EP3500706A1

EP3500706A1 - Acoustically absorptive panel

Info

Publication number: EP3500706A1
Application number: EP17777646.5A
Authority: EP
Inventors: Jorge Manuel MENDES SILVA CASTRO; Paulo Ricardo FERREIRA ALVES; Alfredo DA SILVA ALVES
Original assignee: Artnovion Lda
Current assignee: Artnovion Lda
Priority date: 2016-08-22
Filing date: 2017-08-22
Publication date: 2019-06-26
Also published as: WO2018037345A1

Abstract

Acoustically absorptive panel comprising a porous acoustic absorber having a front surface and a non-planar rear surface; a support frame within which said porous acoustic absorber is coupled; an acoustically transparent front fabric affixed on said front surface of said porous acoustic absorber; wherein the non-planar surface is configured such that, when the acoustically absorptive panel is attached to a planar attachment surface, a chamber comprising a uneven depth air cavity for enhancing sound absorption is defined between said non-planar rear surface and the planar attachment surface, wherein said non-planar rear surface of said porous acoustic absorber has complementary surface configurations whereby such two acoustically absorptive panels may be stacked upon one another by coupling their respective rear surfaces. Said board may be directly attached to the support frame and to the porous acoustic absorber, wherein the porous acoustic absorber is surrounded by the support frame.

Description

D E S C R I P T I O N

ACOUSTICALLY ABSORPTIVE PANEL

Technical field

[0001] The present disclosure relates to the field of acoustics, in particular room acoustics, further in particular to acoustically absorptive panels.

Background Art

[0002] Noise control or acoustical comfort are important matters in industrial fields like construction, health and others. Concomitantly, the growth of processing capacity combined with the development of new, cost efficient, digital signal processing algorithms has given acoustic professionals the tools to create and to optimize new products that may spread the use of acoustical solutions to a wider extent.

[0003] Anywhere in a room, the sound that is heard is the result of a complex combination of direct, indirect and scattered sound waves. Some sound components will be absorbed or transmitted and the indirect and scattered sound that reaches the ear (or the microphone) results from reflections by the surfaces and materials present in that room. Sound waves striking an arbitrary surface are can be reflected, transmitted or absorbed; the amount of energy going into reflection, transmission or absorption depends on acoustic properties of each surface. Thus, it can be customized some of the surfaces and materials to generate a given effect. The reflected sound may be almost completely redirected by large flat surfaces or scattered by a diffused surface. When a considerable amount of the reflected sound is spatially and temporally scattered, this status is called a diffuse reflection, and the surface involved is often termed a diffuser. The absorbed sound may either be transmitted or dissipated.

[0004] In this way, one of the solutions to control the sound in a room is to use sound absorbing panels covering the room's walls or ceilings. Several acoustic panels have been developed and made their way in to the market. Traditionally these panels use solid porous materials and or membranes to promote sound absorption. The surfaces of these solid porous absorbers can be worked to enhance absorption, by giving them a surface, which is superior to the area of coverage. Also, combinations of solid porous absorbers with front membranes are available, using air chambers in between.

General Description

[0005] The present disclosure comprises an acoustically absorptive panel to be mounted on a wall, a ceiling or a corner. This disclosure includes a set-up, using a front fabric, mounted on a solid porous absorber, with a non-planar rear end surface, which defines, together with the surface to which the panel is attached, an air chamber enhancing absorption. A frame conveys structural rigidity to the panel. Furthermore, this disclosure also comprises by using a front board, juxtaposed on a solid porous absorber, with a non-planar rear end surface, which defines, together with the surface to which the panel is attached, an air cha mber enhancing absorption. A frame conveys structural rigidity to the panel. It also allows an adequate choice of front board premium materials depending on the desired visual effect and design.

[0006] The design of the solid porous absorber also encloses two features: the uneven rear end surface and its distance from the mounting surface allows for the panel to be tuned for low frequencies; also a 45^ angle between the front and rear surface enables panels to be mounted on corners.

[0007] The disclosure includes a set-up - in that it uses an acoustically transparent front fabric, which can be made from polyester, juxtaposed on a solid porous absorber, with a non-planar rear end surface, which defines, together with the surface to which the panel is attached, a n air chamber enhancing absorption.

[0008] But it also allows for an adequate choice of front fabric colours and textures depending on the desired visual effect and design. It enables combining acoustical performance with premium design versatility.

[0009] The design of the solid porous absorber, in particular the second layer, also encloses two important features: the rear end surface and its distance from the surface to which the panel is attached allows for the panel to be tuned for low frequencies; also a 45^ angle between the front and rear surface enables the panels to mounted on corners.

[0010] The disclosure discloses a chosen set-up - in that it uses a front board, which can be made from either plastic, wood or other premium materials, juxtaposed on a solid porous absorber, with a non-planar rear end surface, which defines, together with the surface to which the panel is attached, an air chamber enhancing absorption.

