A sound absorbing device

Abstract

The present invention relates to a sound-absorbing device (1) comprising: - a first and second wall (2, 3) spaced along a thickness direction (Z-Z), delimiting the device (1) on opposite sides, and having a respective reference plane (C); - a side wall (4) extending in the thickness direction (Z-Z) connecting the first and the second wall (2, 3) so as to define a chamber (V) with the latter; - a third wall (5) interposed between the first and the second wall (2, 3) along the thickness direction (Z-Z) so as to partition the chamber (V); wherein: - at least two of the first, the second and the third wall (2, 3, 5) comprise a plurality of through openings (6a, 6b, 6c) configured to allow the entry and distribution of sound waves within the chamber (V); - the distance between the first or second wall (2, 3) and the third wall (5) calculated along the thickness direction (Z-Z) has at least one maximum distance value (Zmax) and at least one minimum distance value (Zmin) along a width direction (X-X) or a length direction (Y-Y). - the first and the second wall (2, 3) comprise ridge portions (7a) projecting from the respective reference plane (C) in the thickness direction (Z-Z) along a first direction, and valley portions (7b) projecting from the respective reference plane (C) in the thickness direction (Z-Z) along a second direction opposite the first direction.

Description

Technical Field

[0001] The present invention relates to a sound-absorbing device, in accordance with claim 1.

[0002] The object of the present disclosure is used in the field of equipment for absorbing sound, in particular for reducing noise generated by household appliances or industrial machinery.

[0003] Furthermore, the device object of the present disclosure can be used for the acoustic isolation and / or soundproofing of closed environments, such as dining rooms or work environments.State of the art

[0004] There is a need felt in the state of the art to limit the diffusion of noise produced by household appliances during their operation.

[0005] There is also a need to reduce noise and reverberations in closed environments to increase the quality of sound within the environments themselves, and make the stay of people more pleasant therein.

[0006] Sound-absorbing / sound-insulating panels are known in the state of the art, i.e., acoustic devices which can be integrated in household appliances or fixed to the walls of closed rooms, configured to absorb and limit the diffusion of sound waves.

[0007] The known panels comprise a pair of external walls which are spaced in a thickness direction from an interspace.

[0008] In detail, the external walls are oriented perpendicular to the thickness direction and delimit the interspace from opposite sides.

[0009] As shown in CN203910264U, in some cases, the interspace is at least partially filled with a material having an acoustic insulation function.

[0010] Furthermore, as for example shown in CN110588683A and WO2020107080A1, the interspace can be partitioned by one or more internal walls oriented parallel to the external walls. At least some of said walls comprise a plurality of openings adapted to allow the entry and distribution of sound waves in the interspace.

[0011] It is known to the person skilled in the art that the openings and the interspace constitute an acoustic resonator capable of generating sound dissipation in a specific frequency range.

[0012] It should be noted that the range of frequencies absorbed depends on several parameters, mostly geometric.

[0013] One of the most important geometric parameters for determining the range of frequencies absorbed is the distance between the walls delimiting the interspace.

[0014] Therefore, disadvantageously, the aforementioned known panels, since they have parallel walls, i.e., spaced by the same amount at each point of the panel, are capable of generating appreciable sound dissipations only in a very narrow range of frequencies.

[0015] EP1742201A1 shows multiple embodiments of a sound-absorbing panel in which the interspace has different thicknesses. In particular, in some embodiments the internal wall, which is interposed between a pair of flat external walls, has a non-planar conformation. In other embodiments, only one of the external walls is not flat.

[0016] Although the teachings of EP1742201A1 allows to improve the sound-absorbing performance of panels with all the walls oriented parallel, remains the need to broaden the range of frequencies absorbed.Object of the invention

[0017] In this context, the technical task underlying the present invention is to propose a sound-absorbing device which overcomes the drawbacks of the prior art mentioned above.

[0018] In particular, it is an object of the present disclosure to provide a sound-absorbing device capable of blocking, containing, dissipating the energy of the sound waves generated by the aforesaid household appliances or other civil / industrial equipment in a frequency range which is broader with respect to the panels known in the state of the art.

