COMPOSITE SOUND-DEADENING ELEMENT AND PANEL REALIZED WITH SAID ELEMENT

Abstract: In a sound-absorbing element of the composite type, comprising a first covering sheet (1) and a second covering sheet (2) that contain between them at least one intermediate layer (3) of a filling material, at least one of the covering sheets (1, 2) is provided with a plurality of through holes (4) having suitable dimension and distribution.

Description: COMPOSITE SOUND-DEADENING ELEMENT AND PANEL REALIZED WITH SAID ELEMENT Technical field of the Invention The present invention relates to a sound-absorbing element of the composite type and a panel produced by means of one or more sound-absorbing elements according to the present invention. Background Art Various types of materials are currently known in the art that present sound-absorbing characteristics, such as for instance, foamed materials, glass wool or similar. These materials are often combined between them or fixed to suitable supports to produce sound-absorbing elements and/or panels whose characteristics are determined by the particular type of use to which they are destined. However, most of the sound-absorbing elements currently known often have elevated costs of production, in some cases, it is also necessary to provide for the application of notable volumes of sound-absorbing material to guarantee an effective deadening action. Still in other cases, the weight and/or the difficulty of installation of the elements or of the known sound-absorbing panels make their use a little impracticable. Disclosure of the Invention The task of the present invention is therefore to produce a sound-absorbing element able to solve the above cited drawbacks. Within the scope of this task, one object of the present invention is to provide a sound-absorbing element having elevated sound energy attenuation characteristics. Another object of the present invention is to provide a sound- absorbing element that is particularly economical to produce. Still another object of the present invention is to provide a sound-absorbing element of light weight and limited dimension in thickness. A further object of the present invention is to provide a sound- absorbing element that is particularly versatile in its use and/or in the modes of installation. These purposes are achieved by the present invention, that concerns a sound-absorbing element of the composite type, comprising a first covering sheet and a second covering sheet that contain between them at least one intermediate layer of a filling material, characterised in that at least one of the covering sheets is provided with a plurality of through holes. The composite structure of the sound-absorbing element and the presence of the holes, having suitable characteristics of form, dimension and surface distribution, on at least one of the two covering sheets gives to the same element a particular effectiveness. According to a preferred aspect of the invention, at least one or both the covering sheets are made of PVC, while the intermediate layer is produced with a foamed material of the open- cell type, such as for instance foam rubber or similar. These materials are easily found on the market at limited costs and they can be worked in a simple and economical way. Furthermore, the materials used are all of the flexible type, in such way as to allow the realisation of a sound-absorbing element that adapts itself practically to any type of application or installation. According to another preferential aspect of the invention, all the materials comprising the sound-absorbing element have fireproof characteristics, in a such way as to allow the production of elements or sound-absorbing panels which can be installed even in environments governed by strict fire regulations. In an alternative embodiment of the present invention, both the covering sheets of the sound-absorbing element are equipped with a plurality of through holes. This particular alternative embodiment is particularly useful and effective in the cases in which it is necessary to sound-proof two separate sources of noise interposing only one sound-absorbing element according to the present invention between them. The invention further concerns a sound-absorbing panel comprising one or more sound-absorbing elements according to the present invention. The panel comprises preferably at least one sound-absorbing element in which the first covering sheet and the second covering sheet are joined at least in correspondence to their respective edges. The reciprocally joined edges of the two covering sheets form a peripheral ridge that allows the fixing of the panel to a support structure, or the fixing of the same panel to another panel. Furthermore, in the panel there could also be elastic means for fixing the same panel, as well as one or more stiffening structures that could be integral with the same panel or could be inserted in suitable housings integral with the panel. Brief Description of the Drawings Further characteristics and advantages of the present invention will be more evident from the description that follows, which is by way of example and not limitative, with particular reference to the enclosed schematic drawings in which: - Figure 1 is an enlarged view in cross section of a sound- absorbing element according to a possible embodiment of the invention; - Figure 2 is an enlarged plan view, from the side in which a covering sheet provided with holes is visible, of the sound-absorbing element of Figure 1 ; - Figure 3 is a plan view, from the side of a covering sheet provided with holes, according to a possible embodiment of a sound-absorbing panel comprising an element according to the present invention; - Figure 4 is a cross section view of the panel of Figure 3; - Figure 5 is a plan view, from the side of the covering sheet provided with holes, of another embodiment of a sound-absorbing panel comprising a sound-absorbing element according to the present invention; and - Figure 6 is a cross section view of the panel of Figure 5. Modes for carrying out the