EP1570138A1

EP1570138A1 - Antinoise structure

Info

Publication number: EP1570138A1
Application number: EP03780302A
Authority: EP
Inventors: Jean-Luc Sandoz
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-12-10
Filing date: 2003-10-30
Publication date: 2005-09-07
Anticipated expiration: 2023-10-30
Also published as: ATE348225T1; FR2848232A1; EP1570138B1; ES2276139T3; DE60310450T2; WO2004055284A1; DE60310450D1; AU2003288385A1

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 intended to attenuate, absorb and / or shield 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. 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 production chains are also becoming increasingly noisy.

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, constructions must meet acoustic standards, in order to to make the private or professional environment more comfortable and less tiring.

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 buildings. 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 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 surface configuration homogeneous, 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.

Also known from documents FR-1,064,968, WO-00 / 61,888 and US-4,244,439 anti-noise structures made of a continuous and homogeneous material. These structures have series of parallel blades, forming series of parallel blind channels with their rear bottom or their side wall.

However, these structures have the drawback of constituting monolithic masses generating additional parasitic vibrations. In addition, due to their design, these structures can very difficult to adapt, both dimensionally and structurally, to the surfaces which they cover and to the characteristics of the sound waves which they are responsible for absorbing.

Summary of the invention

One of the main problems that arises is that of being able to develop a structure against the acoustic nuisances of a source of noise located in the same area of space. A second problem is to succeed in finding an acoustic structural panel or partition walls intended to protect the environment, integrating different construction scales to have broadband efficiency, and therefore 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 frequency band, from low frequencies of 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 10 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, and - a set of spacing elements, making a joining between said boards and intended to maintain the free spaces.

In other words, the structure has a three-dimensional configuration which makes it possible to create traps for sound waves. These traps are in the form of gills or captive sound cavities, which are maintained by means of spacers. The boards create a first two-dimensional configuration and the spacers add an additional dimension to the bottom of the gills.

The functional characteristics of this structure based on planks and wooden spacers are to be both structural and acoustic corrective. The structure therefore combines the two functions to be used as a slab or as a load-bearing wall, or as a simple non-structural corrector added to the already existing structure. These wooden components can be assembled 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. The boards are assembled to form a semi-rigid system, each board and each element being able to vibrate by themselves and thus absorb much more low frequencies, compared to the monolithic structures of the state of the art. In addition, on its surface exposed to noise, different 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 boards together, and in a first alternative embodiment, the set of spacer elements may comprise 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 secure the assembly of the set of boards together, and in a second variant embodiment, the set of spacer elements may comprise one or more cross members inserted in each of the boards of the set of boards. This cross member 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 the realization of certain more discreet ceilings, the boards can all be at the same height, with a space and an absorbent insulation at the rear, the structure being able to comprise a layer of an acoustic absorbent. The acoustic corrector can be simple, without hearing 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 area of the set of boards, that is to say - say 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 of sound absorbent which will be positioned parallel to the plane of the structure on the edges opposite the source zone of the offset boards and between the non-offset boards of the assembly of boards. In 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, c 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. But a concrete screed can be added to improve absorption of structural noise. By concrete is meant any material based on hydraulic binder.

To improve the recovery of the shearing forces of the boards together, 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 include a layer of concrete poured on the sound absorbent strips positioned parallel to the plane of the structure and between the non-offset boards of the set of boards, to produce a real slab in one piece.

In yet another embodiment, the offset boards can be arranged so that the acoustic 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 are flush with the edges opposite the source area of the boards which are not offset from the set of boards, that is to say at the rear 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 planks not offset from the plank assembly, 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 which are not offset from the set of boards, i.e. at the rear. of the structure.

