EP1570139B1 - Double-wall acoustic panel - Google Patents

Abstract

The acoustic panel includes two walls (1,2) between which an acoustic absorber (3), such as glass wool, is disposed. The glass wool may be contained in a fine envelope e.g. formed from Mylar (RTM) material. Spacing elements (5) are disposed between the first wall and the absorber, so as to create a curtain of air between the absorber and the first wall.

Description

The present invention relates to an acoustic panel with two walls between which is disposed an acoustic absorbent.

In such a panel, the efficiency of the absorbent can be improved by creating an air gap between the acoustic absorber and the wall that receives the acoustic excitation.

The present invention relates to an acoustic panel of the aforementioned type whose structure can advantageously create this air gap. CH-A-679167 discloses an acoustic panel which has the features of the preamble of claim 1.

The invention is defined by the acoustic panel of claim 1.

The invention thus relates to an acoustic panel comprising a first and a second wall between which is disposed an acoustic absorbent characterized in that, the first wall has, on an inner face facing the acoustic absorber, a plate made of a viscoelastic material, as well as a backing plate, spacing elements (for example parallel grooves, honeycombs, embossing, and / or pins) being distributed in at least one dimension and creating an air gap between the absorbent and the counter plate.

More particularly, the spacer elements may form a two-dimensional network, for example a grid or a honeycomb or an embossing or even pins distributed along these two dimensions.

The grid, the honeycomb or the embossing may constitute a net or a bag inside which the acoustic absorbent is placed. In particular, the net or the bag may be of a thermally conductive material so that it constitutes a heat sink between said walls.

A self-adhesive film carrying said network (for example grid, honeycomb, embossing and / or pins) may be adhered to the acoustic absorbent, in particular on a packaging of the acoustic absorbent, or on the backing plate.

According to a preferred variant, the backing plate is stiffened by an embossing, ribs parallel or not, a honeycomb, pins or bosses.

• la figure 1 représente en vue éclatée un mode de réalisation de l'invention ;
• les figures 2 à 7 illustrent des variantes de l'invention ;
• la figure 8 illustre le niveau d'accélération verticale en fonction de la fréquence d'une plaque en aluminium.

Other features and advantages of the invention will appear better on reading the following description, given by way of non-limiting example, in conjunction with the drawings in which:

• Figure 1 shows an exploded view of an embodiment of the invention;
• Figures 2 to 7 illustrate variants of the invention;
• Figure 8 illustrates the level of vertical acceleration versus frequency of an aluminum plate.

In FIG. 1, the acoustic panel has a first plate 1 which receives the acoustic excitation (arrow F) when the panel is put in place, a second wall 2 and an acoustic absorbent 3, for example glass wool which can be contained in a thin envelope 4 in "Mylar" (Trademark of du Pont).

The plate 1 has on its inner face a plate 17 of viscoelastic material (for example the "Deltane" material from the PAULSTRA Company).

The air knife is made using a mechanical spacer constituted by a grid or an embossing 5, which can be secured to a rigid counterplate 10, or by an embossed counterplate.

The shape of the mesh may be arbitrary, but its size must be such that under the action of the pressures experienced by the absorbent, it must not exceed the area defined by the mesh so that it can not come in contact with the counterplate 10 and that the air gap keeps the desired thickness.

The nature of the material constituting the roasting is chosen according to the environmental constraints of the intended application. This material can be malleable to allow the mesh to marry complicated shapes, provided that during the deformation and under the mounting or use pressures the absorbent 3 can not come into contact with the counterplate 10.

The grid 5 defined can be glued to the inner face of the plate against-10 taking the precaution that the glue does not fill the mesh of the mesh to avoid contact with the sound absorbent.

Absorbent 3 is low density glass wool contained in a thin "Mylar" (trademark) envelope. The spacer may be a wire mesh of 0.5 mm diameter stainless steel and whose mesh is a square of 10 mm side. The reduction in transparency is of the order of 3 to 4 dB.

The grid 5, for example square (Figure 2), can be replaced by a honeycomb 6 (Figure 3) of suitable size. A mesh too small leads to a large bonding surface between the counterplate 10 and the absorbent 3, which reduces the performance.

The netting 8 can be substituted for the netting 8 (FIG. 4) evenly distributed on the inner surface 11 of the counter plate 10. This can be done using a self-adhesive film 9 which carries these pins 8 and which is glued on the surface 11. Alternatively, this film 9 can be just as well glued on the absorbent 3 or its packaging 4 as it exists for some glass wool.

However, care must be taken to avoid the punching of the absorbent which would then promote its contact with the counterplate 10 and thus undesired coupling with the wall 1 receiving the excitation.

The mesh 5 may constitute a net in which the absorbent 3 is placed.

