FR2848232A1 - Wooden anti-noise structure for softening, absorbing and screening noise, has set of planks that are parallel among themselves and arranged edgewise with their longitudinal axis and oriented in direction of source zone - Google Patents

Abstract

The structure (1) has a set of planks (2) that are parallel among themselves and arranged edgewise (3) with their longitudinal axis parallel to a plan (P) of the structure. The planks are oriented in a direction of source zone and separated from one another by a free space (4). Bands of acoustic absorbents are positioned in a parallel way to the plan of the structure on opposite edges to the source zone of the planks.

Description

NOISE STRUCTURE

  The present invention relates to an acoustic structure for attenuating, absorbing and / or shielding noise. The present invention relates to a plate formed from such an acoustic noise structure. The present invention also relates to a ceiling or walls of a room or an external noise barrier fitted with such an acoustic noise structure.

  In general, noise is one of the comfort parameters that is quite often overlooked. It is true that urbanization, the explosion of road traffic, the densification of multi-storey housing are all developments that generate an increasingly noisy environment. In industrial premises, automated chains for production are also always noisier than transfers of parts by hand.

  In the construction sector, and more specifically in residential buildings (villa, building), in buildings open to the public, in commercial buildings or even in industrial premises, construction must meet acoustic standards to make the more comfortable and less tiring private or professional environment.

  State of the art The improvement of the environment from an acoustic point of view is in principle treated by surface panels plated on or against the structures of the buildings. 25 These panels are made of soft and porous materials. Wood is very often used with, for example, fibreboard (density substantially equal to 0.1), cork panels or even micro-perforated panels based on wood fibers.

  These construction elements are applied to existing concrete or metal surfaces. They can therefore be seen as acoustic corrective panels. These 30 acoustic panels are thin, and they offer a smooth surface, with the exception of the perforations. Their absorption characteristics of airborne noise vary according to the density of the panel (a less dense panel will be softer and will therefore absorb better), and the size and number of the perforations which are as many doors trapping high frequency sounds . Given their homogeneous surface configuration, these corrective panels are very good for the absorption of high frequencies, in the range 1200 Hz to 4000 Hz.

  However, they are not structured enough at the surface level to be effective in a lower frequency range, for example from 50 Hz to 1200 Hz. A simple homogeneous panel can only be a limited corrector, because it has a smooth surface. In addition, these panels contain a lot of glue or volatile organic compounds, which is not ideal from an environmental point of view.

  Summary of the invention One of the main problems which arises is that of being able to develop a structure against the acoustic nuisances of a noise source located in the same area of space.

  A second problem is to succeed in finding an acoustic structural panel 15 or partition walls intended to protect the environment, integrating different construction scales to have broadband efficiency, and therefore be suitable in a multitude of environments, from private to commercial, from offices to production plants. A third problem is to provide an efficient panel over the entire 20-frequency band, from low frequencies from 50 Hz to 400 Hz to high frequencies of more than 1600 Hz to 10 kHz.

  A structure, defining a plane, is intended for the absorption or the acoustic correction of sound waves, in the range of the audible frequencies between 50 Hz and 25 kHz, coming from a source zone of sound waves.

  According to the invention, the structure is characterized in that it comprises a set of boards, parallel to each other, arranged on edge, with their longitudinal axis parallel to the plane of the structure, oriented towards the source area and separated from each other by a free space.

  In other words, the structure has a three-dimensional configuration which makes it possible to create traps for sound waves, in the form of oűs or captive cavities. The functional characteristics of this wooden structure are to be both structural and acoustic corrective. The structure therefore combines the two functions to be used as a slab or as a wall or as a simple non-structural corrective element added to the already existing structure. These wooden components can be made without glue, just with screws or nails.

  The basic physical principle is to create a mass - spring mass system that can vibrate and absorb the high energy of low frequencies. To implement this principle, it is necessary to develop a structure rigid enough to vibrate like a wall or a wall. In addition, on its surface exposed to noise, differences in 10 scales of complexity must be found, so as to increase the efficiency of the structure over a wide frequency band.

  In order to secure the assembly of the planks to one another, and in a first alternative embodiment, the structure may include a set of spacers. Each of the spacers can be wedged in the free space between each of the boards. In this way, each of the spacers can make a mechanical connection between these boards. However, and in order to create series of cavities forming sound traps, the spacers have a length less than that of the constituent boards.

