WO2009071963A1

WO2009071963A1 - Silenced air intake for ventilation ducts, silencer for the air intake and method of operation of the air intake and silencer

Info

Publication number: WO2009071963A1
Application number: PCT/IB2007/054913
Authority: WO
Inventors: Daniele Bassi; Alessandro Placci; Emiliano Santi
Original assignee: Eur.Ex S.R.L.
Priority date: 2007-12-04
Filing date: 2007-12-04
Publication date: 2009-06-11
Also published as: EP2232160A1

Abstract

The air intake (1) for establishing atmospheric communication between a first area (V1) and a second area (V2) separated by at least one wall (10) and connected by means of a ventilation system or duct comprises a boxlike body (20) provided with first and second apertures (30, 40) interconnected by a ventilation channel (22) which passes through the said boxlike body and which allows a flow of air to pass between the said first and second areas (V1, V2), and comprises at least one silencing device (50) located inside the said boxlike body (20), to damp any sound waves carried by the air flow passing through the said ventilation channel (22).

Description

TITLE: SILENCED AIR INTAKE FOR VENTILATION DUCTS, SILENCER FOR THE AIR INTAKE AND METHOD OF OPERATION OF THE AIR INTAKE AND SILENCER

DESCRIPTION

The present invention relates to an air intake, particularly one of the type which can be fitted in a wall and which can attenuate any noise propagated through its ventilation channel.

In public and industrial buildings it is frequently necessary to provide adequate ventilation for spaces within buildings, sometimes in conditions in which their windows and doors have to be kept closed. Examples which may be mentioned are the need to ventilate closed areas used as kitchens or boiler rooms, and the need to use suitable air intakes or forced ventilation systems to ventilate rooms located in basements or in closed areas such as a machine room of a dwelling or the holds of a ship. Generally, the ventilation of an area may be accompanied by the troublesome presence of noise which may be propagated in an area communicating with the exterior or with another area through an air intake, or which may be caused by the air moving in the ducts of a ventilation system, or may be generated by fans and/or conditioners forming part of such a system. In order to overcome this problem, the prior art discloses the use of silencers to be placed outside air intakes, to attenuate any noise which may be propagated through the air flow, such as the silencer described in Japanese patent application no. 2004184640 in the name of Komatsu Ltd. Although this solution can enable the problem of noise in ventilation systems to be overcome, its shape is such that it imparts a discontinuous appearance to the wall in question, which some persons may find disagreeable, and which imposes limits and constraints on the architect. Another product available on the market is a device called "Louvres", produced and marketed by the Benson Company of Belgium, which comprises a frame which can be fitted on a partition wall or on the end of a ventilation duct. This device is provided with a plurality of substantially C-shaped metal sections, coated internally with sound- absorbing material and facing each other so as to define a labyrinthine path along which the volume of exchanged air flows. However, it should be borne in mind that, at the present time, the Benson website (www.benson.be) reports that the device in question is suitable for use in hospitals, schools or sports facilities and is not considered appropriate for installation in residential buildings.

According to the description above, the problem of silencing an air intake in a simple, economical and aesthetically pleasing way has not yet been resolved, and the applicant therefore considers it to be an interesting challenge. Furthermore, it would be even better to have an air intake which could damp the sound waves transmitted through the volume of air exchanged by the said air intake, and which would not have to be connected to silencing devices. Such an air intake would make it possible to contain the costs of production and installation of ventilation systems, and also to avoid the presence of aesthetic and/or architectural constraints on the design of areas and rooms of a building. The object of the invention is to provide an air intake, particularly one of the type which can be fitted in a wall and which can attenuate any noise which may be propagated through its ventilation channel, the principal characteristics and method of operation of this air intake being summarized in Claim 1 and in the following dependent claims, while its characteristics are made clear by the following description of some preferred embodiments, illustrated purely by way of non-limiting example in the figures of the five attached sheets of drawings, in which:

Figure 1 is a schematic perspective view of a preferred first embodiment of the air intake according to the invention;

Figure 2 shows the air intake in section along the line H-Il of Figure 1 ; - Figure 3 shows other details of the air intake shown in section along the line Ill-Ill of Figure 2;

