Soundproof shielding and aircraft engine equipment with such soundproof shielding

Abstract

Soundproof shielding and aircraft engine equipment having such soundproof shielding. The present invention relates to a soundproof shielding comprising a honeycomb structure, each cell of the honeycomb structure comprising a conduit extending at least between a first surface (1) and a second surface (3) of the shielding. The conduit is formed between an outer wall (6) and an inner wall (7) of the cell and has a limited cross-section therein. The outer wall (6) and the inner wall (7) have a rounded form without sharp edges. The cell comprises a cavity into which the conduit converges. Thus, each cell is formed to include a resonator with a neck formed by the conduit and the cavity. Each cell is adapted such that the conduit and the cavity are formed on both sides of the inner wall (7). This shielding is particularly suitable for reducing sound waves, especially low frequencies, in the nacelle of aircraft engine equipment.

Description

Technical Field

[0001] This invention relates to the field of sound insulation structures.

[0002] In particular, this invention relates to a soundproof cover with a honeycomb structure. The cover, the subject of this invention, can have a variety of applications, especially in the aviation field, such as in aircraft engine nacelles. Background Technology

[0003] Covers or panels comprising honeycomb structures (i.e., juxtaposed hollow single volumes) are used in many technical fields, particularly in aerospace. They can exhibit excellent rigidity with low weight. For their sound insulation properties, covers comprising honeycomb structures having cells open on one side or at least cells communicating with the exterior of the panel are employed. Such panels are sometimes referred to as sound-absorbing panels.

[0004] Panels or covers with a honeycomb structure can be formed from a variety of different materials, such as plastics, composites, or metals. The cells can have a variety of different geometries. A well-known form of honeycomb structure has cells in the form of right-prismatic prisms with hexagonal bases. The term "honeycomb" is often used to refer to this type of structure with hexagonal cells, but this expression is also misleadingly used to refer to honeycomb panels with other cell forms.

[0005] Therefore, conventional sound-absorbing panels or covers generally include a honeycomb core material inserted between a perforated sheet forming the first side and a solid sheet that blocks the cells and forms the second side of the cover.

[0006] The small cells in a sound-absorbing panel act as small resonators, allowing the absorption of sound waves in a given frequency band. For the resonator to be effective, its absorption band must include the frequencies the panel experiences; currently, the relatively small size of the sound-absorbing panel's cavity corresponds to high frequencies. Therefore, it is difficult to obtain a cellular panel that is effective for certain applications experiencing low frequencies.

[0007] For example, the engine equipment of commercial aircraft includes turbojet engines and nacelles, which can include acoustic shielding to reduce the noise generated during engine operation. However, the acoustic frequencies produced by aircraft engines are relatively low and span a fairly wide range. Depending on the engine under consideration, the low frequencies to be attenuated are, for example, frequencies below 2000 Hz. Using large-diameter engine equipment tends to further reduce the frequency of the sound waves they produce. Currently, this requires large-volume chambers to absorb low frequencies, resulting in thick panels, which are incompatible with aviation applications.

[0008] Document US 2015292413 provides an acoustic absorbing panel in which the geometry of the chambers is modified for application in aircraft engines. Specifically, the chambers of the acoustic shield described in US 2015292413 extend in a curved “S-shape” to elongate these chambers. Increasing the chamber length allows for the absorption of lower frequencies with the same panel thickness compared to straight chambers. However, the frequency band absorbed is limited to the transition to lower frequencies compared to the frequency band absorbed by a shield with straight chambers. Summary of the Invention

[0009] The present invention proposes a soundproof cover with a honeycomb structure, which is improved upon existing covers with constant thickness and comparable weight to allow for sound insulation at low frequencies and over a wide frequency range.

[0010] Therefore, the present invention relates to a soundproof cover comprising a honeycomb structure having a first side and a second side, the honeycomb structure being formed by cells open on the first side and closed on the second side, the cells being juxtaposed along a first, so-called longitudinal direction and a second, so-called transverse direction orthogonal to the longitudinal direction. Each cell includes a conduit extending at least between the first and second sides, the conduit being formed between an outer wall and an inner wall of the cell and having a limited cross-section therebetween. The outer wall and the inner wall have a rounded form without sharp edges. Each cell includes a cavity into which the conduit converges. The cell formation includes a resonator formed by the neck of the conduit and the cavity. The cell is adapted to form such that the conduit and the cavity are formed on both sides of the inner wall.