[0019] A further object of the present description is to provide a sound-absorbing device capable of reducing the excessive reverberation in a room produced by sound waves generated by household appliances or other civil / industrial equipment present in said room in a broad frequency range with respect to the panels known in the state of the art.SUMMARY OF THE INVENTION

[0020] In accordance with the features of claim 1, the object of the present disclosure is a sound-absorbing device configured to absorb, dissipate, attenuate the energy of the sound waves generated for example by household appliances and / or reduce excessive reverberation present in a room in which the aforementioned household appliance is integrated.

[0021] Such a sound-absorbing device comprises a first and a second wall spaced along a thickness direction and delimiting the device opposite sides. In detail, the first and the second wall extend transversely to the thickness direction and have a respective reference plane.

[0022] Furthermore, the device of the present disclosure comprises a side wall extending in the thickness direction for connecting the first and the second wall, and defining a chamber therewith.

[0023] The sound-absorbing device further comprises a third wall interposed between the first and the second wall along the thickness direction so as to partition the chamber.

[0024] At least two among the first, the second and the third wall comprise a plurality of through openings configured to allow the entry and distribution of sound waves within the chamber.

[0025] In the device object of the present disclosure, the distance between the first or the second wall and the third wall, calculated along the thickness direction, has at least a maximum distance value and a minimum distance value along a width direction or a length direction. It should be specified that the width and length direction make a Cartesian triad with the thickness direction.

[0026] Furthermore, both the first and the second wall of the device have ridge portions projecting from the respective reference plane in the thickness direction along a first direction, and valley portions projecting from the respective reference plane in the thickness direction along a second direction opposite the first direction.

[0027] In the light of the above, it is evident to the person skilled in the art that the device object of the present invention, having different distances between the first or the second wall and the third wall and said ridge and valley portions, behaves like a plurality of resonators having different geometric features, and therefore allows to obtain different ranges of sound absorption, dissipation and / or attenuation.

[0028] Therefore, advantageously, the sound-absorbing device object of the present disclosure, being similar to a series of resonators with different geometric properties, is capable of achieving better audible acoustic performance with respect to the panels known in the state of the art.

[0029] In particular, it should be noted that the ridge and valley portions of the first and second wall allow to increase the degrees of freedom on which it is possible to act to make resonators with different properties inside the sound-absorbing device and, therefore, allow to broaden the frequency range in which there is a high absorption.LIST OF FIGURES

[0030] Further features and advantages of the present invention will become more apparent from the description of an exemplary, but not exclusive, and therefore nonlimiting preferred embodiment of a sound-absorbing device, as illustrated in the appended drawings, in which: Figure 1 shows a perspective view of a sound-absorbing device; Figure 2a shows a sectional view of a first example of the device of Figure 1, not encompassed by the wording of the claims; Figure 2b shows an enlargement of some details of Figure 2a; Figure 2c shows a sectional view of a second example of the device of Figure 1, not encompassed by the wording of the claims; Figure 3a shows a sectional view of a third embodiment of a sound-absorbing device according to the present invention; Figure 3b shows a sectional view of a fourth embodiment of a sound-absorbing device according to the present invention; Figure 4 shows a sectional view of a fifth embodiment of a sound-absorbing device according to the present invention; Figure 5 shows a front sectional view of a first form of use of the sound-absorbing device according to the present invention in a kitchen hood of the wall or under-cabinet type; Figure 6 shows a front sectional view of a second form of use of the sound-absorbing device according to the present invention in a kitchen hood of the downdraft type; Figure 7 shows an optional component of the sound-absorbing device according to the present invention; Figure 8 shows a sectional view of a sixth embodiment of a sound-absorbing device according to the present invention, comprising the component of Figure 7. DETAILED DESCRIPTION

[0031] Even if not explicitly highlighted, the individual features disclosed with reference to the specific embodiments shall be understood as accessory to and / or interchangeable with other features disclosed with reference to other embodiments.

[0032] With reference to the appended drawings, the present disclosure relates to a sound-absorbing device 1, i.e., a device configured to absorb, dissipate, attenuate sound energy.

[0033] With reference to figure 1, the sound-absorbing device 1 extends three-dimensionally along a width direction X-X, a length direction Y-Y, and a thickness direction Z-Z.