  In order to achieve a joining of the set of boards to each other, and in a second alternative embodiment, the structure may comprise at least one element inserted in each of the boards of the set of boards. This element can be placed parallel to the plane of the structure and perpendicular to the longitudinal axis of the boards, thereby making a mechanical connection between said boards. For certain more discreet ceilings, the planks can all be at the same height, with a space. and an absorbent insulation on the back, the structure possibly comprising a layer of an acoustic absorbent. The acoustic corrector can be simple, without oue̋ and without insulation, its efficiency then being lower. This continuous layer is positioned parallel to the plane of the structure on the edges opposite the source zone of the set of boards, that is to say ie at the back of the structure.

  In several advantageous embodiments, and in order to create different levels of cavities forming sound traps, some of the boards can be offset relative to other boards not offset from the set of boards. These offset boards are then ordered alternately and in a regular pattern.

  These boards are offset perpendicularly to the plane of the structure, and towards the source area, that is to say towards the front of the structure.

  In order to further improve its efficiency, the structure may include strips 5 of sound absorbent which will be positioned parallel to the plane of the structure on the edges opposite the source area of the offset boards and between the non-offset boards of the assembly. of boards. In a high performance slab system, it can be with hearing, without absorbent or with absorbent.

  In order to facilitate its handling and / or its assembly and its attachment to a support, the structure may include a wooden panel positioned parallel to the plane of the structure and positioned on the edges opposite the source area of the set of boards, that is to say at the rear of the structure. In another embodiment, the structure may further comprise a concrete screed positioned on the wooden panel. On one floor, one panel may be sufficient. However, a concrete screed can be added to improve the absorption of structural noise. By concrete is meant any material based on hydraulic binder.

  To improve the resumption of the shearing forces of the boards between them, the structure may comprise at least one additional connector inserted in the boards not offset from the set of boards parallel to the plane of the structure and perpendicular to the longitudinal axis of the boards. To carry out tensile transfers between connectors, the structure may comprise at least one rod mechanically connecting at least two connectors, positioned parallel to the plane of the structure and parallel to the longitudinal axis between the boards not offset from the set of boards. The structure may comprise a layer of concrete poured on the acoustic absorbent strips positioned parallel to the plane of the structure and between the non-offset boards of the set of boards, in order to produce a real slab in one piece.

  In yet another embodiment, the offset boards can be arranged so that the sound absorbent strips positioned parallel to the plane of the structure on the edges opposite the source area of the offset boards and between the non-offset boards of the 'set of boards come flush with the edges opposite the source area of the boards not offset from the set of boards, that is to say at the edge of the structure.

  To allow installation of the structure in the open air, as a noise barrier for roads, highways and airports, sealing pieces can be positioned on the sound absorbent strips and are flush with the edges opposite the source area of the boards not offset from the set of boards, that is to say at the rear of the structure. To prevent parasitic vibrations of the boards, damping pieces made of a flexible material can be positioned on the edges opposite the source area of the boards that are not offset from the set of boards, i.e. at the rear of the board. structure.

  In one embodiment, some of the boards, arranged alternately in a regular pattern, may favorably have a width less than or equal to their thickness compared to other boards of the set of boards. In an alternative embodiment, the boards with a width less than or equal to their thickness may have a section in the shape of a swallow tail, in order to create a cavity forming sound traps with a large volume but an entrance with a small surface area, generating a vacuum area for more sound absorption.

  To modify the reflections of the sound waves on the structure, the edges, facing the source area, that is to say at the front of the structure, boards of the set of boards, can be grooved. To use all types of materials, the boards in the set of boards can be reconstituted from at least two portions. In a variant, the portions of the boards can be assembled offset from one another in the direction of the source area, that is to say towards the front of the structure. The boards of the set of boards may have an inclination. The boards can be oriented towards the ground as a lampshade as well as for discharging rainwater when the structure is used as a noise barrier exposed to the weather outside.

  A plate or a slab can be formed from an anti-noise structure as described above. A use of an anti-noise structure as described above can be provided by arranging the structure on the walls and / or the ceiling of a room or even as an anti-noise screen outside.