According to an alternative embodiment of the invention, the plate 1 has on its inner face a plate of viscoelastic material 17 (for example the "Deltane" material from the company PAULSTRA) and a counter plate 10 which is embossed in order to to stiffen it and which serves to damp the vibrations of the plate 1 subjected to excitation. This configuration makes it possible to lighten the counterplate 10 (and possibly the plate 17) by decreasing its thickness while maintaining its stiffness by means of the inertia of the walls 18 perpendicular to its surface. These serve as spacer to avoid the contact of the absorbent with the counterplate (Figures 5 to 7).

In the embodiments of FIGS. 6 to 7, the counter-plate 10 may be constituted by a glued plate 20 carrying ridges 18 in one or two dimensions.

In Figure 6, the spacers 18 are ribs of the counterplate 10 formed in one dimension and spaced from each other, generally with a constant pitch.

In FIG. 7, the ribs 18 (distributed in one or two dimensions) of the counter-plate 10 are sufficiently wide for the plate 17 made of viscoelastic material to occupy the hollow portion 19 (see in particular the box of FIG. ).

EXAMPLE 1

A 1.2 mm thick aluminum wall 1 is damped on the one hand by a sheet 17 made of 1 mm thick viscoelastic material and on the other by an aluminum flat backplate of 0 mm. , 5 mm thick.

EXAMPLE 2

An aluminum wall 1 of 1.2 mm thick is damped on the one hand by a sheet 17 of viscoelastic material 0.5 mm thick and on the other hand by a counterplate 10 made of aluminum. 0.3 mm thick embossed with a square mesh of 10 mm side and a rib height of 2 mm (see Figure 6).

• Courbe I : ladite plaque 1 seule ;
• Courbe II : ladite plaque 1 amortie par une feuille 17 en matériau visco-élastique (« Deltane ») de 1 mm d'épaisseur et une contre-plaque plane 10 en aluminium de 0,5 mm d'épaisseur ;
• Courbe III : ladite plaque 1 amortie par une feuille 17 en matériau visco-élastique (« Deltane ») de 0,5 mm d'épaisseur, recouverte en son centre d'une contre-plaque 10 en aluminium (150 mm x 15 mm) de 0,3 mm d'épaisseur gaufrée avec une maille carrée de 10 mm de côté et d'une hauteur de nervure de 2 mm.

FIG. 8 illustrates, for an excitation of 0.1 g of an aluminum plate 1 (210 × 230 mm) 1.2 mm thick, the level of vertical acceleration in m / s ² as a function of the frequency F (between 0 and 3000 Hz), for:

• Curve I : said plate 1 alone;
• Curve II : said plate 1 damped by a sheet 17 of viscoelastic material ("Deltane") of 1 mm thick and a flat aluminum counter-plate 10 of 0.5 mm thick;
• Curve III : said plate 1 damped by a sheet 17 of viscoelastic material ("Deltane") of 0.5 mm thick, covered at its center with a counter-plate 10 of aluminum (150 mm x 15 mm) 0.3 mm thick embossed with a square mesh of 10 mm side and a rib height of 2 mm.

It can be seen that the peaks of vibration (squash I) are well damped in both cases (curves II and III). The stiffening of the backing plate 10 makes it possible, with comparable or better performance, to reduce the thickness of both the viscoelastic sheet 17 and the backplate 10, resulting in a significant weight gain.

Claims (8)

1. An acoustic panel comprising first and second walls between which a sound absorber is disposed, wherein the first wall (1) presents on an inside face facing towards the sound absorber, a plate (17) of viscoelastic material, and also a backing plate (10) carrying spacer elements (5, 18) that are distributed in at least one dimension and that create an air gap between the absorber (3) and the backing plate (10).
2. An acoustic panel according to claim 1, wherein the spacer elements (5, 6, 8, 18) form a two-dimensional array.
3. An acoustic panel according to claim 2, wherein said array comprises a grid, a honeycomb, or embossing.
4. An acoustic panel according to claim 3, wherein the grid, the honeycomb, or the embossing constitutes a net with the sound absorber (3) being placed inside the net.
5. An acoustic panel according to claim 2, wherein the array comprises studs (8) distributed in said two dimensions.
6. An acoustic panel according to any of claims 2 to 5, including a self-adhesive film (9) carrying said array, said film being stuck onto the sound absorber (3), in particular onto packaging of the sound absorber (3).
7. An acoustic panel according to claim 1 or 2, wherein said spacer elements are reinforcing elements secured to the backing plate (10).
8. An acoustic panel according to claim 7, wherein said reinforcing elements are embossing (18), in the form of optionally parallel ribs, a honeycomb, studs, or bosses (4).

Images