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: Noise pollution reduction device Technical field of the invention

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

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

[0003] Since noise reduction requirements vary depending on the environment (meeting room, open-plan office, dedicated Hi-Fi listening room, workshop, call center, hospital room, classroom, or restaurant, etc.), it is preferable to aim for a good balance in the sound environment, that is, a harmonious distribution of the room's spectral response, rather than simply trying to reduce the overall noise level. This spectral balance can be achieved with acoustic correctors that can act on the entire spectral range.

[0004] Acoustic correctors are generally effective at medium and high frequencies but can have poor absorption qualities at low frequencies, which are nevertheless a source of auditory fatigue because they generally originate from fairly distant and diverse sources (nearby factory, mechanical ventilation, elevator shaft, traffic, etc.). It is now recognized that exposure, even at low sound levels, to noises with strong low-frequency components has a significant effect on the discomfort felt by an individual, provided they are subjected to this noise over a long period. In arts and crafts or stationery, it is common to cut out small vignettes, particularly using office hole punches, for example for decorative crafts, such as scrapbooking.One known example is an eyelet punch consisting of a punch that cuts a sheet of paper on an eyelet-shaped die to cut an eyelet in a single operation. One drawback is that the sheet must be removed from the punch to remove the eyelet stuck in the foam of the die before another eyelet can be cut.

[0005] Furthermore, current noise standards apply to empty spaces, whereas the problem of acoustic disturbance arises in practice when there are, for example, several speakers or when machinery is operating. Reverberation time, which is the main criterion for characterizing an enclosed space, is directly linked to the sound absorption performance of the walls. Corrective wall solutions that controls for no-load reverberation time provide very little improvement in these usage configurations where the direct acoustic field controls the sound environment.

[0006] In addition, 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 for potential acoustic correction are increasingly reduced with the use of large glazed areas. To increase the sound reduction performance referred to in the latest noise standards, it becomes necessary to install distributed barriers.

[0008] It is known from document EP2198096B1, filed on behalf 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 layers of a porous material, in which medium- and high-frequency sound waves are effectively attenuated by dynamic absorption through viscous dissipation. The panel is suspended from the wall by elastic elements which also allow for the attenuation of low-frequency sound waves by dynamic absorption through 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] One object 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 noise pollution reduction device, comprising: - an acoustic panel, made of porous material, - at least one elastic suspension element, characterized in that it further comprises at least one first half-shell made of porous material, at least one elastic suspension element being configured to suspend the acoustic panel elastically in a volume of air at least delimited by the first half-shell and such that an air gap is interposed between the acoustic panel and the first half-shell, at least one elastic suspension element 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 include a second porous material half-shell fixed to the first half-shell so as to form an air gap on either side of the acoustic panel.

[0016] The device includes, for example, feet or plates or casters attached to the half-shells allowing the said device to be placed on the ground.

[0017] The first half-shell can be configured to be fixed to a wall.

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

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

[0020] The elastic suspension member may include a leg, 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 features will become apparent from the following description of a particular, but by no means limiting, embodiment of the invention, as well as from the accompanying drawings in which:

[0022] [Fig. 1] The [Fig. 1] shows a perspective view of a first example of the realization of a noise pollution reduction device.

[0023] [Fig.2] Fig.2 shows a schematic vertical cross-sectional view of elements of the noise pollution reduction device of the [Fig.1], seen from the side.

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

[0025] [Fig.4] Fig.4 shows an example of the embodiment of an elastic organ 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 an embodiment of the noise pollution reduction device.

[0029] In these figures, identical elements bear 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. Simple features of different embodiments can also be combined or interchanged to provide other embodiments, without departing from the scope of the invention as defined by the claims.

[0031] "Suspending" is defined as holding the panel solely by means of at least one elastic suspension element.

[0032] The orientation of the noise pollution reduction device with respect to Earth's gravity is defined by "up" and "down".

[0033] Figures 1 and 2 show a first example of the implementation of a noise pollution reduction device 1. In [Fig. 1] an orthonormal coordinate system x / y / z is represented. Gravity acts in the opposite direction to the z direction of this coordinate system.

[0034] As can be seen more clearly in the cross-sectional view of [Fig. 2], the noise 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 element 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 along the x (width) and z (height) directions.

[0035] The acoustic panel 2 generally has the same dimensions as the half-shell(s) 4, for example, a flat, rectangular parallelepiped shape. It is positioned suspended vertically on [Fig. 2]. The width and thickness of the acoustic panel 2 are slightly smaller than 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 achieve this, a gap I of between 0 mm and 5 mm, in particular 2 mm, is provided between the peripheral edge of the acoustic panel 2 and the lateral, bottom, and top edges of the internal wall 4i.

