EP3928311B1

EP3928311B1 - Acoustic attenuation device for propagated sound through surfaces

Info

Publication number: EP3928311B1
Application number: EP20705716.7A
Authority: EP
Inventors: Luca D'ALESSANDRO; Stefano CAVERNI; Giovanni CAPELLARI; Francesco Mori; Simone MEDURI; Sebastiano Conti
Original assignee: Phononic Vibes Srl
Current assignee: Phononic Vibes Srl
Priority date: 2019-02-22
Filing date: 2020-02-20
Publication date: 2024-04-17
Anticipated expiration: 2040-02-20
Also published as: IT201900002569A1; EP3928311A1; WO2020169711A1; EP3928311C0

Description

Technical field

The present invention relates to an acoustic attenuation device for a propagated sound through surfaces, typically characterized by tonal components.
In general, the present invention finds wide application in a diversified range of technical fields, for instance in the field of mechanical and electromechanical motors, such as compressors of home devices, automotive or aircraft engines, in the railway field, etc.

Prior art

Acoustics is the branch of physics that studies sound, the pressure waves that cause it, its propagation and its reception.
The sound is in particular generated by a source, that is a vibrating body that transmits its vibrations to the medium surrounding it, a medium that may be represented by air, water, metals, concrete or other. Still more specifically, looking at the microscopic level, the motion of the particles generates the wave and the sound propagates in the form of a sound wave that propagates forming alternating layers of compressed and rarefied air.
The study of acoustics, in addition to being addressed to mere scientific discovery, was also directed towards technical means that allow controlling the aforementioned propagation of sound for specific needs.
Therefore, on the one hand, tools were studied to amplify or modulate the propagation of sound.
On the other hand, tools were studied, which can attenuate or inhibit it, in order to increase the comfort of a user who uses particular devices or is in generally noisy environments.
The technical fields affected by such a need are manifold.
For instance, the world of engines is affected, whether they are automotive or aeronautical, very noisy due to the movement of the mechanical components during operation, and which generate an uncomfortable environment for vehicle passengers.
The railway world is affected, due to the vibrations caused by the transit of vehicles.
The area of dividing panels between rooms is clearly affected, in particular those panels with the greatest need for soundproofing such as recording studios.
The domestic environment is also affected, for instance due to the noise generated by household appliances. For instance, in the case of fridges, components such as compressors, which are particularly noisy causing annoyance for the user, are adopted.
Various solutions and various devices have been developed, which are capable of counteracting the effect of sound propagation, whether they are general in nature or related to specific technical fields.
US 9,275,622 B2 discloses a device for vibro-acoustic attenuation and/or for the reduction of the transmitted energy, with a housing structure and at least one mechanical resonator connected thereto, wherein the housing structure comprises a plurality of cavities separated by contiguous walls.
Instead, US 2,541,159 A discloses a sound suppressor, which may be directly connected to the vibrating object, comprising a weight and a support for said weight in order to dampen vibrations. A flexible portion is provided in the support, said flexible portion having a substantial mechanical bending hysteresis, namely the ability, when bent, to convert all or a large part of the force required to cause heat bending.
US 7,395,898 B2 provides a panel for noise reduction formed by a plurality of cells, with sheets of flexible material and a plurality of weights; the frequency of acoustic attenuation may be controlled through a selection of the masses of these weights.
FR 3,056,812 A1 provides a structure for blocking the energy of the acoustic waves comprising a cell support structure and at least one resonant membrane covering a cell of the support structure. The resonant membrane comprises at least one weight and has an antiresonance frequency.
Instead CN 103,440,969 A discloses a device comprising an elastic part and a solid metal sphere, the elastic part is fixed on the surface of a transformer and the solid metal sphere is fixed to the end of the elastic part. The device may convert the kinetic energy of the vibration of the transformer into elastic potential energy and thermal energy, in order to reduce the vibration energy of the transformer and to reduce noise emission.
KR 100,315,515 B1 discloses a covering for isolating the noise produced by a compressor using a spring system at the bottom of said covering.
US 9,076,429 B2 relates to metamaterial members for absorbing sound and pressure, and modular systems built of metamaterial members. The metamaterial member includes an outer mass with a cavity formed therein in which a stem coupled to an inner mass is disposed; the inner mass includes an inner core and an outer shell. US 2011/240402 A1 relates to a sound isolation/vibration isolation structure which includes: a hollow frame surrounding an inside space; a film disposed within the inside space, vertically contacting an inside wall of the hollow frame; and a body mass disposed on a top surface of the film.
The devices disclosed in the prior art still have some drawbacks, which may be represented by a non-perfect insulation, by non-optimal absorbent capacities especially with respect to tonal frequencies, by excessive size of the attenuator device or by excessive construction complexity.

