SOUND INSULATION DEVICE

Abstract

A sound insulation device contains at least one rigid support element and at least one elastic membrane element. The rigid support element contains at least one support grid containing a plurality of cells. The elastic membrane element is arranged on the support grid. The sound insulation device is configured to block at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz. The sound insulation device exhibits a negative effective mass below a resonance frequency, where the resonance frequency is given by:

[00001]${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}},$

where A is a pore size of the support grid spun by the membrane element, δ is a thickness of the membrane element, E is an elastic modulus of the membrane element, ρ is a density of the membrane element, and ϑ is a Poisson ratio of the membrane element. The elastic modulus E of the membrane element is ≥8 MPa.

Claims

1-14. (canceled)

15: A sound insulation device, comprising: at least one rigid support element, and at least one elastic membrane element, wherein the at least one rigid support element comprises at least one support grid, wherein the at least one support grid comprises a plurality of cells, wherein the at least one elastic membrane element is arranged on the at least one support grid, wherein the at least one elastic membrane element comprises at least one thermoplastic polyurethane (TPU) membrane, wherein the sound insulation device is configured to block at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz, wherein the sound insulation device exhibits a negative effective mass below a resonance frequency, wherein the resonance frequency is given by ${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}},$ wherein A is a pore size of the at least one support grid spun by the at least one elastic membrane element, δ is a thickness of the at least one elastic membrane element, F an elastic modulus of the at least one elastic membrane element, ρ is a density of the at least one elastic membrane element and ϑ is a Poisson ratio of the at least one elastic membrane element, wherein the elastic modulus F of the at least one elastic membrane element is ≥8 MPa.

16: The sound insulation device according to claim 15, wherein the sound insulation device covers an area of greater than or equal to 0.5 m×0.5 m.

17: The sound insulation device according to claim 15, wherein the resonance frequency ω.sub.0 is ≤5000 Hz.

18: The sound insulation device according to claim 15, wherein the pore size A of the at least one support grid spun by the at least one elastic membrane element is from 1 to 500 mm.sup.2, wherein a proportion of pores to a total area of the at least one elastic membrane element is from 50 to 95%.

19: The sound insulation device according to claim 15, wherein the thickness of the at least one elastic membrane element is in a range of 0.05≤δ≤1 mm.

20: The sound insulation device according to claim 15, wherein the density of the at least one elastic membrane element is in a range of 900 kg/m.sup.3≤ρ≤1200 kg/m.sup.3.

21: The sound insulation device according to claim 15, wherein a geometry of the plurality of cells of the at least one support grid is selected from the group consisting of a triangle, a square, a circle, and a hexagon.

22: The sound insulation device according to claim 15, wherein the sound insulation device has a weight of 0.60 kg/m.sup.2 or less.

23: The sound insulation device according to claim 15, wherein the at least one rigid support element further comprises at least one base element and/or at least one additional support grid.

24: The sound insulation device according to claim 23, wherein the at least one rigid support element further comprises at least one cover element comprising a further support grid having a further plurality of cells, wherein the at least one elastic membrane element is sandwiched between the at least one support grid and the at least one cover element.

25: The sound insulation device according to claim 24, wherein the at least one elastic membrane element is attached to the at least one support grid and/or the at least one cover element by at least one polyurethane based adhesive.

26: A method for manufacturing at least one sound insulation device according to claim 15, configured for blocking at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz, wherein the method comprises: providing the at least one rigid support element; providing the at least one elastic membrane element; and attaching the at least one elastic membrane element to the at least one rigid support element; wherein in an assembled state the sound insulation device exhibits a negative effective mass below the resonance frequency ${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}}.$

27: An article comprising the sound insulation device according to claim 15, wherein the article is selected from the group consisting of a wall sound transmission loss panel; a noise protection installation next to a road, a track, or a fabrication unit; a sound blocking element in an electrical generator casing; a casing rotating elements; and a compressor of air conditioning casings.

28: The sound insulation device according to claim 16, wherein the sound insulation device covers an area greater than or equal to 1 m×1 m.

29: The sound insulation device according to claim 17, wherein the resonance frequency ω.sub.0 is ≤3000 Hz.

30: The sound insulation device according to claim 18, wherein the pore size A of the at least one support grid is from 10 to 100 mm.sup.2.

31: The sound insulation device according to claim 18, wherein the proportion of pores to the total area of the at least one elastic membrane element is from 65% to 85%.

32: The sound insulation device according to claim 19, wherein the thickness of the at least one elastic membrane element is in a range of 0.20≤δ≤0.30 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0088] Further optional details and features of the invention are evident from the description of preferred exemplary embodiments which follows in conjunction with the dependent claims. In this context, the particular features may be implemented in an isolated fashion or in combination with other features. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. Identical reference numerals in the individual figures refer to identical elements or elements with identical function, or elements which correspond to one another with regard to their functions.