[0034] Preferably, but not necessarily, the sound-absorbing device 1 has a panel conformation, i.e., it extends more in the width and length direction X-X, Y-Y with respect to the thickness direction Z-Z.

[0035] It should be specified that the width and length directions X-X, Y-Y make a Cartesian triad with the thickness direction Z-Z. Therefore, the length, width and thickness directions X-X, Y-Y, Z-Z are oriented orthogonally with respect to one another, i.e., they form a tri-orthogonal Cartesian triad reference system.

[0036] As shown in figures 2a, 3a, 3b and 4, the sound-absorbing device 1 comprises a first wall 2 and a second wall 3 spaced along the thickness direction Z-Z.

[0037] In detail, the first and the second wall 2, 3 delimit the device 1 on opposite sides along the thickness direction Z-Z.

[0038] Preferably, if the device 1 has a panel conformation, the first and the second wall 2, 3 respectively make a base surface configured to be fixed / associated with a support element by coupling means, and an upper surface opposite the base surface.

[0039] In accordance with what is shown in figures 2a, 3a, 3b, and 4, the first and the second wall 2, 3 extend transversely to the thickness direction Z-Z in the width and length directions X-X, Y-Y.

[0040] Still preferably, the first and the second wall 2, 3 extend in the width and length directions X-X, Y-Y for the entirety of the extension of the device 1 along such width and length directions X-X, Y-Y.

[0041] Further details on the geometric conformations of the first and the second wall 2, 3 will be given below.

[0042] Referring to figures 1-4, the sound-absorbing device 1 comprises a side wall 4 extending in the thickness direction Z-Z, connecting the first and the second wall 2, 3.

[0043] With reference to the embodiment of Figure 2c, the side wall 4 extends in the thickness direction Z-Z from the second wall 3 to beyond the first wall 2, forming coupling projections 40 to an external body such as a hood.

[0044] Preferably, the side wall 4 outlines the device 1, delimiting it along the width and length directions X-X, Y-Y.

[0045] With reference now to Figure 2a, it should be noted that the side wall 4 has a first edge 41 connected peripherally to the first wall 2, and a second edge 42, opposite the first 41, connected peripherally to the second wall 3.

[0046] The side wall 4 defines a chamber V of a certain volume with the first and the second wall 2, 3.

[0047] According to an aspect, the chamber V is at least partially filled with air. In other words, connecting to the first and to the second wall 2, 3 the side wall 4 confines an air volume inside the chamber V.

[0048] It should be noted that the air volume contained in the chamber V is free to resonate therein; such behaviour can be modelled from the physical point of view by means of known formulas for acoustic resonator systems (for example Helmholtz resonators).

[0049] In view of this, the ratio of the air volume enclosed in the chamber V to the total volume of the device 1 has a percentage value greater than 70%.

[0050] With reference to figures 2a, 2b-4, the device 1 further comprises a third wall 5 interposed between the first and the second wall 2, 3 along the thickness direction Z-Z.

[0051] Preferably, the third wall 5 extends transversely to the thickness direction Z-Z in the width and length directions X-X, Y-Y.

[0052] Further, preferably, the third wall 2, 3 extends in the width and length directions X-X, Y-Y connecting to the side wall 4.

[0053] In detail, the third wall 5 is connected to the side wall along a third edge 43 which is located in an intermediate position between the first and the second edge 41, 42.

[0054] The third wall 5, arranged in the chamber V between the first and the second wall 2, 3, is configured to partition the volume of the chamber V.

[0055] It should be specified that in the context of the present invention, the term partition is intended as dividing the volume of the chamber V into different portions of smaller extension in volume. Such portions of the volume of the chamber V may or may not be placed in fluid communication; therefore, the sound waves are free to partition themselves among the different portions of the volume of the chamber V.

[0056] Preferably, in accordance with what is shown in figure 2a, 3a and 3b, the third wall 5 partitions the chamber V into a first interspace I1 and into a second interspace I2 which extend along the thickness direction Z-Z.

[0057] In detail, the first interspace I1 extends between the first and the third wall 2, 5, while the second interspace I2 between the second and the third wall 3, 5.

[0058] With reference to figure 7, preferably, the device 1 object of the present description comprises a dividing element 8 arranged in at least one among the first and the second interspace I1, I2.

