WO2006069951A1

WO2006069951A1 - Porous lateral sound absorber provided with a local air gap

Info

Publication number: WO2006069951A1
Application number: PCT/EP2005/057050
Authority: WO
Inventors: Hans-Peter Keller; Heinz-Jürgen Mehler; Stefan Janzen
Original assignee: Pelzer Acoustic Products Gmbh
Priority date: 2004-12-23
Filing date: 2005-12-21
Publication date: 2006-07-06
Also published as: DE102004062103A1

Abstract

The invention relates to a space defining element (1) for the sound insulation and especially sound absorption of high-frequency interference, said element comprising a self-supporting, air-permeable carrier layer (2), an air-permeable spacer layer (3) which is in contact with the carrier layer (2) and has a honeycomb structure which is filled with an open-cell cellular material in the surface region opposite the carrier layer, and an air-permeable covering layer (4) arranged on the spacer layer (3). The air-permeable covering layer (4) has an air flow resistance of up to 2500 kNs/m4.

Description

Porous, lateral sound absorber with local air gap

The invention relates to a room delimitation element for sound insulation and absorption of high-frequency noise and the use of this space-limiting element for sound insulation and absorption of high-frequency noise in vehicles.

In order to reduce disturbing sound in vehicles, in particular in aircraft, passive sound insulation must be used, which can both reflect structure-borne noise and absorb airborne sound. Especially for high-frequency noise, such as turbine noise, so far hardly soundproofing elements for room boundary surfaces, such as walls or ceilings are known, which at the same time have a sufficient absorption in addition to the soundproofing effect for medium and low-frequency noise. State of the art are exclusively reverberant trim parts with good sound insulation properties.

Thus, WO 98/14368 A2 describes a sound insulation system for the insulation of low-frequency noise in aircraft. However, this system is not suitable for sound absorption of high-frequency noise, since the air gap, which may be formed for example as a honeycomb structure, is covered with an air-impermeable layer.

EP 0 849 146 A2 also describes a wall element for sound insulation in passenger cabins of aircraft. This Soundproofing element has a complex structure in which not only a local air gap in the form of honeycomb elements but in addition to a lateral air gap is necessary. The carrier material is in this case designed to be permeable to air, while a flexible outer layer is formed impermeable to air and is located by means of an air gap at a small distance from the carrier.

US 4,739,955 A describes a sound insulation system for aircraft which has neither air gap nor absorbent surfaces and therefore is not suitable for sound absorption of high-frequency noise.

Also, EP 0 631 862 A1 describes lining panels for the interior of aircraft, which are therefore not suitable for the sound absorption of high-frequency noise, since they do not comprise any air gap or absorbent surfaces.

Similarly unsuitable are DE 100 41 458 A1 and DE 40 30 478 A1.

Although US Pat. Nos. 4,799,631 A and EP 0 330 338 A2 describe sound insulation elements which also comprise an air gap, this is formed between two air-impermeable layers and therefore functions only as a low-frequency plate absorber.

DE 30 25 617 A1 describes a sound insulation panel in sandwich construction for use in the vicinity of rapid air or gas flows, with a honeycomb core, a plurality of thin sheet formed, extending transversely to the plate cells, with a glued to the honeycomb side outer perforated plate and with a on the another honeycomb side glued outer solid sheet, wherein on the outer side of the perforated plate, a thin layer of porous fiber material is glued, wherein an adhesive the perforated plate from the fiber material isolated, the pores on the holes of the perforated plate define a defined narrowed connection between the outside atmosphere and the cells of the honeycomb core ,

DE 198 04 718 A1 describes a sandwich wall, in particular for a helicopter cell, consisting of an upper and a lower cover skin of fiber composite material and an arranged between these, consisting of upright hollow bodies inner, honeycomb in particular, the sound-saving and moderately simple manner thereby formed sound-absorbing is that the main sound source facing cover skin consists of an open-mesh, covered with a flexible cover film fiber composite mesh with a smaller mesh size than the hollow body inner cross-section.

