Noise pollution reduction device

Abstract

The invention relates to a noise pollution reduction device (1), comprising: - an acoustic panel (2), made of porous material, - at least one elastic suspension element (3). This device further comprises at least one first half-shell (4) made of porous material, the at least one elastic suspension element (3) being configured to elastically suspend the acoustic panel (2) in a volume of air at least delimited by the first half-shell (4) and such that an air gap (LA) is interposed between the acoustic panel (2) and the first half-shell (4), the at least one elastic suspension element (3) being configured to deform freely under the effect of acoustic pressure stresses. Figure 2

Description

Title of the invention: Device for reducing noise pollution Technical field of the invention

[0001] The present invention relates to a device for reducing noise pollution. Technical background

[0002] It may be necessary to reduce noise pollution in all enclosed spaces, both professional and private, with acoustic ambient correction being able to relate not only to levels but also to spectral balance and sound perception in order to improve comfort and listening quality.

[0003] Since the requirements for reducing noise pollution vary depending on the environment (meeting room, open-plan office, room dedicated to Hifi listening ("high fidelity" in French), workshop, telephone call center, hospital room, classroom or restaurant, etc.), it is preferable to aim for a good balance of the sound environment, i.e. a harmonious distribution of the spectral response of the room, rather than simply seeking to reduce the overall noise value. This spectral balance can be obtained by acoustic correctors which can act on the entire spectral range.

[0004] Acoustic correctors are generally effective at medium and high frequencies but can be of poor absorbing qualities at low frequencies which are however sources of auditory fatigue because they generally come from fairly distant sources and of various origins (nearby factory, mechanical ventilation, elevator shaft, traffic, etc.). It is now recognized that exposure, even at low sound levels, to noise with strong low-frequency components, has a significant effect on the discomfort felt by an individual, as soon as he is subjected to this noise over a long period. In creative hobbies or stationery, it is known to cut out small stickers, in particular using office punches, for example for craft decoration purposes, such as for scrapbooking.In particular, an eyelet punch is known comprising a punch that cuts a sheet on an eyelet-shaped die for cutting an eyelet in a single operation. A disadvantage is that the sheet must be removed from the punch to remove the eyelet stuck in the foam from the die before another eyelet can be cut.

[0005] In addition, the noise standards in force concern empty rooms, whereas the problem of acoustic disturbance arises in use when there are, for example, several speakers or when machines are operating. The reverberation time, which is the main criterion for characterizing an enclosed space, is directly linked to the absorption performance of the walls. Corrective wall solutions which allow to control the reverberation time in empty spaces bring very little improvement in these usage configurations where the direct acoustic field controls the sound environment.

[0006] Furthermore, new notions of discretion and confidentiality emerge in the analysis of the causes of dissatisfaction when noise is mentioned as a proven nuisance.

[0007] Furthermore, experience shows that the wall surfaces available in a room to accommodate possible acoustic correctors are increasingly reduced with the use of large glass surfaces. To increase the sound reduction performance referred to in the latest noise standards, it becomes necessary to place distributed obstacles.

[0008] It is known from document EP2198096B1 in the name of the Applicant to improve the acoustic comfort of spaces by means of acoustic panels covering at least locally the walls delimiting these spaces. The acoustic panels used generally comprise one or more thicknesses of a porous material, in which the medium and high frequency sound waves are well attenuated by dynamic absorption by viscous dissipation. The panel is suspended from the wall by elastic members which also allow attenuation of the low frequency sound waves by dynamic absorption by mechanical dissipation.

[0009] Despite excellent overall performance, attenuation in the low frequency part of the acoustic spectrum (between 50Hz and 200Hz) is not optimal. Summary of the invention

[0010] An aim of the present invention is therefore to further improve the absorption of sound waves, particularly in the low frequency part of the acoustic spectrum.

[0011] To this end, the invention relates to a device for reducing noise pollution, comprising: - an acoustic panel, made of porous material, - at least one elastic suspension member, characterized in that it further comprises at least one first half-shell made of porous material, the at least one elastic suspension member being configured to suspend the acoustic panel elastically in a volume of air at least delimited by the first half-shell and so that an air gap is interposed between the acoustic panel and the first half-shell, the at least one elastic suspension member being configured to deform freely under the effect of acoustic pressure stresses.