Figure 4 is a perspective view, broken down into its various components, of a silenced air intake according to one solution which is currently manufactured; - Figs. 5, 6 and 7 show a perspective view of a shell of the boxlike body of the air intake as shown in Figure 4, in successive steps of the fitting of the silencer components into the shell;

Fig. 8 shows the air intake as shown in Figure 4, installed in its working position and in section along the line VIII-VIII; - Fig. 9 shows the air intake as shown in Figure 8, in section along the line IX-IX;

Figs. 10 and 11 show two details of the construction of the connecting and fixing edges of the two shells which form the boxlike body of the air intake as shown in Figures 4 to 9. In the figures, and in Figures 1 to 3 in particular, the number 1 indicates the whole of an air intake which can be used to provide a constant air exchange between a first area Vl and a second area V2, and also to efficiently attenuate the intensity of any sound waves that may be propagated through the exchanged air flow between the said first and second areas Vl and V2, which can be either open or closed areas. The said areas Vl and V2 can be adjacent to each other, and therefore in direct communication with each other through the air intake I, or can be remote from each other and therefore in communication with each other by means of any ventilation system or duct, which is known and is not illustrated, and which can incorporate the air intake I in question. As shown in Figures 2 and 3, the air intake 1 is fitted in a wall 10 which supports and contains it, and it comprises a boxlike body 20 of substantially parallelepipedal shape, made from rigid materials, for example from plastics, metal and/or other suitable materials which can be used for the purpose (see below). The boxlike body 20 is provided with a first aperture 30 and a second aperture 40 which longitudinally delimit a ventilation channel 22. This channel 22 is enclosed in the said boxlike body 20 and keeps the areas Vl and V2 in constant atmospheric communication with each other. The channel 22 has a shape which varies along its longitudinal axis A and comprises an intermediate portion 23, connected to the said first and second apertures 30 and 40 by two opposing portions 32 which are substantially identical and which have a smaller cross section than that of the said intermediate portion 23. As shown in Figure 2, the intermediate portion 23 houses a central baffle 52 which divides it into two substantially identical and symmetrical parts. The portion 23 and the said baffle 52 are designed in such a way that each corresponding free section of the channel 22 has a minimum size which is close to but greater than that of a cross section of either of the end portions 32, in order to prevent the formation of constrictions which could adversely affect the free exchange of air between the said first and second areas Vl and V2. Additionally, the said channel 22 is shaped symmetrically about a vertical median plane M which comprises the said longitudinal axis A and which is shown in Figure 2 only, where it coincides with the section line III III and cuts the baffle 52 in half, thus dividing the air current into two flows which are substantially identical and symmetrical with respect to each other. The baffle 52 can be produced economically from a single layer of a specified material, or alternatively it can have a multi-layer structure, thus providing better silencing characteristics. With particular reference to Figures 2 and 3, the said baffle 52 can, for example, comprise at least one pair of outer first layers 522, made from sound-absorbing material, joined together in a sandwich configuration by a second intermediate layer 524 made from any material having good acoustic insulation properties.

For clarity, it should be noted that a material called "sound-insulating" or "acoustic insulating" tends to attenuate the mechanical energy associated with sound waves that strike it, thus transmitting only a portion of the incident mechanical energy, while a "sound-absorbing" material which is struck by the same sound waves tends to break them down within itself, thus reflecting only a portion of them. Therefore a multi-layer body which comprises at least one layer of sound-absorbing material and at least one layer of acoustic insulating material tends to combine the reactions described above, thus making the absorption of mechanical energy from the incident sound waves highly effective.

By way of example, the outer sound-absorbing first layers 522 can be made from mineralized wood wool, while the sound-insulating second layer 524 can comprise a simple lead sheet. According to the description above, the baffle 52 can be considered to be an acoustic shield for minimizing the mechanical energy associated with sound waves incident on it, to impede the free propagation of these sound waves along the ventilation channel 22. In particular, the shield 52 can disperse some of the sound waves incident on it, by reflecting them towards the periphery of the channel 22 by means of the sound-absorbing first layers 522, but more importantly it can attenuate the mechanical energy transmitted to it by the remaining incident sound waves, by means of the sound-insulating second layer 524.

