EP2472018B1 - Acoustically absorbing assembly - Google Patents

Description

Technical area

The present invention relates to an acoustically absorbent assembly intended to constitute a wall element arranged in an enclosure, such as for example an apartment, a concert hall, the passenger compartment of a vehicle etc., and making it possible to control the state of acoustic absorption thereof.

Prior art

We know that the control of sound absorption by walls has called for various devices including passive absorption elements made of porous materials having the property of transforming into heat the sound vibrations they received due to phenomena. friction to which these materials were subjected due to these vibrations.

It is known that the use of such absorbent elements has a certain number of drawbacks, namely in particular their size and their weight as well as their ability to absorb sound vibrations only in reduced domains of the spectrum.

It has also been proposed to use rigid wall elements perforated with a series of holes distributed regularly over their surface, these perforated holes having diameters of the order of 5 to 6 mm. It has been found that such absorbent elements have significant drawbacks and in particular very low efficiency if they were not combined with porous elements.

(impédance de la toile) $${\mathrm{Z}}_{\mathrm{air}}=-\mathrm{jcot}(\mathrm{\omega }\mathrm{D}/{\mathrm{c}}_0\cos \left(\mathrm{\theta }\right)$$

(impédance de l'air) $$\mathrm{Z}\left(\mathrm{\theta }\right)={\mathrm{Z}}_{\mathrm{air}}\left(\mathrm{\theta }\right)+{\mathrm{Z}}_{\mathrm{mpp}}\cos \mathrm{\theta }$$

It was established that one could determine an acoustic impedance Z of the assembly made up of the fabric and the volume of air included between this one and the full rear wall so that one has: $${\mathrm{Z}}_{\mathrm{MPP}}=\mathrm{r}+\mathrm{i\text{'}m}$$

(impedance of the fabric) $${\mathrm{Z}}_{\mathrm{air}}=-\mathrm{jcot}((\mathrm{\omega }\mathrm{D}/{\mathrm{<figure-callout\; id="0"\; label="vs"\; filenames="imgf0001.png"\; state="\{\{state\}\}">vs</figure-callout>}}_0\cos \left(\mathrm{\theta }\right)$$

(air impedance) $$\mathrm{Z}\left(\mathrm{\theta }\right)={\mathrm{Z}}_{\mathrm{air}}\left(\mathrm{\theta }\right)+{\mathrm{Z}}_{\mathrm{mpp}}\cos \mathrm{\theta }$$

et de façon statistique en intégrant la valeur de α(θ) on obtient l'absorption globale d'un panneau, à savoir: $${\alpha }_{\mathit{globale}}={\displaystyle {\int }_{o°}\mathrm{\alpha }\left(\mathrm{\theta }\right).\sin 2\mathrm{\theta }.\mathrm{d\theta }}$$

The absorption coefficient α (θ) is thus obtained, that is to say the impedance for a determined incidence panel θ: $$\mathrm{\alpha }\left(\mathrm{\theta }\right)=4\mathrm{Re}\left\{\mathrm{Z}\left(\mathrm{\theta }\right)\right\}/{\left[1+\mathrm{Re}\left\{{\mathrm{Z}}_{\mathrm{MPA}}\left(\mathrm{\theta }\right)\right\}\right]}^2+{\left[\mathrm{lm}\left\{\mathrm{Z}\left(\mathrm{\theta }\right)\right\}\right]}^2$$

and statistically by integrating the value of α (θ) we obtain the overall absorption of a panel, namely: $${\alpha }_{\mathit{overall}}={\displaystyle {\int }_{o°}\mathrm{\alpha }\left(\mathrm{\theta }\right).\sin 2\mathrm{\theta }.\mathrm{from}}$$

It has thus been established that the absorption spectrum, that is to say the curve representing the variation in the absorption of the aglobal wall as a function of the sound frequency emitted, is related to the diameter of the micro-perforations, and that , all parameters being equal, aglobal absorption was better in the high frequencies when the diameters of the micro-perforations were larger. Conversely, for micro-perforations of smaller diameter the absorption was improved in the low frequencies.

It was proposed according to the document WO 2008/017737 A1 to use an acoustic absorbing assembly intended to constitute, inside an enclosure, at least one wall element, this assembly comprising one or two supports provided with micro-perforations whose diameter is less than 2mm, remarkable in that that the support or supports extend substantially parallel to an adjacent wall, and the acoustic assembly comprises at least two series of micro-perforations distributed on said support.