Summary of the invention

An object of the present invention is to overcome the drawbacks of the prior art.
A particular object of the present invention is to provide a device allowing an effective attenuation of the sound propagation field.
A further particular object of the present invention is to provide a device able to be indifferently applied on a plurality of devices without a particular structural or functional adaptation.
Another object is to provide a device that is compact, so as not to particularly affect the overall dimensions of the component or structure which it is applied to, that is robust to be durable over time.
These and other objects are achieved by an acoustic attenuation device for propagated sound through surfaces according to the characteristics of the appended claims that form an integral part of the present disclosure.
An idea underlying the present invention is to provide an acoustic attenuation device for propagated sound through according to claim 1.
Advantageously, the present solution allows exploiting in a combined and synergistic manner the acoustic attenuation effect by exploiting both the mechanical energy dissipation at the movable element along with a first acoustic attenuation effect given by the first opening, and the sound-absorbing effect of the subsequent cavity, thus ensuring a better insulation in a low insulation thickness. Mainly the acoustic attenuation device is particularly advantageous in frequency tonal applications, namely the applications in which the generated sound is very well characterized in terms of frequency of the propagated sound wave.
Preferably, the at least one first opening of each of the attenuation modules defines the at least one movable element preferably surrounding the at least one movable element. This solution allows a sound wave that is evenly incident on the movable element.
In an embodiment, each of the attenuation modules further comprises a plurality of second openings which put the innermost connection layer in fluid communication with the outermost layer, to further attenuate the propagated sound.
This additional effect, which exploits the sound-absorbing effect of the perforated panels, allows a further insulation and a better performance of the acoustic attenuation device.
Still more preferably, the at least one first opening is concave in section and the plurality of second openings individually have convex sections.
Advantageously this aspect exploits the generation phenomenon of stationary waves in resonance with the own frequency of the cavity to allow insulation from a certain range of frequencies belonging to the sound wave, and the overall attenuation effect is thus further improved.
Preferably the innermost layer comprises an adhesive layer for gluing to the at least one surface. This solution is particularly practical and suitable for a plurality of uses for applications even very different from each other.
Still preferably, the intermediate layer comprises a support structure for the attenuation modules.
Said support structure according to an embodiment of the invention comprises outer support elements overlaying on the intermediate layer and facing the outermost layer, the movable elements being connected to the outer support elements.
This solution is particularly advantageous in that it can make the intermediate layer in two parts, each of relatively simple construction, thus affecting times, costs and any possibility of errors during the production phase.
According to a different embodiment of the invention the support structure comprises inner support elements facing the innermost layer at the first openings, the movable elements being connected on the inner support elements. According to an aspect of the invention the inner support elements define at least two of the first openings, different from each other.
This configuration is particularly advantageous for the structural robustness of the intermediate layer and consequently of the entire device.
Preferably the movable elements are substantially circular or squared.
According to a further aspect, the present invention provides a compressor enclosed in a casing having at least one outer surface, which comprises an acoustic attenuation device according to the invention associated with said at least one outer surface.
This application is particularly advantageous and suitable for the structural typology of the component identified as sound source.
Further features and advantages will become more apparent from the following detailed description of preferred, but not exclusive, embodiments of the present invention and from the dependent claims that outline preferred and particularly advantageous embodiments of the invention.