[0011] But it also allows for an adequate choice of front board materials depending on the desired visual effect and design. It enables combining acoustical performance with premium design versatility.

[0012] The design of the solid porous absorber (the second layer) also encloses two features: the rear end surface and its distance from the surface to which the panel is attached allows for the panel to be tuned for low frequencies; also a 45^ angle between the front and rear surface enables the panels to mounted on corners.

[0013] The panel now disclosed uses an acoustically transparent front fabric, which can be made from premium materials, juxtaposed on a solid porous absorber, with a non-planar rear end surface, which defines, together with the surface to which the panel is attached, an air chamber. This panel discloses a chosen set-up - with a front fabric, covering a solid porous absorber, which creates an air chamber between the panel and the surface. But it also allows for an adequate choice of materials depending on the desired visual effect and design.

[0014] The front fabric acts like an acoustically transparent decorative element, which allows for the sound to reach the solid porous absorber. It can be made 100% in microfiber polyester with a density of 145 gr/m². This fabric, made in warp knitting, is brushed in one side.

[0015] The next element is a solid porous absorber. Sound energy is dissipated by simultaneous actions of viscous and thermal mechanisms. Sound absorbers are used to dissipate sound energy and to minimize its reflection. In this way, when sound passes th rough the acoustically transparent front fabric, it penetrates a high-porosity foam, entering in a network of interconnected pores, where viscous and thermal interaction cause acoustic energy to be dissipated and converted in to heat. The absorption coefficient a is defined as the ratio between the energy absorbed by a given material and the energy incident upon its surface. It is commonly used as a measure of absorption efficiency of a given material and it is known to vary with the frequency of the incident wave.

[0016] The material's density influences dramatically sound absorption behavior. If the fibers are packed too loosely, there will be little energy lost as heat. However if they are packed too densely, penetration suffers and the air motion cannot generate enough friction to be effective. [0017] The porous absorber can be made from resins such as polyester urethane, polyether urethane or melamine and polyimide foam. Polyurethane foam - open-cell foam made of polyester urethane or polyether urethane; the standard density for acoustical polyurethane foam is 20 kg/m³ to 30 kg/m³.

[0018] Melamine Foam (extra fire proof) - open-cell foam made of melamine resin as BASOTEC, with a density range from 7 kg/m³ to 12 kg/m³; Fire rate: Germany DIN 4102-1- Class Bl; US - UL 94 V0 HF 1; UK -BS476 - Part7.

[0019] Porous absorbers are in fact thermal materials and usually not effective sound barriers. Besides the density of the material, sound absorption effectiveness also depends on the thickness of the material, and on the airspace between the porous absorber and the hard surface to which the panel is attached.

[0020] In this panel, foam thickness may vary from 10 mm up to 150 mm. The need for significant thickness compared to operating sound wavelength makes porous absorbers dramatically inefficient and impractical at low frequencies. There is a correlation between the wavelength and absorption coefficient. When a sound wave passes through the panel and hits the rigid surface, in particular a wall, for instance, pressure will be high, but air particle velocity will be zero because the sound waves cannot supply enough energy to shake the wall. At a quarter wavelength from the wall however, pressure is zero, and air particle velocity is maximal. At half wavelength particle velocity is minimal hence absorption is also minimal. At a quarter wavelength from the wall, it will have maximum absorption effect because the particle velocity is maximal.

[0021] In this way, by creating a space between the porous material and the hard surface to which the panel is attached, in particular wall or ceiling, and by varying the length of that space, it is possible to tune and to increase absorption efficiency for lower frequencies.

[0022] This air chamber also allows for the panel to work as a Helmholtz resonator, where a lumped mass of air is forced in and out of a vent. One end of the vent is open into a sealed enclosure, in particular a wall, with volume V, in particular an air chamber, and the other end is free to radiate into open air. A sound wave striking the open end of the device will excite the resonant system, making the plug of air vibrate according to its length and radius and the stiffness provided by the compression of the enclosed volume V. [0023] Furthermore, when a series of panels is framed or enclosed into the wall's surface, the air is confined to that chamber, acting as an independent air mass, similar to what happens with the air inside a speaker column.

[0024] The front board acts like a perforated decorative element, which allows for the sound to reach the solid porous absorber. It can be made from medium density fiberboard (MDF), a particleboard panel with improved fire behavior (fire retardant) and a decorative melamine surface, for interior uses, providing an easy to clean and scratch & stain resistant surface.

[0025] MDF panels are classified according to the criteria defined by EN 14322 - Wood-based panels - Melamine faced boards for interior uses.

[0026] Regarding reaction to fire and according to EN 13986, MDF panels are classified as B-sl, dO (Euroclass definition by EN 13501-1).

[0027] The front panel can assume several combinations of materials and perforation or micro- perforation patterns, either by simple or elongated holes, according to the desired design and visual effect. In terms of design, several combinations are possible: MDF standa lone or covered by wood leaf or laminated with a decorative resin paper. A bar-code effect can also be used with parallel bars varying from vary from 2 to 23 mm. Board thickness may vary from 2 to 20 mm, with density variation 830 to 930 Kg/m³. Wood leafs with 0.2 to 3 mm of thickness from a natural wood source may be applied to the board surface, as well as decorative resin paper.

