EP0926656A1 - Sound-insulating structure with body containing absorbant porous material - Google Patents

Abstract

The structure (11) consists of a body (12) of a porous material which absorbs acoustic energy, e.g. a slab or partition of wood concrete. It incorporates at least one tubular component (13) which forms a cavity. The tubular component is embedded in the material and has a series of equally spaced bores of 0.5 - 20 mm diameter, the dimensions of the bores and cavity being selected to give optimum absorption of noise at a predetermined acoustic frequency. The cavity of the tubular component, which is 30 - 50 mm in diameter, can be empty or filled with an absorbent material. The structure can have a series of parallel tubular components of different sizes to absorb noises at different frequencies, and the structure can incorporate a system for vibrating the air column inside the tubular components in an opposite phase to the acoustic wave to be damped.

Description

The present invention relates to a structure noise canceling comprising a body of porous material absorbing acoustic energy.

It finds a particularly application important although not exclusive in the field of the absorption of noise or noise, as well as in that of the modification of the orientation of sound waves from a source determined, inside a dwelling, of a industrial building, or vehicle, or the open air, especially around environments particularly noisy like highways and / or the airports.

We already know shock absorbers noises essentially based on absorption by porous materials such as porous concrete, wool mineral or other.

We also know devices (FR-A-2 222 715) using constituted resonators by hollow tubular elements with air chambers closed on three sides.

There are also (FR-A-2 553 808) elements sound absorbing construction comprising a masonry wall provided with at least one absorber forming a slotted resonator, itself constituted by a longitudinal internal cavity which extends parallel to the facing and which communicates with the exterior by means of said slot.

We also know (FR-A-2 533 058) a component of sound absorbing construction formed from sheets with networked alveolar cavities or nests bees.

We also know (DE 94 08118) an absorbent wall comprising pipes or channels fixed to a support rigid and whose orifices are directed towards the source of noise.

Such devices have drawbacks.

In fact, they are generally not easy to manufacture, and do not allow to amortize enough noise according to requirements always increased by public authorities, users, car manufacturers, etc.

The present invention aims to provide a structure noise canceling responding better than those previously known to the requirements of the practice, in particular in that that it allows a much better absorption of acoustic frequencies, the latter being selected according to the noise environment specific, which allows, rather than absorbing average way all the nuisances, to absorb especially those that are actually and really important in the type environment and configuration concerned.

This is achieved inexpensively and easily enforce.

To this end, the invention notably proposes a noise canceling structure comprising a material body porous absorbing acoustic energy and comprising at least one tubular element defining a cavity, said element being embedded in the middle of the mass of the absorbent material with several holes regularly arranged on the wall of said element, each hole forming a resonator neck, the dimensions of said cavity and the holes being arranged to allow optimized absorption of a determined acoustic frequency.

By dimensions of the cavity is meant times the cross section and the length, defining the volume of air interested in the resonance.

By definition a resonator is made up of a capacity defining a volume cavity V connected outwardly through a section neck or conduit and of determined length. The air included in the pass acts like a mass, the air included in the cavity acting like a spring.

The result is a system that is substantially and more or less coarsely tuned which has a frequency of resonance (fr).

In practice, the collar (s) are generally defined by one or more holes, associated with one or more several portions of volume.

The holes are drilled in the wall of the element tubular, the height of the necks then being that of the thickness of the wall of the tubular element.

But the passes can also be advantageously made up of small calibrated tubes planted in the wall.

avec n = nombre de trous et H = hauteur corrigée du col de résonateur

c dépend notamment du gaz contenu dans le volume, en l'espèce l'air, soit 340 m/s.

H est quant à lui donné par la formule : H = πd 2 4(1+K 1 d)

avec K₁ par exemple égal à 0,8 et d : diamètre du ou des trous.

In the case of holes of diameter d , for an air volume V, the frequency fr is given by formula Fr = vs 2π nH V

with n = number of holes and H = corrected height of the resonator neck

c depends in particular on the gas contained in the volume, in this case air, ie 340 m / s.