Although particularly efficient for the absorption of frequencies between 300 and 4000 Hz, the acoustic assembly described above is less effective for the absorption of frequencies between 4000 and 8000 Hz.

Other acoustic absorbent assemblies are known from DE 100 22 902 A1 , EP 0 013 513 A1 and EP 2,078,796 A1 .

Statement of the invention

The object of the present invention is to propose an acoustic assembly having an enlarged acoustic absorption band compared to the acoustic assemblies of the prior art, this acoustic assembly being intended to constitute, for example, a false wall of a room, ie a partition or a ceiling, but also an interior coating of a vehicle etc.

The present invention thus relates to an acoustic absorbent assembly intended to constitute, inside an enclosure, at least one wall element, this assembly comprising at least two supports provided with micro-perforations, remarkable in that said supports are superimposed.

According to a preferred embodiment of the invention, said supports do not include several series of micro-perforations having different diameters.

Thus, in a first embodiment of the invention, the acoustic assembly may consist of two supports (rigid wall or stretched canvas) each provided with a series of orifices which are distributed evenly over the surface said supports by forming respective meshes either of square shape or of triangular shape. The applicant has demonstrated that this acoustic assembly retains its sound absorption capacity even when it is placed behind a support not comprising micro-perforations or when it frames a support not comprising micro-perforations. Thus the invention provides according to claim 1, an acoustic absorbing assembly intended to constitute, inside an enclosure, at least one wall element, this assembly comprising at least two superimposed supports provided with micro-perforations, characterized in that the assembly further comprises a support not comprising micro-perforations, said support being superimposed with the two supports provided with micro-perforations, not framed by the supports provided with micro-perforations and disposed on the visible side when the assembly is placed in the enclosure.

In this embodiment according to the invention, the visible element consists of the support not comprising micro-perforations. This is particularly advantageous, because it is thus possible to exploit the aesthetic virtues (for example printing, lacquering) of the support element not comprising micro-perforations.

According to a particularly preferred embodiment, the acoustic assembly according to the invention consists of at least three parallel supports each comprising a series of micro-perforations, as defined above, remarkable in that said supports are superimposed.

According to an even more preferred embodiment, the acoustic assembly according to the invention consists of three parallel supports each comprising a series of micro-perforations, remarkable in that said supports are superimposed.

In this embodiment, when the acoustic assembly according to the invention is placed near an adjacent wall, the support comprising a series of micro-perforations closest to the adjacent wall is preferably 50 mm from the support comprising a series of contiguous micro-perforations. The support comprising a series of micro-perforations furthest from the adjacent wall is preferably 30 mm away from the support comprising a series of contiguous micro-perforations.

In the context of the present invention, the term “superimposed” does not imply that said supports are in contact with each other on all or part of their surface.

According to a preferred embodiment of the invention, said supports extend substantially parallel to each other.

According to another preferred embodiment of the invention, said supports are inscribed in planes forming between them an angle between 1 and 45 degrees.

Preferably, the supports of the acoustic assembly according to the invention consist of stretched sheets, in particular made of polyvinyl chloride (PVC) films, the thickness of which will preferably be between 0.1 and 0.3 mm, but may also be formed of rigid elements.

According to another preferred embodiment, the supports of the acoustic assembly according to the invention consist of textiles or any other flexible or rigid material.

The distance between the different supports each comprising a series of micro-perforations is preferably between 10 and 90 mm and even more preferably between 20 and 60 mm.

When the acoustic assembly according to the invention is placed near an adjacent wall, the distance between the acoustic assembly according to the invention and said adjacent wall is preferably between 100 and 400 mm and even more preferably between 250 and 350 mm.

Preferably the micro-perforations are circular in shape and are preferably distributed in a mesh of square, triangular or rectangular shape.

Preferably the micro-perforations have a diameter less than 2mm, even more preferably less than 1mm and quite preferentially less than or equal to 0.5mm.

Preferably, the supports comprising a series of micro-perforations have a density of micro-perforations greater than 1000 micro-perforations / m ² , more preferably greater than 30,000 micro-perforations / m ² , even more preferably greater than 300,000 micro-perforations / m ² and quite preferably greater than 400,000 micro-perforations / m ² . Those skilled in the art are able to determine the optimal density of micro-perforations as a function of. This can in particular be adapted according to the nature of the material constituting said support.

