Claims:WE CLAIM:
1. An acoustic panel for selectively absorbing acoustic energy, said acoustic panel comprising:
- a first layer having a first surface, and a second surface, said first layer characterized by having a predetermined mass per unit area and a first predetermined thickness;
- a second layer having a first surface, and a second surface, said first surface of said second layer being in contact with said second surface of said first layer, said second layer characterized by having a predetermined air flow resistivity and a second predetermined thickness; and
- a third layer in contact with said second surface of said second layer, said third layer having a third predetermined thickness.
2. The acoustic panel as claimed in claim 1, wherein said predetermined mass per unit area of said first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2.
3. The acoustic panel as claimed in claim 1, wherein said first predetermined thickness is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, more preferably the thickness is 3 mm.
4. The acoustic panel as claimed in claim 1, wherein said predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4.
5. The acoustic panel as claimed in claim 1, wherein said second predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably the thickness is 50 mm.
6. The acoustic panel as claimed in claim 1, wherein said third predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably the thickness is 50 mm.
7. The acoustic panel as claimed in claim 1, wherein
- said first layer comprises at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC), and/or
- said second layer comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool, and/or
- said third layer comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof.
8. The acoustic panel as claimed in claim 1 is characterized by having an acoustic absorption coefficient of 0.5 or greater at 125 Hertz and 250 Hertz, and 0.1 for frequencies greater than 800 Hertz.
9. An acoustic panel for selectively absorbing acoustic energy, said acoustic panel comprising:
- a first layer having a first surface, and a second surface, said first layer characterized by having a predetermined mass per unit area and a first predetermined thickness, said first layer comprises at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC);
- a second layer having a first surface, and a second surface, said first surface of said second layer being in contact with said second surface of said first layer, said second layer characterized by having a predetermined air flow resistivity and a second predetermined thickness, wherein said second layer comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool; and
- a third layer in contact with said second surface of said second layer, said third layer having a third predetermined thickness, wherein said third layer comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof;
wherein said predetermined mass per unit area of said first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2;
wherein said first predetermined thickness is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, more preferably 3 mm;
wherein said predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4;
wherein said second predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm; and
wherein said third predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm.
10. The acoustic panel as claimed in claim 9 is characterized by having an acoustic absorption coefficient of 0.5 or greater at 125 Hertz and 250 Hertz, and 0.1 for frequencies greater than 800 Hertz.
, Description:FIELD OF THE INVENTION
The present invention relates to the field of acoustics, and particularly to an acoustic panel, which is configured for selectively absorbing acoustic energy.
BACKGROUND OF THE INVENTION
Humans are naturally equipped to listen to speech in an open environment. Constructing structures resulted in an unfamiliar environment for human speech to work. In a jungle environment, low frequencies pass off without obstruction due to their longer wavelengths, but higher frequencies reflect from tree trunks and branches to a degree which creates a high frequency reverberation. Such an environment is suitable to speech intelligibility as the information of a word is contained in the consonants (which are relatively high in frequency) and the shape of the word is contained in the vowels (which are relatively low in frequency). In the environments we speak and listen in the modern world, low frequencies have nowhere to go and they reflect from the structures (say concrete/brick walls) which create a low frequency reverberation. The higher energy of lower frequencies masks the higher frequencies thus masking the information in a word. This reduces speech intelligibility. This school of thought therefore requires that low frequencies be absorbed such that a balanced sound environment can exist.
Additionally, in a smaller room, standing waves are created as the lower frequencies reflect between surfaces resulting in room modes. The standing waves create maxima and minima at locations across the room which depend on the room dimensions. This does not happen above the Schroeder frequency (above which, the room is considered a diffuse field). To reduce the effect of room modes, containing the reflection that results in creation of the standing waves proves to be an effective method. This too requires that low frequencies be absorbed.
There are multiple such environments which require low frequency absorption which is a challenge. A common solution is resonating absorbers.