The boxlike body 20 is lined internally with a covering 54 which is shaped so as to delimit the channel 22. The covering 54 can comprise a third layer 542 of sound-absorbing material, or, more efficiently, it can have a multi-layer structure comprising at least the said sound-absorbing third layer 542, joined to a fourth layer 544 produced from a resilient material which has sound-insulating properties. The covering 54 can therefore reflect in a damped way the sound waves incident on its surface adjacent to the channel 22, and can therefore be considered to be a sound wave damper. For convenience of illustration, in Figures 2 and 3 the covering 54 has only one pair of the said third and fourth layers 542 and 544. Also by way of example, the sound-absorbing third layer 542 can be produced from mineralized wood wool, while the resilient fourth layer 544 can be produced from mineral wool or polyester fibre or natural fibre. According to the description above, the boxlike body 20, being rigid, can be considered to be an outer protective shell for the covering 54. The combination of all the sound-absorbing third layers 542 which externally delimit the channel 22 can be considered to be an inner shell 24, and these shells 20 and 24 are joined together resiliently by means of at least one fourth layer 544 which acts as an interface between these shells. The combination of the outer shell 20, the inner shell 24 and the resilient intermediate layer 544 forms a damped oscillator 27 which can dissipate the mechanical energy absorbed from any sound waves which strike the shell 24.

In other words, the covering 54 can both reflect in a damped way the sound waves incident on any part of its sound-absorbing third layer 542, and dissipate the mechanical energy absorbed from the sound waves incident on it, by means of the damped oscillations of the oscillator 27.

As shown in Figures 2 and 3, the boxlike body 20 can also be covered externally with a further fifth layer 25 made from sound-insulating and at least partially resilient material, to decouple the air intake 1 from the wall 10 acoustically. This fifth layer 25 can therefore be made, for example but not exclusively, from closed-cell expanded polyethylene or with a sandwich-type polyethylene-lead- polyethylene structure, such as that described above. Alternatively, the acoustic decoupling between the boxlike body or shell 20 and the wall 10 can be obtained by means of a discontinuous structure, for example but not exclusively of a grid type, to provide mutual contact at a plurality of points.

Also according to the description above, the combination of the damping shell 54 and the acoustic shield 52 can be considered to be a silencing device 50 carried internally by the boxlike body 20 for damping any sound waves which may be propagated through the flow of air exchanged between the first and second areas V1 and V2. This is because, if the air intake 1 were to be struck by sound waves, these waves would be intercepted by the shield 52 which is housed transversely in the channel 22. The shield 52 can deflect a considerable portion of the sound waves incident on it towards the covering 54 which internally delimits the channel 22, while the second sound-insulating layer 524 can damp the remainder of the sound waves which attempt to propagate transversely with respect to the shield 52. Because of the presence of the first sound-absorbing layer 522 and of the third sound-absorbing layer 542, the sound waves incident on the periphery of the body 54, including those originating directly from the outside and those previously deflected by the shield 52, are made to undergo a sequence of damped reflections, providing maximum dispersion of the mechanical energy carried by these sound waves. Finally, the remainder of the mechanical energy given up by the sound waves incident on the periphery of the covering 54 is dissipated by the damped oscillations of each part of the third layer 542 with respect to the boxlike body 20.

According to the description above, the combination of the damping covering 54 and the baffle 52 is such that the boxlike body 20, which comprises both of these, can substantially be considered to be an acoustic anechoic chamber. This is because the boxlike body 20 is insulated from the sound waves arriving from the outside through its walls and can damp the sound waves propagated inside the body 20 through the channel 22. With reference to Figures 4 to 8, an industrially produced design of the air intake according to the invention will now be described. The boxlike body 20 is made so as to have dimensions which are multiples of those of a UNI double format building brick (12 x 12 x 24 cm) and the said boxlike body is formed by two identical shells 120 and 220, made for example by the injection moulding of plastics material, using, for example, polypropylene or other suitable plastics material. Each of the aforesaid shells is provided with a thickened perimetric edge, half of which is grooved as indicated by 55 in the detail of Figure 10 while the other half has a projecting bead 56 complementary to the groove 55, and the boundaries between these two different male and female profiles are located in the centres of the short sides of the two identical shells, the whole arrangement being such that, when the said shells are joined together with one of them rotated through 180° with respect to the other, the male edge 56 of one shell enters the grooved or female edge 55 of the other shell, thus forming a perfectly centred and substantially airtight joint between the shells. Figure 10 shows how the joint between the said profiles 55 and 56 creates a coupling of the labyrinth type which is favourable to sealing and to the acoustic insulation of the boxlike body 20 from the external environment. Figure 4 and the detail of Figure 11 also show that the said shells have teeth 57 with wedge-shaped outwardly facing heads, made in one piece with the male profile 56 and projecting from it, these teeth being inserted, when the shells are joined together to form the boxlike body 20, into corresponding slots 58 provided on the female profile 55, and being snap-locked under the edge of the shell carrying this profile 55, thus fixing the shells 120 and 220 together.