  Description of the drawings The invention will be well understood and its various advantages and various characteristics will emerge more clearly from the following description of the nonlimiting exemplary embodiment, with reference to the appended schematic drawings, in which - Figure 1 represents a perspective view rear of a first embodiment of the noise canceling structure according to the invention; - Figure 2 shows a side view of the first embodiment according to Figure 1 - Figure 3 shows a front plan view of the first embodiment according to Figure 1i - Figure 4 shows a front perspective view of a second embodiment making the noise reduction structure in accordance with the invention; - Figure 5 shows a side view of the second embodiment according to Figure 4; - Figure 6 shows a front perspective view of a third embodiment of the noise canceling structure according to the invention; - Figure 7 shows a side view of the third embodiment according to Figure 6; - Figure 8 shows a front plan view of the third embodiment according to Figure 6; - Figure 9 shows a front perspective view of a fourth embodiment of the noise reduction structure according to the invention; - Figure 10 shows a side view of the fourth embodiment according to Figure 9 - Figure 11 shows a front perspective view of a fifth embodiment of the noise reduction structure according to the invention; - Figure 12 shows a side view of the fifth embodiment according to Figure 11; - Figure 13 shows a rear cutaway perspective view of a sixth embodiment of the noise reduction structure according to the invention; - Figure 14 shows a cutaway side view of the sixth embodiment according to Figure 13; - Figures 15 to 20 show a perspective view of six different embodiments of connectors for the sixth embodiment according to Figure 13; - Figure 21 shows a perspective view cut away from a seventh embodiment of the noise reduction structure according to the invention; - Figure 22 shows a front cutaway view of an eighth embodiment of the noise reduction structure according to the invention; - Figure 23 shows a side view of the eighth embodiment according to Figure 22; - Figure 24 shows a rear perspective view of a ninth embodiment of the noise canceling structure according to the invention; - Figure 25 shows a rear perspective view of a tenth embodiment of the noise reduction structure according to the invention; - Figure 26 shows a perspective view of a eleventh embodiment of the noise reduction structure according to the invention; - Figure 27 shows a front perspective view of a twelfth embodiment of the noise canceling structure according to the invention - Figure 28 shows a side view of the twelfth embodiment according to Figure 27; - Figure 29 shows a partial front side perspective view of a thirteenth embodiment of the noise reduction structure according to the invention; - Figure 30 shows a side view of the thirteenth embodiment according to Figure 29; - Figure 31 shows a perspective view from above of a fourteenth embodiment of the noise reduction structure according to the invention; and - Figure 32 shows a side view of the fourteenth embodiment according to Figure 31.

  Detailed description The main construction models for corrective office or residential panels, self-supporting slabs and / or walls are illustrated below. In a first embodiment of the noise reduction structure, shown in FIGS. 1 to 3, this structure (1) is in the form of a non-structural corrective panel, which can be fixed to the support, such as a ceiling or wall. The noise canceling structure (1) comprises a set of boards (2). The boards (2) are parallel to each other and define a plane (P) for the structure (1).

  The boards (2) are arranged on their rear edge (3), having their longitudinal axis (L) parallel to the plane (P) of the structure (1). The boards (2) are thus oriented towards the source area (S), from which the sound waves (O) originate towards the front of the structure (1). The boards (2) are regularly separated from each other by a free space (4).

  The boards (2) are all separated by spacers (6) or spacer board, most often in the form of a block of plywood, solid wood or other equivalent. The spacers (6) ensure cohesion and mechanical attachment of the boards (2) to each other, as well as maintaining the free spaces (4) at their determined width. Three series of spacers (6) were used in the embodiment according to Figure 3, with two series wedged at each of the ends and a series located in the center of the structure (1).

  At the rear of the noise reduction structure (1), a layer of sound absorbing material (7) is arranged. The sound absorbent (7) generally has a low density, of the order of 0.05. The acoustic absorbent (7) is chosen, for example, from the following materials, alone or in a mixture, of rock wool type, low density wood fibers, based on hemp stalks, recycled rubbers, blown old paper, glass wool, clay beads, honeycombed polystyrene or others. This layer (7) is joined for example by gluing on the rear edges (3) of the 20 boards (2). This structure is very effective over a wide band. It is built with standard elements (planks) and therefore very economical. Depending on the structural characteristics required, this basic structure can be adapted.

  In a second embodiment of the noise reduction structure, shown in Figures 4 and 5, this structure (8) is in the form of a structural panel. The structure (8) comprises a first set of rear boards (9). The rear boards (9) are mutually parallel and are arranged on their rear edge (3), having their longitudinal axis (L) parallel to the plane of the structure (8). The rear boards (9) are thus oriented towards the source area, from which the sound waves originate towards the front of the structure (8). The rear boards (9) 30 are regularly separated from each other by a first series of free spaces (11). A second set of front boards (12) is provided parallel to the first set of rear boards (9), the front boards (12) being positioned between each of the rear boards (9) being offset towards the noise source towards the 'front of the structure (8). The front boards (12) are regularly separated from each other by a free space (13). The static height of the structure (8) is increased by the offset.