Typically, resonating absorbers known in the art comprising a membrane having a predetermined mass per unit area, wherein the membrane is placed over a cavity having a predetermined depth. The conventional solution employs wood wool, or MDF as the membrane and rock wool, glass wool and/or air is used in the cavity.
One disadvantage of the conventional panel is that the wood wool or the MDF is not waterproof and is easily damaged by water or moisture over a period.
Another disadvantage is that the wood wool or the MDF employed in the conventional panel is prone to termite attack.
Yet another disadvantage is that the conventional panels or conventional solutions do not provide absorption only in the 125 Hz and 250 Hz octave bands. It is observed that the conventional panels either absorb the higher frequencies as well or have very low absorption at and around the 125 Hz and 250 Hz octave bands.
Still another disadvantage of the conventional panels or conventional solutions is that the cost of materials and installation is exorbitantly high.
Thus, there is felt a need for overcoming one or more drawbacks associated with conventional acoustic panels and/or conventional solutions.

OBJECTS OF THE INVENTION
Some of the objects of the presently disclosed invention, of which at the minimum one object is fulfilled by at least one embodiment disclosed herein are as follow:
An object of the present invention is to provide an alternative, which overcomes at least one drawback encountered in the existing prior art;
Another object of the present invention is to provide an acoustic panel;
Still another object of the present invention is to provide an acoustic panel for selectively absorbing acoustic energy;
Yet another object of the present invention is to provide an acoustic panel for selectively absorbing acoustic energy in and around the octave bands; and
Another object of the present invention is to provide an acoustic panel for selectively absorbing acoustic energy, wherein the material and the installation of the acoustic panels is economic.
Other objects and benefits of the present invention will be more apparent from the following description which is not intended to bind the scope of the present invention.
SUMMARY OF THE INVENTION
The present invention relates to an acoustic panel, which is configured for selectively absorbing acoustic energy. In particular, the present invention provides an acoustic panel which is configured for selectively absorbing acoustic energy in and around the octave bands.
In accordance with an aspect of the present invention, an acoustic panel is provided, wherein the acoustic panel is configured for selectively absorbing acoustic energy and reducing noise pollution and/or noise levels in the vicinity of thereof. In accordance with the present invention the acoustic panel comprises a first layer having a first surface, and a second surface, the first layer characterized by having a predetermined mass per unit area and a first predetermined thickness, a second layer having a first surface, and a second surface, the first surface in contact with the second surface of the first layer, the second layer characterized by having a predetermined air flow resistivity and a second predetermined thickness, and a third layer in contact with the second surface of the second layer, the third layer having a third predetermined thickness.
In accordance with an embodiment of the present invention, the predetermined mass per unit area of the first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2to 2.4 Kg/m2, the first predetermined thickness is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, the predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4, the second predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferable 50 mm, the third predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm.
In accordance with an embodiment of the present invention, the first layer comprises at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC), and/or the second layer comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool, and/or the third layer comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof.
In another aspect the present invention provides an acoustic panel for selectively absorbing acoustic energy, the acoustic panel comprises a first layer having a first surface, and a second surface, the first layer characterized by having a predetermined mass per unit area and a first predetermined thickness, the first layer comprises at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC), a second layer having a first surface, and a second surface, the first surface in contact with the second surface of the first layer, the second layer characterized by having a predetermined air flow resistivity and a second predetermined thickness, wherein the second layer comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool; and a third layer in contact with the second surface of the second layer, the third layer having a third predetermined thickness, wherein the third layer comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof, wherein the predetermined mass per unit area of the first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2, wherein the first predetermined thickness is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, wherein the predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4, wherein the second predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm and wherein the third predetermined thickness is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm.
In accordance with the present invention, the acoustic panel is characterized by having an acoustic absorption coefficient of 0.5 or greater at 125 Hertz and 250 Hertz, and 0.1 for frequencies greater than 800 Hertz.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present invention will now be described with the help of the accompanying drawing, in which:
FIG. 1 illustrates a schematic cross-sectional view of an acoustic panel for selectively absorbing acoustic energy in accordance with an aspect of the present invention; and
FIG. 2 illustrates a graph of absorption of sound at various frequencies, with the acoustic panel of the present invention installed in an enclosure and without the acoustic panel installation.