The object of the present invention is in contrast to provide an improved room boundary element for sound insulation, which in addition to the soundproofing for low, medium and high-frequency noise and simultaneous broadband high absorption and has a very simple and self-supporting structure with the widest possible use already used and proven materials, so that the space-limiting element can be easily manufactured and installed. In a first embodiment, the object of the invention is achieved by a space limiting element 1 for sound insulation and in particular for sound absorption of high-frequency noise, comprising a self-supporting, air-impermeable carrier layer 2, an air-permeable spacer layer 3 made of a honeycomb structure in contact with the carrier layer 2 and filled with an open-cell foam in the area opposite the carrier layer 2, and an air-permeable cover layer located on the spacer layer 3 4, wherein the air-permeable cover layer 4 has an air flow resistance of up to 2500 kNs / m ⁴ .

Surprisingly, it was found that the best sound absorption of high-frequency noise could be achieved if, on the one hand, the carrier layer 2, which ensures that the space-limiting element 1 is self-supporting, air-impermeable and thus good sound insulation and all layers thereon, such as Spacer layer 3 or the cover layer 4 are formed permeable to air. It has been observed that low air flow resistance of the cap layer 4 results in high absorption of high frequencies, while high air flow resistance has reduced absorption of high frequency noise but better absorption of low frequency noise. The air flow resistance of the air-permeable cover layer 4 is preferably up to 1000 kNs / m ⁴ , more preferably up to 500 kNs / m ⁴ and most preferably up to 100 kNs / m ⁴ . As high-frequency sound is considered in the present invention, sound having a frequency of at least 2000 Hz. In order for the space limiting element 1 according to the invention to require no additional reinforcement, it can advantageously withstand static loads of structures already existing in the usual framework. According to the invention the honeycomb structure in the surface area opposite the support layer 2 is filled with an open-celled foam. The open-cell foam ensures improved sound absorption. It is possible to fill the honeycomb core partially or completely with the foam. The foam must in this case have a good connection with the side walls of the honeycomb core, so that the foam is fixedly embedded in the honeycomb core. Introduction of the foam in the honeycomb structure can be carried out in various ways. For example, melamine resin foam at a temperature of 200 ⁰ C under pressure partially or completely penetrate into the corresponding cells. The Zeilpenetrationstiefe depends on the foam thickness and the cell dimensions, such as the width and depth. Thus, it is possible to partially or completely fill the honeycomb structure by appropriate control of the foaming parameters. Of particular importance in this case is that if necessary, in a further processing step, the support surface of the honeycomb structure must be freed from adhering foam to firmly connect the carrier layer 2 or the cover layer 4 with the honeycomb core.

In principle, all foam types are suitable for filling the honeycomb core. However, for the purposes of the present invention, flame-retardant or nonflammable foams, for example of melamine resin foam or phenolic resin foam, are particularly preferred. Of course, in the sense of the lowest possible weight and a low density of the foam is required. For the purposes of the present invention, foams having a density in the range from 5 to 20 kg / m ³ are therefore particularly preferred. The air flow resistance of the foam should preferably be in the range of 10 to 1500 kNs / m ⁴ . If the air flow resistance is too high, the sound absorption quality is too low. If the air flow resistance is too small, an insufficient sound absorption is likewise given.

The porosity of the foam is preferably 0.4 to 0.99, in particular 0.8 to 0.99. Porosity in the sense of the present invention describes the ratio of the pore volume to the total volume. As a result, the flow resistance is significantly influenced.

Another parameter that can be stated regardless of the type of porous material is the tortuosity or the structural factor. The concept of tortuosity is used for various physical properties of porous materials. In principle, the parameter tortuosity covers the fact that the pores form channels that are not straight but curved and have a variable cross-section. The simplest definition of tortuosity in the sense of the present invention is the ratio of an actual path length between inlet and outlet surface to the distance between the two, so the shortest path length. Also this size is like the porosity dimensionless. For the purposes of the present invention, the tortuosity is in the range of 1.5 to 5. Outside this specified range, the sound absorption quality is not sufficient.