[0089] Specifically, in the figures:

[0090] FIG. 1 shows an exemplary embodiment of a sound insulation device according to the present invention;

[0091] FIG. 2 shows experimental results of a sound transmission loss curve in comparison to numerical simulation;

[0092] FIG. 3 shows numerical simulation results showing effect of membrane elastic modulus on sound transmission loss;

[0093] FIG. 4 shows numerical simulation results showing effect of membrane density on sound transmission loss;

[0094] FIG. 5 shows experimental results on effect of cell size of a support element on sound transmission loss; and

[0095] FIGS. 6A to D show comparison of cell geometries.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0096] In FIG. 1, schematically an exemplary embodiment of a sound insulation device 110 according to the present invention is shown. The sound insulation device 110 may be a light-weight sound insulation device. The sound insulation device 110 may have a weight of 0.60 kg/m.sup.2 or less. The sound insulation device 110 may cover an area of greater or equal than 0.5 m×0.5 m. Preferably the sound insulation device 110 may cover an area of more than or equal to 1 m×1 m. The sound insulation device 110 may have a size of 1.07 m×1.07 m×0.02 m.

[0097] The sound insulation device 110 comprises at least one rigid support element 112 and at least one elastic membrane element 114. For example, the elastic membrane element 114 may comprise at least one thermoplastic Polyurethane (TPU) membrane and/or at least one rubber membrane. Other membrane elements 114 are, however, possible. The support element 112 may be configured as a holding structure. The support element 112 may be monolithic. The support element 112 may have a circular and/or plate-like shape. The support element 112 may be a very stiff ground support. For example, the support element 112 may have a compressibility of 2 N/m.sup.2 of maximum 500 μm. The support element 112 may have a maximum flexibility given by R=a.sup.4/D with “a” being the, circularly defined, area of the support element and D its bending stiffness, wherein R may be ≤10, preferably ≤1.

[0098] The rigid support element 112 comprises at least one support grid 118. The support element 112 may additionally comprise at last one base element 116 and/or at least one additional support grid, in particular in order to provide sufficient rigidity and/or stiffness to the support element 112. The support grid 118 may provide sufficient rigidity and/or stiffness alone such that no additional base element 116 and/or support grid are necessary. For example, the rigid support element 112 may comprise two support grids, e.g. laminated to each other. The support grid 118 may comprise at least one first surface, such as an upper surface, on which the elastic membrane element 114 may be placed. The support grid 118 may comprise at least one second surface, opposing the first surface, which may be configured as outer surface of the sound insulation device 110. The support element 112 may be configured to protect the elastic membrane element 114 from physical stress. Specifically, the support element 112 may have mechanical properties such that it limits the maximum curvature of the membrane to 20 times the membrane thickness, preferably 15 times. The maximum bending curvature may indicate maximum of the bending curvature allowed by the base element 116. The support element 112 may have a compressive strength in a range from 1.00 MPa to 7.00 MPa. The support element 112 may have a density in a range from 20 kg/m.sup.3 to 100 kg/m.sup.3. The support element 112 may have a plate shear longitudinal direction strength in a range from 1.3 MPa to 3.86 MPa, preferably 2 to 3.8, more preferably 2.5 to 3.5 and modulus in a range from 0.070 GPa to 0.162 GPa, preferably 0.08 to 0.16, more preferably 0.1 to 0.15. The support element 112 may have a plate shear transverse direction strength in a range from 0.62 MPa to 2.17 MPa, preferably 0.65 to 2.1, more preferably 0.7 to 2, and modulus in a range from 0.042 GPa to 0.100 GPa, preferably 0.045 to 0.1, more preferably 0.05 to 0.095. The support element 112 may have a thickness of 10 mm. Mechanical strength of the support element 112 may be of importance to the function of the sound insulation device. The support element 112 may be completely fixed and immobile. The elastic membrane element 114 is arranged on the support grid 118. The membrane element 114 may be arranged on the support grid 118 such that the membrane element 114 is as inflexibly as possible.