[0011] Compared to chambers with the same thickness of cover constructed according to existing technology, this chamber configuration allows for the acquisition of resonators suitable for handling low frequencies. In particular, the spiral geometry allows for a particularly long resonator neck with a potentially small cross-section, while maintaining a significant volumetric cavity. Furthermore, this geometry imparts impedance to the chamber, thereby reducing incident noise.

[0012] Each chamber of the cover may have a generally spiral cross-section in a longitudinal cutting plane perpendicular to the lateral direction.

[0013] The inner wall of the chamber in the cover and the outer wall of the adjacent chamber can meet, so as to form only a transverse wall that separates the chamber and the adjacent chamber at the first surface. Therefore, there is no loss of acoustic surface between the chambers. Specifically, the inner wall of the chamber in the cover and the outer wall of the adjacent chamber can meet at the first surface, thus forming an acute angle between them to form a transverse edge at the first surface. In this case, the transverse wall that separates the chamber from the adjacent chamber at the first surface is thus limited to the form of a transverse edge. This configuration facilitates the entry of sound waves into the chamber of the cover.

[0014] The piping in each compartment can successively include:

[0015] ●The first part, the first part extending from the first surface of the soundproof covering towards the second surface of the soundproof covering, and

[0016] ● A curved second section, the curved second section including an inlet and an outlet, and forming an angle between 90° and 180° between the direction of the pipe at the inlet of the second section and the direction of the pipe at the outlet of the second section.

[0017] The first part of the pipe can be approximately symmetrical along a transverse plane perpendicular to the first surface.

[0018] The outer and inner walls can advantageously have a rounded form without sharp edges.

[0019] The small chamber forming the neck of the resonator and the cavity are, for example, sized such that the resonant frequency of the resonator is less than 2000 Hz.

[0020] The first surface may include an impedance sheet that allows the chamber of the cover to communicate with the outside of the cover.

[0021] The inner wall of each chamber may include a perforation that fluidly links the neck to the cavity of the resonator.

[0022] The present invention also relates to an aircraft engine device comprising a nacelle and an engine, wherein the inner surface of the nacelle and / or the outer surface of the engine casing have soundproof coverings as previously described. Attached Figure Description

[0023] Other specific features and advantages of the present invention will become clearer from the following description.

[0024] In the accompanying drawings, given as a non-limiting example:

[0025] - Figure 1 The existing soundproof coverings are illustrated using a three-dimensional diagram;

[0026] - Figure 2 The three-dimensional diagram illustrates this. Figure 1 The honeycomb structure of the soundproof covering;

[0027] - Figure 3 The schematic cross-sectional view is shown. Figure 1 and Figure 2 The honeycomb structure has four adjacent cells;

[0028] - Figure 4 The schematic cross-sectional view illustrates two juxtaposed chambers of a soundproof cover according to an embodiment of the present invention;

[0029] - Figure 5 By comparing a conventional Helmholtz resonator with one that is based on... Figure 7 The principle of the invention is illustrated in a schematic cross-sectional view by comparing the soundproof cover chambers of the embodiments of the invention described in detail in the previous section.

[0030] - Figure 6 and Figure 7 The schematic cross-sectional view illustrates two juxtaposed chambers of a soundproof cover according to an embodiment of the present invention;

[0031] - Figure 8 and Figure 9 A schematic cross-sectional view illustrates juxtaposed chambers with soundproof coverings according to an embodiment of the invention;

[0032] - Figure 10 This is represented by a similar view. Figure 9 Variations of the embodiments;

[0033] - Figures 11 to 13 A schematic cross-sectional view illustrates juxtaposed chambers with soundproof coverings according to an embodiment of the invention;

[0034] - Figure 14 The three-dimensional diagram illustrates the following: Figure 7 The soundproof covering of the embodiment;

[0035] - Figure 15 The aircraft engine equipment is schematically shown in a cross-sectional view, with the nacelle of the engine equipment equipped with soundproof coverings. Detailed Implementation

[0036] Throughout the following description, the terms "cover" and "panel" are generally interchangeable. In fact, a soundproof panel is generally intended to be attached to a support element and constitutes a cover in that sense. Furthermore, the panel is not limited to a flat geometry. Similarly, a soundproof cover includes a honeycomb structure formed from panels, which may be attached to a support element and may or may not have the elasticity to allow it to conform to said support element.