[0028] The next element is a solid porous absorber. Sound energy is dissipated by simultaneous actions of viscous and thermal mechanisms. Sound absorbers are used to dissipate sound energy and to minimize its reflection. In this way, when sound passes through the perforated board, it penetrates a high-porosity foam, entering in a network of interconnected pores, where viscous and thermal interaction cause acoustic energy to be dissipated and converted in to heat. The absorption coefficient a is defined as the ratio between the energy absorbed by a given material and the energy incident upon its surface. It is commonly used as a measure of absorption efficiency of a given material and it is known to vary with the frequency of the incident wave.

[0029] The density of the material influences the sound absorption behavior. If the fibers are packed too loosely, there will be little energy lost as heat. However if they are packed too densely, penetration suffers and the air motion cannot generate enough friction to be effective. [0030] The porous absorber can be made from resins such as polyester urethane, polyether urethane or melamine and polyimide foam. Polyurethane foam - open-cell foam made of polyester urethane or polyether urethane; the standard density for acoustical polyurethane foam is 20 kg/m³ to 30 kg/m³.

[0031] Melamine Foam (extra fire proof) - open-cell foam made of melamine resin as BASOTEC, with a density range from 7 kg/m³ to 12 kg/m³; Fire rate: Germany DIN 4102-1- Class Bl; US - UL 94 V0 HF 1; UK -BS476 - Part7.

[0032] Porous absorbers are in fact thermal materials and usually not effective sound barriers. Besides the density of the material, sound absorption effectiveness also depends on the thickness of the material, and on the airspace between the porous absorber and the hard surface to which the panel is attached.

[0033] In this panel, foam thickness may vary from 10 mm up to 150 mm. The need for significant thickness compared to operating sound wavelength makes porous absorbers dramatically inefficient and impractical at low frequencies.

[0034] There is a correlation between the wavelength and absorption coefficient. When a sound wave passes through the panel and hits the rigid surface, in particular a wall, for instance, pressure will be high, but air particle velocity will be zero because the sound waves cannot supply enough energy to shake the wall. At a quarter wavelength from the wall however, pressure is zero, and air particle velocity is maximal. At half wavelength particle velocity is minimal hence absorption is also minimal. At a quarter wavelength from the wall, it will have maximum absorption effect because the particle velocity is maximal.

[0035] In this way, by creating a space between the porous material and the hard surface to which the panel is attached, in particular wall or ceiling, and by varying the length of that space, it is possible to tune and to increase absorption efficiency for lower frequencies.

[0036] This air chamber also allows for the panel to work as a Helmholtz resonator, where a lumped mass of air is forced in and out of a vent. One end of the vent is open into a sealed enclosure, in particular a wall with volume V, in particular an air chamber and the other end is free to radiate into open air. A sound wave striking the open end of the device will excite the resonant system, making the plug of air vibrate according to its length and radius and the stiffness provided by the compression of the enclosed volume V. [0037] Furthermore, when a series of panels is framed or enclosed into the wall's surface, the air is confined to that chamber, acting as an independent air mass, similar to what happens with the air inside a speaker column.

Brief Description of the Drawings

[0038] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of disclosure.

[0039] Fig. la is a perspective view of the front of an acoustically absorptive panel according to the disclosure.

[0040] Fig. lb is a perspective view of the rear surface of an acoustically absorptive panel according to the disclosure.

[0041] Fig. 2 is a perspective view of the 3 material components of an acoustically absorptive panel according to the disclosure, including front fabric, a structural frame and an acoustically absorptive foam panel.

[0042] Fig. 3a is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and aligned between all edges of both panels.

[0043] Fig. 3b is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, jointed slightly apart by the shapes of the rear surfaces and aligned between all edges of both panels.

[0044] Fig. 3c is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and not aligned between all edges of both panels.

[0045] Fig. 3d is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, jointed slightly apart by the shapes of the rear surfaces and not aligned between all edges of both panels.

[0046] Fig. 4 is a cross section of an upper perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and perfectly aligned between all edges of both panels.

[0047] Fig. 5a is a perspective upper view of the front surface of the solid porous absorber, with a cross section resembling a half ellipse. [0048] Fig. 5b is a perspective upper view of the front surface of the solid porous absorber, with a cross section resembling adjacent half circles with constant radius.

[0049] Fig. 5c is a perspective upper view of the front surface of the solid porous absorber, with a cross section resembling a sinusoidal wave.

[0050] Fig. 5d is a perspective upper view of the front surface of the solid porous absorber, with a two-dimensional array of three-dimensional shapes.

[0051] Fig. 6a is a perspective view of the rear surface of an acoustically absorptive foam panel.

[0052] Fig. 6b is a perspective view of the rear surface of an acoustically absorptive foam panel with a cross-section generally resembling a square wave in a two-dimensional array of three- dimensional shapes.