In the centres of their rectangular bases, the shells 120 and 220 have the apertures 30 and 40 which are more fully described below and which, regardless of the rotation of the shells through 180° which is carried out before they are joined together, remain perfectly aligned with each other along the said axis A of Figure 1 , owing to their central locations on the said walls as described above. The layers and baffles of sound-absorbing and sound-insulating material required for the operation of the equipment can easily be placed within the shells 120 and 220 while these are open. As shown in Figures 4 and 5, the first step is to mount inside each shell 120, 220 the parties which form the inner covering 54 as described with reference to Figures 2 and 3, and which comprises U-shaped bodies 154, made from sound- absorbing material, for example material of the type having the trade name of Edilfiber®, made from recycled PET bottles, or other materials having similar sound- absorbing characteristics, which form an annular inner covering of the lateral walls of the said shells and are held in position by linear appendages 200 formed in one piece with the base walls of the shells and by bracket-like appendages 201 formed in one piece with the lateral walls of the shells. The first appendages 200 hold the covering bodies 154 against the lateral walls of the shell, while the other appendages 201 hold the said bodies 154 against the base walls of the shells. The parallel branches of the said lateral covering bodies 154 have recesses of identical depth in their parts facing the outside of the shell, forming seats 59 in this covering for the purposes described above. After the said lateral covering bodies 154 have been positioned, mats 254 forming the inner covering of the base walls of the shells 120 and 220 are installed, these mats being made from the same material as that used to form the said lateral covering bodies 154, and being provided in their centres with holes 60 which closely circumscribe internal projections 130 and 140 of the inlet and outlet apertures 30 and 40 of the air intake according to the invention, as shown in the detail of Figure 6.

The mats 254 are kept in contact with the base walls of the shells 120 and 202 by brackets 202 of inverted L-shape, formed in one piece with the said base wall or otherwise associated therewith. The holes visible in the aforesaid brackets 202 and 201 are discharge holes required for the production of these components and are not provided to meet specific functional requirements.

As shown in Figures 8, 9, 4-6, the inner edges of the said inner projections 130 and 140 of the apertures 30 and 40 have projecting appendages 61 made in one piece with them and spaced at equal angular intervals, the most remote parts of these appendages lying on a theoretical plane which contains the bases of the said seats 59 of the lateral covering bodies 54, this arrangement being provided because, in a subsequent step of assembly, a parallelepipedal baffle 52 is inserted into one of the two shells 120 and 220, the baffle having both sound-absorbing and sound- insulating properties, and being made for example from the material having the trade name Stratifon 40® or from other materials with similar sound-absorbing and sound- insulating characteristics. The baffle 52 engages with the said seats 59 with its larger face bearing . on these seats and also on the said projections 61, and projects from the shell in which it is mounted for a distance equal to the depth of the portion with which it engages with the seats 59 of the shell, in such a way that, when the two shells 120 and 220 are joined and fixed together, the projecting part of the baffle 52 engages with the seats 59 of the lateral covering body 154 of the other shell, as shown in Figures 8 and 9 which correspond, respectively, to the schematic views in Figures 2 and 3. The assembly of the lateral insulating parts 154 and 254 and the central baffle 52 forms the silencing element indicated by the number 50 in the schematic version shown in Figures 2 and 3, while the free inner channel of the air intake is also indicated here by the number 22.

