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Title:
A SOUND BARRIER MATERIAL
Document Type and Number:
WIPO Patent Application WO/2014/148912
Kind Code:
A1
Abstract:
A sound barrier material (1) comprising a host elastomer (2) and multiple metallic scatterers (3) arranged in a repeating cell structure with a lattice constant (a) inside said host elastomer (2), wherein said metallic scatterers are attached on a metallic mesh (4).

Inventors:
WANG, Litian (Fagertunveien 32, Bekkestua, N-1357, NO)
NILSEN, Rino (Parkveien 46, Gressvik, N-1621, NO)
JENSEN, Alf, Egil (Halden, N-1757, NO)
WU, Hong (Harebakkveien 48, Sarpsborg, N-1727, NO)
GIL, Miriam, Cebrian (Halden, N-1757, NO)
YANFENG, Wang (Halden, N-1757, NO)
Application Number:
NO2014/000026
Publication Date:
September 25, 2014
Filing Date:
March 15, 2014
Export Citation:
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Assignee:
ØSTFOLD UNIVERSITY COLLEGE (N-1757 Halden, NO)
International Classes:
E04B1/84; F16F7/116; G10K11/162; G10K11/172
Foreign References:
US20050194209A12005-09-08
US3421597A1969-01-14
CN102237079A2011-11-09
US20120061176A12012-03-15
US20050109557A12005-05-26
US5245141A1993-09-14
Other References:
C. J. NALLY: "Membran-type metamaterials; Transmission loss of multi- cell arrays", JOURNAL OF APPLIED PHYSICS, vol. 109, 17 May 2011 (2011-05-17), XP012146945
H. ZAO ET AL.: ""Low frequency acoustic absorption of localized resonances: Experimental and theory", JOURNAL OF APPLIED PHYSICS, vol. 107, 27 January 2010 (2010-01-27), XP012133175
H. H. HUANG ET AL.: "Wave attenuation mechanism in an acoustic metamaterial with negative mass density", NEW JOURNAL OF PHYSICS, vol. 11, 1 January 2009 (2009-01-01), XP020154288
Attorney, Agent or Firm:
WU, Hong (Høgskolen i Østfold, Halden, N-1757, NO)
Download PDF:
Claims:
1. A sound barrier material (1) comprising a host elastomer (2) and multiple metallic scatterers (3) arranged in a repeating cell structure with a lattice constant (a) inside said host elastomer (2), wherein said metallic scatterers are attached on a metallic mesh (4). See figure 1

2. Said sound barrier material (1) of claim 1, wherein said cell structure is square or triangular.

3. Said sound barrier material (1) any of the claims claim 1 to 2, wherein said lattice constant is 25 mm or less.

4. Said sound barrier material (1) of claim 3, wherein a diameter (d) of said metallic scatterers (3) is in the range 50% to 70% of said lattice constant (a), and a diameter of the holes in mesh is in the range 5% to 10% of the lattice constant (a).

5. Said sound barrier material (1) any of the claims 1 to 4, wherein said metallic scatterers (3) are discs.

6. Said sound barrier material (1) of claim 5, wherein said metallic scatterers (3) are disc with or without a repeating surface structure in the either side of said metallic scatterers (3).

7. Said sound barrier material (1) of any of the claims 1 to 6, wherein said host elastomer (2) has the hardness lower than Shore A80.

8. Said sound barrier material (1) of claim 7, wherein said host elastomer (2) is made of a plastic material.

9. Said sound barrier material (1) of any of the claims 1 to 8, wherein said metallic mesh (4) is made of wire with diameter less than 1 mm (one millimeter).

10. A method for the manufacture of a sound barrier material (1) comprising the

following steps:

-attaching metal discs (3) on the metallic mesh (4)

-ruling said metallic scatterers (3) with metallic mesh (4) and host (2) together

Description:
A SOUND BARRIER MATERIAL

[0001] The present invention relates to the field of sound barrier materials with sound damping properties in the audible area.

[0002] Materials with good damping capacity have numerous applications in noise

control and vibration damping related to many industries. Damping capacity for polymeric materials (e.g. elastomer) is very high compared to metallic materials.

[0003] The present invention comprises a substantially periodic array of structures

disposed in a viscoelastic or elastic medium.

[0004] US Patent application PCT/US2008/086918 (WO 2009/085724 Al) discloses a sound barrier comprising a substantially periodic layers structures disposed in a first medium having a first density, the structures being made of a second medium having a second density different from the first density, wherein one of the first and second media is a porous medium other than a porous metal, the porous medium having a porosity, and wherein the other of the first and second media is a viscoelastic or elastic medium.

[0005] US Patent application PCT/US2008/086918 (WO 2009/085724 Al) discloses a sound barrier using a phononic crystal with viscoelastic materials.

[0006] The structure of the materials described above are not comparable with present invention, because they have uniform layered-structures.

Short summary of the invention

[0007] It is an object of the present invention to disclose a sound barrier material that can be used in the hearing range of humans. The structure of the material and individual characteristics of the elements making up the material provides the best sound-absorbing properties, which can be coated or mounted on existing construction due to their moderated physical strength.

[0008] In an embodiment the invention is a two-dimensional material comprising a host elastomer and multiple metallic scatterers arranged in a repeating cell- structure with a lattice constant inside the host elastomer, wherein the metallic scatterers are fixed on a metallic net/mesh. See figure 1.

[0009] The present sound barrier material according to the invention has good sound damping properties in the hearing range of humans.