H is given by the formula: H = π d 2 4 (1+ K 1 d )

with K ₁ for example equal to 0.8 and d: diameter of the hole or holes.

According to the invention, and for an annoying frequency determined to absorb, corresponding to the frequency resonant fr from the resonator, so it's going to be possible to size the device according to the neck and cavity dimensions, i.e. basically playing on the length and the cross section of the useful cavity, and the cross section of the hole (s), i.e. their number and their diameter.

• la cavité de l'élément tubulaire est vide ; Par cavité vide on entend une cavité vide de matériau, c'est-à-dire qu'elle est simplement remplie d'air.
• la cavité de l'élément tubulaire est remplie de matériau poreux absorbant ; Dans ce cas, on observe en effet que la cavité continue malgré tout à se comporter comme une colonne d'air jouant un rôle de ressort, compte tenu du caractère poreux du matériau.Il en résulte par contre un plus grand étalement des fréquences.
• l'élément tubulaire est un tube ouvert de chaque côté, par exemple cylindrique ou sensiblement cylindrique.

In advantageous embodiments, one and / or the other of the following arrangements are also used:

• the cavity of the tubular element is empty; By empty cavity is meant an empty cavity of material, that is to say that it is simply filled with air.
• the cavity of the tubular element is filled with porous absorbent material; In this case, we observe that the cavity still continues to behave like an air column playing a spring role, given the porous nature of the material. However, this results in greater frequency spreading.
• the tubular element is a tube open on each side, for example cylindrical or substantially cylindrical.

Curiously, and when the tube is oriented perpendicular to the sound waves, the capacity of the volume V which must a priori be closed for operate effectively as a resonator, operate also satisfactorily even with tubes open, as if the volume of resonant air limited itself to fictitious walls inside of the tube.

This is advantageously further improved when the length dimensions of the tube and the position respective of the pass whose location corresponds to a sound order node, are such that the end of the tube are also located on a wave node whose frequency must be absorbed.

Advantageously, the tubular element can also be partitioned, thereby presenting closed tube portions, spaced from each other, with mixed walls.

• le diamètre de l'élément tubulaire est compris entre 30 mm et 50 mm quelle que soit sa longueur ;
• le diamètre équivalent du col est compris entre 5 mm et 20 mm ;
• l'élément tubulaire comporte plusieurs trous sur ses parois latérales, par exemple situé du même côté que les ondes à amortir ;
• l'élément tubulaire est obturé de chaque côté et le trou est par exemple percé dans une des obturations d'extrémité ;
• le corps est en forme de plaque ou de paroi rigide ;
• le corps est en forme ou sensiblement en forme de nappe ou de feuillard souple ;
• le corps est en forme ou sensiblement en forme allongée autour d'un axe, par exemple en forme de boudin cylindrique ;
• la structure comporte plusieurs éléments tubulaires identiques ;
• elle comporte plusieurs éléments tubulaires différents accordés sur des fréquences différentes ;
• les éléments tubulaires sont disposés sensiblement parallèlement, et par exemple espacés régulièrement les uns des autres ;
• la structure comporte de plus des moyens de mise en vibration de la colonne d'air interne à l'élément tubulaire en opposition de phase avec l'onde acoustique à amortir ;
• le matériau absorbant est constitué par du béton de bois, c'est-à-dire obtenu à partir d'un mélange de ciment, de fibres de bois et d'eau ;
• l'élément tubulaire s'étend sur la totalité ou sensiblement la totalité de la longueur du corps ;
• l'élément tubulaire comporte un élément tubulaire interne concentrique, l'espace compris entre l'élément externe et l'élément interne d'une part, et à l'intérieur du tube interne d'autre part, constituant deux résonateur distincts ;
• le ou les trous sont formés par des petits conduits tubulaires traversant la paroi de l'élément tubulaire ;
• les petits conduits sont par exemple perpendiculaires à l'axe de l'élément tubulaire et s'étendent à l'intérieur et/ou à l'extérieur de l'élément tubulaire ;
• le diamètre des trous est compris entre 0,5 mm et 20 mm, avantageusement entre 0,5 mm et 5 mm, par exemple de l'ordre de 1 mm à de l'ordre de 2 mm ;
• la longueur des tubes est comprise entre 50 cm et 4 m, par exemple entre 50 cm et 1 m.