[0012] The noise pollution reduction device may have one or more of the following characteristics taken alone or in combination.

[0013] The thickness of the acoustic panel is for example between 40mm or 100mm.

[0014] The thickness of the air gap between the acoustic panel and the first half-shell can be between 5mm and 15mm, in particular equal to 12.5mm.

[0015] The device may comprise a second half-shell made of porous material fixed to the first half-shell so as to form an air gap on either side of the acoustic panel.

[0016] The device comprises, for example, bases or plates or casters fixed to the half-shells allowing said device to be placed on the ground.

[0017] The first half-shell may be configured to be attached to a wall.

[0018] The first half-shell and / or the second half-shell and / or the acoustic panel are made of porous material, particularly thermo-compressed fibrous material or cellular material.

[0019] The elastic suspension member comprises for example: - first and second mounting devices allowing the installation of said member between the first half-shell and the acoustic panel, and - a spring portion located between the first and second mounting devices.

[0020] The elastic suspension member may comprise a tab, one end of which is connected to the first mounting device and which, at a distance from this end, carries a second mounting device, such as a hook. Brief description of the figures

[0021] Other advantages and characteristics will appear on reading the following description of a particular embodiment of the invention, but in no way limiting, as well as the appended drawings in which:

[0022] [Fig. 1] [Fig. 1] shows a perspective view of a first example of an embodiment of a noise pollution reduction device.

[0023] [Fig.2] [Fig.2] shows a schematic vertical sectional view of elements of the noise pollution reduction device of [Fig.l], seen from the side.

[0024] [Fig.3] [Fig.3] shows another example of the acoustic panel, seen from the side.

[0025] [Fig.4] [Fig.4] shows an example of the embodiment of an elastic member of suspension.

[0026] [Fig.5] [Fig.5] shows a graph of the absorption coefficient (%) as a function of the acoustic background frequency (Hz) for a noise pollution reduction device through the air gap and the acoustic panel (curve A) and through the first half-shell (curve B).

[0027] [Fig.6] [Fig.6] shows a graph of the sound reduction index (dB) depending on the frequency of the acoustic wave (Hz) of the noise pollution reduction device.

[0028] [Fig.7] [Fig.7] shows a view similar to [Fig.2] for a second example of the embodiment of the noise pollution reduction device.

[0029] In these figures, identical elements have the same reference numbers. Detailed description

[0030] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments, without departing from the scope of the invention, as defined by the claims.

[0031] The term “suspending” is defined as holding the panel solely by means of at least one elastic suspension member.

[0032] The terms "up" and "down" define the orientation of the noise pollution reduction device relative to Earth's gravity.

[0033] Figures 1 and 2 show a first example of an embodiment of a noise pollution reduction device 1. In [Fig.l] an orthonormal x / y / z reference frame is shown. Gravity acts in the opposite direction to the z direction of this reference frame.

[0034] As best seen in the sectional view of [Fig.2], the noise pollution reduction device 1 comprises a rigid acoustic panel 2, made of fibrous material or more generally of porous material (which also includes cellular materials), at least one elastic suspension member 3 and at least one first half-shell 4 also made of fibrous material or more generally of porous material. The rigid half-shell therefore extends in the directions x (width) and z (height).

[0035] The acoustic panel 2 generally has the same dimensions as the half-shell(s) 4, for example a parallelepiped, flat and rectangular shape. It is positioned suspended vertically on the [Fig.2]. The dimension of the acoustic panel 2 in width and thickness is slightly less than that of the internal dimensions of the half-shell(s) 4 so that when the panel 2 is suspended, it does not touch the internal walls 4i of the half-shell 4. To do this, a gap I of between 0mm and 5mm is provided, in particular equal to 2mm between the peripheral edge of the acoustic panel 2 and the lateral, bottom and top parts of the internal wall 4i.

[0036] The thickness (along the y direction of [Fig.l]) of the acoustic panel 2 is for example between 40mm and 100mm. For wall solutions, the thickness can be lower, for example 45mm and for solutions of the claustra type for example 60mm.