[0053] Fig. 7a is a perspective view of the upper surface of front fabric.

[0054] Fig. 7b is an upper view of the design and cuts of the flattened front fabric.

[0055] Fig. 8a is a perspective view of a supportive frame with a triangular section.

[0056] Fig. 8b is a cross section of a perspective view of a supportive frame with a triangular section.

[0057] Fig. 8c is a perspective view of a supportive frame with a squared section.

[0058] Fig. 8d is a cross section of a perspective view of a supportive frame with a squared section.

[0059] Fig. 8e is a perspective view of a supportive frame with a rectangular section.

[0060] Fig. 8f is a cross section of a perspective view of a supportive frame with a rectangular section.

[0061] Fig. 9a is a cross-section perspective of the present disclosure represented on a wall- mounted system.

[0062] Fig. 9b is a cross-section of the present disclosure represented on a wall-mounted system.

[0063] Fig. 9c present disclosure represented on a corner-mounted system.

[0064] Fig. 9d present disclosure represented on perspective of a corner-mounted system.

[0065] Fig.lOa is the final aspect and cross-section present disclosure represented on perspective of a framed or enclosed wall-mounted system.

[0066] Fig.lOb is the aspect and cross-section of resultant air chamber represented on perspective of a framed or enclosed wall-mounted system. [0067] Fig. 11a is a perspective view of the front of an acoustically absorptive panel according to the disclosure.

[0068] Fig. lib is a perspective view of the rear surface of an acoustically absorptive panel according to the disclosure.

[0069] Fig. 12 is a perspective view of the 3 material components of an acoustically absorptive panel according to the disclosure, including a perforated rigid or semi-rigid board, a structural frame and an acoustically absorptive foam panel.

[0070] Fig. 13a is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and aligned between all edges of both panels.

[0071] Fig. 13b is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, jointed slightly apart by the shapes of the rear surfaces and aligned between all edges of both panels.

[0072] Fig. 13c is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and not aligned between all edges of both panels.

[0073] Fig. 13d is a perspective view of 2 identical acoustically absorptive panels according to the disclosure, jointed slightly apart by the shapes of the rear surfaces and not aligned between all edges of both panels.

[0074] Fig. 14 is a cross section of an upper perspective view of 2 identical acoustically absorptive panels according to the disclosure, perfectly stacked by the shapes of the rear surfaces and not aligned between all edges of both panels.

[0075] Fig. 15 is a perspective view of the front of an acoustically absorptive foam panel.

[0076] Fig. 16a is a perspective view of the rear surface of an acoustically absorptive foam panel.

[0077] Fig. 16b is a perspective view of the rear surface of an acoustically absorptive foam panel with a cross-section generally resembling a square wave in a two-dimensional array of three-dimensional shapes.

[0078] Fig. 17a-e is a demonstration in perspective views of several front boards, perforated by simple or elongated holes in a pattern.

[0079] Fig. 18a present invention represented on a wall-mounted system.

[0080] Fig. 18b present invention represented on a corner-mounted system. [0081] Fig. 18c present invention represented on perspective of a corner-mounted system.

[0082] Fig.l9a final aspect and cross-section present invention represented on perspective of a framed or enclosed wall mounted system.

Detailed Description

[0083] As illustrated in the figure la and lb, a typical panel according to this disclosure includes a frame 2 which may be composed of lengths of timber suitably joined to form a rectangular or other desired shaped frame, with a triangular, square or rectangular cross section as referred on 7, 16 and 17. A front fabric 1 is stretch mounted, glued or moulded to the front face of the solid porous absorber 3 and external face of frame 2, as referred on 11, 13 and 15.

[0084] Front fabric 1 is 100% made from polyester in warp knitting, (Fig 7b) and brushed in one side, allowing for a variety of colours and textures.

[0085] Front fabric 1 is stretch mounted, glued or moulded to frame 2 and to solid porous absorber 3. Foam absorbent panel 3 is surrounded by frame 2 and connects directly to Front fabric 1. The frame 2 operates as a structural element avoiding any distortion of the entire panel. Frame 2 can present multiple shapes, as exemplified on 6 or 16 or 17.

[0086] The solid porous absorber foam on component 3 is comprised of front surface 9 which may present several patterns of relief (Fig. 5a, Fig. 5b, Fig. 5c, Fig. 5d), and a rear surface 8. The rear surface of the solid porous absorber 3 may adopt several shapes including the ones represented in Figures 6a and 6b, resembling multiple trapezoidal shapes with a quadrangular wave cross-section.

[0087] Due to their symmetry, 2 foam absorbent panels 3 can be stacked perfectly, allowing for a smaller storage space as shown in figure 3a. Other similar shapes for the rear surface 8 of the solid porous absorber 3 can be applied, even if they do not allow for a perfect stacking, as shown in figures 3c.

[0088] Fig 9a shows a cross section of the solid porous absorber 3.

