorber according to any one of claims 1 to 6, characterized in that the thickness of the first and second three-dimensional knitted fabrics is 10 to 20 mm. The sound absorber according to any one of claims 1 to 7, characterized in that the support plate has a plurality of circular openings that are densely arranged two-dimensionally in a plan view. The sound absorber according to any one of claims 1 to 7, characterized in that the support plate has a plurality of corrugated openings that are densely arranged two-dimensionally in a plan view. A sound absorber according to any one of claims 1 to 9, characterized in that the support plate is made of paperboard. A sound absorber according to any one of claims 1 to 10, characterized in that the thickness of the support plate is 30 to 50 mm. The sound absorber according to any one of claims 1 to 11, characterized in that the sound absorber is arranged so as to be substantially parallel to the vertical direction when used. The sound absorber according to any one of claims 1 to 12, characterized in that the sound absorber has an absorption band in the sound range of at least 300 to 10,000 Hz. The sound absorber according to any one of claims 1 to 13, characterized in that the sound absorber suppresses reverberation at least in the sound range of 250 to 1000 Hz.

Images