[0010] The material also can be made flexible, allowing it to be mounted or attached on the construction where sound barriers are needed. This simplifies the planning, construction and maintenance phase, and reduces the associated costs.

[0011] In an embodiment the thickness of the host elastomer is below 1 cm (one

centimeter). The thickness of the sound barrier material is important for the weight and flexibility of the product. A lower thickness will usually make the material more applicable.

[0012] According to an embodiment of the invention the internal structure of the unit cell is important, and the lattice constant is 25 mm or less.

[0013] Further, in an embodiment the diameter of the metallic scatterers is in the range 50% to 70% of the lattice constant, and a diameter of the holes in the metallic mesh is the range 5% to 10% of the lattice constant.

[0014] The hardness of the material is of importance for the damping effect. In an

embodiment the hardness of the host elastomer is lower than Shore A50. Drawings

[0015] The attached figures illustrate some embodiments of the claimed invention.

[0016] Fig. 1 illustrates the elements making up the material according to an embodiment of the invention in Fig 1.

[0017] Fig. 2 shows the measurement result of transmission loss of the material samples with different compositions, where the measurement is carried out using the

Impedance Tube method.

[0018] With reference to the attached drawings the device and system according to the invention will now be explained in more details.

[0019] The invention is in an embodiment, as illustrated in Fig. 1, a novel sound barrier material (1) comprising a host elastomer (2) and multiple metallic scatterers (3) arranged in a repeating cell structure with a lattice constant (a) on a metallic mesh (4) inside the host elastomer (2), wherein the metallic scatterers (3) can be either disc, ring, or square with thickness below 2 mm (two millimeters).

[0020] The metallic scatterers (3) can be made of different metallic materials, e.g.

aluminum or ferrous metals.

[0021] Fig 1 illustrates in a section view that the sound barrier material (1) is composed of unit cells with a lattice constant (a).

[0022] In an embodiment the cell structure is square or triangular.

[0023] Further, in Fig. 1 it is shown that the sound barrier material (1) has a thickness (t).

According to an embodiment of the invention a thickness (t) of the host elastomer

(2) is below 1 cm (one centimeter).

[0024] It is found that the relationship among the lattice constant (a) and the scatterers (3) and the mesh (4) is important in order to achieve the desired damping capacity. According to an embodiment of the invention the lattice constant (a) is 25mm or less.

[0025] Further, with reference to Fig. 1 illustrating in a section view a single unit cell, the diameter (d) of the metallic scatterers (3) is in the range 50% to 70% of the lattice constant (a), and a diameter of the holes in the mesh (4) in the range 5% to 10% of the lattice constant (a) according to an embodiment of the invention.

[0026] The shape of the metallic scatterers will influence the damping capacity of the material. According to an embodiment of the invention the metallic scatterers (3) are metallic geometrical forms, such as disc, or ring, or square, with thickness below 2 mm (two millimeters).

[0027] According to an embodiment of the invention the metallic scatterers (3) are discs, which can secure good adhesion between the mesh (4) and the metallic scatterers

(3) .

[0028] In construction materials, a certain hardness is required. According to an

embodiment of the invention the host elastomer (2) has lower than Shore A70.

[0029] It has been found that a hardness of at most Shore A70 gives a material the

required mechanical strength, and it has been verified in experiments that this hardness also results in a good damping property of the material.

[0030] According to an embodiment of the invention the host elastomer (2) is made of plastic material. [0031] Such a plastic material may be either polyurethane, or silicone, or rubber that are resilient, flexible, durable and viscoelastic materials, with certain hardness at the same time are sufficient for achieving the damping effect.

[0032] According to an embodiment of the invention the coating elastomer (4) has the hardness lower than Shore A50.

[0033] According to an embodiment of the invention the mesh (4) is made of metal.

[0034] The transmission loss for three samples of sound barrier material has been

investigated. The results for the frequencies between 500 Hz and 3000 Hz can be seen in Fig. 2. The three samples HI, H2, H3 are categorized according to the arrangement of scatterers (3): Sample HI is without scatterers; Sample H2 has scatterers with outer diameter 7.5 mm (seven point five millimeters); Sample H3 has scatterers with outer diameter 10.0 mm (ten millimeters) (See Table 1). The result indicates that the diameter and areal of scatterers plays a central role in enhancing transmission loss.

[0035] According to an embodiment the invention is also a method for the manufacture sound barrier material (1) comprising the following steps;

-arranging the metallic scatterers (3) on the on the metallic mesh (4)

-ruling the metallic scatterers (3) and the metallic mesh (4) into forming laminar structure.

[0036] A soft elastomer, such as e.g. silicon (SI) or rubbers, may be chosen as host

material (2) because of its low modulus which is essential to achieve low frequency band gap. The modulus or hardness can be tuned so that an optimal sound damping can be reached.

[0037] Other soft elastomers can be used, for example, high fire or heat resistant

elastomers.

[0038] In this embodiment steel is chosen as scattered material because of its high

density. In addition it is widely available at low cost. Other non-ferrous metals can also be used.

[0039] To verify the advantages of the sound barrier material according to the invention, a series of tests have been conducted. Figure 2 show the transmission loss for the three samples with steel scatterers specified in Table 1.

T ble

Table I: Specification for the three samples with steel mesh in a hard silicone host material and with flat rings as scatterers.

Rings

Sample 0inner 0outer Thickness

HI NA NA NA

H2 3.2 mm 6.5 mm 0.5mm

H3 5.3 mm 10.0 mm 1.0mm

Steel mesh: Aperture width: 1.25mm

Wire diameter: 0.25mm