[0037] Figure 1 The diagram schematically illustrates a soundproof barrier known from the prior art. This soundproof barrier comprises small cells A1, A2, A3, A4, etc., arranged juxtaposed along two mutually orthogonal directions to form a honeycomb structure. Arbitrarily, the first direction D1 in which the cells are arranged is referred to as the longitudinal direction, and the second direction D2, orthogonal to the first direction D1, is referred to as the transverse direction. A third direction D3 is defined as being orthogonal to both the first and second directions D2.

[0038] On the first side 1 of the covering, the chambers A1…A4 are open. The perforated sheet 2 covers these chambers, thereby allowing the chambers A1…A4 to communicate with the external environment.

[0039] On the second side 3, the chambers A1…A4 are closed, for example by blocking the bottom of the chamber by a solid sheet.

[0040] To better explain the honeycomb structure, Figure 2 Unperforated sheet 2 locations Figure 1 The soundproof covering. The cells of the honeycomb structure shown here are referred to as square, meaning their volume is almost the volume of a right prism extending from the base of a square between the first face 1 and the second face 3 of the soundproof covering. In the example shown here, the cells are juxtaposed to form a regular grid. Thus, it is evident that, except for the cells located at the edges of the covering, each cell is adjacent to two cells in the longitudinal direction and two cells in the transverse direction.

[0041] Figure 3 It indicates Figure 1 and Figure 2 The honeycomb structure of the soundproofing material shown in the figure is along Figure 1 and Figure 2 The diagram shows four chambers A1…A4 defined by a longitudinal cutting plane P. The cutting plane P longitudinally passes through the chambers of the soundproof covering and, in the case of a flat covering or panel, is orthogonal to the first surface 1 and the second surface 3. Each chamber is separated from its adjacent chamber by a transverse wall 4, which is straight and connects the first surface 1 and the second surface 3, which are orthogonal to it. Similarly, longitudinal walls 5 separate the chambers in the longitudinal direction.

[0042] the following Figures 4 to 15This refers to all or part of a soundproof covering that corresponds to several different embodiments of the invention given as examples. In particular, Figures 4 to 14 The edge of the chamber according to different embodiments of the present invention and Figure 3 A cross-sectional view of a cutting plane similar to the cutting plane. In order to... Figures 1 to 3 To simplify the comparison with conventional honeycomb structures Figures 4 to 14 As understood in the embodiments presented herein, the cross-section of the chamber of the soundproof cover according to the invention is shown (by thick lines) as it is stacked on top of each other. Figures 1 to 3 On the cross-section of a small chamber with a conventional structure (fine thread).

[0043] Figure 4 This indicates two small chambers C1 and C2 of a soundproof cover conforming to an embodiment of the present invention.

[0044] In this invention, each cell of the honeycomb structure has a cross-section defined along a cutting plane P by an outer wall 6 and an inner wall 7. The outer wall 6 and the inner wall 7 form a conduit. This conduit flows into a closed cavity. Thus, each cell forms a resonator similar to a Helmholtz resonator, whose neck is formed by the conduit.

[0045] The pipe is curved, such that the pipe and the cavity are formed on either side of the inner wall 7.

[0046] As in Figures 4 to 13 In the case of the embodiments presented, the chamber can therefore have an overall spiral shape. This spiral shape corresponds to an approximately two-dimensional spiral shape.

[0047] Figure 4 Each chamber in the embodiment shown herein has, in the longitudinal direction, a shape consistent with that of the embodiment described herein. Figure 3 The two chambers in the prior art shown are approximately the same size. At the first surface 1, each chamber C1, C2 is open and has the same dimensions as according to... Figure 3 The open surfaces of the two chambers in the prior art are roughly corresponding to the open surfaces shown in the figure.