LIST OF NUMERALS
The following is the list of numerals and their meaning as used in the present specification.
100 - Acoustic Panel
102 - First layer
102a - First surface
102b - Second surface
104 - Second layer
104a - First surface
104b - Second surface
106 - Third layer
W - Wall
DETAILED DESCRIPTION
All the terms and expressions, which may be technical, scientific or otherwise, as used in the present invention have the same meaning as understood by a person having ordinary skill in the art to which the present invention belongs, unless and otherwise explicitly specified.
In the present specification, and the claims, the articles “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
The term “comprising” as used in the present specification and the claims will be understood to mean that the list following is non-exhaustive and may or may not include any other extra suitable features or elements or steps or constituents as applicable.
Further, the terms “about” or “approximately” used in combination with ranges relating to sizes of parts, or any other physical properties or characteristics, are meant to include small variations that may occur in the upper and/or lower limits of the ranges of the sizes.
The present invention relates to the field of acoustics, and particularly to an acoustic panel, which is configured for selectively absorbing acoustic energy. In particular, the present invention provides an acoustic panel which is configured for selectively absorbing acoustic energy in and around the octave bands.
The present invention provides an acoustic panel, which is configured to selectively absorb sound energy at various frequencies and hence reduce the noise pollution, increase speech intelligibility, improve clarity of treble sections of music, reduce reverberation of lower frequencies and the acoustic panel area required for the above advantages is reduced as compared to the conventional panels.
The present invention is now described hereinbelow with reference to the accompanying drawing, wherein FIG. 1 illustrates a schematic cross-sectional view of an acoustic panel for selectively absorbing acoustic energy in accordance with an aspect of the present invention, and FIG. 2 illustrates a graph of absorption of sound at various frequencies, with the acoustic panel of the present invention installed in an enclosure and without the acoustic panel installation.
In an aspect, the present invention provides an acoustic panel, wherein the acoustic panel is configured to selectively absorb acoustic energy and reduce the noise in and around the surrounding in which the acoustic panel is installed.
FIG. 1 illustrates a schematic cross-sectional view of an acoustic panel for selectively absorbing acoustic energy in accordance with an aspect of the present invention, wherein the acoustic panel (100) comprises a first layer (102) having a first surface (102a), and a second surface (102b), the first layer (102) characterized by having a predetermined mass per unit area and a first predetermined thickness (t1).
In accordance with the present invention, the acoustic panel (100) further includes a second layer (104) having a first surface (104a), and a second surface (104b), the first surface (104a) is in contact with the second surface (102b) of the first layer (102), the second layer (104) is characterized by having a predetermined air flow resistivity and a second predetermined thickness (t2).
In accordance with the present invention, the acoustic panel (100) further includes a third layer (106) in contact with the second surface (104b) of the second layer (104), the third layer (106) having a third predetermined thickness (t3).
In accordance with an embodiment of the present invention, the predetermined mass per unit area of the first layer (102) is in the range of 1 Kg/m2 to 3 Kg/m2. In accordance with another embodiment of the present invention, the predetermined mass per unit area of the first layer (102) is in the range of 1.2 Kg/m2 to 2.4 Kg/m2.
In accordance with an embodiment of the present invention, the first predetermined thickness (t1) of the first layer (102) is in the range of 2 mm to 10 mm. In accordance with another embodiment of the present invention, the first predetermined thickness (t1) of the first layer (102) is preferably in the range of 3 mm to 5 mm. In one embodiment the first predetermined thickness (t1) is 3 mm. In another embodiment the first predetermined thickness (t1) is 4 mm. In accordance with the present invention, it is found that if the first layer is PVC foam sheet and its thickness is less than 3 mm, the material loses stability and strength as it cannot sustain the weight and breaks. If the first layer is PVC foam sheet and the thickness is greater than 5 mm, it is observed that the desired absorption coefficient is not achieved. The inventor of the present invention has tested 12 mm thick PVC foam sheet (with surface density of 5 Kg/m2) and found that the absorption coefficient for 125 Hz and 250 Hz octave bands was less than 0.35, which are very less and not desired.