In this case, each portion of tube has at least one neck.

• the diameter of the tubular element is between 30 mm and 50 mm whatever its length;
• the equivalent diameter of the neck is between 5 mm and 20 mm;
• the tubular element has several holes on its side walls, for example located on the same side as the waves to be damped;
• the tubular element is closed on each side and the hole is for example drilled in one of the end closings;
• the body is in the form of a plate or rigid wall;
• the body is shaped or substantially in the form of a sheet or flexible strip;
• the body is in shape or substantially in elongated shape around an axis, for example in the shape of a cylindrical rod;
• the structure comprises several identical tubular elements;
• it comprises several different tubular elements tuned on different frequencies;
• the tubular elements are arranged substantially parallel, and for example regularly spaced from each other;
• the structure further comprises means for vibrating the column of air internal to the tubular element in phase opposition with the acoustic wave to be damped;
• the absorbent material consists of wood concrete, that is to say obtained from a mixture of cement, wood fibers and water;
• the tubular member extends over all or substantially the entire length of the body;
• the tubular element comprises a concentric internal tubular element, the space between the external element and the internal element on the one hand, and inside the internal tube on the other hand, constituting two distinct resonator;
• the hole or holes are formed by small tubular conduits passing through the wall of the tubular element;
• the small conduits are for example perpendicular to the axis of the tubular element and extend inside and / or outside the tubular element;
• the diameter of the holes is between 0.5 mm and 20 mm, advantageously between 0.5 mm and 5 mm, for example of the order of 1 mm to of the order of 2 mm;
• the length of the tubes is between 50 cm and 4 m, for example between 50 cm and 1 m.

The invention will be better understood on reading the description of particular embodiments which follows, given by way of nonlimiting examples.

• Les figures 1A et 1B montrent une nappe munie de tubes résonnants selon un premier mode de réalisation de l'invention.
• La figure 2 montre un exemple de tube utilisé dans la nappe des figures 1A et 1B.
• Les figures 3A et 3B montrent un autre mode de réalisation de tube résonnant dans un corps absorbant de forme globalement cylindrique.
• La figure 4 montre en coupe selon IV-IV de la figure 5 un autre mode de réalisation d'un tube utilisable selon l'invention.
• La figure 5 montre, en coupe transversale, une structure munie de tubes résonnants selon la figure 4.
• La figure 6 montre schématiquement le principe de fonctionnement d'une structure absorbante selon l'invention avec amortissement dynamique.
• La figure 7 est une courbe de performance mettant en évidence un pic d'absorption à 160 hertz pour une structure d'absorption selon un mode de réalisation de l'invention centrée sur cette fréquence.
• La figure 8 montre deux courbes permettant d'apprécier le coefficient d'absorption d'une dalle poreuse pleine et d'une dalle poreuse comportant des éléments tubulaires selon l'invention.
• La figure 9 montre un mur amortisseur qui comprend une structure antibruit cylindrique selon le mode de réalisation de l'invention décrit aux figures 3A et 3B.
• La figure 10 montre schématiquement la modification de l'orientation et de l'intensité des ondes sonores, obtenues avec un mur antibruit respectivement démuni et muni d'un amortisseur du type correspondant à la figure 9.
• La figure 11 est un autre mode de réalisation vu en coupe latérale d'une structure antibruit selon un mode de réalisation de l'invention avec éléments tubulaires concentriques.