Preferably, each of the processed materials is incombustible and / or complies with the safety-relevant standards that apply, for example, to aircraft interior linings. Preferably the layer thickness ratio of cover layer 4 to spacer layer 3 is in a range of 1: 1 to 1: 5, more preferably in a range of 1: 3 to 1: 4, most preferably 1: 2. Conditions, the sound absorption effect is ideal for high-frequency noise optimal.

The spacer layer 3 is advantageously permeable to air permeable to the layer and particularly preferably designed as a honeycomb structure. Because the air gap or the spacer layer 3 is not formed laterally but preferably locally in honeycomb form, these honeycombs can form so-called Helmholtz resonators, which represent particularly efficient sound absorbers, especially for high-frequency noise.

In contrast to the prior art, no additional lateral, open air gap between the carrier material and the local air gap must be provided in the inventive room limitation element 1 for sound insulation, which considerably simplifies the production of the room boundary element 1 according to the invention and also the handling during installation. Preferably, the web spacing of the honeycomb is in a range of 2 to 40 mm, more preferably in a range of 4 to 18 mm, and most preferably 12 mm. The air gap or the spacer layer 3 is advantageously made of paper or paper-like material, more preferably of flame-retardant paper material, which is sold for example by DuPont under the brand NOMEX ^® . Preferably, the cover layer 4 may consist of several sub-layers 5 to 8. Preferably, the cover layer 4 or at least one of the sub-layers 5 is perforated. Particularly preferably, the covering layer 4 or at least one sub-layer 5 is microperforated or micro-perforated, most preferably the hole diameter of the micro-perforation is 0.1 to 5 mm, in particular 0.2 to 3 mm. Due to the perforation of the covering layer 4 or at least one lower layer 5 of the covering layer 4, the honeycombs of the spacer layer 3 can act as Helmholz resonators and the covering layer 4 can nevertheless have a particularly low air flow resistance.

The hole area ratio, that is, the ratio of the perforated area to the non-perforated area of the microperforated layer is preferably 0.1 to 20%, more preferably 0.2 to 5%. The layer thickness of the spacer layer 3 is preferably in a range of 2.5 to 15 mm, more preferably 3 to 10 mm, and most preferably 6 mm. The density of the spacer layer 3 is advantageously within a range

from 25 to 75 kg / m ^3. Advantageously, the covering layer 4 as a whole has a layer thickness in a range from 0.8 to 22 mm, particularly preferably in a range from 1 to 2 mm. In this case too, the covering layer can consist of different sublayers 5 to 8. Adjacent to the spacer layer 3 may be a grid or net-like or perforated plate 7, which preferably has a thickness in the range of 0.2 to 4 mm and a density in the range of 250 to 1500 kg / m ³ . This plate 7 can advantageously from Metal preferably consist of polymers. The plate 7 is advantageously perforated, slotted, latticed or net-shaped, in each case with an open area of 2 to 65%, preferably 25 to 35%.

Optionally, a film 5 may be provided as the next sub-layer which is perforated or slit and has a thickness in the range of 0.05 to 2 mm and a density in the range of 950 to 2700 kg / m ³ . This layer is preferably made of plastic, metal foil or incombustible, resin impregnated paper and having a density in the range of 950 to 1350 kg / m ² .

Optionally, a porous layer 8 with a specially selected air flow resistance, depending on the objective, whether more medium or high-frequency noises are to be absorbed, may be provided as the next sub-layer, preferably having a layer thickness in the range of 0.3 to 4 mm and a density in a range of 150 to 600 kg / m ³ and an air flow resistance in a range of 20 to 5000 kNs / m ⁴ , preferably 500 to 2500 kNs / m ⁴ . This layer 8 is preferably made of textile material, for example glass fibers, mineral fibers, aramid fibers, polypropylene or polyester microfiber or fine fibers and / or resin-bonded cotton felt.