[0059] In detail, the dividing element 8 is designed to fill the interspace I1, I2 in which it is arranged along the thickness, width and length directions X-X, Y-Y, and Z-Z.

[0060] Preferably, the dividing element 8 is configured to come into contact with the walls which define the interspace in which it is inserted, so as to be locked therein.

[0061] Preferably, the dividing element 8 is configured to partition the interspace I1, I2 (Fig. 2a) in a plurality of air volumes 80.

[0062] In the embodiment of figure 7, the dividing element 8 is grid-shaped and has a plurality of through cavities extending along the thickness direction Z-Z and delimiting respective air volumes.

[0063] In detail, the cavities may or may not be geometrically identical to each other.

[0064] Advantageously, the dividing element 8 allows to obtain a fair distribution of the sound waves in the device 1, and therefore a regular dissipation of the sound energy.

[0065] According to an aspect, at least two of the first, the second and the third wall 2, 3, 5 comprise a plurality of through openings 6a, 6b, 6c configured to allow the entry and distribution of sound waves within the chamber V.

[0066] Preferably, each wall 2, 3, 5 has respective through openings 6a, 6b, 6c.

[0067] Optionally, a plurality of openings can also be obtained on the side wall 4.

[0068] It should be noted that the chamber-openings system constitutes what in acoustics is defined as acoustic resonator or Helmholtz resonator. It has long been known that acoustic resonators can be employed to generate sound dissipations in a specific frequency range. Such a range of dissipated frequencies varies depending on multiple parameters, including: material used to make the resonator (density, elastic modulus, damping), surface extension of the opening, geometric shape of the opening, volume of the resonance chamber.

[0069] In the device object of the present description, it should be noted that the volume of the resonance chamber, and therefore the range of frequencies dissipated, depends directly on the spacing of the walls 2, 3, 5 along the thickness direction Z-Z.

[0070] With reference now to figures 2-4, the through openings 6a, 6b on the first and second wall 2, 3 put the volume of the chamber V in fluid communication with the environment outside the device 1.

[0071] Therefore, the through openings 6a, 6b on the first and second wall 2, 3 allows sound waves to enter the chamber V.

[0072] The through openings 6c on the third wall 5 put different portions of the volume of the chamber V in fluid communication and therefore allow to partition the sound waves inside the chamber V. In particular, with reference to figure 2a, the through openings 6c on the third wall 5 put the first and the second interspace I1, I2 in communication.

[0073] Each opening is characterized by a surface extension A a1 , A a2 , A a3 thereof.

[0074] In detail, the openings 6a, 6b, 6c belonging to a same wall 2, 3, 5 may or may not have a same surface extension A a1 , A a2 , A a3 .

[0075] In the embodiments shown in figures 2a, 3a and 3b the openings belonging to the same wall have the same surface extension.

[0076] In contrast, in the embodiment of figure 4 the openings belonging to the first and to the second wall have different surface extensions.

[0077] Preferably, the openings 6a, 6b of the first and the second wall 2, 3 have greater surface extensions with respect to the openings 6c of the third wall 5.

[0078] Preferably, the through openings 6a, 6b, 6c are defined by means of circular-section through holes and the variation of the surface extension of the opening is obtained by increasing / reducing the characteristic radius of the hole.

[0079] However, in alternative embodiments the through openings 6a, 6b, 6c may have sections which are rectangular, square, hexagonal and of any other geometric form.

[0080] In the preferred embodiment, the first and the second wall 2, 3 have circular through holes having a diameter comprised between 2 and 10 mm, while the third wall 5 has circular through holes having a diameter comprised between 0.1 and 1 mm.

[0081] In detail, for each wall it is possible to define a respective porosity value P1, P2, P3. In the context of the present invention the porosity value of a wall P1, P2, P3 is calculated as the ratio between the sum of the surface extensions of the openings A a1 , A a2 , A a3 of a same wall and the surface extension of the wall A p1 , A p2 , A p3 itself.

[0082] In formula: P i = ∑ j = 1 N i A ai , j A pi

[0083] Where P i is the porosity value of the i-th wall considered, N i is the number of openings present on the i-th wall, A ai,j is the surface extension of the j-th opening of the i-th wall, A pi is the surface extension of the i-th wall.