This refers to the accompanying drawings in which:

• FIGS. 1A and 1B show a sheet provided with resonant tubes according to a first embodiment of the invention.
• FIG. 2 shows an example of a tube used in the ply of FIGS. 1A and 1B.
• FIGS. 3A and 3B show another embodiment of a tube resonating in an absorbent body of generally cylindrical shape.
• Figure 4 shows in section on IV-IV of Figure 5 another embodiment of a tube usable according to the invention.
• FIG. 5 shows, in cross section, a structure provided with resonant tubes according to FIG. 4.
• FIG. 6 schematically shows the operating principle of an absorbent structure according to the invention with dynamic damping.
• FIG. 7 is a performance curve showing an absorption peak at 160 hertz for an absorption structure according to an embodiment of the invention centered on this frequency.
• FIG. 8 shows two curves making it possible to assess the absorption coefficient of a solid porous slab and of a porous slab comprising tubular elements according to the invention.
• FIG. 9 shows a damping wall which comprises a cylindrical noise reduction structure according to the embodiment of the invention described in FIGS. 3A and 3B.
• FIG. 10 schematically shows the modification of the orientation and the intensity of the sound waves, obtained with an anti-noise wall respectively lacking and provided with a damper of the type corresponding to FIG. 9.
• Figure 11 is another embodiment seen in side section of an anti-noise structure according to an embodiment of the invention with concentric tubular elements.

Figures 1A and 1B show a structure 1 noise reduction for example a slab 2 or wall in acoustically absorbent material formed by concrete of wood, i.e. a composite material with a mixture of cement, wood and water.

In the following we will use the same numbers of reference to designate identical elements.

The slab has, embedded in the middle of its mass and centered in thickness with respect to the walls flat, several tubular elements 3, 4, 5 parallel, plastic, for example polyethylene whose length is slightly less than that of the slab, for example smaller from 5 to 10 cm on each side and whose cross section is constant.

More specifically, the slab here has four 3 cylindrical elements, of the same diameter, by example equal to 10 cm, open to each of their ends 6, and arranged symmetrically of each side of the slab relative to a central axis.

It then comprises two elements 4 in the form of flattened cylinder, of larger oval section transverse dimension equal for example to 30 cm, and closed at each end by plugs 7 no porous, for example constituted by cylinders in concrete.

Finally, it is provided as a cylindrical central element 5, 20 cm in diameter, open at its ends 8.

Each tubular element is pierced with several holes 9 and 10, evenly spaced, for example every 30 cm, alternately on one side of the tube and on the other, for example offset from each other to others so as not to be opposite.

The holes are sized for, depending on the tube diameters used for example for reasons for sizing the slab itself, allow the absorption of three frequencies resonant disturbers more particularly referred to in this context.

Figure 2 shows the tubular element 3 in perspective.

Figures 3A and 3B show another mode of production of a noise-canceling structure 11 comprising a substantially cylindrical body 12, made of concrete absorbent, and a cylindrical tubular element 13 closed on both sides by plugs 14 no acoustically porous.

The tube 13 is coaxial with the body, by example of a diameter equal to a third of the diameter of the body.

The tube is pierced with a single orifice 15 for example located near a plug, without however the position of the hole in relation to the plug either influencing the absorption of the wave frequency more particularly targeted.

FIG. 3B is a perspective view of which the end of the tubular element has been shown outside the body for explanatory purposes.

It goes without saying that this end is actually drowned in the absorbent material.

FIG. 4 shows another embodiment, in longitudinal section, of a tubular element 20 according to the invention, for example made of plastic flexible, elongated around an axis 21 and defining the cavity 22 of a determined volume, between the walls longitudinal 23 and the closed ends 24 of the item.

It includes a single neck 25, for example made up by a small cylindrical tube 26 high greater than its diameter, for example three times superior.

Referring to Figure 5, the tube 20 is by example embedded in a flexible sheet 27 of wool glass, the tube 26 of the neck being directed towards the source noise 28, but still drowned in the sheet, the latter being for example used in the soundproofing in a car interior.

The sheet thus comprises several tubes 20 identical, parallel, evenly spaced, by example deviated from each other by one dimension equal to the diameter of the tubes.

Figure 6 expresses the principle of operation a noise barrier implementing protection additional active consisting in exciting the column of air from the tubular element so as to create a reverse sound vibration of the incident sound wave at amortize.

The wall of porous material 30, provided with elements tubular 31 excited according to wave 32 shown in mixed line in the figure, compensates for the incident wave 33 in solid lines in the figure, which gives a resulting wave 34 of almost zero amplitude (line interrupted 34 in the figure).