[0089] The rear surface 8, of the solid porous absorber 3, connects to a surface 27 through the minor bases of the trapezoidal shapes 18, thus creating air cavities 19 between surface 27 and the larger bases of the trapezoidal shapes. The air cavities 19 allow air pa rticles to flow, while maintaining substantial velocity. [0090] With the present disclosure, the variable depth rear air cavity which is created between the surface 8 and the wall surface 27 maximizes sound absorption by positioning a significant portion of the foam away from the wall 20 where absorption would be minimal.

[0091] The variable depth rear air cavity 22 shown in Fig. 9c, has a major impact on low frequency absorption. By using the sides 6 and 6' angled surface of the embodiment to attached corner wall surface 26. The exposed positioning has all parts of foam away from the wall 23 where absorption is improved for bigger wavelengths. At a quarter wavelength from the wall, pressure is zero, and air particle velocity is maximal. By placing the porous material, a quarter wavelength from the wall, it will have maximum absorption effect because the particle velocity is maximal.

[0092] This disclosure includes a 45^ and 315^ angle between front and rear surfaces 6 and 6' of solid porous absorber 3 on Fig. 2 allowing for a perfect fit solution for corners in any room. Chemical or mechanical fixing system can be applied to frame 2 in order to correctly attach the panel to the wall.

[0093] Furthermore, in each embodiment, the front surface 4 of fabric 1 facing the incident sound waves presents an acoustically transparent surface area that creates the sound absorption characteristics on that side. By using the basic principle from a Helmholtz resonator, a lumped mass of air is forced in and out of a vent or cavities in the front fabric 1. A sound wave striking the open end of the full solution will excite the resonant system, making the plug of air vibrate according to its length and radius and the stiffness provided by the compression of the enclosed volume.

[0094] On the wall-mounted system, represented by Fig. 9a the present disclosure creates the air cavity 19. By using an extra frame sealing all the sides of the series of adjacent panels, extra performance can be obtained by the effect of an airtight chamber. This effect can also be obtained by enclosing a series of panels in a wall-mounted system, as shown on Fig. 10a. The resulting airtight chamber 19 is represented on Fig 10b.

[0095] In both one and two-dimensional designs, this is most easily accomplished by trowelling a mastic on the wall surface to be covered and attaching the foam material. In this way, all foam sections, in contact with mounting surface, will be assured of being bonded to the surface. [0096] The sealed rear air cavity 19 and method of attachment may provide additional sound absorption in the low frequency ranges due to increased air flows from the high pressure exterior surface of the foam to the ambient lower pressure interior air cavity.

[0097] The pressure gradient is created by sound waves impinging on the mounting surface. Near the mounting surface, the particle velocity is low and the pressure is high. Since the wavelength of low frequency sound is larger, the foam material and mounting surface are in the high-pressure zone at low frequencies. Thus, by sealing the variable depth air cavity 19, sound must pass through the interstices of the foam to equalize the pressure imbalance caused by the sound, thus enhancing sound absorption.

[0098] As illustrated in the figure 11a and lib, a typical panel according to this disclosure includes a frame (2) which may be composed of lengths of timber suitably joined to form a rectangular or other desired shaped frame, with a triangular, square or rectangular cross section as referred by the references (7), (16) and (17). A board 1 which may vary in thickness is suitably attached to the front faces of the frame 2, as referred on 11, 13 and 15.

[0099] Board 1 is made from of rigid or semi-rigid materials, which can be covered with premium design materials like wood or decorative resin paper. Board 1 is attached to fra me 2 and to solid porous absorber 3. Foam absorbent panel 3 is surrounded by frame 2 and connects directly to board 1. The frame 2 operates as a structural element of board 1 avoiding any distortion of the entire panel. Frame 2 can present multiple shapes, as exemplified on 6 or 16 or 17.

[00100] Board 1 can exhibit multiple patterns of simple or elongated holes or drawings, as shown on figures 17a, 17b, 17c, 17d, 17e. The chosen perforated groove allows for tuning the panel to different sound frequencies. 2 or more boards 1, as shown on figure 17e, with a specific perforation design, joined together in any surface can convey the appearance of different 3D optical illusion patterns.

[00101] The solid porous absorber foam on component 3 is comprised of a rear surface 8 and a front flat surface 9. The rear surface of the solid porous absorber 3 may adopt several shapes including the ones represented in Figures 16a and 16b, resembling multiple trapezoidal shapes with a quadrangular wave cross-section.

[00102] Due to their symmetry, 2 foam absorbent panels 3 can be stacked perfectly, allowing for a smaller storage space as shown in figure 3a. Other similar shapes for the rear surface 8 of the solid porous absorber 3 can be applied, even if they do not allow for a perfect stacking, as shown in figures 13c.

[00103] Fig 18a shows a cross section of the solid porous absorber 3.

[00104] The rear surface 8, of the solid porous absorber 3, connects to a surface 27 through the minor bases of the trapezoidal shapes 18, thus creating air cavities 19 between surface 27 and the larger bases of the trapezoidal shapes.