Brief description of the drawings

The invention is illustrated with reference to the following figures, provided by way of non-limiting example, in which:

Figure 1 illustrates an exploded view of an example of the acoustic attenuation device;
Figure 2 illustrates a front view from outside of the intermediate mechanical attenuation layer of the acoustic attenuation device of Figure 1;
Figure 3 illustrates a detail of the acoustic attenuation device of Figure 1;
Figure 4 illustrates a detail of the acoustic attenuation device of Figure 1;
Figure 5 illustrates a detail of an example of the acoustic attenuation device;
Figure 6 illustrates a front view from inside of the intermediate layer of the acoustic attenuation device of Figure 6;
Figure 7 illustrates a detail of an embodiment of the acoustic attenuation device according to the invention;
Figure 8 illustrates an exploded view of an example of the acoustic attenuation;
Figure 9 illustrates a front view of the intermediate layer of the acoustic attenuation device of Figure 8;
Figure 10 illustrates a front view of the intermediate layer of the acoustic attenuation device of a different example of the acoustic attenuation device ;
Figure 11 illustrates a plane example of the attenuation device.

In the different figures, analogous elements will be indicated with analogous reference numbers.

Detailed description

With reference to the enclosed Figure 1, reference number 100 wholly indicates an example of an acoustic attenuation device.
As it may be noticed, this example provides a whole cylindrical structure of the device. It is emphasized that this is an exemplifying and not limiting example for the acoustic attenuation device, as it will be explained hereinafter in greater detail.
The acoustic attenuation device 100 is of the layered type, in particular comprising at least three layers.
Specifically, the acoustic attenuation device 100 comprises a connection innermost layer 101, adapted to associate the acoustic attenuation device 100 with at least one surface (not shown). The innermost layer 101 may for instance comprise an adhesive layer for gluing to the at least one surface. It is also possible to provide an innermost layer 101 entirely made by said adhesive layer. Nothing prevents from adopting different solutions. For instance, it is possible to provide an innermost laminate layer with magnetic connection elements to be connected to the at least one surface.
The acoustic attenuation device 100 further comprises an intermediate layer 102 comprising a plurality of attenuation modules 103. Said layer is adapted to a first attenuation of the propagated sound wave.
The acoustic attenuation device 100 further comprises an outermost acoustic attenuation layer 104, comprising at least one closure surface 105. Said layer is adapted to a second attenuation of the propagated sound wave.
In the cylindrical exemplifying example of Figure 1, it is possible to notice a construction of the acoustic device both in a curved configuration for making a side surface of the acoustic device 100, and in a plane configuration for making a base surface. The coupling between side surface and base surface is provided by a coupling collar 106 that is perimetral to the base surface.
In Figure 2 the intermediate layer 102 with the plurality of attenuation modules 103 is in particular visible. It is in particular highlighted how each of the attenuation modules 103 comprises at least one movable element 201 defined by at least one first opening 202. Preferably, as visible, the first opening 202 surrounds the movable element 201. In this example the movable element is substantially circular, but nothing prevents from adopting different shapes. The first openings 202 are further preferably concave in section. When hit by a propagated sound from a source, the movable element 201 vibrates relative to the first opening 202 in a resonant manner, so as to attenuate the propagated sound by mechanical dissipation. Still more specifically, the pressure field defined by the propagated wave that hits the surface of the movable element 201 with normal speed component causes the vibration in a resonant manner of the movable element 201 inside the opening 202 and a subsequent energy absorption from the propagated sound wave. The at least one first opening 202 further acts as an inlet for the acoustic field that propagates towards the subsequent layer, causing the mechanical effect due to the vibration of the movable element to be added to a first purely acoustic attenuation effect.
In Figure 3 the outermost layer 104 comprising the closure surface 105 is in particular visible. The closure surface 105 defines at least one cavity 301 facing and adapted to encapsulate the movable elements 201 of the attenuation modules 103. By means of the cavity 301 the propagated sound is attenuated by the sound-absorbing effect. Specifically, the cavity 301 behaves as a so-called "resonant acoustic cavity", namely a closed space whose delimitation walls reflect the sound waves that thus remain trapped therein.
The combination of the mechanical and acoustic effects thus allows an effective acoustic attenuation.
For supporting the movable elements 201 inside the first openings 202 a support structure is provided.