  The rear and front boards (9 and 12) are all separated by spacers (6) which ensure cohesion and mechanical attachment of all the boards (9 and 12) to each other, as well as maintaining free spaces ( 11) at their determined width. Gates for access to the rear free space (11) are thus created. To make the corresponding self-supporting structural slab, a wooden plate (14) is joined 10 behind the structure (8) on the rear edges (3) of the rear boards (9) of the first set. This wooden plate (14) can constitute a floor for an exploited room. The noise canceling structure (16) of a third embodiment, shown in Figures 6 to 8, is substantially similar to the noise canceling structure (8) of the second embodiment described above. For higher requirements in terms of sound absorption, acoustic absorbent has been added in the form of strips (17) positioned in the free space (11) of the first set of rear boards (9).

  The strips (17) are glued to each of the rear edges (18) of the front boards (12) of the second offset assembly as well as to the spacers (6).

  In the case of the second and third embodiments for a slab for example (see FIG. 8), gates (19) generating access to the free spaces (11) between the rear boards (9) of the first set are obtained by the spacers (6). For structural reasons of sliding of the section made up of the boards (9 and 12) by the effect of shear flux when the structure is bent (slab in flexion), the gills 25 (19) are interrupted when arriving towards the supports of the structure (8 and 16), about one fifth of the span length from the support. The structure (8 and 16) thus comprises longer spacers (21) for the resumption of shearing.

  This interruption of the oue̋s (19) allows it to withstand well the shearing forces with connecting elements (22) calculated for this purpose, mechanically fixing the boards 30 (9 and 12) and the spacer (21) together without reducing the function structural acoustics (8 and 16). Indeed, near the walls, the sounds are already partially attenuated by their reverberation on the slab-wall angle and the noise source is significantly weaker compared to the center of the slab.

  The noise canceling structure (23) of a fourth embodiment, shown in Figures 9 and 10, is substantially similar to the noise canceling structure (16) of the third embodiment described above. When these acoustic absorbing structures, already described above, are used as slabs, with dwellings or offices 5 located on the slab, the structure (23) must have the function of acoustic absorber for aerial sound, at level of the lower ceiling, plus the function of sound absorbing structure (impact noise like heels, etc.) at ground level or upper floor. Solid state sound physics show that to absorb this impact noise, a mass - spring - mass type system is also required, as for low air frequencies. In this case, the concept of the structure will evolve favorably towards the mix of wood - concrete or even heavy material wood, for example of clay brick, plaster, lime-based materials or others. For example, a layer of concrete (24) is poured on the wooden plate (14) secured to the rear of the structure 15 (23). This concrete is thus placed in a floating layer (24) on the wooden floor (14), of the screed type. This concrete screed (24) can constitute a slab for a floor (14) and absorb structural noise.

  As an example only, the width of the rear boards (9) is substantially equal to 210 mm and their thickness substantially equal to 58 mm. The wooden floor (14) has a thickness substantially equal to 22 mm. These very simple structures can be manufactured in modules with a width allowing manual or mechanized carrying. The complete panel is then constructed by juxtaposition of several basic modules of constant width (for example substantially 1 m in width). The noise canceling structure (26) of a fifth embodiment, shown in Figures 11 and 12, is substantially similar to the noise canceling structure (23) of the fourth embodiment described above. Each of the boards of the first set of rear boards (9) or of the second set of front boards (12) is made up of two portions (27 and 28) joined together. These two portions (27 and 28) 30 can be in laminated planks or in agglomerated panels or the like. For the manufacture of acoustic corrective structures, planed solid planks are often the most economical raw material. But the structures can be made with glued planks (duo, glued laminated wood) or plywood type panels or particle boards or with other materials other than wood (plastic, glass, sheet metal or others. ..) In a sixth embodiment of the anti-noise structure, shown in Figures 13 and 14, this structure (29) is in the form of a structural panel 5 mixed wood - concrete. The structure (29) comprises a first set of rear boards (9). The rear boards (9) are mutually parallel and are arranged on their rear edge (3), having their longitudinal axis (L) parallel to the plane of the structure (29). The rear boards (9) are thus oriented towards the source area, from which the sound waves originate towards the front of the structure (29). The 10 rear boards (9) are regularly separated from each other by a first series of free spaces (I 1).

  A second set of front boards (12) is provided parallel to the first set of rear boards (9), the front boards (12) being positioned between each of the rear boards (9) being offset towards the noise source 15 towards the front of the structure (29). The front boards (12) are regularly separated from each other by a free space (13). The static height of the structure (29) is increased by the offset.