[00105] The air cavities 19 allow air particles to flow, while maintaining substantial velocity.

[00106] With the present disclosure, the variable depth rear air cavity which is created between the surface 8 and the wall surface 27 maximizes sound absorption by positioning a significant portion of the foam away from the wall 20 where absorption would be minimal.

[00107] The variable depth rear air cavity 22 shown in Fig. 18b, has a major impact on low frequency absorption. By using the sides 6 and 6' angled surface of the embodiment to attached corner wall surface 26. The exposed positioning has all parts of foam away from the wall 23 where absorption is improved for bigger wavelengths. At a quarter wavelength from the wall, pressure is zero, and air particle velocity is maximal. By placing the porous material, a quarter wavelength from the wall, it will have maximum absorption effect because the particle velocity is maximal.

[00108] This disclosure includes a 45^ and 315^ angle between front and rear surfaces 6 and 6' of solid porous absorber 3 on Fig. 12 allowing for a perfect fit solution for corners in any room. Chemical or mechanical fixing system can be applied to frame (2) in order to correctly attach the panel to the wall.

[00109] Furthermore, in each embodiment, the front surface (4) of board 1 facing the incident sound waves presents a perforated or grooved surface area that create the sound absorption characteristics on that side. By using the basic principle from a Helmholtz resonator, a lumped mass of air is forced in and out of a vent or cavities, represented for any front panel at 17a, 17b, 17c, 17d, 17e. A sound wave striking the open end of the full solution will excite the resonant system, making the plug of air vibrate according to its length and radius and the stiffness provided by the compression of the enclosed volume.

[00110] On the wall-mounted system, represented by Fig. 18a the present disclosure creates the air cavity 19. By using an extra frame sealing all the sides of the series of adjacent panels, extra performance can be obtained by the effect of an airtight chamber. This effect can also be obtained by enclosing a series of panels in a wall-mounted system, as shown on Fig. 19a. The resulting airtight chamber 19 is represented on Fig 19b.

[00111] In both one and two-dimensional designs, this is most easily accomplished by troweling a mastic on the wall surface to be covered and attaching the foam material. In this way, all foam sections, in contact with mounting surface, will be assured of being bonded to the surface.

[00112] The sealed rear air cavity 19 and method of attachment may provide additional sound absorption in the low frequency ranges due to increased air flows from the high pressure exterior surface of the foam to the ambient lower pressure interior air cavity.

[00113] The pressure gradient is created by sound waves impinging on the mounting surface. Near the mounting surface, the particle velocity is low and the pressure is high. Since the wavelength of low frequency sound is larger, the foam material and mounting surface are in the high-pressure zone at low frequencies. Thus, by sealing the variable depth air cavity 19, sound must pass through the interstices of the foam to equalize the pressure imbalance caused by the sound, thus enhancing sound absorption.

[00114] The present disclosure includes an acoustically absorptive panel comprising:

a porous acoustic absorber defining an area of coverage over a planar surface and having a front surface and a non-planar rear surface,

a support frame,

an acoustically transparent front fabric affixed on said front surface of said porous acoustic absorber and said support frame

a chamber comprising a uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

[00115] In an embodiment, the front surface of said porous acoustic absorber panel is planar.

[00116] In an embodiment, the front surface of said porous acoustic absorber has a total surface area greater than said area of coverage.

[00117] In an embodiment, the front surface of said porous acoustic absorber has a cross- section resembling a half ellipse. [00118] In an embodiment, said front surface of said porous acoustic absorber has a cross- section resembling a sinusoidal wave.

[00119] In an embodiment, said front surface of said porous acoustic absorber has a cross- section generally resembling adjacent half-circles with constant or variable radius.

[00120] In an embodiment, said front surface of said porous acoustic absorber has a cross- section generally resembling a square wave.

[00121] In an embodiment, said front surface of said porous acoustic absorber has a cross- section generally resembling a triangular wave.

[00122] In an embodiment, said front surface of said porous acoustic absorber has a cross- section generally resembling a saw tooth wave.

[00123] In an embodiment, said front surface of said porous acoustic absorber has a cross- section having upwardly and downwardly angled portions with flattened upper and lower extremities.

[00124] In an embodiment, said front surface of said porous acoustic absorber has a cross- section resembling a pattern ascertained through calculation of a number theory sequence.

[00125] In an embodiment, said front surface of said porous acoustic absorber has a two- dimensional array of three-dimensional shapes thereon.

[00126] In an embodiment, each of said shapes comprises a parallelepiped.

[00127] In an embodiment, each of said shapes comprises a part-sphere.

[00128] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a fixing mechanism to said planar surface on which said panel is attached.

[00129] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a total surface area greater than said area of coverage. In an embodiment, said non-planar rear surface of said porous acoustic absorber angles with the said front surface of said porous acoustic absorber by a 45° angle on one end and by a 315 ° angle on the other end.