In Figure 4 a support structure formed by a series of outer support elements 401 integrally connected to said movable elements 201 according to the present example is visible. In particular, in the present example it is possible to provide the intermediate layer 102 as composed of a perforated sheet 402 on which the outer support elements 401 engage. In particular, the outer support elements 401 are overlaying on the intermediate layer 102 and face the outermost layer 104. The outer support elements 401 are cross-shaped, with a central body 403 from which four connection arms 403 depart, at whose ends are connected, preferably integrally, the two movable elements 201 at two opposite ends and two secondary movable elements 405 at the other two ends, with additional attenuation function of the mechanical type. Clearly the movable elements 201 are arranged at the openings of the perforated sheet 402, forming the first opening 202. The secondary movable elements 405 may have equal or different shape from the movable elements 201. It is possible to differently arrange movable elements 201 and secondary movable elements 405. It is also possible not to use said secondary movable elements 405 and to provide axial outer support elements 401, with the sole central body 403 and two connection arms 404 with the movable elements 201 at the ends.
The perforated sheet 402 may be connected to the various support elements 401 by gluing, welding, magnets, etc., forming together the intermediate layer 102.
In Figure 5 an example of the acoustic attenuation device 100 is represented. Said example differs from the example of Figure 3 in that each of the attenuation modules 103 further comprises a plurality of second openings 501. Preferably the second openings 501 are individually convex in section, still more preferably it is micro-holes. The second openings 501 put the innermost layer 101 in fluid communication with the outermost layer 104, to further attenuate the propagated sound. Indeed, the friction generated on the wave passing through the micro-perforated structure causes the transformation of further acoustic energy into heat and an even more effective attenuation by the attenuation device 100.
From Figure 6 it is possible to better identify the arrangement of the second openings 501 in the example of Figure 5 by a front view from the inside of the intermediate layer 102. In this case the openings, due to the presence of the cross-shaped outer support elements 401, concentrate around the openings of the perforated sheet 402 and are not present at the presence of the secondary movable elements 405. It is clearly possible to provide the second openings 501 also distributed in the portions corresponding to the secondary movable elements.
In Figure 7 an embodiment of the attenuation device 100 is represented. The present embodiment according to the invention discloses the acoustic attenuation device wherein at least one movable element 201 of the intermediate layer 102 is at least partially hollow inside and comprises at least one entrance hole 701 facing from its inside towards said innermost layer 101. This structure makes the movable element 201, when hit by the propagated sound, further attenuate the latter. As a result, the resonance phenomenon is exploited with own frequency of opening and cavity to allow the absorption of a certain range of frequencies belonging to the sound wave, and therefore the overall attenuation effect of the attenuation device 100 is improved.
In Figure 8 an example providing a different conformation of the intermediate layer 102 is represented. In this case a different shape of movable elements 801, which are substantially squared, is provided. It is herein reiterated that nothing prevents a different conformation, even rectangular, the chosen shapes in the represented examples being dictated by simplicity of production. Clearly, a conformation variation of the movable elements involves a conformation variation of the underlying openings. Any way the intermediate layer 102 comprises a perforated sheet 802 whereon the movable elements 801 are provided. Furthermore, as visible in Figure 9 by means of a front view of the intermediate layer 102 without the movable elements 801, a different support structure of the movable elements 801 is provided. In particular, the support structure comprises inner support elements 901 facing the innermost layer 101 at the first openings 202. The movable elements 201 are thus connected overlaying on the inner support elements 901.
In the present example the inner support elements 901 are cross arranged, dividing the opening of the perforated sheet 802 into four equal sectors, thus generating four first openings 202 equal to each other once the movable elements 801 have been connected overlaying. An example illustrated in Figure 10 is further provided. In particular, said example differs from the previous one in the conformation of the support structure. The inner support elements 901 of the support structure are made in this case of two edges on two sides of each opening of the perforated sheet 802, the edges being integrally connected with the movable element 801. In this case the inner support elements 901 define at least two first openings 202, different from each other.
The examples and embodiments herein described in connection with the cylindrical conformation of the acoustic attenuation device 100 are particularly advantageous for the application in the field of compressors. An aspect of the invention is thus directed to a compressor enclosed in a casing having at least one outer surface comprising un acoustic attenuation device according to the invention associated with the at least one outer surface. This application is particularly advantageous and suitable for the structural typology of the component identified as sound source.
In Figure 11, a possible plane configuration of the acoustic attenuation device 100, particularly suitable for the application in dividing panels for rooms that require particular acoustic soundproofing, is then represented. The layered structured is the same and an intermediate layer 102 may be used according to any one of the above described embodiments or examples.