As shown in Figures 4 and 5, the shells 120 and 220 are provided on their inner and outer surfaces with ribs 62 which act as reinforcements, which internally limit the contact between the box and the covering materials 154 and 254, thus limiting the transmission of sound waves between the two parts, and which externally ensure that the boxlike element formed by them is fixed effectively to the mortar for fixing in the wall 10. Finally, Figures 4, 8 and 9 show how the apertures 30 and 40 are also provided with outer collars 230 and 240 aligned with the inner collars 130 and 140, the latter being provided with conical edges 63 to form a sealed joint with a portion of tube 64 for extending at least one of the two apertures 30 or 40 of the equipment concerned towards the outside. In the example shown in figures 8 and 9, the boxlike element 20 is installed in one face of the wall 10, for example the inner face, and therefore the edge 230 is substantially flush with this face, and a ventilation grille G1 , preferably of the type having a grid or filter (not shown) for impeding the passage of insects, can be mounted on this edge. On the other hand, the tube 64 is mounted on the aperture 40 and is cut to size so that its other end adjoins the outer face of the wall 10, where a ventilation grille G2 similar to the internal one is provided. However, it should be understood that the boxlike element 20 can be located in any inner part of the wall 10 and that the accompanying tube 64 can be divided into two parts so that it can be mounted on both of the apertures 30 and 40.

It should be understood that the protection of the invention extends to the variant construction in which the boxlike element 20 is intended to form part of any ventilation duct, for example by forming an intermediate and/or final portion of a duct with the said boxlike element, which can be extended or replaced by a portion of the said ventilation duct.

As an aid to understanding, with particular reference to Figures 2 and 8 of the appended drawings, it can be pointed out that the air intake 1 with the attached silencing device 50 can be used to implement a method for treating the sound waves which are propagated between two areas which are put into atmospheric communication with each other by means of an air intake or by means of a ventilation system, in such a way as to attenuate the intensity of the said sound waves. This method comprises, initially, the step of dividing the sound waves passing through the channel 22 of the air intake in question into a first and a second portion which are distinct from each other, in order to treat them independently. This step of dividing the sound waves passing through the channel 22 into distinct first and second portions comprises the subsidiary step of treating the sound waves of the first portion in such a way that their direction of propagation is kept substantially unchanged, and the subsidiary step of treating the sound waves of the second portion in such a way that they are dispersed along the ventilation channel 22.

In particular, the step of dividing the sound waves passing through the channel 22 into first and second portions is followed by a step of attenuating the intensity of the first portion of sound waves by propagation through the baffle 52, and by the step of attenuating the intensity of the second portion of sound waves, which comprises a subsidiary step of damping the second portion of sound waves by means of a plurality of damped reflections between the said baffle 52 and the inner covering body 54, 154, 254 of the boxlike element 20, and a subsidiary step of absorbing the mechanical energy associated with the second portion of sound waves by means of the damped oscillator 27. It should be noted that the step of attenuating the intensity of the first portion of sound waves by propagation through the baffle 52 and the step of attenuating the intensity of the second portion of sound waves are substantially simultaneous. It is clear from the above description that the air intake I with the associated silencing device 50 makes it possible to reduce the flow of mechanical energy and consequently that of the noise associated with sound waves propagated in the volume of air exchanged through the said air intake. In particular, the use of the air intake 1 provides a number of advantages, including economy and considerable ease of installation, since the silencing device 50 is structurally integrated with the air intake 1 which can be fitted inside the wall 10 and can be finished simply by mounting suitable ventilation grilles, as indicated by G1 and G2 in Figures 8 and 9, on the outer apertures 30 and 40. The alignment of the inlet and outlet apertures of the air intake with each other considerably simplifies the installation. All the materials used for the construction of the air intake, including those mentioned above, are such that they provide the air intake with the following characteristics: mould-proofing, antibacterial and self-extinguishing properties, waterproofing and non-deformability, 100% recyclability, and suitability for installation in walls of different thicknesses, for example from 25 to 45 cm. It should be understood that the air intake 1 and the silencer 50 as described and illustrated can be modified and varied in numerous ways as regards construction, without departing from the guiding principle of the invention, as claimed below.