[0099] The support grid 118 comprises a plurality of cells 120. The support grid 118 may be or may comprise a mesh. Specifically, the support grid 118 may be a porous substrate such as a honeycomb. A geometry of the cells 120 of the support grid 118 may be selected from the group consisting of triangle, square, circular and hexagon. Geometry of the support structure may affect the resonance behavior of the membrane element 114. The support grid 118 specifically may be or may comprise a rectangular matrix having one or more rows and one or more columns. The rows and columns specifically may be arranged in a rectangular fashion. It shall be outlined, however, that other arrangements are feasible, such as nonrectangular arrangements. As an example, hexagonal arrangements are also feasible, wherein the base element may be a honeycomb base panel. Preferred geometry for the cells 120 may be a square cell geometry, specifically in terms of increase in blockage of noise energy. At the same time, solidity of the support structure may be of importance. In order to avoid side wise movement of the support structure or to have higher mechanical strength, a hexagonal cell geometry may be preferred. Other arrangements are feasible. Moreover, usage of a support grid comprising a plurality of openings allows for reducing weight of the overall structure.

[0100] The support grid 118 may have various patterns of graded cells sizes. The support grid 118 may have a uniform structure with identical cell size. Alternatively, the support grid 118 may have a non-uniform structure. For example, the cells 120 may have a cell size from 2 to 10 mm, preferable from 3 to 5 mm. For example, the support grid 118 may be a honeycomb structure with cell diagonal length of 3 mm. For example, the support grid 118 may be a honeycomb structure with cell diagonal length of 4.75 mm.

[0101] The support element 112, and in particular the support grid 118, may comprise one or more of: metal, ceramic, polyamide, fiber-reinforced polymer, glass, polyacrylate and aramid. For example, the support grid may comprise a metal grid and/or a grid of glass fibers and/or a grid of aramid fibers, wherein light weight materials are preferred. For example, the support element 112 may comprise an aluminum honeycomb. Specifically, as outlined above, the sound insulation device 110 may have a weight of 0.60 kg/m.sup.2 or less.

[0102] The support element 112 furthermore may comprise at least one cover element, not shown here. The cover element and the support grid 118 may have identical mechanical and physical properties such as mechanical strength. The cover element may comprise a further support grid comprising a plurality of cells. The geometry and arrangement of the cells of the further support grid may be identical or different to the geometry and arrangement of the support grid of the base element 116. The membrane element 114 may be sandwiched between the support grid 118 and the cover element. The membrane element 114 may be attached to the support grid 118 and/or the cover element by at least one polyurethane based adhesive.

[0103] The sound insulation device 110 is configured to block at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz. The sound insulation device 110 may be configured to block more or equal than 50%, preferably more or equal than 70%, most preferably more or equal than 90%, of acoustic energy transmission at the frequency range of 60 Hz to 500 Hz. Decrease of sound intensity across a barrier may be defined by transmission loss Transmission Loss=10log.sub.10 (W.sub.incident/W.sub.transmitted), wherein W.sub.incident is the incident power at one side of the sound insulation device and W.sub.transmitted is the transmitted power at an opposing side of the sound insulation device.

[0104] The sound insulation device 110 may be a metamaterial device. The sound insulation device 110 exhibits a negative effective mass below a resonance frequency ω.sub.0, wherein the resonance frequency ω.sub.0 is given by

[00009]${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}},$

[0105] wherein A is a pore size of support grid 118 spun by the membrane element 114, δ is a thickness of the membrane element 114, E an elastic modulus of the membrane element 114, ρ is a density of the membrane element 114 and ϑ is a Poisson ratio of the membrane element 114. The elastic modulus E of the membrane element 114 is ≥8 MPa. For frequencies below ω.sub.0, the effective mass of the system is negative leading to high sound transmission loss at low frequencies. The resonance frequency ω.sub.0 may be ≤5000 Hz, preferably ≤3000. The resonance frequency may be from 1000 Hz to 5000 Hz, preferably 1000 Hz to 3000 Hz.

[0106] FIG. 2 shows sound transmission loss curves of the sound insulation device 110, wherein sound transmission loss STL in dB as a function of frequency fin Hz is shown. Curve 122 shows experimental results using a honeycomb support element with cell diagonal length of 3 mm and 0.2 mm thick rubber membrane and curve 124 shows for this setup the numerical simulation results. In the experimental setup a loudspeaker was placed at a distance of 10 cm in front of the sound insulation device 110 and a microphone was placed at a distance of 10 cm behind the sound insulation device 110 for recording transmitted sound. The sound transmission loss curves show high values at a lower limit of frequency range, coming to a dip point at the resonance frequency, and increasing towards higher frequencies. The resonance frequency, in this embodiment at 932, separates the negative and positive effective density regions. This point represents a zero effective density where the membrane resonates resulting in the sound transmission loss dip. High sound transmission loss at the low frequency region is the result of negative density or negative effective mass.