Industrial applicability

Advantageously, the present invention allows obtaining an excellent sound attenuation, with reduced dimensions, particularly in terms of thickness, and providing various application possibilities without the need for an ad hoc redesign.
Among the applications of the present invention, there are: mechanical and electromechanical motors, such as compressors, automotive or aircraft engines, soundproof rooms and any technical field in which it is possible to identify a dividing surface that has to be soundproofed and that divides a sound source from a receiver.
Considering the description herein reported, the skilled person will be in the position to conceive further changes and variants, in order to meet contingent and specific needs.
It is clear that, where there are no technical incompatibilities evident to the skilled person, the configurations of specific elements described with reference to some examples can be used in embodiments herein described.
For instance, it is possible to use movable elements with inner cavity in the examples comprising a support structure with inner support elements.
Therefore, the embodiments herein described are to be intended as non-limiting examples of the invention.

Claims

Acoustic attenuation device (100) for propagated sound through surfaces, said acoustic attenuation device (100) being of the layered type and comprising:
- an innermost connection layer (101), adapted to associate said acoustic attenuation device (100) with at least one surface;

- an intermediate layer (102), comprising a plurality of attenuation modules (103), each of said attenuation modules (103) comprising at least one movable element (201) defined by at least one first opening (202), said at least one movable element (201) being adapted to vibrate relative to said at least one first opening (202) in a resonant manner when hit by said propagated sound, to attenuate said propagated sound by mechanical dissipation;

- an outermost layer (104), comprising at least one closure surface (105) defining at least one cavity (301) facing said movable elements (201) and adapted to encapsulate said movable elements (201) of said attenuation modules (103) of said intermediate layer (102), to further attenuate said propagated sound by sound-absorbing effect;
characterized in that at least one movable element (201) of said intermediate layer (102) is at least partially hollow inside and comprises at least one entrance hole (701) facing from its inside said innermost layer (101), so as to further attenuate said propagated sound when said entrance hole (701) is hit by said propagated sound.
Acoustic attenuation device (100) according to claim 1, wherein said at least one first opening (202) of each of said attenuation modules (103) defines said at least one movable element (201) preferably surrounding said at least one movable element (201).
Acoustic attenuation device (100) according to claim 1 or 2, wherein each of said attenuation modules (103) further comprises a plurality of second openings (501) that put said innermost layer (101) in fluid communication with said outermost layer (104), to further attenuate said propagated sound.
Acoustic attenuation device (100) according to claim 3, wherein said at least one first opening (202) has a concave section and said plurality of second openings (501) individually have convex sections.
Acoustic attenuation device (100) according to any one of claims 1 to 4, wherein said innermost layer (101) comprises an adhesive layer for gluing to said at least one surface.
Acoustic attenuation device (100) according to any one of claims 1 to 5, wherein said intermediate layer (102) comprises a support structure for said attenuation modules (103).
Acoustic attenuation device (100) according to claim 6, wherein said support structure comprises outer support elements (401) overlying on said intermediate layer (102) and facing said outermost layer (104), said movable elements (201) being connected to said outer support elements (401).
Acoustic attenuation device (100) according to claim 6, wherein said support structure comprises inner support elements (901) facing said innermost layer (101) at said first openings (202), said movable elements (201) being connected to said inner support elements (901).
Acoustic attenuation device (100) according to claim 8, wherein said inner support elements (901) define at least two of said first openings (202), different from each other.
Acoustic attenuation device (100) according to any one of claims 1 to 9, wherein said movable elements (201) are circular or squared.
Compressor enclosed in a casing having at least one outer surface, characterized by comprising an acoustic attenuation device (100) according to any one of claims 1 to 10 associated with said at least one outer surface.