[0036] The thickness (along the y-direction of [Fig. 1]) of the acoustic panel 2 is, for example, between 40 mm and 100 mm. For wall-mounted solutions, the thickness may be smaller, for example 45mm and for solutions of the screen type for example 60mm.

[0037] The thickness of the acoustic panel 2 can be constant along its entire height. According to another 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 the central thickness.

[0038] According to an example of an embodiment more clearly visible in [Fig.4], the suspension of the panel 2 is achieved by means of the elastic suspension member 3 which includes a first and second mounting devices 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 within the space delimited by the internal walls 4i of the half-shells 4.

[0039] The elastic suspension member 3 includes, for example, a leg 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 whose other end extends into a leg 12.

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

[0041] The suspension leg 3c can be tilted relative to the leg 12, in a vertical plane P, downwards and upwards, by means of an elastic deformation of the spring 3b, as symbolized by the opposing arrows Fl and F2 in [Fig. 4]. This deformation occurs in the direction of a rotation of the two opposite ends of the spring 3b relative to each other, around the axes XrX'i and X2-X'2 respectively. As its coils are not contiguous, 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 leg 3c away from the vertical plane P, in a plane parallel to the axis Xi-X'i, relative to the leg 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 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 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 5mm and 15mm, in particular equal to 12.5mm.

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

[0045] For example, there is 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, which is positioned upright and vertical.

[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, one 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 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 of polyester fibers or more generally of porous material, which also includes cellular materials.

[0049] One or both half-shells 4, 5 may be covered with a neutral, porous, non-absorbent fabric such as polyester. The covering allows the device 1 to be customized by the choice of color or patterns for the aesthetic integration of the device 1 into a wide variety of environments.

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

[0051] The noise 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 feet 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. 1]).

[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 on the order of the dimensions of the acoustic panel 2 or greater, the pressure exerted on the acoustic panel 2 is almost in phase across its entire surface, it will trigger its operating mode. Such a circuit has a very low resonant frequency but exhibits strong damping provided by a bandwidth wide enough to self-adapt to the lower resonant frequencies of most rooms.

[0053] For higher acoustic wave frequencies, but on the order of a fraction of the dimensions of the acoustic panel 2, the panel reacts according to its bending modes and thus absorbs acoustic energy, which is transformed into mechanical energy. Since the elastic suspension elements 3 allow the panel 2 to vibrate freely, all 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] Device 1 therefore combines in itself 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 acoustic frequencies above 1000Hz,

[0057] • the conversion into deformation energy of a flexing panel for the mid-range 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. Regarding the third mechanism, it is integrated into device 1 according to the invention by the suspended panel 2 and the air gap LA between the panel 2 and the internal wall 4i of the half-shell 4.

[0060] The air gap LA interposed between the acoustic panel 2 and the half-shells 4, 5 significantly enhances the absorption performance in the low frequencies by forming acoustic screens that break the sound propagation of noises and thus allow the creation of islands on either side of the panel 2.

[0061] By combining three physical mechanisms allowing sound acoustic absorption, the device 1 according to the invention allows very wide band acoustic absorption (from 50 Hz to 10000 Hz).

[0062] Device 1 also reduces reverberation time. It improves speech intelligibility and enhances listening comfort.

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

[0064] By way of example, [Fig. 5] shows the contribution of the different absorption mechanisms for an example embodiment of 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 incorporating the contribution of the blade air between the acoustic panel 2 and a half-shell 4 for mid-frequency acoustics 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] Device 1 therefore implements a combination of these different mechanisms and the acoustic absorption effects are added at each frequency.

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

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

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

[0072] The example of 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] The one in [Fig. 4] is, for example, made from a spring metal wire, which is shaped to comprise four sections extending one after the other, namely a section forming a mounting tab 3a for the component 3 on the first half-shell 4, a section forming a helical spring 3b, a section forming a suspension tab 3c, and a section forming a hook 3d for attaching the panel 2 by an edge. The spring 3b thus 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 lugs 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 with respect to the axes of these springs 3b is low. The weight of the panel 2 therefore only has a minor influence on the dimensioning of the springs 3d, whose stiffness 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 leg 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 leg 3c, in each hook 3d.

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

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

[0078] In addition, leg 3c can form the spring portion of organ 3 or, at the very least, be part of it, by being able to be elastically bent.

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

[0080] Fig. 7 shows a second example of an embodiment of 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 is fixed to a wall 7, such as a room wall, for example by gluing or screwing. The walls of the first half-shell 4, the acoustic panel 2, and the wall 7 are parallel to each other in the absence of vibration of device 1.

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

Claims

Demands

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

7. Noise pollution reduction device (1) according to any 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 of thermo-compressed fibrous material or of cellular material.

8. Noise pollution reduction device (1) according to any one of the preceding claims, characterized in that the elastic suspension member (3) comprises: - a first mounting device (3a) and a 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) has 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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