[0048] For reference Figure 15 In more detail, in the lateral direction, the honeycomb structure includes... Figures 1 to 3 The longitudinal wall 5 shown in the prior art is similar to the longitudinal wall 5. The outer wall 6 and the inner wall 7 are orthogonal to the longitudinal wall 5. The cross-section or surface of such a pipe channel, starting from the open surface of the small chamber and extending toward the bottom of the small chamber, has a narrowing section (forming a cross-sectional restriction on the pipe channel).

[0049] For example, in Figure 4As in this embodiment and in many other conceivable embodiments, the conduits of chambers C1 and C2 comprise a first portion of conduit beginning at the open surface of the chamber (at the first surface 1 of the soundproof cover) and facing towards the second surface 3 of the soundproof cover, followed by a second curved portion. In this embodiment, the second curved portion forms a 180° angle in the cutting plane P between the direction of the conduit at its inlet and the direction of the conduit at its outlet. In other words, the conduit forms a semi-circle at the second portion before merging into the cavity of the chamber. In the illustrated example, the 180° curved portion of the second portion of the conduit turns to a direction that is generally parallel to the third direction D3 at its inlet and oriented from the first surface 1 towards the second surface 3, and the curved portion has an outlet that is also generally parallel to the third direction D3 and oriented from the second surface 3 towards the first surface 1.

[0050] The second part flows into the cavity (i.e., the closed volume with a variable cross-section).

[0051] The narrowing section of the pipe can be continuous, gradual, or not, and extends through the first part of the pipe or through both the first and second parts of the pipe.

[0052] The chamber can therefore have a size at the inlet of the pipe, which is measured between the outer wall 6 and the inner wall 7 at the open surface of the chamber, that forms the inlet, which is greater than the first dimension d1 between the outer wall 6 and the inner wall 7, measured at the pole between the first part and the second part along the first direction D1.

[0053] The first dimension d1 can be larger than the second dimension d2 measured along the third direction D3, at the curved portion of the pipe parallel to and tangential to the second surface 3 of the cover, between the outer wall 6 and the inner wall 7. Therefore, the second dimension d2 is measured at the point where the pipe forms a 90° bend in the cutting plane P relative to the overall direction of the first portion of the pipe (i.e., the third direction D3). Thus, at the point where the second dimension d2 is measured, the pipe is oriented in the first direction D1.

[0054] The second dimension d2 can be greater than the third dimension d3 measured along the first direction D1 between the outer wall 6 and the inner wall 7 at the entrance of the cavity.

[0055] For reference Figure 15 As shown in more detail, since the chambers are confined between parallel longitudinal walls 5, they have constant dimensions in the second direction D2. Therefore, the cross-section of the pipe passage is rectangular, and the surface of this cross-section is proportional to the distance between the outer wall 6 and the inner wall 7.

[0056] Figure 5 The principles of the present invention are illustrated. Figure 5On the left side, a cross-section of a Helmholtz resonator known in the prior art is shown schematically. The Helmholtz resonator includes a closed cavity 8 with a volume V, which communicates with the outside via a small tube (referred to as the neck 9) of length L and cross-section A.

[0057] The natural frequency F0 of a standard Helmholtz resonator is as follows:

[0058]

[0059] Where c is the speed of sound.

[0060] Therefore, in this invention, each chamber forms a pseudo-Helmholtz resonator, the neck of which is formed by a conduit from the inlet of the chamber and a cavity into which the conduit flows.

[0061] exist Figure 5 In the image, the neck of the chamber is shown in shadow, while the cavity is represented by dotted textures.

[0062] Compared to the prior art where a small chamber forms a volume and a neck is formed by the opening of a perforated sheet at the top of the chamber, the length L of the neck formed by the channel through the chamber in this invention is greatly increased, which reduces the natural frequency of the resonator.