  The rear and front boards (9 and 12) are all separated by spacers (6) which ensure cohesion and mechanical attachment of all of the boards 20 (9 and 12) to each other, as well as maintaining free spaces (11) to their determined width. A shear connector (31) is inserted into a notch of corresponding thickness formed by a saw cut in each of the boards of the first set of rear boards (9), or even in the strips of sound absorbent (17), transversely by relative to their longitudinal axis (L) and in the plane of the structure 25 (29).

  For larger spans of the structure (29), the section may be mixed in wood - concrete, with the wood acting in traction, and the concrete acting in compression. A layer of concrete (32) is therefore poured into the free spaces (11) between the rear boards (9), to form a slab. In this case, the concrete (32) will come as far as 30 the acoustic absorbent (17).

  For the composite section to be effective, it will be necessary to interpose the connector (31) working to resist the shear flow of the composite section. The shear connector (31) strengthens the cohesion of the wood with the concrete of the layer (32). The number of these connectors (31) is studied as a function of the shear forces to be used to make the mixed wood - concrete section fully function. But any type of transverse connector (31) can be used (metal rod, board or transverse slat, etc.). The shear connector (31) is used close to the supports (maximum shear flow) for slabs in a single span, bearing on two supports.

  Six different embodiments of connectors for the sixth embodiment have been shown in Figures 15 to 20. The connector of Figure 16 is in the form of a thin sheet having an inverted L-shaped section (33). The connector of Figure 17 is in the form of a thin sheet having a profile (34) with a side projecting wing (35). The connector of Figure 18 is in the form of a thin sheet with a T-profile (36).

  The rear rib of the inverted L (33) or T (36) profile or the wing (35) has holes (35a) to allow the rear boards (9) to be screwed onto the rear edge (3). This horizontal rib stiffens the sheet metal of the connector (33, 34 and 36) which will then be able to accept higher thrusts from the concrete of the layer (32). This screwing can take up transverse tensile forces from the concrete block (32) relative to the wooden block, more particularly at mid-span.

  Perforations (37) have been provided in the sheet metal of the shear connectors (31, 33, 34 and 36) to allow the concrete and its aggregates to flow through these perforations (37) to completely block the free spaces. (11) between the rear boards (9). After setting, the concrete (32) will thus be completely blocked by these connectors (31, 33, 34 and 36) and the connection of the concrete to the wooden structure will be perfect with total efficiency.

  A seventh embodiment of the noise canceling structure, shown in Figure 21, 25 is substantially similar to the noise canceling structure (29) of the sixth embodiment described above. In the case of a slab with a structure (38) in two spans bearing on three supports, the forces on the slab are reversed with traction in the concrete of the layer (32) and compression in the wood of the boards rear and front (9 and 12).

  The two shear connectors (39) placed on either side of the support are completed by bolted metal threaded rods (41) taking up the tensile forces. The connectors of Figures 19 and 20 have perforations (42) to allow anchoring of the threaded rods (41). The threaded rods (41) are positioned at the free spaces (11) between two rear boards (9) and are embedded in the concrete layer (32).

  In an eighth embodiment of the noise reduction structure, shown in FIGS. 22 and 23, this structure (43) takes up a principle substantially similar to that of the third embodiment. The structure (43) is constructed with regular alternation of wide rear boards (9) and thin offset boards (44). Between the wide rear boards (9) and the offset fine boards (44) are provided spacers (6) creating the spacing. The thin planks (44) have a width less than or equal to their thickness compared to the wide rear planks (9). The structure (43) is open so as to allow sounds to penetrate through the oue̋s (19) created by the spacing of the boards (9 and 44).

  At the rear and on the rear edges (18) of the offset fine planks (44) are strips of an acoustic absorbent (17). The forward shift of the thin boards (44) is provided so that the bands of an acoustic absorbent (17) come flush with the rear edges (3) of the wide rear boards (9). The structure (43) comprises boards offset vertically or of different widths (44), to create a niche trap sounds. Then, the horizontal spacing of the boards (9 and 44) opens the gates (19), creates another level of sound trap. Finally, at the rear of the thin board (44), a bahde of insulation (17) absorbs the sounds that have penetrated into the hearing 20 (19).