[0037] The thickness of the acoustic panel 2 may be constant over the entire height of the panel 2. According to another exemplary embodiment, the opposite edges of the acoustic panel 2, such as the top and bottom edges, have respective thicknesses less than the central thickness of the panel 2 ([Fig. 3]). The thickness of the opposite edges is for example more than twice less than the central thickness.

[0038] According to an exemplary embodiment better visible in [Fig. 4], the suspension of the panel 2 is achieved by means of the elastic suspension member 3 which comprises a first and second mounting device 3a, 3d allowing the installation of said member 3 between the first half-shell 4 and the acoustic panel 2, and a spring part 3b located between the first and second mounting devices 3a, 3d and therefore inside the space delimited by the internal walls 4i of the half-shells 4.

[0039] The elastic suspension member 3 comprises, for example, a tab 3c, one end of which is connected to the first mounting device 3a and which, at a distance from this end, carries a second mounting device, such as a hook 8 and the other end of which is extended by a tab 12.

[0040] At a distance from the spring part 3b, the tab 12 comprises a closed loop 9 which delimits a passage 10 for the rod of a fixing member such as a screw for example.

[0041] The suspension tab 3c can be tilted relative to the tab 12, in a vertical plane P, downwards and upwards, by means of an elastic deformation of the spring 3b, which is symbolized by the opposite arrows F1 and F2 in [Fig.4]. This deformation takes place in the direction of a rotation of the two opposite ends of the spring 3b relative to each other, around respectively the axes XrX'i and X2-X'2. Since its turns are not touching, the spring 3b can also easily deform in the direction of an angular displacement of its two ends relative to each other around an axis orthogonal to the axis XI-XY. This allows a lateral tilting of the suspension tab 3c away from the vertical plane P, in a plane parallel to the axis Xi-X'i, relative to the tab 12.

[0042] The at least one elastic suspension member 3 is therefore configured to suspend the acoustic panel 2 elastically in a volume of air at least delimited by the first half-shell 4 and so that an air gap LA is interposed between the acoustic panel 2 and the first half-shell 4, the at least one elastic suspension member 3 being configured to deform freely under the effect of acoustic pressure stresses.

[0043] The thickness of the air gap between the acoustic panel 2 and the first half-shell 4 and between the acoustic panel and the second half-shell 5 is for example between 5 mm and 15 mm, in particular equal to 12.5 mm.

[0044] The elastic suspension members 3 have a very low stiffness to be put into traction-compression action by acoustic pressure stresses and to allow stresses along the three axes x, y and z.

[0045] For example, there are one or more elastic suspension members 3 configured to suspend one side of the acoustic panel 2, the other three sides remaining free. The elastic suspension member(s) 3 suspend, for example, the upper edge of the acoustic panel 2 arranged straight, vertically.

[0046] According to another example, the device 1 comprises one or more elastic suspension members 3 configured to suspend two opposite sides of the acoustic panel 2 such as the top edge and the bottom edge as illustrated in [Fig.2]. The device 1 may comprise three or four elastic suspension members 3, for example an upper member 3 and two lower members 3 or four members 3 distributed at the four corners of the panel 2.

[0047] In the embodiment of Figures 1 and 2, the noise pollution reduction device 1 further comprises a second half-shell 5 made of fibrous (or more generally porous) material fixed to the first half-shell 4 so as to form an air gap on either side of the acoustic panel 2 arranged centrally between the two half-shells 4, 5. The walls of the half-shells 4, 5 and of the acoustic panel 2 are parallel to each other in the absence of vibration of the device 1.

[0048] The acoustic panel 2 and / or the first half-shell 4 and / or the second half-shell 5 are for example made of thermo-compressed fibrous material, for example polyester fibers or more generally of porous material, which also includes cellular materials.

[0049] One or the other or both half-shells 4, 5 may be covered with a porous fabric neutral with respect to absorption such as polyester-based. The coating allows the device 1 to be customizable by the choice of color or patterns for the aesthetic integration of the device 1 in very varied environments.

[0050] The half-shells 4, 5 are fixed together, for example, by interlocking and / or gluing and / or screwing. The half-shells 4, 5, once fixed together, have, for example, the shape of a rectangular parallelepiped.