Claims

1. Air intake (1) for establishing atmospheric communication between a first area (Vl) and a second area (V2) separated by at least one wall (10) and connected through a ventilation system or duct, characterized in that it comprises a boxlike body (20) provided with first and second apertures (30, 40) interconnected by a ventilation channel (22) which passes through the said boxlike body and which allows a current of air to pass between the said first and second areas (Vl, V2), and in that it comprises at least one silencing device (50) located inside the said boxlike body (20), to damp any sound waves carried by the air flow passing through the said ventilation channel (22).

2. Air intake according to Claim 1 , characterized in that the said boxlike body (20) which contains the silencing device (50) inside it is designed so that it can be mounted inside the said wall (10) either inside a ventilation duct or with a connection thereto, and in that its apertures (30, 40) open into the said areas (V1 , V2) or into the said ventilation duct, in such a way that the said silenced air intake is not visible and does not create problems or constraints in respect of architecture.

3. Air intake according to one or both of the preceding claims, characterized in that the said ventilation channel (22) extends along at least one axis (A) positioned between the said first and second apertures (30, 40), and in that the said silencing device (50) comprises acoustic shielding means (52) placed inside the said boxlike body (20) and capable of minimizing the mechanical energy associated with any sound waves carried by the flow of air passing through the ventilation channel (22) and interacting with the said acoustic shielding (52).

4. Air intake according to any one or more of the preceding claims, characterized in that the said silencing device (50) also comprises sound wave damping means

(54) which cover the inner walls of the said boxlike body (20).

5. Air intake according to any one or more of the preceding claims, characterized in that the said ventilation channel (22) comprises an intermediate portion (23) which houses the said acoustic shielding means (52) and which is connected to the said first and second apertures (30, 40) through two outer portions (32) of the said channel, which are substantially identical to each other and each of which has a smaller cross section than any cross section of the said intermediate portion (23) of the channel (22).

6. Air intake according to Claim 5, characterized in that the ventilation channel (22) is shaped in such a way that each free cross section of this channel which allows a current of air to pass, including the free sections of the said intermediate portion (23), has a minimum size which is close to but greater than the size of a cross section of any of the said outer portions (32).

7. Air intake according to Claim 3, characterized in that the said acoustic shielding means (52) comprise at least one baffle which is positioned transversely with respect to each said axis (A) and which is produced from at least one or more layers (522, 524) of materials capable of preventing the free propagation of sound waves along the said ventilation channel (22).

8. Air intake according to Claim 7, characterized in that each layer making up the said shielding baffle (52) comprises one or more layers of sound-absorbing material

(522) capable of reflecting in a damped way the sound waves incident on it, and comprises at least one layer (524) of acoustic insulating material capable of dissipating the mechanical energy transmitted by any sound waves incident on it, this at least one layer (524) preferably being placed between the said sound-absorbing layers (522).

9. Air intake according to Claim 4, characterized in that the said sound wave damping means (54) which cover the inner surface of the said boxlike body (20) and which delimit the said ventilation channel (22) comprise at least one sound-absorbing layer (542) joined to at least one resilient layer (544).

10. Air intake according to Claim 9, characterized in that the said resilient layer (544) is in contact with the inner lateral surface of the said boxlike body (20) in such a way that the sound-absorbing layer (542) can oscillate in a damped way with respect to the said boxlike body (20) by means of the interposition of the corresponding said fourth resilient layer (544), the whole arrangement being such as to form a damped oscillator assembly (27) capable of dissipating mechanical energy, associated with sound waves incident on each said sound-absorbing layer (542).

11. Air intake according to Claim 10, characterized in that the said boxlike body (20) is made from any suitable substantially rigid material, and in that the said sound- absorbing layer (542) which delimits the said ventilation channel (22) forms a shell (24) contained inside the said boxlike body (20) and connected to the latter by the interposition of at least one resilient layer (544) in such a way that the said sound- absorbing shell (24) can oscillate with respect to the said boxlike body (20) to form a damped oscillator (27) which can dissipate the mechanical energy generated by any sound waves incident on the said sound-absorbing shell (24).

12. Air intake according to Claim 11 , characterized in that the said boxlike body (20) is covered externally by at least one layer (25) of at least one sound-insulating material, which acoustically decouples the said air intake (1) from the wall (10) which contains it.