[00130] In an embodiment, said non-planar rear surfaces of said porous acoustic absorber have complementary surface configurations whereby two panels may be stacked upon one another.

[00131] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a square wave. [00132] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a square wave in a two-dimensional array of three dimensional shapes thereon.

[00133] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a sinusoidal wave.

[00134] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a triangular wave.

[00135] In an embodiment, said support frame is made from a rigid material, providing structural rigidity to said panel.

[00136] In an embodiment, said support frame has rectilinear frame segments.

[00137] In an embodiment, said frame structures form said support frame have a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber.

[00138] In an embodiment, said acoustically transparent front fabric is affixed on said front surface of said porous acoustic absorber and on side face of said support frame.

[00139] In an embodiment, said acoustically transparent front fabric is molded on said front surface of said porous acoustic absorber and on side face of said support frame.

[00140] In an embodiment, at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

[00141] It is also disclosed an acoustically absorptive panel comprising: a porous acoustic absorber defining an area of coverage over a planar surface and having a front surface and a non-planar rear surface, said non-planar rear surface having a total surface area greater than said area of coverage, said non-planar rear surface making with the said front surface a 45° angle on one end and a 315 ° angle on the other end, said non-planar rear surface having a fixing mechanism to said planar surface on which said panel is attached;

a support frame made from a rigid material, providing structural rigidity to said panel, said support frame having rectilinear frame structures, said rectilinear frame structures having a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber;

an acoustically transparent front fabric stretch mounted on said front surface of said porous acoustic absorber and on side face of said support frame;

at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a variable depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber acting as an acoustical absorbing chamber enhancing sound absorption.

[00142] It is disclosed an acoustically absorptive panel comprising:

a board made from a rigid or semi-rigid material, said board being juxtaposed to the said front surface of said porous acoustic absorber, said board being perforated by simple or elongated holes,

a support frame,

[00143] In an embodiment, said front surface of said porous acoustic absorber is planar.

[00144] In an embodiment, said board made from a rigid or semi-rigid material is perforated by simple or elongated holes in a pattern.

[00145] In an embodiment, said board made from a rigid or semi-rigid material is perforated by simple or elongated holes in a pattern which resembles a sound wave.

[00146] In an embodiment, said board made from a rigid or semi-rigid material has a pattern of relief.

[00147] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a total surface area greater than said area of coverage.

[00148] In an embodiment, said non-planar rear surfaces of said porous acoustic absorber have complementary surface configurations whereby two panels may be stacked upon one another.

[00149] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a square wave. [00150] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a square wave in a two-dimensional array of three dimensional shapes thereon.

[00151] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a sinusoidal wave.

[00152] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a cross-section generally resembling a triangular wave.

[00153] In an embodiment, said non-planar rear surface of said porous acoustic absorber has a fixing mechanism to said planar surface on which said panel is attached.

[00154] In an embodiment, said support frame is made from a rigid material, providing structural rigidity to said panel.

[00155] In an embodiment, said support frame has rectilinear frame segments.

[00156] In an embodiment, said frame structures form said support frame has a front face juxtaposed to the rear surface of said board made from a rigid or semi-rigid material and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber.

[00157] In an embodiment, at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

[00158] It is disclosed an acoustically absorptive panel comprising: a porous acoustic absorber defining an area of coverage over a planar surface and having a planar front surface and a non-planar rear surface, said non-planar rear surface having a total surface area greater than said area of coverage, said non-planar rear surface having a fixing mechanism to said planar surface on which said panel is attached, a support frame made from a rigid material, providing structural rigidity to said panel, said support frame having rectilinear frame structures, said rectilinear frame structures having a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber,

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes, at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a variable depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

[00159] It is disclosed an acoustically absorptive panel comprising:

a porous acoustic absorber defining an area of coverage over a planar surface and having a planar front surface and a non-planar rear surface, said non-planar rear surface having a total surface area greater than said area of coverage, said non-planar rear surface having a fixing mechanism to said planar surface on which said panel is attached,

a support frame made from a rigid material, providing structural rigidity to said panel, said support frame having rectilinear frame structures, said rectilinear frame structures having a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber,

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes in a pattern,

at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a variable depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

[00160] It is disclosed an acoustically absorptive panel comprising:

a porous acoustic absorber defining an area of coverage over a planar surface and having a planar front surface and a non-planar rear surface, said non-planar rear surface having a total surface area greater than said area of coverage, said non-planar rear surface having a fixing mechanism to said planar surface on which said panel is attached, a support frame made from a rigid material, providing structural rigidity to said panel, said support frame having rectilinear frame structures, said rectilinear frame structures having a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber,

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes in a pattern which resembles a sound wave,

[00161] It is disclosed an acoustically absorptive panel comprising:

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes, said board made from a rigid or semirigid material having a pattern of relief,

[00162] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.