• les supports comprenant 30 000 micro-perforations/m2, et dont les micro-perforations ont un diamètre de 0.5mm,
• les supports comprenant 300 000 micro-perforations/m2, et dont les micro-perforations ont un diamètre de 0.2mm,
• les supports comprenant 400 000 micro-perforations/m2, et dont les micro-perforations ont un diamètre de 0.15mm et
• les supports comprenant 500 000 micro-perforations/m2, et dont les micro-perforations ont un diamètre de 0,10 mm.

In an entirely preferred embodiment of the invention, the supports comprising a series of micro-perforations are chosen from the group comprising:

• substrates comprising 30,000 micro-perforations / m2, and whose micro-perforations have a diameter of 0.5mm,
• substrates comprising 300,000 micro-perforations / m2, and whose micro-perforations have a diameter of 0.2mm,
• substrates comprising 400,000 micro-perforations / m2, and whose micro-perforations have a diameter of 0.15mm and
• substrates comprising 500,000 micro-perforations / m2, and whose micro-perforations have a diameter of 0.10 mm.

The supports used in the context of the present invention are advantageously provided with a peripheral border forming a harpoon. Said harpoon allows the supports according to the invention to be fixed to side members.

Any other method of fixing said supports can be envisaged, among these we may notably mention clips and staples.

According to a preferred embodiment of the invention, said spar is a heddle. According to an even more preferred embodiment of the invention, all the supports included in the acoustic assembly according to the invention are fixed on the same rail.

Brief description of the figures

• la figure 1 est une vue partielle schématique en perspective d'un support micro-perforée utilisable dans le cadre de la présente invention.
• la figure 2 est un dessin schématique en coupe verticale d'un exemple de disposition d'un ensemble acoustique selon l'invention par rapport à un plafond.
• la figure 3 est un graphique représentant la variation d'un ensemble acoustique mise en œuvre suivant la figure 2, en fonction de la fréquence sonore,
• la figure 4 est un dessin schématique en coupe verticale d'un exemple de disposition d'un ensemble acoustique selon l'invention par rapport à un plafond.
• la figure 5 est un graphique représentant la variation d'un ensemble acoustique mise en œuvre suivant la figure 4, en fonction de la fréquence sonore,
• la figure 6 est un dessin schématique en coupe verticale d'un exemple de disposition d'un ensemble acoustique selon l'invention par rapport à un plafond.
• la figure 7 est un graphique représentant la variation d'un ensemble acoustique mise en œuvre suivant la figure 6, en fonction de la fréquence sonore,
• la figure 8 est un dessin schématique en coupe verticale d'un exemple de disposition d'un ensemble acoustique selon l'invention par rapport à un plafond.
• la figure 9 est un graphique représentant la variation d'un ensemble acoustique mise en œuvre suivant la figure 8, en fonction de la fréquence sonore,

A non-limiting example will be described below, an embodiment of the present invention, with reference to the attached drawing in which:

• the figure 1 is a partial schematic perspective view of a micro-perforated support usable in the context of the present invention.
• the figure 2 is a schematic drawing in vertical section of an example of arrangement of an acoustic assembly according to the invention with respect to a ceiling.
• the figure 3 is a graph representing the variation of an acoustic assembly implemented according to the figure 2 , depending on the sound frequency,
• the figure 4 is a schematic drawing in vertical section of an example of arrangement of an acoustic assembly according to the invention with respect to a ceiling.
• the figure 5 is a graph representing the variation of an acoustic assembly implemented according to the figure 4 , depending on the sound frequency,
• the figure 6 is a schematic drawing in vertical section of an example of arrangement of an acoustic assembly according to the invention with respect to a ceiling.
• the figure 7 is a graph representing the variation of an acoustic assembly implemented according to the figure 6 , depending on the sound frequency,
• the figure 8 is a schematic drawing in vertical section of an example of arrangement of an acoustic assembly according to the invention with respect to a ceiling.
• the figure 9 is a graph representing the variation of an acoustic assembly implemented according to the figure 8 , depending on the sound frequency,

Best way to realize the technical invention

We have represented on the figure 1 a canvas 3, implemented in particular at figures 2 , 4 , 6 and 8 , which is provided with micro-perforations d1 which are regularly distributed over its entire surface (300,000 micro-perforations / m2). These perforations, which are circular, have a diameter of 0.2 mm.

The figures 2 and 4 present a first embodiment of the acoustic assembly 1 according to the invention. This assembly comprises a support not comprising micro-perforations 2 (here a stretched PVC canvas) and two supports provided with micro-perforations 3 as described in figure 1 . All these supports extend substantially parallel to an adjacent wall and the supports provided with micro-perforations are placed between the support not comprising micro-perforations and an adjacent wall. In the case presented to the figure 2 , the spaces delimited by the supports are open to the outside. In the case presented to the figure 4 , the spaces delimited by the supports are closed.