The covering layer 4 advantageously comprises a textile covering layer 6 as outer sub-layer. The thickness of this lining layer 6 is advantageously 0.3 to 5 mm and very particularly preferably 0.5 to 1.5 mm. The density of the textile cladding layer 6 according to the invention is advantageously 100 to 600 kg / m ³ and very particularly preferably 350 to 550 kg / m ³ . The air flow resistance of the textile cladding layer 6 according to the invention is preferably 100 to 2000 kNs / m ⁴ and very particularly preferably 500 to 800 kNs / m ⁴ . The textile lining layer 6 is preferably made of a material selected for example from the group Lantal ^® 3817 LS / 35, Lantal ^® 3286 LS / 330 Lantal ^® 3254 LS / 408, 857/600 Basic Lantal ^®, 3M Thinsulate ^®, polypropylene microfiber resin-bonded cotton felt, Sandler ^® sawasorb ^®, ^® Caruso, Innovatec ^® PP, Libeltec ^® QW-500, PES felt, Lantal Melair ^® ^®, particularly preferably from Lantal ^® 3254 LS / 408th The entire space-limiting element 1 advantageously has a total thickness in a range of 4 to 9 mm and a basis weight in a range of 0.9 to 1.9 kg / m ² .

In a further embodiment, the object underlying the invention is achieved by the use of the room boundary element 1 for sound insulation and sound absorption of high-frequency noise in passenger transport means.

Preferably, the space-limiting element 1 is used as a side wall cladding and / or ceiling cladding of aircraft, water and in particular of aircraft. The space-limiting element 1 can preferably also be used for sound insulation and sound absorption in elevators, door linings, trunk linings, as a headliner in motor vehicles or aircraft cabins or as a cabin partition in aircraft cabins or similar applications. Description of the figures:

The space delimiting element 1 consists of the carrier layer 2, the spacer layer 3 thereon. The covering layer 4 is thereon, which in turn is obligatory from the lower layers 6 and 7, optionally from the lower layers 5 and / or 8 can exist. The sublayers 5 to 8 are:

a mesh or net-like or perforated plate 7,

optionally a perforated or microperforated layer 5,

optionally a porous layer 8, and

a textile covering layer 6.

2 shows the measurement results for the sound absorption effect for different embodiments of the room boundary element 1.

Fig. 3 shows the comparison of a foam filled honeycomb core with an unfilled honeycomb core.

EXEMPLARY EMBODIMENTS:

Comparative Example:

On a 0.65 mm thick airtight sheet of aramid, which is sold by DuPont under the brand name NOMEX ^® , with a basis weight of 0.6 kg / m ² as a support layer 2 was a 3.3 mm thick honeycomb structure 3 with a spacing of 3 mm from non-combustible paper from DuPont (NOMEX ^®) applied. On top of this, again a 0.7 mm thick mesh grid 7 made of aramid fibers was applied, which had a basis weight of 0.42 kg / m ² . The net grid 7 was connected to a 0.1 mm thick microperforated sheet 5 made of polyamide, which had a weight per unit area of 0.27 kg / m ² . In this microperforated film 5 again a 0.55 mm thick layer of Thinsulate ^® 7200 material 8 having a basis weight of 0.13 kg / m ² and an air flow resistance of 1500 kNs / m ⁴ is applied. In this Thinsulate ^® layer 8 a 4.7 mm thick layer 6 of the material was as the last layer 3254 LS / 408 Lantal the company as a textile lining material having a basis weight of 0.25 kg / m ² and an air flow resistance of 680 kNs / m ⁴ applied. In order not to impair the air flow resistance, the individual layers were glued together pointwise.