In accordance with an embodiment of the present invention, the predetermined air flow resistivity of the second layer (104) is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4. In accordance with another embodiment of the present invention, the predetermined air flow resistivity of the second layer (104) is in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4. In accordance with an embodiment, the air flow resistivity of the second layer is 20 x 103 N-s/m4.
In accordance with an embodiment of the present invention, the second predetermined thickness (t2) of the second layer (104) is in the range of 20 mm to 100 mm. In accordance with another embodiment of the present invention, the second predetermined thickness (t2) of the second layer (104) is in the range of 25 mm to 75 mm. In one embodiment the second predetermined thickness (t2) is 50 mm.
In accordance with an embodiment of the present invention, the third predetermined thickness (t3) of the third layer (106) is in the range of 20 mm to 100 mm. In accordance with another embodiment of the present invention, the third predetermined thickness (t3) of the third layer (106) is in the range of 25 mm to 75 mm. In one embodiment the third predetermined thickness (t3) is 50 mm.
In accordance with an embodiment of the present invention, the first layer (102) comprises at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC), wherein the at least one material has mass per unit area in the range of 1 Kg/m2 to 3 Kg/m2 and preferably the at least one material has mass per unit area in the range of 1.2 Kg/m2 to 2.4 Kg/m2. Further, the thickness of 2 mm to 10 mm and preferably 3 mm to 5 mm has been found to most effective for low frequency absorption. In an embodiment the thickness of 3 mm is preferred.
In accordance with an embodiment of the present invention, the second layer (104) comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool, wherein the at least one material is characterized by having air flow resistivity in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4. In accordance with an embodiment, the air flow resistivity of the second layer is 20 x 103 N-s/m4. In accordance with an embodiment, the air flow resistivity of the rock wool is approximately 20,000 N-s/m4, whereas that of the glass wool is approximately 18,000 N-s/m4. Further, the thickness of 20 mm to 100 mm and preferably 25 mm to 75 mm, more preferably the thickness is 50 mm, of the second layer or the rock wool or polyurethane foam, or the glass wool, has been found to most effective for reducing noise and/or reverberations. If the second layer (104) is not present, it is observed that the absorption coefficient drops significantly.
In accordance with an embodiment of the present invention, the third layer (106) comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof. The thickness of the third layer (106) or that of the gas that is found to be most effective is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably the thickness is 50 mm.
In another aspect of the present invention, an acoustic panel (100) for selectively absorbing acoustic energy is disclosed, wherein the acoustic panel (100) comprises a first layer (102) having a first surface (102a), and a second surface (102b), the first layer (102) is characterized by having a predetermined mass per unit area and a first predetermined thickness (t1), the first layer (102) comprises or is made of at least one material selected from the group consisting of polyvinyl chloride (PVC), polyvinyl chloride (PVC) foam sheet, and wood plastic composite (WPC), a second layer (104) having a first surface (104a), and a second surface (104b), the first surface (104a) is in contact with the second surface (102b) of the first layer (102), the second layer (102) is characterized by having a predetermined air flow resistivity and a second predetermined thickness (t2), wherein the second layer (104) comprises at least one material selected from the group consisting of rock wool, polyurethane foam, and glass wool, and a third layer (106) in contact with the second surface (104b) of the second layer (104), the third layer (106) having a third predetermined thickness (t3), wherein the third layer (106) comprises at least one gas selected from the group consisting of air, nitrogen, and a combination thereof, wherein the predetermined mass per unit area of the first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2, wherein the first predetermined thickness (t1) is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, more preferably 3 mm, wherein the predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4, wherein the second predetermined thickness (t2) is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm and wherein the third predetermined thickness (t3) is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm.