In one embodiment, some of the boards, ordered 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's tail, in order to create a cavity forming sound traps with a large volume but a small area entrance, generating a depression 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 zone, 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 to evacuate rainwater when using the structure 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 clearly understood and its various advantages and various characteristics will become more apparent from the following description of the nonlimiting exemplary embodiment, with reference to the appended schematic drawings, in which:

- Figures 1 to 3 respectively show a rear perspective view, a side view and a front plan view of a first embodiment of the noise reduction structure according to the invention; - Figures 4 and 5 respectively show a front perspective view and a side view of a second embodiment of the noise reduction structure according to the invention;

- Figures 6 to 8 respectively show a front perspective view, a side view and a front plan view of a third embodiment of the noise reduction structure according to the invention;

- Figures 9 and 10 respectively show a front perspective view and a side view of a fourth embodiment of the noise reduction structure according to the invention; - Figures 11 and 12 respectively show a front perspective view and a side view of a fifth embodiment of the noise reduction structure according to the invention;

- Figures 13 and 14 respectively show a rear cutaway perspective view and a cutaway side view of a sixth embodiment of the noise canceling structure according to the invention;

- 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 rear cutaway perspective view of a seventh embodiment of the noise canceling structure according to the invention;

- Figures 22 and 23 respectively show a front cutaway perspective view and a side view of an eighth embodiment of the noise reduction structure according to the invention;

- Figures 24 to 26 each show a rear perspective view of a ninth, a tenth and an eleventh embodiment of the noise reduction structure according to the invention;

- Figures 27 and 28 respectively show a front perspective view and a side view of a twelfth embodiment of the noise reduction structure according to the invention; - Figures 29 and 30 respectively show a partial front side perspective view and a side view of a thirteenth embodiment of the noise reduction structure according to the invention; and

- Figures 31 and 32 respectively show a perspective view from above and a side view fourteenth embodiment of the noise reduction structure according to the invention.

detailed description

The main construction models for office or residential corrective panels, slabs and / or self-supporting walls are illustrated below. In a first embodiment of the noise reduction structure, shown in Figures 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 reduction 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 originate

(O) 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 one 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 of acoustic absorbent (7) is joined for example by gluing on the rear edges (3) of the boards (2). This structure is very effective over a wide band. It is built with standard boards 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 in the direction of the source zone, from which the sound waves originate in the direction of the front of the structure (8). The rear boards (9) are regularly separated from each other by a first series of free spaces (H). 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) to their specific width. Gates to access the rear rear space (11) are thus created. To make the corresponding self-supporting structural slab, a wooden plate (14) is secured to the rear of 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 reduction structure (8) of the second embodiment described above. For greater requirements in terms of sound absorption, sound absorbent has been added in the form of strips (17) positioned in the room (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 Figure 8), louvers (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 composed of the boards (9 and 12) by the effect of shear flux when the structure is bent (slab in flexion), the gills (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 gills (19) makes it possible to withstand well the shearing forces with connections (22) calculated for this purpose, mechanically fixing together the boards (9 and 12) and the spacer (21) without reducing the acoustic function of the structure (8 and 16). Indeed, near the walls, the sounds are already partially attenuated by their reverberation on the slab-wall angle. The noise source is significantly lower 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 located on the slab, the structure (23) must have the function of acoustic absorber for aerial sound, at the level from the lower ceiling, plus the function of the sound absorbing structure (impact noise such as 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 combination of wood - concrete or even wood - heavy material, 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 (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. By way of 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) can be in laminated boards or in agglomerated panels or equivalent. For the manufacture of acoustic corrective structures, solid planed boards are often the most economical raw material. However, the structures can be made with glued boards (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 noise reduction structure, shown in

Figures 13 and 14, this structure (29) is in the form of a composite wood-concrete structural panel. 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 rear boards (9) 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 (29). The front boards (12) are regularly separated from each other by an Hebrew 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 joining of all of the boards (9 and 12) therebetween, as well as maintaining the free spaces (11) at 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 (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 up to 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 in order to make the mixed wood - concrete section work fully. 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 wing protruding laterally (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 can then 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) were made 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, 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 efforts of traction. 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

Figures 22 and 23, this structure (43) uses 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 boards (44) have a width less than or equal to their thickness with respect to the wide rear boards (9). The structure (43) is open so as to allow sounds to penetrate through the gills (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 strips of sound absorbent (17) are 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) close the gills (19), creates another level of sound trap. Finally, behind the thin board (44), an insulating strip (17) absorbs the sounds that have entered the hearing (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 mm. The width of the offset fine boards (44) is substantially equal to 20 mm and their thickness substantially equal to 58 mm. 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) plus 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 hearing (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 crosspieces (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 the edge of each of the rear boards (9) . The rear edge (18) of all the thin boards (44) is pressed against the crosspiece (47).