[0063] Figures 6 to 14 Alternative embodiments of the invention are presented based on the principles previously described. These embodiments particularly share the fact that the outer wall 6 and inner wall 7 of the conduit defining the chambers have rounded forms without sharp edges so as not to impede wave propagation within the chambers. Furthermore, the longitudinally juxtaposed chambers are nested relative to each other without any dead zone volume. This avoids any loss of acoustic surface and maximizes the performance of the covering in terms of sound insulation.

[0064] Figure 6 Two chambers C1 and C2 of the soundproof covering according to an embodiment of the invention are presented in particular, wherein the geometry of the chambers visible in cross-section along the cutting plane P is based on an ellipse 10 represented by thin lines. In particular, the outer wall 6 visible in the cutting plane P follows the line of the ellipse 10 on a portion or more of the ellipse 10, especially at least partially on the portion linking the first surface 1 to the second surface 3 (and fully shown in this example).

[0065] exist Figure 6 In the examples represented in the previous reference, Figure 4 The dimensions d1, d2, and d3 are constrained such that d1 > d2 > d3.

[0066] Figure 7Two chambers C1 and C2 of a soundproof cover according to an embodiment of the invention are presented, wherein the geometry of the chambers visible in cross-section along the cutting plane P is based on a circle 11 represented by a thin line. In particular, the outer wall 6 visible in the cutting plane P at least partially follows the line of the circle 11 at the portion linking the first surface 1 to the second surface 3.

[0067] exist Figure 7 In the examples represented in the previous reference, Figure 4 The dimensions d1, d2, and d3 are constrained such that d1 > d2 > d3.

[0068] Figure 8 The diagram illustrates four chambers C1…C4 of a soundproof cover according to an embodiment of the invention. This embodiment is particularly characterized by the following specific feature: the first portion of the conduit between the chamber inlet and the beginning of the curved second section exhibits symmetry or quasi-symmetry along a plane P2 orthogonal to the cutting plane P and the first surface 1 of the cover. This apparent symmetry allows for the treatment of acoustic behavior with virtual symmetry.

[0069] Figure 9 This illustrates four small chambers C1…C4 of a soundproof covering according to an embodiment of the present invention, the soundproof covering resembling… Figure 8 The cover, like the inner wall, has a chamber, the first portion of which has a pipe that is symmetrical or quasi-symmetrical along plane P2. Specifically, it has a generally “V” shaped cross-section in the cutting plane P. In the second portion of the pipe, a 180° curve is formed (relative to the overall direction of the “V” shaped first portion, i.e., the third direction D3), and the outer wall 6 at least partially follows the circular shape of construction 12. Since the second portion of the inner wall 7 also extends substantially parallel to the outer wall 6 in the form of an arc, the dimensions d1, d2, and d3 are approximately equal in this embodiment.

[0070] The geometry has a very narrow and very long neck, which allows for significant sound attenuation at low frequencies.

[0071] Figure 10 It indicates Figure 9 The four chambers C1…C4 of the variation of the soundproof covering are shown in the figure. The geometry of the chambers is exactly the same. Figure 10 In a variant, the outer wall 6 includes a perforation 13 that allows fluid to pass between the neck of the resonator formed by the chamber and its cavity. The perforation 13 may include one or more orifices that pass through the inner wall 7.

[0072] This reduces the acoustic impedance of the resonator. However, this reduction is achieved at the cost of altering the acoustic symmetry of the treatment. This objective can be achieved in all embodiments of the invention, and especially in reference to... Figures 4 to 14In the described embodiment, a perforated portion 13 is formed.

[0073] Figure 11 This illustrates three small chambers C1…C3 of a soundproof covering according to an embodiment of the present invention. The configuration of the pipes is similar to… Figure 9 The configuration of the chamber covered by the conduit is such that the conduit in its first section is symmetrical or quasi-symmetrical along plane P2. The second section of the conduit is curved and adapted such that the direction of the conduit at the outlet of this second section is oriented 180° relative to the overall direction of the "V-shaped" first section (i.e., the third direction D3). However, the overall geometry of the chamber is different from that of the conduit. Figure 9 Compared to the previous embodiment, the chambers are wider. Specifically, the openings of the chambers on the first surface 1 are greatly widened, the "V-shape" formed by the first part of the channel is more open, and the neck of the resonator formed by the channel is elongated. This increases the volume of the cavity. Therefore, lower frequencies can be handled. However, the number of chambers per square meter of the cover is reduced, and the mechanical properties of the cover may be reduced.