Fig. 2 illustrates the measurement results for layer systems containing all of these aforementioned layers or some selected layers. Thus, the curve a) for the absorption behavior of the carrier layer 2 according to the embodiment alone with the spacer layer 3, the curve b) for the absorption behavior of the carrier layer 2 according to the embodiment, the spacer layer 3 with the textile cladding layer 6, the curve c) for the absorption behavior of the backing layer 2 according to the embodiment, the distance layer 3, the Thinsulate ^® layer 8 with the textile cladding layer 6, the curve d) for the absorption behavior of the backing layer 2 according to the embodiment, the distance layer 3, the perforated aluminum layer 7 and the Thinsulate ^® layer 8 with the textile cladding layer 6, and the curve e) for the absorption behavior of the carrier layer 2 according to the comparative example, the spacer layer 3, a perforated aluminum layer 7 and the Thinsulate ^® layer 8 with the textile lining layer. 6

The measurement of the airborne sound absorption at normal sound incidence were carried out in Kundt's tube according to DIN EN 52215.

Exemplary embodiment:

Analogously to the comparative example, the same materials were used. However, the honeycomb core was filled with a commercially available melamine resin foam. For this purpose, the melamine resin foam was pressed under pressure and temperature in the open honeycomb. The honeycomb core was completely filled. Foam overhanging the webs of the honeycomb core was removed by sanding.

FIG. 3 shows that the honeycomb core filled with foam absorber exhibits improved sound absorption compared to the unfilled honeycomb core, especially at low and medium frequencies.

Claims

claims:

1. Space limiting element (1) for sound insulation and in particular for sound absorption of high-frequency noise, with a self-supporting, air-impermeable carrier layer (2), with the carrier layer (2) in contact air-permeable spacer layer (3) made of a honeycomb structure, in which the carrier layer (2) opposite surface area is filled with an open-cell foam, and one on the spacer layer

(3) located air-permeable cover layer (4), wherein the air-permeable cover layer (4) has an air flow resistance of up to 2500 kNs / m ⁴ .

2. Space limiting element (1) according to claim 1, characterized in that the layer thickness ratio of the cover layer

(4) to spacer layer (3) in a range of 1 to 1 to 1 to 5, in particular 1 to 2, is located.

3. Room delimiting element (1) according to claim 1 or 2, characterized in that the spacer layer (3) is completely filled with foam.

4. Raumbegrenzungselement according to any one of claims 1 to 3, characterized in that the foam comprises melamine resin or phenolic resin.

5. Room delimiting element according to one of claims 1 to 4, characterized in that the foam has a porosity of 0.4 to 0.9, in particular 0.8 to 0.9.

6. Raumbegrenzungselement according to any one of claims 1 to 5, characterized in that the foam has a tortuosity in the range of 1.5 to 5.

7. Raumbegrenzungselement (1) according to one of claims 1 to 6, characterized in that the cover layer (4) is perforated.

8. space limiting element (1) according to one of claims 1 to 7, characterized in that the covering layer (4) comprises a textile cladding layer (6).

9. space limiting element (1) according to one of claims 1 to 8, characterized in that the spacer layer (3) has a layer thickness of 2.5 to 15 mm, in particular a layer thickness of 3 to 5 mm.

10. Space delimiting element (1) according to one of claims 1 to 9, characterized in that the covering layer (4) has a layer thickness of 0.8 to 22 mm, in particular a layer thickness of 1 to 2 mm.

11. Raumbegrenzungselement according to any one of claims 1 to 10, characterized in that the cover layer is microperforated, in particular with holes of a diameter of 0.1 to 5 mm, in particular 0.2 to 3 mm and a hole area proportion of 0.1 to 20%, in particular 0.2 to 5%

12. Use of the space limiting element (1) according to one of claims 1 to 11 for sound insulation and sound absorption of high-frequency noise in passenger transport.

13. Use according to claim 12 as a side inner lining of air, water and in particular of aircraft.