A sound-absorbing panel (100) comprising a first cardboard layer (1) provided with a set of through slots (11), a second cardboard layer (2) provided with a set of through holes (21) and a third cardboard layer (3) not provided with through holes or slots.
The present patent application for industrial invention relates to an improved sound-absorbing panel.
As it is known, the term "sound-absorption" indicates the capability of a material to absorb sound energy. In fact, when a sound wave is incident on a wall that separates two areas, the sound wave is partially reflected in the originating area, partially absorbed by the wall and partially transmitted in the adjacent area.
A material is defined as sound-absorbing when it allows for converting a good part of the sound energy that crosses the material into energy; it generally being thermal energy.
More precisely, the function of sound-absorbing materials is to reduce reverberation, i.e. the roaring sound and the echo, inside adjoining areas. Practically speaking, in closed spaces, the total noise that is perceived is determined by the reflection of the sound waves by the walls that define the area, especially when the walls are made of smooth compact materials, which are defined as reflecting.
Therefore, the main function of a sound-absorbing material is not to reflect and hinder the propagation of sound waves, but to reflect the sound energy incident on the material as least as possible in order to reduce reverberation.
In general sound-absorbing materials are porous or fibrous materials that are capable of dissipating part of the sound energy in their interstices: in fact, porous materials, such as open cell foam - i.e. melamine or polyurethane - or fibrous materials, such as wood fibers, rock or glass wool, polyester fibers, heavy fabrics and felts, have a high sound absorption coefficient. On the contrary, hard compact materials with a high specific weight, such as marble, ceramic, glass, cement and the like, have a very low sound absorption coefficient and are therefore highly reflecting.
Therefore, sound-absorbing materials are basically high-porosity materials that can be purchased in rolls in order to make customized panels according to the user requirements or finished products in the form of panels with predefined regular dimensions.
In particular, the sound-absorbing panels that are intended to be installed inside internal walls and partitions are generally made of plasterboard, which is a largely used material especially for false ceilings and light-weight partitions.
More precisely, the acoustic insulation of partition walls, between two spaces or living areas, is generally obtained by using plasterboard counter walls separated from the existing wall by means of an empty space filled with sound-absorbing material (generally glass wool).
The sound insulation power of such a wall increases when the thickness of the empty space increases, i.e. when the distance between the plasterboard counter wall and the existing wall increases so that the empty space can receive a higher amount of sound-absorbing material.
In view of the above, it must be noted that the sound absorption of a porous material is very high for medium-high frequency waves. Vice versa, in order to achieve a good absorption of low-frequency sound waves, it is necessary to increase the thickness of the porous sound-absorbing material considerably. Therefore, the sound-absorbing panels for indoor use, which are largely used in living and working spaces, as well as in booths and fairs, must have a good thickness-efficacy ratio in order to minimize the volume while guaranteeing a good sound absorption.
In fact, the sound-absorbing panels that are intended to be used in closed spaces, such as fair booths and the like:
Consequently, the need to meet these conflicting requirements often impairs the reverberation reduction capability of the said sound-absorbing panels.
The purpose of the present invention is to remedy the aforementioned drawbacks of the prior art by devising a sound-absorbing panel that is efficacious, versatile, light-weighted, simple and easy to install.
The sound-absorbing panel of the invention comprises at least three layers, of which:
In particular, the use of environmental-friendly materials, such as for example cardboard, in a larger and larger scale suggested the opportunity of evaluating the sound-absorbing properties of similar materials in such manner to use environmental-friendly materials also to improve the acoustic comfort of households, working and/or sales spaces.
In view of the above the cardboard sound-absorbing panel of the invention is light-weighted, completely recyclable and produced with a low-cost technology.
For the purpose of clarity the description of the sound-absorbing panel according to the invention continues with reference to the attached drawings, which have an illustrative, but not limiting value, wherein:
With reference to
The sound-absorbing panel (100) of the invention comprises a first layer (1), a third layer (3) and a second layer (2) advantageously interposed between the said first layer (1) and the said third layer (3).
The said first (1), second (2) and third layer (3) have a thickness comprise between 5 mm and 30 mm and are made of corrugated, alveolar or honeycomb cardboard.
The first layer (1) is provided with through slots (11), which are identical and regularly spaced, advantageously having a length comprised between 20 cm and 30 cm and a width comprised between 4 mm and 2 cm.
The second layer (2) is provided with a series of through holes (21) which are identical and regularly distributed, having a diameter comprised between 2 cm and 5 cm.
Advantageously, the sound-absorbing panel (100) of the invention also comprises a fourth layer (4) made of woven-non-woven fabric, which is interposed between the said first layer (1) and the said second layer (2).
In particular, the said fourth layer (4) preferably has a weight/m2 comprised between 200 g and 600 g.
It must be stated that specific tests were made in order to increment the sound-absorbing power of a cardboard panel.
In particular, the said tests were made in order to obtain an improved sound-absorbing panel with high sound-absorbing power, which is capable of considerably reducing the echo effect and the interference caused by it in closed areas that are typically very noisy, such as for example restaurants, fairs, classrooms, canteens and the like.
The other evaluation of the tests referred to the resistance of the cardboard sound-absorbing panel, in view of the various applications as indicated above.
In particular, the evaluation was made with reference to the possibility of creating self-standing structures defined as "islands" in large closed areas, in which users can communicate without any background noise. Specifically, the coupling of the cardboard sound-absorbing panel of the invention, for example, allows for creating fair booths, convention rooms and meeting rooms in trade show areas.
Moreover, specific tests were made to devise a cardboard sound-absorbing panel with higher absorption power for a selected frequency range. In particular, tests were made in order to favor the absorption by the cardboard sound-absorbing panel of the invention of the frequencies comprised between 400 Hz and 3,000 Hz, i.e. the most important frequencies for the diffusion of the human voice. In view of the above, the cardboard sound-absorbing panel will contribute to reduce the acoustic pollution in working areas, such as call centers and open-space offices in general.
It must be noted that noise attenuation tests were made in suitable test areas that allowed for objectively measuring the environmental impact of the introduction of a cardboard sound-absorbing panel according to well-defined dimensional specifications.
In particular, in compliance with the UNI EN ISO 354 regulations, the tests used to evaluate the noise attenuation are based on the evaluation of the reverberation time variations in a test area known as reverberation chamber.
More precisely, the reverberation chamber was used to measure the reverberation time variation determined by the introduction of a cardboard sound-absorbing panel.
It must be noted that the reverberation time coincides with the number of seconds that are necessary for the sound to decay by 60 dB (decibels) under the intensity level of the original sound.
By applying normative formulas, the characterization of the reverberation time allowed to define the alpha coefficient that refers to the cardboard absorption properties.
Upon changing the frequency, the evaluation of cardboard panels with different shapes allowed to identify the most appropriate shapes and dimensions of the cardboard panels.
Moreover, the large amount of data allowed for identifying the shapes of the less performing cardboard panels in terms of absorption in order to evaluate a possible use of the said panels in not particularly noisy areas.
In particular, the tests have given the best results with the sound-absorbing panel (100) according to the invention, according to the embodiment shown in
In any case, it must be noted that the sound-absorbing panel (100) according to the invention can have any shape and be customized and coated with any material or fabric, while maintaining a high absorbing power.