Invention With reference to the Figures 1 and 2, the sound-absorbing element 10 according to the invention comprises a first covering sheet 1 and a second covering sheet 2 containing between them an intermediate layer 3 of a filling material. According to a preferred aspect of the present invention, the covering sheet 2 is provided with a plurality of through holes 4 having suitable forms, dimensions and distribution according to the particular type of application. The covering sheet 2, provided with holes 4, is oriented preferably toward the sound source of which it is desired to attenuate the emitted energy. In this way, most of the energy of an incident sound wave penetrates into the layer of filling material 3, comprising preferably an open-cell foamed material, and is attenuated due to the phenomenon of absorption and of internal reflection. The sound energy released beyond the covering sheet 1 , which is in the opposite part of the sound source with respect to the sound-absorbing element 10 according to the invention, is notably attenuated. The dimensions of the holes 4 and their surface distribution on the covering sheet 2 are determined on the basis of the particular type of application of the sound-absorbing element 10. It should, however, be underlined that the holes 4 can have any form in section, and that their dimensions, as well as their distribution, vary in relation to the particular type of application. These factors influence the dispersion of the sound energy in the field of frequencies and could be selected in such a way as to be effective within a determined frequencies range, in particular the range of the audible frequencies generally between around 20 and 20,000 Hz. The covering sheets 1 and 2 are preferably made of PVC, while the intermediate layer 3 comprises an open-cell foamed material, such as for instance foam rubber. All the materials used for the production of the sound-absorbing element 10 according to the invention have fireproof characteristics and preferably comprise flexible materials. That allows the production of particularly safe and versatile sound-absorbing panels. Furthermore, the use of PVC guarantees a particularly resistant product, washable and with limited costs. The sound-absorbing element according to the invention can also be produced by providing both the covering sheets 1 and 2 with a plurality of holes. In this case, the covering element could be used for instance to insulate two sound sources by interposing between them the sound-absorbing element provided in this alternative embodiment. Figures from 3 to 6 show some possible embodiments of panels comprising a sound-absorbing element 10 according to the present invention. Figures 3 and 4 show a sound-absorbing panel 100, comprising at least one sound-absorbing element according to the present invention, that is produced in substantially square or rectangular form. In this embodiment of the panel 100, the covering sheets 1 and 2 are joined together in proximity to, or in correspondence of, their respective perimeter edges, for instance by means of thermo- welding and/or stitching, in a such way as to form a peripheral ridge 20. This peripheral ridge 20 facilitates the fixing of the panel 100 to a support (not shown) or to another similar panel, i.e. produced with one or more sound-absorbing elements according to the invention. The panel 100 could comprise a stiffening structure, consisting for instance of a plurality of bars 30 located along the sides of the panel 100, which could be made integral with the same panel. The stiffening structure is preferably inserted inside the panel 100 and it could be made integral with the covering sheets 1 and 2 by means of stitching or thermo-welding of the sheets 1 and 2 around the bars 30. The stiffening structure can be supplied as component separate from the panel, and be inserted into suitable housings integral with the same panel. That allows the transport and/or the storage of the same panel to be advantageously simplified. This embodiment adapts itself to the installation on internal walls of buildings or of other environments to be sound-proofed, for instance on the internal walls of factories, gyms, discos or similar establishments. Alternatively, the same panel 200 could easily be used to produce the separating walls that acoustically insulate different portions of the same common environment. In the form of embodiment illustrated in the Figures 5 and 6, the panel 200 has a substantially circular form in plan and comprises elastic means 40 that allows its application to particular apparatuses to be insulated. The panel 200 as produced assumes the form of α "cap" that could be applied to tubs or vertical cylinders of particular industrial installations that require noise attenuation. Also in this case, the panel 200 could comprise a stiffening structure for instance consisting of a plurality of radial bars 50 inserted inside the panel 200 and fixed to it by means of thermo- welding or by stitching one of the covering sheets, for instance the sheet 1, around them. Alternatively, similarly to the preceding embodiment, the stiffening structure could comprise separate elements to be inserted and fixed in suitable housings integral with the same panel. The results of tests made on sound-absorbing panels produced in conformity with some examples of embodiment according to the invention are reported below. EXAMPLE 1 A series of experimental tests were effected employing a sound-absorbing element produced by means of a couple of sheets in PVC between which was sandwiched an intermediate layer of an open-cell foamed material. The covering sheets 1 and 2 comprised a substance from in PVC sheets of around 650 g/m 2 , while the intermediate layer comprised a foam rubber sheet of one centimeter in thickness. The holes made in the covering sheet 2 had substantially circular section with equal diameter of around 3 mm and a substantially uniform distribution of around 5000 holes/m 2 . The tests were initially made by producing a simple cap of coverage applied to a tumbler destined to the working of products for taps and fittings, with an upper opening of 150 cm diameter and capacity of 600 liters. The phonometer used for the measurements reported in this exampie was the model 7178-P, provided with a 7479 filter for a third-octave bands, produced by the firm MIP OY (Finland) conforming to I.E.C. norms. 