[0107] Preferably, the elastic modulus E of the membrane element 114≥8 MPa, preferably between 8 MPa and 25 MPa, preferably between 8.5 and 20 MPa for elongations up to 10%. FIG. 3 shows numerical simulation of the sound transmission loss of cell 120 on the sound insulation device for three values of elastic modulus E, specifically for 3 MPa (curve 126), 7 MPa (curve 128) and 11 MPa (curve 130). For this simulation the following membrane properties may be used: a membrane density of 1000 kg/m.sup.3, thickness 0.25 mm, and Poisson ratio of 0.49, assuming that the boundaries of the membrane element 114 are completely motionless. By increasing the elastic modulus the resonance frequency may be shifted towards higher frequencies.

[0108] Preferably, the density of the membrane element 114 may be in a range of 900 kg/m.sup.3≤ρ≤1200 kg/m.sup.3. FIG. 4 shows numerical simulation of the effect of membrane density on the sound transmission loss for three values of the density of the membrane element 114, namely for 1000 kg/m.sup.3 (curve 132), for 2000 kg/m.sup.3 (curve 134), for 3000 kg/m.sup.3 (curve 136). As the density increases the resonance frequency may be shifted towards higher frequencies, however, in expense of increased weight of the sound insulation device 110. Therefore, the membrane density may be towards a lower limit of an available material with the required elastic modulus.

[0109] Preferably, the thickness of the membrane element 114 may be in a range of 0.05≤δ≤1 mm, preferably 0.1≤δ≤0.5 mm, most preferably in a range of 0.20≤δ≤0.30 mm. However, the thickness increases the vibrating mass increases, too. The thickness may be selected such the vibrating mass is on the one hand not too big and on the other hand that the membrane element 114 is thick enough to avoid rupturing. Therefore, intermediate thickness of the membrane element 114 is preferred.

[0110] The support gird 118 may comprise a plurality of pores spun by the membrane element 114, wherein each of the pores may have a pore size A. The pore size A may be from 1 to 500 mm.sup.2, preferably from 5 to 300 mm.sup.2, most preferably from 10 to 100 mm.sup.2. A proportion of the pores to the total area of the membrane element 114 may be from 50% to 95%, preferably from 60% to 90%, most preferably from 65% to 85%. Preferably, the Poisson ratio ϑ of the membrane element 114 may be in a range of 0.47≤ϑ≤0.50. Preferably, the membrane element 114 may have an ultimate elongation from 10 to 400%, preferably from 50 to 350%, more preferably from 100 to 300%.

[0111] FIGS. 6A to C show embodiments of cell geometry of cells 120. In FIG. 6A a triangular geometry is shown having an effective radius of

[00010]$\frac{\frac{3}{4}{r}^2}{3r}=\frac{r}{4}.$

In FIG. 6B a square geometry is shown having an effective radius of

[00011]$\frac{2r^2}{4r}=\frac{r}{2}.$

In FIG. 6C a hexagonal geometry is shown having an effective radius of

[00012]$\frac{\frac{\sqrt{3}}{4}{r}^2}{6r}=\frac{r}{2\sqrt{3}}.$

Geometry of the support element 112 may affect resonance behavior of the membrane element 114. Preferably the cells 120 may have a square geometry, in particular in view of increase in blockage of noise energy. At the same time, solidity of the support element 112 may be of importance. In order to avoid side wise movement of the support element 112 and/or to have higher mechanical strength, a hexagonal mesh may be used. FIG. 6D demonstrates the effect of cell geometry on sound transmission loss of the sound insulation device 110 for equal cell perimeters for triangle (curve 136), hexagon (curve 138) and square (curve 140), wherein the sound transmission loss STL in dB as a function of frequency fin Hz is depicted. The simulation was based on a rubber membrane element 114 with thickness of 0.25 mm, density of 1000 kg/m3, elastic modulus of 7 MPa, and Poisson's ratio of 0.49.

[0112] FIG. 5 shows an effect of cell size of cells 120 on sound transmission loss, wherein the sound transmission loss STL in dB as a function of frequency fin Hz is depicted. The cell size refers to the diagonal distance of the openings in the support grid 118. For FIG. 5 two honeycomb structures with cell diagonal length of 3 mm (curve 142) and 4.75 mm (curve 144) were tested with a 0.2 mm thick rubber membrane 114. Decreasing the size of the openings on the support grid 118 may increase the average sound transmission loss. A limiting factor may be the weight of the overall structure.

LIST OF REFERENCE NUMBERS

[0113] 110 sound insulation device

[0114] 112 support element

[0115] 114 membrane element

[0116] 116 base element

[0117] 118 support grid

[0118] 120 Cell

[0119] 122 Curve

[0120] 124 Curve

[0121] 126 Curve

[0122] 128 Curve

[0123] 130 Curve

[0124] 132 Curve

[0125] 134 Curve

[0126] 136 Curve

[0127] 138 Curve

[0128] 140 Curve

[0129] 142 Curve

[0130] 144 Curve