[0074] Figure 12 This illustrates three small chambers C1…C3 of a soundproof covering according to an embodiment of the present invention. The configuration of the pipes is similar to… Figure 11 The configuration of the chamber of the resonator is such that the tube is symmetrical or quasi-symmetrical along plane P2 in its first section. The second section of the tube forms a bend of 180° or nearly 180° (approximately 160° in this particular case). Shortening the first section of the tube elongates the second section, but most importantly, increases the volume of the resonator cavity. This allows for handling lower frequencies, but the shorter “V” shape of the first section of the tube increases the acoustic impedance of the chamber.

[0075] Figure 13 This indicates five small chambers C1…C5 of a soundproof covering according to an embodiment of the present invention. Figure 13 In one embodiment, the second portion of the conduit forms a 90° curve turn in the cutting plane P between the direction of the conduit at its inlet and the direction of the conduit before it merges into the cavity of the resonator. In other words, the second portion merges into the cavity in a direction orthogonal to its inlet direction. The first portion of the conduit extends approximately along a third direction D3, and the inlet in the cavity is approximately in a second direction D2.

[0076] Figure 14 express Figure 8 A three-dimensional view of an embodiment. The chambers of the covering are separated from each other in the lateral direction D2 by mutually parallel longitudinal walls 5. The outer wall 6 and inner wall 7 of the chambers extend perpendicularly to the longitudinal walls 5.

[0077] This diagram shows a perforated plate 2 separated from the rest of the soundproof cover, which forms the first surface 1 of the soundproof cover. In all embodiments of the invention, the first surface of the soundproof cover may advantageously include an impedance layer, i.e., a perforated sheet 2 (e.g., similar to perforated sheets used in the prior art) or a metal mesh (sometimes referred to as wire mesh) on the inlet side of the neck.

[0078] Conversely, on its second side 3, the soundproofing cover comprises a solid sheet 14 that forms the second side 3 and provides good mechanical cohesion to the soundproofing coating and, if necessary, closes the chamber on the second side 3.

[0079] Because the coating has small chambers with open surfaces that are square or rectangular, it has good effectiveness for flow in both the longitudinal direction D1 and the transverse direction D2.

[0080] Because the inner wall 7 of the chamber meets the outer wall 6 of the longitudinally adjacent chamber so as to form only a transverse wall at the first surface 1, there is no loss of acoustic surface at the first surface 1. In particular, in the illustrated example, the transverse wall visible between the two chambers at the first surface 1 is limited to a folded edge or joint edge between the inner wall 7 of the chamber and the outer wall 6 of the adjacent chamber.

[0081] More specifically, the inner wall 7 of the chamber of the cover and the outer wall 6 of the adjacent chamber meet at the first surface 1. The inner wall 7 and the outer wall 6 of the adjacent chamber form an acute angle between them (i.e., an angle less than 90° measured between the walls on the inner side of the acoustic cover). This forms a lateral edge at the first surface 1. This configuration is similar to... Figure 6 As shown in the diagram, a transverse vertical wall extends between two adjacent chambers. This configuration means that if the connection between adjacent chambers at the first surface 1 is made by a rounded wall, sound waves can easily enter the chambers of the acoustic shield without being reflected on the first surface 1.

[0082] The soundproof shielding according to the invention can be produced from a variety of different materials, particularly metals, plastics, or composite materials. The soundproof shielding can be obtained through a variety of different manufacturing methods (e.g., by assembling individual components). For example, the individual component can form the inner wall of a chamber and the outer wall of adjacent chambers. The individual component can be obtained by folding metal sheets, or by injection molding or composite materials. The longitudinal walls can be constructed from flat sheet metal, flat plastic panels, or composite materials. The assembly can be obtained, for example, by welding or bonding.

[0083] Cellular structures can be alternatively obtained through additive manufacturing based on plastic or metal materials.