13. Air intake according to Claim 12, characterized in that the said outer sound- insulating covering (25) comprises at least one lead sheet covered with closed-cell expanded polyethylene on at least one of its lateral faces.

14. Air intake according to Claim 8, characterized in that the said sound-insulating layer (524) comprises at least one lead sheet covered with closed-cell expanded polyethylene on at least one of its lateral faces.

15. Air intake according to Claim 9, characterized in that the said resilient layer (544) comprises mineral wool or polyethylene fibre or natural fibre.

16. Air intake according to any one or more of the preceding claims, characterized in that the said first aperture (30) and the said second aperture (40) are aligned with each other on the same axis (A).

17. Air intake according to Claim 1 , characterized in that the said boxlike body (20) is made in such a way that its dimensions are multiples of those of a UNI double format (12 x 12 x 24 cm) building brick.

18. Air intake according to Claim 1, characterized in that the said boxlike body (20) is formed by two identical shells (120, 220) made for example by the injection moulding of plastics material, each said shell being provided with a thickened perimetric edge, half of which has a grooved or female profile (55) while the other half has a projecting bead (56) forming a male profile complementary to the aforesaid female profile (55), and the boundaries between these two different profiles are, for example, located in the centres of the short sides of the two identical shells, the whole arrangement being such that, when the said shells are joined together, with one of them rotated through 180° with respect to the other, the said male edge (56) of a shell enters the grooved edge (55) of the other shell, forming a perfectly centred joint with a labyrinth profile which consequently forms a substantial seal between the said shells, this joint being very suitable for the sealing and acoustic insulation of the boxlike body (20) with respect to the external environment.

19. Air intake according to Claim 18, characterized in that the said shells (120, 220) have teeth (57) with wedge-shaped heads, made in one piece with the male profile (56) of the joining edge and projecting from it, these teeth being inserted, when the shells are joined together to form the boxlike body (20), into corresponding slots (58) provided on the said female profile (55), and being snap-locked under the edge of the shell carrying this profile (55), thus fixing the said shells together.

20. Air intake according to Claim 18, characterized in that the said shells (120, 220) have the inlet and outlet apertures (30, 40) of the ventilation channel (22) in the centres of their rectangular bases, these apertures remaining in perfect alignment with each other along the common axis (A) because of their central location on the said wall, regardless of the rotation of 180° imparted to the shells before they are joined together.

21. Air intake according to Claim 18, characterized in that the layers and baffles of sound-absorbing and sound-insulating material required for the operation of the said silenced air intake are easily located in the said shells (120, 220) when the shells are open, these layers and baffles remaining correctly located in the shells when the said shells are joined together to form the said boxlike body (20) which contains the silencing device (50).

22. Air intake according to Claim 21 , characterized in that, in a first step, U-shaped covering bodies (154) are mounted in each of said shells (120, 220), so as to form when assembled an annular inner covering of the lateral walls of the said shells, this covering being preferably kept in place by appendages (200) formed in one piece with the base walls of the said shells and by appendages (201), of bracket shape for example, formed in one piece with the lateral walls of the shells, the said first appendages (200) being made to hold the covering (154) against the lateral wall of the shell, while the other appendages (201) hold the said covering (154) against the base wall of the said shell.

23. Air intake according to Claim 22, characterized in that, in a step following the installation of the said lateral covering (154), mats (254) of inner covering of the base walls of the said shells (120, 220) are installed in each of the said shells (120, 220), these mats being made of the same material as that which forms the said lateral covering (154) and being provided centrally with holes (60) which closely circumscribe inner projections (130, 140) of the inlet and outlet apertures (30, 40) of the air intake in question, the mats (254) being kept in contact with the base walls of the corresponding shells (120, 220) by appendages (202) formed in one piece with this base wall or fixed in another way to this wall.

24. Air intake according to the preceding claims, characterized in that the said inner lateral (154) and base (254) coverings are made from the same sound- absorbing material, of the type having the trade name Edilfiber®, produced by recycling PET bottles, or from other equivalent materials.