[0084] It should be specified that each wall has a certain surface extension A p1 , A p2 , A p3 which the person skilled in the art is capable of detecting by means of traditional techniques for spatial measurements.

[0085] Preferably, the porosity value P3 of the third wall 5 is lower with respect to the porosity value P1, P2 of the first and the second wall 2, 3.

[0086] Further, preferably, the porosity value of the first and the second wall P1, P2 is greater than 0.01 while the porosity value of the third wall P3 is less than 0.01.

[0087] With reference to figures 2-4, the distance between the first or the second wall 2, 3 and the third wall 5, calculated in the thickness direction Z-Z, has at least a maximum distance value Z max and a minimum distance value Z min along the width or length direction X-X, Y-Y.

[0088] With reference to figure 2b, it should be specified that maximum and minimum distance value Z max , Z min are intended as the absolute values of the distances between the first or the second wall 2, 3 and the third wall 5 calculated in the thickness direction Z-Z, respectively at the points in which they are most spaced apart and close together.

[0089] Furthermore, it should be specified that the maximum and minimum distance value Z max , Z min are different, in particular, as can also be seen from figure 2b, the maximum distance value Z max is larger in modulus than the minimum distance value Z min .

[0090] Preferably, moving along the length or width direction X-X, Y-Y the value of the distance between the first or the second wall 2, 3 and the third wall 5 varies with continuity between Z max and Z min . Therefore, preferably, there are no sudden variations in distance between the first or the second wall 2, 3 and the third wall 5 along the length or width direction X-X, Y-Y. In other words, moving along the length and / or width directions X-X, Y-Y from the point at which the maximum distance value Z max is detected, all the distance values between the maximum distance value Z max and the minimum distance value Z min are recorded.

[0091] In the embodiments shown in figures 3a, 3b and 4, both the distance between the first wall 2 and the third wall 5 and the distance between the second wall 3 and the third wall 5 have maximum and minimum distance values Z max , Z min .

[0092] In this regard, it should be specified that the maximum and minimum distance values between the first and the third wall 2, 5 may or may not coincide with the maximum and minimum distance values between the second and the third wall 3, 5.

[0093] Preferably, the maximum and minimum distance values Z max , Z min are selected within the range of values having 1 mm and 50 mm as ends.

[0094] It should be noted that the device 1 object of the present disclosure, having different distances between the first or the second wall 2, 3 and the third wall 5, behaves like a plurality of resonators having different geometric features and therefore capable of generating sound dissipations in different frequency ranges. Therefore, advantageously, the device 1 object of the present invention is capable of generating appreciable sound dissipations in a greater frequency range with respect to the panels known in the state of the art. In fact, in accordance with what is reported above in the state of the art, the behaviour of the known panels is similar to that of a single resonator.

[0095] With reference to figures 3a and 3b, the first and the second wall 2, 3 have a respective reference plane C and comprise respective ridge and valley portions 7a, 7b projecting from the respective reference plane C along the thickness direction Z-Z in opposite directions.

[0096] In detail, the ridge portions 7a project from the respective reference plane C along the thickness direction Z-Z in a first direction, while the valley portions 7b project from the respective reference plane along the thickness direction Z-Z in a second direction opposite the first.

[0097] It should be specified that reference plane C is intended to indicate a fictitious plane, interposed between the ridge and valley portions 7a, 7b, representative of the extension of the wall along the length and width directions X-X, Y-Y. By way of example, in accordance with what is shown in figures 3a, 3b the reference plane C may be the intermediate plane between the ridge and valley portions 7a, 7b.

[0098] According to the invention, both the first and the second wall 2, 3 have a wavy conformation with respect to the reference plane C. In detail, such a wavy conformation has alternating ridge portions 7a connected to the valley portions 7b.

[0099] It should be specified that such waviness can extend on a wall along the direction of width X-X, length Y-Y or a combination thereof. For example, in the embodiment of figure 1, the second wall 3 has concentric waves extending simultaneously along the width and length direction X-X, Y-Y.

[0100] In the embodiments of figures 3a, 3b and 4, the third wall 5 is flat and both the first and the second wall 2, 3 have a wavy conformation.