[0051] The noise pollution reduction device 1 with two half-shells 4, 5 does not need to be fixed to a wall. It can be mobile. It can include bases or plates or casters 6 fixed to the half-shells 4, 5 and allowing said device 1 to be placed on the ground (see [Fig.l]).

[0052] In operation, considering that an incident acoustic wave (represented by an arrow in [Fig.2]) impacts a face of the device 1, for low frequencies whose wavelength is of the order of the dimensions of the acoustic panel 2 or greater, the pressure exerted on the acoustic panel 2 is almost in phase over its entire surface and will trigger its operating mode. Such an assembly has a very low natural resonance frequency but has strong damping provided by a bandwidth wide enough to self-adapt to the first natural frequencies of most rooms.

[0053] For higher acoustic wave frequencies but of the order of a fraction of the dimensions of the acoustic panel 2, the latter reacts according to its bending modes and thus absorbs acoustic energy transformed into mechanical energy. The elastic suspension members 3 allow the panel 2 to vibrate freely, all the natural modes are potentially active.

[0054] For medium / high frequencies, the device 1 behaves like a double layer of porous material allowing viscous dissipation to act at small scales.

[0055] The device 1 therefore combines three of the most important physical mechanisms leading to a sound absorption effect, namely in order of frequency efficiency:

[0056] • viscous dissipation in a porous material for high frequencies acoustics greater than 1000Hz,

[0057] • the conversion into deformation energy of a bending panel for the medium acoustic frequencies between 200Hz and 1000Hz, and

[0058] • the conversion into displacement energy of a passive piston with low admittance for low acoustic frequencies between 50Hz and 200Hz.

[0059] The first two absorption mechanisms have already been implemented in the devices known from document EP2198096. Concerning the third mechanism, it is integrated into the device 1 according to the invention by the suspended panel 2 and the air blade LA between the panel 2 and the internal wall 4i of the half-shell 4.

[0060] The air blade LA interposed between the acoustic panel 2 and the half-shells 4, 5 and significantly reinforces the absorption performance in the low frequencies by forming acoustic screens making it possible to break the sound propagation of noise and thus to create islands on either side of the panel 2.

[0061] By combining three physical mechanisms enabling sound absorption, the device 1 according to the invention enables very broadband sound absorption (from 50 Hz to 10000 Hz).

[0062] The device 1 also makes it possible to reduce the reverberation time. It improves speech intelligibility and improves listening comfort.

[0063] Furthermore, the device 1 has a small footprint, can be recycled and has a reasonable cost price.

[0064] For information purposes, [Fig.5] shows the contribution of the different absorption mechanisms for an example of embodiment of the device 1, namely

[0065] • curve A: viscous dissipation in a porous material for high acoustic frequencies above 500Hz,

[0066] • curve B: similar to curve A but also integrating the contribution of the blade of air between the acoustic panel 2 and a half-shell 4 for medium acoustic frequencies between 200Hz and 500Hz, and

[0067] • curve C: 1a conversion into displacement energy of a passive piston at low ad mittance for low acoustic frequencies between 50Hz and 200Hz.

[0068] The device 1 therefore implements a combination of these different mechanisms and the acoustic absorption effects are added at each frequency.

[0069] This accumulation is represented in [Fig.6] which shows the acoustic attenuation index R in dB of the device 1 as a function of the frequency.

[0070] Measurements on the absorption performance of the device 1 according to the invention have shown values ​​of the overall absorption coefficient greater than: aw = 0.95 (according to the European standard EN ISO 11 654) and an NRC “Noise Reduction Coefficient” index greater than: NRC = 0.89 (according to the American standard ASTM 423).

[0071] The sound attenuation index of the device 1 is sufficient to create a real screen for sound waves over a very wide frequency spectrum.

[0072] The embodiment of the elastic suspension member 3 described in relation to [Fig.4] may be the same as that known from document EP2198096, but of course other elastic suspension members may be envisaged.

[0073] That of [Fig.4] is for example made from a spring metal wire, which is shaped so as to comprise four portions extending one from the other, namely a portion forming a tab 3a for mounting the member 3 on the first half-shell 4, a portion forming a helical spring 3b, a portion forming a suspension tab 3c and a portion forming a hook 3d for hooking the panel 2 by one edge. The spring 3b therefore connects the tab 12 to one end of the suspension tab 3c, the other end of which is provided with the hook 8.