[0084] The soundproof cover thus developed allows for the absorption of lower frequency sound waves than soundproof covers of the same thickness constructed according to known prior art. Industrial implementation of the cover according to the invention is readily achieved through a configuration with a honeycomb structure ( wherein the cells of which are laterally separated by parallel longitudinal walls).

[0085] The present invention is preferably applicable to the formation of soundproof panels for nacelles of aircraft engine equipment. Figure 15 The aircraft engine assembly is schematically shown in cross-section. The aircraft engine assembly includes an engine 15, a turbojet engine equipped with a fan 16, and the engine is mounted in a nacelle 17. A cover 18 may be mounted in the nacelle and more generally in the engine assembly at several different points, particularly exposed to sound waves. The cover 18 may be mounted to at least partially form the interior surface of the forward portion of the nacelle of the aircraft engine assembly. The cover 18 may be mounted in the central region of the interior surface of the nacelle at the rear of the fan 16. The cover 18 may also be mounted on the interior surface of the rear portion of the nacelle. The cover 18 may also be mounted on the casing of the engine 15.

[0086] Previous examples are mentioned by way of non-limiting example. The acoustic masking developed in this invention is applicable to any aircraft component whose surface is subjected to acoustic stimulation when the aircraft is in operation.

Claims

1. A soundproof cover comprising a honeycomb structure having a first surface (1) and a second surface (3), the honeycomb structure being formed of cells (C1…C6) open on the first surface (1) and closed on the second surface (3), the cells (C1…C6) being juxtaposed along a first, so-called longitudinal direction (D1) and a second, so-called transverse direction (D2) orthogonal to the longitudinal direction (D1); Each small room includes - A conduit extending at least between the first surface (1) and the second surface (3), the conduit being formed between the outer wall (6) and the inner wall (7) of the chamber and having a limiting cross-section thereof, the outer wall (6) and the inner wall (7) having a rounded form without sharp edges, and -Cavity (8), the pipe flows into the cavity. This causes the chamber to form a resonator, the resonator including a neck (9) formed by the conduit and the cavity. Its features are, The chambers are adapted to form the conduit and the cavity (8) on both sides of the inner wall (7); each chamber has a generally spiral cross section in a longitudinal cutting plane (P) perpendicular to the transverse direction (D2); and the longitudinally juxtaposed chambers are nested relative to each other.

2. The soundproof covering according to claim 1, wherein, The inner wall (7) of the chamber of the soundproof cover meets the outer wall (6) of the adjacent chamber so as to form only a transverse wall that separates the chamber and the adjacent chamber at the first surface (1).

3. The soundproof covering according to claim 2, wherein, The inner wall (7) of the chamber of the soundproof cover and the outer wall (6) of the adjacent chamber meet at the first surface (1), thereby forming an acute angle between them to form a lateral edge at the first surface (1).

4. The soundproof covering according to any one of claims 1 to 3, wherein, The pipeline successively includes: ●The first part, the first part extends from the first surface (1) of the soundproof cover toward the second surface (3) of the soundproof cover, and ●The second part forms a bend including an inlet and an outlet, and an angle between 90° and 180° is formed between the direction of the pipe at the inlet of the second part and the direction of the pipe at the outlet of the second part.

5. The soundproof covering according to claim 4, wherein, The first part of the pipe is approximately symmetrical along a transverse plane (P2) perpendicular to the first surface.

6. The soundproof covering according to any one of claims 1 to 3, wherein, The conduit and cavity (8) forming the neck (9) of the resonator are sized such that the resonant frequency of the resonator is less than 2000 Hz.

7. The soundproof covering according to any one of claims 1 to 3, wherein, The first surface (1) includes an impedance sheet that allows the chamber of the soundproof cover to communicate with the outside of the soundproof cover.

8. The soundproof covering according to any one of claims 1 to 3, wherein, The inner wall (7) of each chamber includes a perforation (13) that fluidly links the neck (9) to the cavity (8) of the resonator.

9. An aircraft engine assembly, the aircraft engine assembly comprising a nacelle and an engine, wherein, The inner surface of the nacelle and / or the outer surface of the engine casing have a soundproof covering as described in any one of claims 1 to 8.

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