This crosspiece (47) makes 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) does not no longer requiring the presence of spacers. The strips of an acoustic absorbent (17) are flush with the rear edges (3) of the wide rear boards (9), as well as the rear surface of the crosspiece (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 openings (19) have in this way a small area entrance leading to a larger underlying volume. The gills (19) function as a vacuum 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 connecting crosspieces (47). These crosspieces (47) are pressed against the rear edges (3) of the wide rear boards (9) and of the thin boards not offset in the swallow tail (49) all arriving at the same level. Between the crosspieces (47) are provided two layers of sound absorbent (7), of the same thickness as the crosspieces (47) and fixed on the rear edges (3) of the wide rear planks (9) and of the thin planks not offset 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 be advantageously 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 wood in autoclave with metal salts (more penalizing from an ecological point of view to the destruction of the panel), or by a design being it -even constructive protection against 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 planks (9) are thus oriented towards the source area, from which come sound waves towards the front of the structure (54). The rear boards (9) 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 (6) which ensure cohesion and mechanical attachment of all the boards (9 and 12) to each other, as well as maintaining free spaces to 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 water infiltration as much as possible. in the acoustic 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 couples 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 material flexible are positioned on the rear edges (3) of the non-offset rear boards (9). This creates a mass - spring - mass system, which functions like 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 waterproof.

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) could be replaced by other variants of roofs, 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 inclination of this wooden roof (63) are adjusted on the basis of criteria such as protection against rain on the front face of the structure (58), the return of the wave of sound waves more or less high on the road (more open in the case of very steep roads and more closed 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 even different noise reduction structures.

Claims

1. Structure, defining a plane (P), intended for the absorption or the acoustic correction of sound waves, in the range of audible frequencies between 50 Hz and 10 kHz, coming from a source area of sound waves ( S), characterized in that it comprises:

- a set of boards (2), mutually parallel, arranged on edge (3), with their longitudinal axis (L) parallel to the plane (P) of the structure (1), oriented towards the source area (S) and separated from each other by a free space (4), and

- A set of spacers (6), securing between said boards (2) and intended to maintain the free spaces (4).

2. Structure according to claim 1, characterized in that the set of spacers comprises a set of spacers (6), each of the spacers (6) being wedged in the free space (4) between each of boards (2), the spacers (6) having a length less than that of said boards (2).

3. A structure according to claim 1, characterized in that the set of spacers comprises one or more crosspieces (47) inserted in each of the boards (9) of the set of boards, parallel to the plane of the structure (46), and perpendicular to the longitudinal axis (L) of the boards (9, 44).

4. Structure according to claim 2 or 3, characterized in that it comprises a layer of acoustic absorbent (7) positioned parallel to the plane (P) of the structure (1) on the edges (3) opposite to the source area (S) of the set of boards (2).

5. A structure according to one of claims 2 to 4, characterized in that some of the boards (12) are offset with respect to other non-offset boards (9) of the set of boards, ordered alternately according to a regular pattern, perpendicular to the plane of the structure (8), and towards 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).

8. A 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).

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 board assembly.

10. A structure according to one of claims 6 to 9, characterized in that it comprises a layer of concrete (32) poured over the bands of sound absorbent (17) positioned parallel to the plane of the structure (29) and between the non-offset boards (9) of the set of boards.

11. A structure according to one of claims 5 to 10, characterized in that the offset boards are arranged so that the sound absorbent strips (17) positioned parallel to the plane of the structure on the edges opposite 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 the source area (3) of the non-offset boards (9) of the set of boards.

12. Structure according to claim 11, characterized in that sealing parts (57) are positioned on the acoustic absorbent strips (56) and are flush with the edges opposite the source area (3) of the boards not offset ( 9) of the set of boards.

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 of boards.

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.

15. Structure according to claim 14, characterized in that the boards with a width less than or equal to their thickness have a section in the shape of a swallow's tail (49).

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 set of boards, are grooved.

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) boards are assembled offset from each other in the direction of the source area.

8. 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 l rainwater, when using the structure as a noise barrier (58) exposed to the weather outside.