Claims

C L A I M S

1. Acoustically absorptive panel comprising:

a porous acoustic absorber having a front surface and a non-planar rear surface;

a support frame within which said porous acoustic absorber is coupled;

an acoustically transparent front fabric affixed on said front surface of said porous acoustic absorber;

wherein the non-planar surface is configured such that, when the acoustically absorptive panel is attached to a planar attachment surface, a chamber comprising a uneven depth air cavity for enhancing sound absorption is defined between said non-planar rear surface and the planar attachment surface,

wherein said non-planar rear surface of said porous acoustic absorber has complementary surface configurations whereby such two acoustically absorptive panels may be stacked upon one another by coupling their respective rear surfaces.

2. Panel according to the previous claim wherein the front surface of said porous acoustic absorber panel is planar, has a cross-section of substantially a half ellipse, has a cross- section of substantially a sinusoidal wave, has a cross-section of substantially adjacent half- circles with constant or variable radius, has a cross-section of substantially a square wave, has a cross-section of substantially a triangular wave, has a cross-section of substantially a saw tooth wave, has a cross-section having upwardly and downwardly angled portions with flattened upper and lower extremities, or has a cross-section of substantially a pattern ascertained through calculation of a number sequence.

3. Panel according to claim 1 wherein said front surface of said porous acoustic absorber has a two-dimensional array of three-dimensional shapes thereon.

4. Panel according to claim 3, wherein each of said shapes comprises a parallelepiped or a part-sphere.

5. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has a fixing mechanism to said planar surface on which said panel is attached.

6. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has a total surface area greater than said area of coverage.

7. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber angles with the said front surface of said porous acoustic absorber by a 45° angle on one end and by a 315 ° angle on the other end.

8. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has a cross-section of substantially: a square wave, a square wave in a two-dimensional array of three dimensional shapes thereon, a sinusoidal wave, or a triangular wave.

9. Panel according to any of the previous claims, wherein said support frame is made from a rigid material, providing structural rigidity to said panel.

10. Panel according to any of the previous claims, wherein said support frame has rectilinear frame segments.

11. Panel according to any of the previous claims, wherein said frame structures form said support frame have a forward face and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber.

12. Panel according to any of the previous claims, wherein said acoustically transparent front fabric is affixed on said front surface of said porous acoustic absorber and on side face of said support frame.

13. Panel according to any of the previous claims, wherein said acoustically transparent front fabric is molded on said front surface of said porous acoustic absorber and on side face of said support frame.

14. Panel according to any of the previous claims, wherein at least one area of the said non- planar rear surface of said porous acoustic absorber defines a chamber comprising an uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

15. Acoustically absorptive panel comprising:

a support frame,

a chamber comprising an uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption,

wherein said board is directly attached to the support frame and to the porous acoustic absorber, the porous acoustic absorber being surrounded by the support frame.

16. Panel according to any of the previous claims, wherein said front surface of said porous acoustic absorber is planar.

17. Panel according to any of the previous claims, wherein said board made from a rigid or semi-rigid material is perforated by simple or elongated holes in a pattern.

18. Panel according to any of the previous claims, wherein said board made from a rigid or semi-rigid material is perforated by simple or elongated holes in a pattern which resembles a sound wave.

19. Panel according to any of the previous claims, wherein said board made from a rigid or semi-rigid material has a pattern of relief.

20. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has complementary surface configurations whereby such two acoustically absorptive panels may be stacked upon one another by coupling their respective rear surfaces.

21. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has a cross-section of substantially: a square wave, a square wave in a two-dimensional array of three dimensional shapes thereon, a sinusoidal wave, or a triangular wave.

22. Panel according to any of the previous claims, wherein said non-planar rear surface of said porous acoustic absorber has a fixing mechanism to said planar surface on which said panel is attached.

23. Panel according to any of the previous claims, wherein said support frame is made from a rigid material, providing structural rigidity to said panel.

24. Panel according to any of the previous claims, wherein said support frame has rectilinear frame segments.

25. Panel according to any of the previous claims, wherein said frame structures form said support frame has a front face juxtaposed to the rear surface of said board made from a rigid or semi-rigid material and an inner face juxtaposed to the said non-planar rear surface of said porous acoustic absorber.

26. Panel according to any of the previous claims, wherein at least one area of the said non- planar rear surface of said porous acoustic absorber defines a chamber comprising a uneven depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.

27. Acoustically absorptive panel comprising:

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes,

28. Acoustically absorptive panel comprising:

29. Acoustically absorptive panel comprising:

30. Acoustically absorptive panel comprising:

a board made from a rigid or semi-rigid material, said board made from a rigid or semi-rigid material being juxtaposed to the said front surface of said porous acoustic absorber, said board made from a rigid or semi-rigid material being perforated by simple or elongated holes, said board made from a rigid or semirigid material having a pattern of relief, at least one area of the said non-planar rear surface of said porous acoustic absorber defines a chamber comprising a variable depth air cavity bounded by the said non-planar rear surface of said porous acoustic absorber and said planar surface on which said panel is attached, said chamber enhancing sound absorption.