In still another aspect of the present invention, an acoustic panel (100) for selectively absorbing acoustic energy is disclosed, wherein the acoustic panel (100) comprises a first layer (102) having a first surface (102a), and a second surface (102b), the first layer (102) is characterized by having a predetermined mass per unit area and a first predetermined thickness (t1), the first layer (102) comprises or is made of polyvinyl chloride (PVC) or polyvinyl chloride (PVC) foam sheet, a second layer (104) having a first surface (104a), and a second surface (104b), the first surface (104a) is in contact with the second surface (102b) of the first layer (102), the second layer (102) is characterized by having a predetermined air flow resistivity and a second predetermined thickness (t2), wherein the second layer (104) comprises rock wool, and a third layer (106) in contact with the second surface (104b) of the second layer (104), the third layer (106) having a third predetermined thickness (t3), wherein the third layer (106) comprises air, wherein the predetermined mass per unit area of the first layer is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2, wherein the first predetermined thickness (t1) is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, more preferably 3 mm, wherein the predetermined air flow resistivity is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4, wherein the second predetermined thickness (t2) is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm, and wherein the third predetermined thickness (t3) is in the range of 20 mm to 100 mm, preferably in the range of 25 mm to 75 mm, more preferably 50 mm.
In accordance with the embodiments of the present invention, the acoustic panel (100) is characterized by having an acoustic absorption coefficient of 0.5 or greater at 125 Hertz and 250 Hertz, and 0.1 for frequencies greater than 800 Hertz.
FIG. 2 illustrates a graph of absorption of sound at various frequencies, with the acoustic panel of the present invention installed in an enclosure and without the acoustic panel installation.
In accordance with an embodiment of the present invention the acoustic panel can be employed for reducing noise or reverberations in a room by installing the same in the room or the hall wherein the noise must be reduced. More specifically, the first layer (102), which may be made of PVC or WPC as discussed herein above, is glued to a frame, which may be made of aluminium or wood. In an embodiment, aluminium is preferred over wood. Further, a second layer which can be of rock wool, or polyurethane foam, or glass wool or a combination thereof and which may be enclosed in a plastic bag or the like is held in place adjacent to the second surface of the first layer with the help of a wire mesh. A plastic mesh can also be used. The second layer can be stacked by any other method also and the present invention is not limited by these methods disclosed herein. Further, the frame can be secured to a wall (W) of a room, wherein the noise or reverberations is/are to be reduced. The frame can be secured by any know means such as by using fasteners to the wall such that a third layer of air or a gap is defined between the second surface of the second layer (rock wool) and the surface of the wall. The thickness of the third layer so configured can be in the range of 20 mm to 75 mm, preferably the gap is 50 mm.
The air gap or the gas layer or the third layer can be configured in multiple ways and is not restricted to the way discussed/disclosed herein above. For example, a bag such as a plastic bag can be used to configure the gas or air layer, wherein the gas or the air is filled in the bag, and the bag is stacked on the second surface of the second layer between the second surface of the second layer and the wall surface.
The above-mentioned panel is secured to the wall (W) such that the first surface (102a) of the first layer (102) faces away from the wall surface, that is, it faces the room side. If the configuration is changed such that the first or second surface (104a or 104b) second layer (104) faces the room side, and the first surface (102a) of the first layer (102) faces the wall (W), then the acoustic panel so formed do not function as an absorber membrane.