We have represented on the figure 3 a diagram showing the absorption spectrum obtained by the acoustic unit 1 shown in the figure 2 thus formed as a function of the applied sound frequency. It can thus be seen in this figure that the maximum absorption of this set is situated at a frequency of the order of 1000 Hz and that for an absorption of 0.5 this extends from a frequency of approximately 500 Hz up to approximately 2,500 Hz, or approximately a frequency interval of the order of 2000 Hz.

We have represented on the figure 5 a diagram showing the absorption spectrum obtained by the acoustic assembly 1 shown in the figure 4 thus formed as a function of the applied sound frequency. It can thus be seen in this figure that the maximum absorption of this set 1 is located at a frequency of the order of 800 Hz and that for an absorption of 0.5 this extends from a frequency of approximately 150 Hz up to approximately 1800 Hz, i.e. approximately a frequency interval of the order of 1.650 Hz.

The results presented to figures 3 and 5 indicate that the acoustic assembly 1 according to the invention has an efficiency at least equal to the acoustic systems of the art anterior, even when placed behind a stretched canvas.

The figures 6 and 8 present another embodiment of the acoustic assembly 1 according to the invention. This acoustic assembly consists of three parallel supports 3 each comprising a series of micro-perforations whose diameter is less than 2mm. In the case presented to the figure 6 , the spaces delimited by the supports 3 are open to the outside. In the case presented to the figure 8 , the spaces delimited by the supports 3 are closed.

We have represented on the figure 7 a diagram showing the absorption spectrum obtained by the acoustic assembly 1 shown in the figure 6 thus formed as a function of the applied sound frequency. It can thus be seen in this figure that a maximum of absorption of this set is located at a frequency comprised 1000 Hz and 8000 Hz and that for an absorption of 0.5 this extends from a frequency of approximately 300 Hz up to approximately 8000 Hz, i.e. approximately a frequency interval of the order of 7300 Hz.

We have represented on the figure 9 a diagram showing the absorption spectrum obtained by the acoustic assembly 1 shown in the figure 8 thus formed as a function of the applied sound frequency. It can thus be seen in this figure that the maximum absorption of this set 1 is situated at a frequency of the order of 2000 Hz and that for an absorption of 0.5 this extends from a frequency of approximately 140 Hz up to approximately 5000 Hz, i.e. approximately a frequency interval of the order of 4860 Hz.

It will be noted, in this embodiment, the excellent efficiency of the acoustic assembly 1 for absorbing frequencies above 2000 Hz, while the acoustic assemblies of the prior art were often deficient in this part of the spectrum. The present invention therefore makes it possible to substantially extend the width of the sound spectrum for which the absorption obtained is effective.

Claims (9)

1. A sound-absorbing assembly (1) designed to form, within an enclosure, at least one wall element, this assembly (1) comprising at least two stacked supports (3) provided with micro-perforations, characterized in that the assembly (1) also comprises a support (2) not including micro-perforations, said support being stacked with the two supports provided with micro-perforations, not framed by the supports provided with micro-perforations and arranged on the visible side when the assembly (1) is placed in the enclosure.
2. An acoustic assembly (1) according to claim 1, characterized in that it consists of at least three parallel supports (3) each comprising a series of micro-perforations, characterized in that the supports (3) are stacked.
3. An acoustic assembly (1) according to any one of the preceding claims, characterized in that the supports are made of stretched sheets, in particular made of polyvinyl chloride (PVC) films.
4. An acoustic assembly (1) according to any one of the preceding claims, characterized in that the supports are made of textiles or any other flexible or rigid materials.
5. An acoustic assembly (1) according to any one of the preceding claims, characterized in that the distance between the different supports (3), each comprising a series of micro-perforations, is between 10 and 90mm.
6. An acoustic assembly (1) according to claim 2, characterized in that said micro-perforations have a diameter of less than 2mm.
7. Acoustic assembly (1) according to any one of the preceding claims, characterized in that the micro-perforations are circular in shape and are preferably distributed according to a mesh having a square, triangular or rectangular shape.
8. An acoustic assembly (1) according to any one of the preceding claims, characterized in that the micro-perforations have a diameter of less than 1mm.
9. An acoustic assembly (1) according to any of the preceding claims, characterized in that the supports comprising a series of micro-perforations have a micro-perforation density greater than 1,000 micro-perforations/m².

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