  By way of example only, the width of the rear boards (9) is substantially equal to 80 mm and their thickness substantially equal to 58 min. The width of the offset thin boards (44) is substantially equal to 20 nun and their thickness substantially equal to 58 rmi. The spacers (6) have a square section substantially equal to 20 mm. The width of the insulating strips (17) is substantially equal to 98 mm and their thickness substantially equal to 30 mm. The acoustic function of the panel will be optimized by varying the following four adjustment parameters: the thickness of the boards (44), giving the first level of absorption, with wide openings for low frequencies (thickness of the board (44) more 30 thickness of the spacer (6)) - the offset of the spacer (6) relative to the upper board, knowing that for a non-structural corrector, the spacer (6) can be omitted; - the width of the hole (19), given by the thickness of the spacer (6) or horizontal offset of the boards; and - the absorbent (17), and its microstructural definition, that is to say its density, its exposed surface or its profile and its own composition.

  When we increase these four dimensions of this structure, the panel improves in the low frequency range, from 50 Hz to 1000 Hz. When we decrease the four dimensions of this structure, the panel improves in the high frequency range , from 500 Hz to 2000 Hz. Depending on the needs of the construction, these four parameters will be changed in one direction or the other.

  The noise canceling structure (46) of a ninth embodiment, shown in Figure 24, is substantially similar to the noise canceling structure (43) of the eighth embodiment described above. Only two elements (47) are inserted parallel to the plane of the structure (46) and perpendicular to the longitudinal axis (L) of the boards (9 and 44), in a notch cut in each of the rear boards (9). The edge 15 (18) of all the thin boards (44) is pressed against the element (47). The element (47) realizes in this way a mechanical connection between the wide rear planks (9) and the thin planks (44) which remain separated from each other to create the gills (19), the structure (46) no longer requiring the presence of spacers. The strips of sound absorbing material (17) are flush with the rear edges (3) of the wide rear boards (9), as well as the rear surface of the connection element (47).

  The noise canceling structure (48) of a tenth embodiment, shown in Figure 25, is substantially similar to the noise canceling structure (46) of the ninth embodiment described above. The thin boards (49) have a section in the shape of a swallow's tail. The oue̋s (19) have in this way a small area entrance leading to a larger underlying volume. The ears (19) function as a depression cavity which better absorbs sound waves.

  In an eleventh embodiment of the noise reduction structure, shown in FIG. 26, this structure (51) has an alternation of wide rear planks (9) and thin planks not offset in swallow tail (49) and three connection elements 30 (47). These connection elements (47) are pressed against the rear edges (3) of the wide rear boards (9) and of the thin boards not offset in swallow tail (49) all arriving at the same level. Between the connection elements (47) are provided two layers of sound absorbent (7), of the same thickness as the elements (47) and fixed on the rear edges (3) of the wide rear planks (9) and of the thin planks not staggered in swallow tail (49).

  The noise canceling structure (52) of a twelfth embodiment, shown in Figures 27 and 28, is substantially similar to the noise canceling structure (43) of the eighth embodiment described above. The edges (53), of the planks (9 and 44) of the alternating planks, facing the noise source zone, are provided with grooves grooved in the longitudinal direction (L). With the field (53) of the boards (9 and 44) thus shaped so as to create a rough surface, the high frequencies will be reflected and canceled out by telescoping. This absorbent profile (53) of the boards may only be provided on the wide rear board (9), the sounds entering the free space (11) at the front of the thin board (44) being already partially trapped. . These grooves make it possible to improve the acoustic efficiency of the structure (52).

  The thirteenth and fourteenth embodiments are in the field of noise barriers for roads, highways, railways and airports. The principle of this acoustic structure can advantageously be adapted to an acoustic screen for the sound of road traffic and the acoustic protection of inhabited areas close to the motorized transport network. The first additional characteristic is that of durability with respect to the weather, either by chemical treatments of the woods in autoclave with metal salts (more penalizing from an ecological point of view to the destruction of the panel), or by a design being itself constructive protection from the weather. The second additional characteristic is that of presenting in the upper part of the structure a construction which reduces the effect of a rebounding noise wave on the upper line of the structure.

  The noise canceling structure (54) of the thirteenth embodiment, shown in Figures 29 and 30, comprises a first set of rear boards (9). The rear boards (9) are mutually parallel and are arranged on their rear edge (3), having their longitudinal axis (L) parallel to the plane of the structure (54). The rear boards (9) are thus oriented towards the source zone, from which the sound waves originate towards the front of the structure (54). The rear boards (9) 30 are regularly separated from each other by a free space.

  A second set of front boards (12) is provided parallel to the first set of rear boards (9), the front boards (12) being positioned between each of the rear boards (9) being offset towards the noise source towards the 'front of the structure (54). The front boards (12) are regularly separated from each other by a free space (13). The static height of the structure (54) is thus increased by the offset.