In accordance with an embodiment of the present invention, the first layer (102), the second layer (104), and the third layer (106) can each be made of one or more sub-layers, provided that:
- the mass per unit area of the first layer (102) is in the range of 1 Kg/m2 to 3 Kg/m2, preferably in the range of 1.2 Kg/m2 to 2.4 Kg/m2 and the overall thickness is in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 5 mm, more preferably the thickness is 3 mm;
- the air flow resistivity of the second layer (104) is in the range of 15 x 103 N-s/m4 to 25 x 103 N-s/m4, preferably in the range of 18 x 103 N-s/m4 to 22 x 103 N-s/m4 and the thickness is in the range of 20 mm to 100 mm, preferably 25 mm to 75 mm, more preferably the thickness is 50 mm; and
- the thickness of the third layer (106) is in the range of 20 mm to 100 mm, preferably 25 mm to 75 mm, more preferably the thickness is 50 mm.
The present invention is now described with reference to the following example which is provided to illustrate the present invention more clearly and not the limit the scope thereof.
Example:
An acoustic panel was manufactured in accordance with the embodiments of the present invention, wherein the acoustic panel comprised of a polyvinyl chloride foam sheet layer of 3 mm in thickness and 2 m x 2 m in length and breadth, a rock wool layer having a thickness of 50 mm, and length and breadth of 2 m each was stacked on one surface of the polyvinyl chloride foam sheet layer. The two layers of polyvinyl chloride and the rock wool layer were formed into an assembly held together by aluminium framing. A wood frame could have been equally used for the same purpose. The polyvinyl chloride foam sheet layer was glued to the frame and the rock wool layer, which as enclosed in a plastic bag, was held in place adjacent to the second surface of the polyvinyl layer by wire mesh. A plastic mesh could also be used. The frame was secured to a wall of a room, wherein the noise or reverberations where to be reduced, by securing the frame to the wall such that a third layer of air or a gap was defined between the second surface of the second layer (rock wool) and the surface of the wall. The thickness of the third layer so configured was 50 mm.
The acoustic panel so configured was tested for noise reduction. Specifically, the absorption values of the acoustic panel were measured in a reverberation chamber as per ASTM C-423/ISO 354 testing method. Typical absorption values are tabulated in Table – I herein below.
Table – I
# Third Octave Band
(Hz) Absorption Coefficient (± 0.1)

1 100 0.53
2 125 0.41
3 160 0.71
4 200 0.61
5 250 0.32
6 315 0.26
7 400 0.21
8 500 0.14
9 630 0.08
10 800 0.07
11 1000 0.05
12 1250 0.05
13 1600 0.03
14 2000 0.03
15 2500 0.04
16 3150 0.04
17 4000 0.05
18 5000 0.05
The following instruments (list in Table – II herein below) were employed to get the values/data in Table – I above:
Table – II
# Instrument Name Type Model No.
1 Multi-channel data acquisition system1 3560 D
2 1/2” random incidence microphone2 378B20
3 Power Amplifier1 2716
4 Omni Directional sound source1 Omni Power 4296
5 Reverberation room 80 m3
1. Bruel & Kjear, Denmark
2. PCB, USA
APPLICATION OF THE PRESENT INVENTION
The acoustic panel of the present invention can be employed as a sound absorbers, which include but are not limited to, aeroplanes, submarines, industrial sheds, auditorium (walls and ceilings), home theatres, AC ducting, railway stations, metro-stations, metros, bus-stands, seminar halls, class-room (walls and ceilings), balcony ceilings to absorb road noise, industrial equipment enclosures, recording studios, monitoring rooms, audiometry laboratories, audio testing laboratories, live arenas, concerts, stadiums, vehicles, airports, cafes, restaurants, cinema halls, meeting rooms, etc.
TECHNICAL ADVANCES AND ADVANTAGES OF THE INVENTION
The presently disclosed invention, as described herein above, provides several technical advances and advantages including, but not limited to, an acoustic panel for selectively absorbing acoustic energy, wherein the acoustic panel when installed in an enclosure such as a room or a hall or the like,
? Improves speech intelligibility;
? Improves clarity of the trebly sections of the music;
? Reduces reverberation of lower frequencies in the range of 60 Hz to 550 Hz;
? Requires less material and/or panel area;
? wherein the acoustic panels are economical and easy to manufacture and install; and
? wherein the acoustic panels are water and termite resistant.