25. Air intake according to Claim 23, characterized in that the inner edges of the said inner projections (130, 140) of the apertures (30, 40) of the ventilation channel (22) have projecting appendages (61) made in one piece with them, these appendages being spaced at equal angular intervals and having their most remote parts lying on the same theoretical plane as that which contains the bases of seats of equal depth (59) provided on the parts of the parallel branches of the said lateral coverings (154) facing the open front of the corresponding shell, this arrangement being provided because, in a subsequent step of assembly, a parallelepipedal baffle (52) is inserted into one of the two shells, the baffle having both sound-absorbing and sound-insulating properties and engaging the said seats (59), bearing with its larger face on the bases of these seats and on the said projections (61) and projecting from the shell in which it is mounted by a distance equal to the height of its portion which engages with the said seats (59) of this shell, in such a way that, when the two shells (120, 220) are joined and fixed together, the projecting part of the said baffle (52) engages with the seats (59) of the lateral covering (154) of the other shell, the assembly of the said lateral insulating parts (154, 254) and the said central baffle (52) forming the silencing element (50) according to the invention.

26. Air intake according to Claim 25, characterized in that the said central baffle (52) is made from material having the trade name of Stratifon 40® or from other equivalent material.

27. Air intake according to the preceding claims, characterized in that the said shells (120, 220) are provided on their inner and outer surfaces with ribs (62) which act as reinforcements, which internally limit the contact between the box and the said sound-absorbing covering materials (154, 254), thus limiting the transmission of sound waves between the two parts, and which externally ensure that the boxlike element (20) formed by them is fixed effectively to the mortar for fixing in the wall (10).

28. Air intake according to the preceding claims, characterized in that the said apertures (30, 40) are also provided with collars (230, 240) which are located outside the corresponding shells (120, 220) and are aligned with the said inner collars (130, 140), which are provided with conical inner edges (63) for forming a sealed joint with at least one portion of tube (64) for extending a corresponding at least one of the said apertures (30, 40) towards the outside, the said air intake being completed by the application of ventilation grilles (G1 , G2), preferably of the type having grids or filters to impede the passage of insects, to the outer ends of the said tube and to any one of the said apertures which does not have a tube attached.

29. Silencing device (50) for silencing a ventilation system comprising a ventilation channel (22), characterized in that it comprises acoustic shielding means (52) according to one or more of the preceding claims, placed inside the said ventilation channel (22), and in that it comprises sound wave damping means (54), also according to one or more of the preceding claims, which delimit the said ventilation channel (22), the said shielding means (52) and the said damping means (54) being capable of interacting to attenuate the intensity of the sound waves propagated with the volume of air flowing through the said ventilation channel (22).

30. Method for treating the sound waves inside an air intake (I) or at a silencer (50) according to one or more of the preceding claims, in such a way as to attenuate the intensity of the said sound waves, characterized in that it comprises a step of dividing the said waves into distinct first and second portions in order to treat the said first and second portions of the said sound waves independently.

31. Method according to Claim 30, characterized in that the said step of dividing the said waves into distinct first and second portions comprises the subsidiary step of treating the said sound waves of the said first portion in such a way that their direction of propagation is kept substantially unchanged, and comprises the subsidiary step of treating the said sound waves of the said second portion in such a way that they are dispersed along a ventilation channel (22).

32. Method according to any one or more of the preceding claims, characterized in that the said step of dividing the said waves into distinct first and second portions is followed by a step of attenuating the intensity of the said first portion of the said sound waves by propagation through at least one sound-insulating layer associated with acoustic shielding means (52), and by the step of attenuating the intensity of the said second portion of the said sound waves by interaction with the means (54, 154, 254) for damping sound waves.

33. Method according to Claim 32, characterized in that the said step of attenuating the intensity of the said second portion of the said sound waves comprises a subsidiary step of damping the said second portion of the said sound waves by means of a plurality of damped reflections between at least one sound- absorbing layer associated with the said means (54, 154, 254) for damping sound waves and at least one sound-absorbing layer associated with the said acoustic shielding means (52), and a subsidiary step of absorbing the mechanical energy associated with the said second portion of the said sound waves by means of at least one damped oscillator (27) associated with the said means (54, 154, 254) for damping sound waves.

34. Method according to any one or more of the preceding claims, characterized in that the said step of attenuating the intensity of the said first portion of the said sound waves and the step of attenuating the intensity of the said second portion of the sound waves are substantially simultaneous.