  The rear and front boards (9 and 12) are all separated by spacers 5 (6) which ensure cohesion and mechanical attachment of all the boards (9 and 12) to each other, as well as maintaining free spaces at their determined width.

  The free space between the rear boards (9) is completely filled with an acoustic absorbent material (56).

  The rear and front planks (9 and 12) are inclined downwards towards the ground to promote the flow of water on the front face of the structure (54), in order to avoid infiltration as much as possible. water in the sound absorbent (56). The water trapped in the acoustic absorbent (56) would increase its density and cause it to lose its acoustic properties. In addition, the board incorporates a negative profile like a drop of water, to drop the water arriving on the edge at the front of the board. Sealing pieces (57) are also positioned on the sound absorbing material (56) and are flush with the rear edges (3) of the non-offset rear boards (9).

  In a fourteenth embodiment of the noise reduction structure shown in Figures 31 and 32, this structure (58) comprises a set of rear boards (9) and a set of boards shifted forward (59). The front boards (59) are directly joined to the rear boards (9) to form torques in a similar manner to the portions of the fifth embodiment. A spacer (6) is provided between two pairs of rear (9) and front (59) boards. The free space between the rear boards (9) behind the front boards (59) is completely filled with an acoustic absorbent material (56).

  To improve the performance of very low frequency acoustic absorbers, the structure (58) is fixed to its support (61) by interfacing between the support (61) and the absorbing structure an elastomer damping washer (62), allowing the structure (58) to compress against its support (61). These pieces of flexible material are positioned on the rear edges (3) of the non-offset rear boards (9). 30 A mass-spring-mass system is thus created, which functions as a Helmotz resonator. By fixing this structural panel on elastomeric supports (62), or absorbent rubber, the structure (58) can deform by crushing its supports, and thus absorb the low frequencies.

  At the rear of the acoustic screen (58), a water tightness will be developed over the entire surface, to protect the absorbent (56). This protection can be made of tar paper, polyethylene film (thermoplastic polymer), sheet metal, or other. Particular attention will be paid to the connection of the sealing strips, so that these connections are also watertight.

  A roof (63) is placed on the structure (58). For reasons of efficiency on the wave effect, this roof (63) has an overhang in relation to the exposed face of the structure (58). This has the effect of returning the wave of sound waves towards the interior of the road, rather than letting it bounce off the crest of the structure (58). To fragment this wave and break its potential energy, this roof (63) develops a horizontal profile in a broken line, which has the consequence of breaking the wave at each positive or negative edge of the horizontal broken line. An example of a very efficient roof is developed in document FR-2.813.904. The example of this roof (63) may be replaced by other roof variants, made of sheet metal, glass or plexiglass or even with other materials with equivalent performance.

  This roof (63) is held by a stabilization arm (64) and it is adjustable in inclination as a function of the length of this arm (64). The length and the inclination of this wooden roof (63) are adjusted on the basis of criteria such as the protection against rain of the front face of the structure (58), the return of the wave of sound waves more or 20 less high on the road (more open in the case of very narrow roads and more ferned for flat reliefs), and the architectural desire for integration into the site.

  The acoustic screen also works without a roof, but its efficiency is then lower, as well as its durability, even with timber treated in autoclave with chemical treatment in the mass. The present invention is not limited to the embodiments described and illustrated. Many modifications can be made without departing from the framework defined by the scope of the set of claims.

  The different embodiments described above can be combined to create yet different noise-reducing structures.

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Claims (14)