[0101] Therefore, according to the invention, the first and the second wall 2, 3 both have the wavy conformation. The third wall 5 can be planar or also wavy.

[0102] Preferably, as also shown in figures 3a and 3b, the reference planes C are oriented orthogonally with respect to the thickness direction Z-Z, and the third wall is flat and also oriented orthogonally with respect to the thickness direction Z-Z. Therefore, it can be said that the first, the second and the third wall 2, 3, 5 extend along the width and length directions X-X, Y-Y in a substantially parallel manner.

[0103] With reference to figure 4, preferably, the ridge portions 7a comprise a plurality of first through openings 60, and the valley portions 7b comprise a plurality of second through openings 61.

[0104] Still more preferably, the first and the second through openings 60, 61 have different geometric features. In detail, the first through openings 60 have a greater surface extension with respect to the second through openings 61 or vice versa.

[0105] For example, in the embodiment of figure 4, the second wall 3 has openings with greater surface extension at the ridge portions 7a, otherwise the first wall 2 has openings with greater surface extension at the valley portions 7b.

[0106] Advantageously, the presence of openings having different geometric features allows to further broaden the range of sound frequencies dissipated. In fact, in accordance with the above, the geometry and in particular the area of the opening significantly influence the dissipation properties of the resonators. Therefore, the effect of the presence of openings having different geometric features is similar to that of a series of resonators having different openings and thus capable of dissipating different frequency ranges.

[0107] With reference to figures 3a, 3b and 4, the device 1 object of the present description may comprise further internal walls 9, arranged between the first and the second wall 2, 3, in addition to the third wall 5. For such further internal walls 9 what is said in relation to the third wall 5 applies , mutatis mutandis.

[0108] At most one among the first, second, third and further walls 2, 3, 5, 9 is impervious, i.e., it has no openings.

[0109] In the embodiment of Figure 8, the dividing element 8 is arranged in the second interspace I2 and extends along the thickness direction Z-Z between the third wall 5 and the further internal wall 9. Preferably, the further internal wall 9 partitions the second interspace I2 defining an interspace portion I2' in which it is arranged by the dividing element 9.

[0110] The dissipater 1 object of the present invention can be made of different types of materials or combinations thereof, such as PET, PP, PVC, aluminium, and the like.

[0111] Preferably, the walls 2, 3, 4, 5 and 9 have a thickness comprised between 0.1 mm and 20 mm.

[0112] It should be specified that the thickness and the construction material of the walls also affect the sound dissipation properties of the device 1. In fact, the walls, when exposed to sound waves, resonate by plate effect, generating sound dissipations at certain frequencies. It is known that the frequencies dissipated by the wall / plate resonance phenomenon depend on several factors, including the wall / plate thickness, the presence of openings, the extension of the openings, the wall / plate construction material.

[0113] In embodiments not shown in the accompanying drawings, it is possible to broaden the sound dissipation range of the device 1, creating localized variations in the thickness of the walls.

[0114] Furthermore, it should be noted that the uneven distribution of the above-mentioned holes locally changes the rigidity of the walls, changing the dynamic behaviour thereof in resonance. Therefore, in addition to broadening the range of dissipated frequencies for the generation of a series of resonators having different properties, such an uneven distribution of holes is capable of further broadening the range of dissipated frequencies, also acting on the resonance of the walls.

[0115] With reference to figures 5 and 6, a kitchen hood 100 for extracting cooking fumes is also an object of the present invention.

[0116] It should be specified that kitchen hood 100 is intended as both wall or below-cabinet hoods, i.e., facing above the cooking hobs (Figure 5), and as downdraft hoods, i.e., those integrated with the entire cooking hob (Figure 6).

[0117] The kitchen hood 100 object of the present invention comprises suction members 101 configured to generate a suction flow of the cooking fumes. Such suction members 101 are known to the person skilled in the art; therefore, it is not necessary to describe them in detail.

[0118] Furthermore, the kitchen hood 100 comprises at least one sound-absorbing device 1 according to the above. In detail, the at least one device 1 is arranged in proximity of the suction members 101 so as to dissipate, at least partially, the sound waves generated by their operation.