Figure 7 shows a performance curve 39 absorption on a scale of 0 to 1, of a absorbent structure according to the invention with a wall 13 cm thick concrete, with several tubes 5 cm in diameter, each pierced with a hole a few millimeters in diameter, showing a peak absorption at 160 Hz (the frequencies being indicated on the ordinate).

The curves in Figure 8 show the improvement absorption obtained with the same structure without tubular element (curve 40), and with an element tubular (curve 41), according to the invention, centered on 400 Hz.

Figure 9 shows a wall 42 partly comprising high a tubular structure 12 according to the mode of embodiment described with reference to FIGS. 3A and 3B.

Figure 10 shows the sound wave path without structure (solid line 43) and with structure (in dash 44) on a wall with or without the structure of figure 9.

There is a change in intensity and the direction taken by the sound waves emitted.

Thanks to such a system, which can still be improved by providing several tubular elements according to the invention of different diameter, arranged in horizontal tablecloth on the top of the wall, we can win up to 5 db in sound level, when you place yourself near building 45 several meters from the wall.

Figure 11 shows another embodiment of a structure 46 according to the invention comprising a cylindrical internal tubular element 47 coaxial with a cylindrical external tubular element 48, each being drilled with at least one hole to form two concentric resonant cavities, centered on two different waves.

As it goes without saying, and as it results from what precedes the present invention is not limited to more particularly described embodiments, but on the contrary embraces all variants, and in particular those where the tubular element is square, rectangular, or cross section banana shape.

Claims (19)

Noise canceling structure (1, 11) comprising a body (2, 12, 27) of porous energy absorbing material acoustic, characterized in that it comprises at at least one tubular element (3, 4, 5; 13; 20; 31; 47, 48) defining a cavity, said element being embedded in the middle of the mass of absorbent material and drilled with several holes (10, 15, 25) regularly arranged on the side wall of said element, each hole forming a resonator neck, the dimensions of said cavity and holes being arranged for allow optimized frequency absorption determined acoustics. Structure according to claim 1, characterized in that the cavity of the tubular element is empty. Structure according to claim 1, characterized in that the element cavity tubular is filled with absorbent porous material. Structure according to any one of previous claims, characterized in that the tubular element (3, 4, 5; 13; 20; 31; 47, 48) is a cylindrical or substantially cylindrical tube. Structure according to claim 4, characterized in that the diameter of the element tubular is between 30 mm and 50 mm. Structure according to any one of previous claims, characterized in that the equivalent diameter of the hole is between 5 mm and 20 mm. Structure according to any one of claims 1 to 5, characterized in that the equivalent diameter of the hole is between 0.5 and 5 mm. Structure according to any one of previous claims, characterized in that the tubular element (4, 13) is closed off from each side. Structure according to any one of previous claims, characterized in that the body (2) is in the form of a plate or rigid wall. Structure according to any one of claims 1 to 8, characterized in that the body (27) is in the form of a sheet or flexible strip. Structure according to any one of claims 1 to 8, characterized in that the body (12) is shaped or substantially elongated around an axis. Structure according to any one of previous claims, characterized in that it has several tubular elements identical. Structure according to any one of previous claims, characterized in that it has several tubular elements different tuned on different frequencies. Structure according to any one of claims 12 and 13, characterized in that the tubular elements are arranged substantially in parallel. Structure according to any one of previous claims dependent on the claim 2, characterized in that it comprises additionally means for vibrating the column air inside the tubular element in opposition to phase with the acoustic wave to be damped. Structure according to any one of previous claims, characterized in that the tubular member extends over all or substantially the entire length of the body. Structure according to any one of previous claims, characterized in that the tubular member has a tubular member internal concentric, the space between the external element and the internal element on the one hand, and inside the inner tube on the other hand, constituting two distinct resonators. Structure according to any one of previous claims, characterized in that the hole is formed by a small tubular conduit (26) passing through the wall of the tubular element. Structure according to any one of previous claims, characterized in that the absorbent porous material is wood concrete.

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