  1. Structure, defining a plane (P), intended for the acoustic abs o of sound waves, in the frequency range and 10 kHz, coming from a source zone of sound waves which it comprises a set of plates (2), paral on edge (3), with their longitudinal axis (L) parallel (1), oriented towards the source area (S) and separated a free space (4).   2. Structure according to claim 1, characterized in set of spacers (6), each of the spacers (6) free (4) between each of the boards (2), making a c said boards (2), and having a length ir boards (2).   3. Structure according to claim 1, characterized in that q an element (47) inserted in each of the boards (9) parallel to the plane of the structure (46) and per longitudinal (L) of the boards (9, 44) and providing a c said boards (9, 44).   4. Structure according to claim 2 or 3, characterized in a layer of acoustic absorbent (7) positioned parallel structure (1) on the edges (3) opposite to the area under planks (2).   5. Structure according to one of claims 2 to 4, characterized boards (12) are offset from other plai the set of boards, ordered alternately perpendicular to the plane of the structure (8), and in direction ption or correction nces audible between 50 Hz res (S), characterized in that, between them, arranged ru plane (P) of the structure from each other by that it includes a bit stuck in space mechanical connection between lower than that of said I (it includes at least the set of boards) endicularly to the axis (mechanical connection between that which includes an element at the plane (P) of this (S) of the set of ée in that some of the non-offset ches (9) of e in a regular pattern, ction of the source area.   6. Structure according to claim 5, characterized in that it comprises bands of sound absorbent (17) positioned parallel to the plane of the structure (16) on the edges opposite to the source area (18) of the offset boards (12 ) and between the non-offset boards (9) of the set of boards.   7. Structure according to claim 6, characterized in that it comprises a wooden panel (14) positioned parallel to the plane of the structure (8) on the edges (3) opposite the source area of the set of boards ( 9), and in that it comprises a concrete screed (24) positioned on the wooden panel (14). 10 8. Structure according to claim 5 or 6, characterized in that it comprises at least one additional connector (31) inserted in the non-offset boards (9) of the set of boards parallel to the plane of the structure (29) and perpendicular to the longitudinal axis (L) of the boards (9). 15 9. Structure according to claim 8, characterized in that it comprises at least one rod (41) mechanically connecting at least two connectors (39), positioned parallel to the plane of the structure (38) and parallel to the longitudinal axis (L) between the non-offset boards (9) of the set of boards. 20 10. Structure according to one of claims 6 to 9, characterized in that it comprises a layer of concrete (32) poured over the acoustic absorbent strips (17) positioned parallel to the plane of the structure (29) and between the non-offset boards (9) of the set of boards.   1 1. Structure according to one of claims 5 to 10, characterized in that the offset boards are arranged so that the acoustic absorbent strips (17) positioned parallel to the plane of the structure on the edges opposite to the source area (18) offset boards (44) and between the non-offset boards (9) of the set of boards are flush with the edges opposite to the source zone (3) of the non-offset boards (9) of the board set .   12. Structure according to claim 11, characterized in that sealing parts   (57) are positioned on the sound absorbent strips (56) and are flush with the edges opposite the source area (3) non-offset boards (9) of (57) are positioned on the sound absorbent strips (56 ) and come flush with the edges opposite the source area (3) of the non-offset boards (9) of the set of boards. the set of boards. 13. Structure according to one of the preceding claims, characterized in that   13. Structure according to one of the preceding claims, characterized in that damping pieces (62) made of a flexible material are positioned on the edges opposite the source area (3) of the non-offset boards (9) of the set 10 of boards. damping pieces (62) made of a flexible material are positioned on the edges opposite the source area (3) of the non-offset boards (9) of the set 10 of boards. 14. Structure according to one of the preceding claims, characterized in that   14. Structure according to one of the preceding claims, characterized in that some of the boards (44), ordered alternately in a regular pattern, have a width less than or equal to their thickness compared to other boards (9 ) of the set of boards. some of the boards (44), arranged alternately in a regular pattern, have a width less than or equal to their thickness with respect to other boards (9) of the set of boards. 15. Structure according to claim 14, characterized in that the width boards   15. Structure according to claim 14, characterized in that the boards with a width less than or equal to their thickness have a tail-shaped section less than or equal to their thickness have a section in the shape of a swallow's tail (49). swallow (49). 16. Structure according to one of the preceding claims, characterized in that the   16. Structure according to one of the preceding claims, characterized in that the edges, facing the source area (53) of the boards (9, 44) of the edge assembly, facing the source area (53) boards (9, 44) of the set of boards are grooved. boards, are grooved. 17. Structure according to one of the preceding claims, characterized in that the   17. Structure according to one of the preceding claims, characterized in that the boards of the set of boards are formed from at least two portions (27, 28, 59), and in that the portions (27, 28, 59) of the boards are assembled offset from one another in the direction of the boards of the set of boards are formed from at least two portions (27, 28, 59), and in that the portions (27, 28, 59) of the boards are assembled offset from one another in the direction of the source area. source area. 18. Structure according to one of the preceding claims, characterized in that the   18. Structure according to one of the preceding claims, characterized in that the boards (9, 12) of the set of boards have an inclination and in that they are oriented towards the ground as a lampshade and for discharging the rainwater, when using the structure as a noise barrier (58) exposed planks (9, 12) of the plank assembly have an inclination and in that they are oriented towards the ground as a lampshade and for discharging rainwater, when the structure is used as a noise barrier (58) exposed to the weather outside. outside weather. Applicant 10 Agent   Applicant 10 Agent Jean-Luc SANDOZ Jean-Luc SANDOZ Cabinet LAURENT & CHARRAS Cabinet LAURENT & CHARRAS