651 , 804 type 2, and with an overload indicator. The instrument used to directly measure the instant non- weighted maximum acoustic value (peak), had a time slope constant not greater than 100 microseconds. The methodology used to carry out the phonometric detection of the present example conforms to the prescriptions contained in C.E.E norms, and in D.L 277/91. In particular, the measurements were taken 1 m from the external edge of the tumbler and at a height 1.50 m. The results are reported in the following Table 1 , in which the quantity dB(A) is the logarithmic magnitude that defines the pressure, the power and the sound intensity; (A) indicates the use of a filter that simulates the weighted frequency response curve of the human ear. 0/23668 10 Table 1 FREQUENCY ANALYSIS dB (A) Frequency (Hz) without cap with caj 25 77.4 75.4 31.5 79.7 77.2 40 66.0 60.0 50 82.3 76.0 63 64.8 66.0 80 74.1 74.3 100 79.1 79.0 125 75.3 72.7 160 83.6 77.4 200 77.1 74.4 250 74.3 72.5 315 77.9 72.5 400 78.6 75.7 500 80.5 77.4 630 81.2 76.7 800 83.2 76.0 1000 82.6 74.9 1250 84.3 74.1 1600 83.4 71.7 2000 85.5 70.8 2500 86.5 * 70.8 3150 84.2 69.0 4000 80.8 67.0 5000 75.3 63.0 6300 72.5 60.0 8000 69.0 58.7 10000 63.0 53.6 12500 58.7 48.4 16000 51.4 40.0 20000 43.0 35.6 The frequency analysis show, therefore, a meaningful reduction of the sound level beginning from 125 Hz up to 20,000 Hz. In some cases, the noise reduction exceeds around 18% of incident sound energy, above all in the intermediate and upper audible frequencies. The LeqdB (A) values i.e. the values of the continuous level equivalent (which is the constant level that a static noise with the same acoustic total energy would have) were also calculated. The values of L eq dB (A) detected and calculated underline a reduction of beyond 10 decibel, i.e. a value that allows the use of the sieve provided with only the cap as silencer in the ambit of the norm defined by D.L. 277/ 91. EXAMPLE 2 Example 2 used the same conditions of Example 1 , therefore the same noise source (tumbler) and the same measurement instrumentation. However, the sieve was completely enshrouded and wound in a sound-absorbing element according to the present invention. In other words, the sound-absorbing element used comprised in this case a coverage element (or cap) and an external side covering that surrounded the tumbler entirely. With this layout, a noise attenuation of greater than 50% was obtained, above all in correspondence of the middle and upper frequencies in the audible frequencies range. The sound-absorbing element according to the invention of equal effectiveness to other sound-absorbing materials, therefore presents notable advantages, not only from the point of view of weight, but in particularly reduced dimensions, in ease of installation, as well as from the point of view of the costs and of the simplicity of production. Furthermore, it should be stated that the thickness of the sound-absorbing element according to the present invention, like the panel produced with it, takes up very little space, allowing it to be used for a wide range of uses.

Claims: CLAIMS 1. Sound-absorbing element of the composite type, comprising a first covering sheet and a second covering sheet which contain between them at least one intermediate layer of a filling material, characterised in that at least one of said covering sheets is provided with a plurality of through holes. 2. A sound-absorbing element according to Claim 1 , characterised in that said covering sheets and said at least one intermediate layer are made of flexible materials. 3. A sound-absorbing element according to Claim 1 , characterised in that said covering sheets and said at least one intermediate layer are made of fireproof materials. 4. A sound-absorbing element according to Claim 1, characterised in that at least one of said covering sheets are made of PVC. 5. A sound-absorbing element according to Claim 1, characterised in that said first covering sheet and said second covering sheet are made of PVC. 6. A sound-absorbing element according to Claim 1 , characterised in that said at least one intermediate layer is made of a foamed material of the open-cell type. 7. A sound-absorbing element according to any of the preceding Claims, characterised in that both said covering sheets are provided with a plurality of through holes. 8. Sound-absorbing panel, characterised by comprising at least one flexible sound-absorbing element according to any of Claims 1 to 7. 9. A sound-αbsorbing panel according to Claim 8, characterised in that said first covering sheet and said second covering sheet of said at least one sound-absorbing element are joined together at least in correspondence of their respective edges. 10. A sound-absorbing panel according to Claim 9, characterised in that the edges of said first covering sheet and of said second covering sheet joined to each other form a peripheral ridge suitable to allow the fixing of a panel to a support structure and/or to at least another of said panels. 11. A sound-absorbing panel according to Claim 9, characterised in that it comprises elastic means for allowing the fixing of said panel. 12. A sound-absorbing panel according to Claim 8, characterised in that it comprises one or more stiffening structures integral with said panel. 13. A sound-absorbing panel according to Claim 12, characterised in that said one or more stiffening structures are inserted into the inside of said at least one sound-absorbing element.

Inventors: SPANO' DOMENICO, SPANO', DOMENICO
Applicants: SPANO DOMENICO, TELONI SPANDOTEL DI SPANO DOME, SPANO', DOMENICO, TELONI SPANDOTEL DI SPANO' DOMENICO
Application year: 1999
Main classification: E04B1
IPC codes: E04B1