[0074] Thanks to the significant inclination of the legs 3c of the lower members 3 such that their hooks 3d are lower than their springs 3b, the moment of the weight of the panel 2 relative to the axes of these springs 3b is low. The weight of the panel 2 can therefore only intervene to a small extent in the dimensioning of the springs 3d, the stiffness of which can be low, in order to facilitate horizontal vibrations of the panel 2.

[0075] The panel 2 can therefore vibrate perpendicular to its main faces by an elastic deformation of the spring part 3b in the direction of a tilting of the tab 3c relative to the first mounting device 3a, around the axis of the spring 3b, and of a pivoting of the panel 2 relative to each tab 3c, in each hook 3d.

[0076] Panel 2 can also vibrate parallel to its main faces, thanks to the ability of the 3c legs to tilt laterally.

[0077] It is also possible to fix the tab 3a to the acoustic panel 2 and the hook 3d to an axis fixed to the first half-shell 4.

[0078] Furthermore, the tab 3c can form the spring portion of the member 3 or, at the very least, be part of it, being able to be elastically curved.

[0079] Also, the members 3 may not be made of a metal wire. For example, they may be made of polymer, by injection, in which case they may be in one piece with a part of the acoustic panel 2. Other embodiments of the members 3 are possible, such as for example using additive manufacturing or 3D printing.

[0080] [Fig.7] shows a second example of embodiment of the device 1.

[0081] This example differs from the previous one in that the reduction device noise pollution 1 does not include a second half-shell 4, the first half-shell 4 being fixed to a wall 7, such as a room wall, for example by gluing or screwing. The walls of the first half-shell 4, of the acoustic panel 2 and of the wall 7 are parallel to each other in the absence of vibration of the device 1.

[0082] The other characteristics of this embodiment are identical to the first embodiment.

Claims

Claims

1. Device for reducing noise pollution (1), comprising: - an acoustic panel (2), made of porous material, - at least one elastic suspension member (3), characterized in that it further comprises at least one first half-shell (4) of porous material, the at least one elastic suspension member (3) being configured to suspend the acoustic panel (2) elastically in a volume of air at least delimited by the first half-shell (4) and so that an air gap (LA) is interposed between the acoustic panel (2) and the first half-shell (4), the at least one elastic suspension member (3) being configured to deform freely under the effect of acoustic pressure stresses.

2. Noise pollution reduction device (1) according to the preceding claim, characterized in that the thickness of the acoustic panel (2) is between 40mm and 100mm.

3. Noise pollution reduction device (1) according to one of the preceding claims, characterized in that the thickness of the air gap between the acoustic panel (2) and the first half-shell (4) is between 5mm and 15mm, in particular equal to 12.5mm.

4. Noise pollution reduction device (1) according to one of the preceding claims, characterized in that it comprises a second half-shell (5) made of porous material fixed to the first half-shell (4) so ​​as to form an air gap on either side of the acoustic panel (2).

5. Noise pollution reduction device (1) according to the preceding claim, characterized in that it comprises bases or plates or casters (6) fixed to the half-shells (4, 5) allowing said device (1) to be placed on the ground.

6. Noise pollution reduction device (1) according to one of claims 1 to 3, characterized in that the first half-shell (4) is configured to be fixed to a wall (7).

7. Noise pollution reduction device (1) according to one of the preceding claims, characterized in that the first half-shell (4) and / or the second half-shell (5) and / or the acoustic panel (2) are made of porous material, in particular thermocompressed fibrous material or cellular material.

8. Noise pollution reduction device (1) according to one of the preceding claims, characterized in that the elastic suspension member (3) comprises: - a first mounting device (3a) and second mounting device (3d) allowing the installation of said member (3) between the first half-shell (4) and the acoustic panel (2), and - a spring part (3b) located between the first and second mounting devices (3a, 3d).

9. Noise pollution reduction device (1) according to the preceding claim, characterized in that the elastic suspension member (3) comprises a tab (3c) one end of which is connected to the first mounting device (3a) and which, at a distance from this end, carries a second mounting device, such as a hook (8).

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