Claims

1. Sound-absorbing device (1) comprising: - a first and a second wall (2, 3) spaced along a thickness direction (Z-Z) and delimiting the device (1) on opposite sides, said first and second wall (2, 3) extending transversely to the thickness direction (Z-Z) and having a respective reference plane (C); - a side wall (4) extending in the thickness direction (Z-Z) connecting the first and second wall (2, 3), the side wall (4) defining with the first and the second wall (2, 3) a chamber (V); - a third wall (5) interposed between the first and the second wall (2, 3) along the thickness direction (Z-Z) so as to partition said chamber (V); wherein: - at least two of the first, the second and the third wall (2, 3, 5) comprise a plurality of through openings (6a, 6b, 6c) configured to allow the entry and distribution of sound waves within the chamber (V); - the distance between the first or the second wall (2, 3) and the third wall (5) calculated along the thickness direction (Z-Z) has at least one maximum distance value (Zmax) and at least one minimum distance value (Zmin) along a width direction (X-X) or a length direction (Y-Y), said width and length directions (X-X, Y-Y) making with the thickness direction (Z-Z) a Cartesian triad characterized in that the first and the second wall each comprise: - ridge portions (7a) projecting from the respective reference plane (C) in the thickness direction (Z-Z) along a first direction; - valley portions (7b) projecting from the respective reference plane (C) in the thickness direction (Z-Z) along a second direction opposite the first direction.

2. Device (1) according to claim 1, wherein the ridge portions (7a) comprise a plurality of first through openings (60), and the valley portions (7b) comprise a plurality of second through openings (61).

3. Device (1) according to claim 2, wherein the first openings (60) have a greater surface extension than the second openings (61) or vice versa.

4. Device (1) according to any one of claims 1 to 3, wherein at least one of the first and the second wall (2, 3) has a wavy conformation with respect to the reference plane (C), said wavy conformation having the ridge portions (7a) alternating and connected to the valley portions (7b).

5. Device (1) according to claim 4, wherein the first and the second wall (2, 3) both have the wavy conformation.

6. Device (1) according to any one of claims 1 to 5, wherein: - the reference plane (C) is oriented orthogonally with respect to the thickness direction (Z-Z), - the third wall (5) is flat and oriented orthogonally to the thickness direction (Z-Z).

7. Device (1) according to any one of the preceding claims, wherein the first, the second and the third wall (2, 3, 5) have: - a certain surface extension (Ap1, Ap2, Ap3); - a plurality of through openings (6a, 6b, 6c), each opening being characterized by its own surface extension (Aa1, Aa2, Aa3); - a porosity value (P1, P2, P3) defined as the ratio between the sum of the surface extensions of the openings (Aa1, Aa2, Aa3) of a wall (2, 3, 5) and the surface extension (Ap1, Ap2, Ap3) of the wall (2, 3, 5) itself; the porosity value (P3) of the third wall (5) being lower than the porosity value (P1, P2) of the first and second wall (2, 3).

8. Device (1) according to claim 7, wherein the porosity value of the first and second wall (P1, P2) is greater than 0.01, whereas the porosity value of the third wall (P3) is lower than 0.01.

9. Device (1) according to claim 7 or 8, wherein the openings (6a, 6b) of the first and second wall (2, 3) have greater surface extensions than the openings (6c) of the third wall (5).

10. Device (1) according to any one of the preceding claims, wherein: - the third wall (5) partitions the chamber into a first interspace (I1) extending along the thickness direction (Z-Z) between the first and the third wall (2, 5), and a second interspace (I2) extending along the thickness direction (Z-Z) between the second and the third wall (3, 5); - the device comprises a dividing element (8) arranged in one of the first and second interspace (I1, I2) and configured to fill it at least partially along the thickness, width and length directions (Z-Z, X-X, Y-Y), said dividing element (8) being configured to divide the relative interspace (I1, I2) into a plurality of air volumes (80).

11. Kitchen hood (100) comprising: - suction members (101) configured to generate a suction flow of the cooking fumes; - at least one sound-absorbing device (1) according to any one of claims 1 to 10, said device (1) being arranged in proximity of the suction members (101) so as to dissipate the sound waves generated by their operation.

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