WO2015079289A1

WO2015079289A1 - A sound absorbing panel

Info

Publication number: WO2015079289A1
Application number: PCT/IB2013/060484
Authority: WO
Inventors: Jesper Nielsen
Original assignee: Kvadrat Soft Cells A/S
Priority date: 2013-11-28
Filing date: 2013-11-28
Publication date: 2015-06-04
Also published as: KR20160079023A; EP3080522B1; KR102044727B1; EP3080522A1

Abstract

The invention pertains to a panel (2) to be mounted on a surface inside a building, said panel (2) comprising: a substantially rigid frame (4), a front, cover (8) placed en said frame (4) and being configured to face away from said, surface, onto which the panel (2) is to be mounted; one or mere sound absorbing elements (10) placed within said frame (4) in such a way that, a first air gap (12) is formed between the one or mare sound absorbing elements (10) and the surface when the panel (2) is mounted on said surface, and a second air gap (14) is formed between the one or more sound absorbing elements (10) and the front cover (8), wherein the panel (2) further comprises a first air passage (18) between the first and second air gap (12, 14) and means for providing an airstream through said first air passage (18).

Description

A SOUND- ABSORBING PANEL

TECHNICAL FIELD

The present invention ert ins to panels thai can be used to cover interior surfaces in buildings,- for instance in auditoriums, open-plan offices, eta and more -specifically to such panels for use- in buildings with thermally activated building systems (TABS) in which balancing acoustics and thermal comfort is a ei!-recoanized challenge.

BACKGROUND OF THE INVENTION

in such fields as architecture and interior design there is often a need for panels -for covering of boundaries of a room, such as the ceiling, the walls-,- or partitions placed within the room. Such panels can serve purel aesthetic purposes, but can also be used to actively alter a room's characteristics, for instance relating to. acoustic and thermal properties of the room.

Panels used to determine the acoustic properties of a room often comprise a frame structure- supporting a plate of a sound-absorbing material,, such as mineral wool, gypsum or a thin wood membrane. Although such panels can offer quite- excellent solu- tions relating to acoustic regulation of rooms, the thermal properties ef such panels, such as their thermal transparency, are seldom optimal and may in fact be very far from, optimal. It is a problem with known panels simultaneously to optimize the acoustic properties and ti e thermal properties and hen.ce to use the- anels In an attempt to optimize the overall comfort of a room, l.n US 4330,048 a sound barrier panel is described. Said sound barrier is for isolating a noise source- of the type emanating from manufacturing areas for food. The sound barrier comprises a panel made of sound attenuating, material having a plurality of longitudinally extending side by side co-planar sections separated by V-shaped ribs -so as to define a plurality of longitudinally extending side- b side cavities. The canities are provided with acoustical absorptive material therein so h i the sound waves emanating from the nois sourc are first absorbed by the acoustical absorptive material and thereafter partly attenuated by the panel and partly deflected thereb so as to be absorbed again by the acoustical absorptiv material. The panel is preferably transpar- errt and portions of at least some cavities may be left free, of acoustical absorptive material so a to provide undisforted vision from one side of the panel to the opposite ssde thereof. The sound harrier is intended to foe disposed so that trie open faces of the cavities confront the noise source. Alternatively, the cavities are separated by fiat panel sections instead of V-shaped ribs, which sections am free of acoustics! absorptive material to provide und¼torted vision there through.

In US 2009/0178882 is: described another sound panel - a so called acoustic: panel ^■· and a method, is disclosed for an improved acoustic panel comprising a sound absorbing; member defined by a first and second face surface and a piuralrfy of peripheral edges. A sound blocking member is defined by a first and second face surface and a plurality of peripheral edges. The first face surface of the sound blocking member is secured relative to the second face surface of the sound absorbing member fo blocking the transmission of sound through it. in another, embodiment, the first face surface of the sound blocking member is spaced relative to the second face surface of the sound absorbing member for decoupling the sound blocking member from the sound absorbing member.

A -problem with the above mentioned panels is that the are thermally isolating as well as sound absorbing, which render them practically useless in building thermally activated building systems, wherein usually the ceiling is water cooled. in order to balance th acoustic and thermal comfort of a ^'building, especially one that is equipped with thermally .activated systems (TABS),, the applicant of the present application has in EP 2 444 581 suggested a sound dampening, but thermally transparent pane! comprising a substantially rigid frame, a front face and a rear face, one or more sound-absorbing elements, and sub-regions that acoustically connect the front face of the panel with the rear face of the panel, and in which sub-regions sound-absorbing elements are not present, whereby said sub-regions ensure thermal transmission through the panel, the panel comprising brackets that together with frame portions- provide receptacles for said sound-absorbing elements, wherein said- brackets corn- prise a central portion provided with apertures for providin access of a sound field to side faces of the sound-absorbing elements.

However, in many practical situations the above mentioned panel has proven to Impair the operation of the. TABS due to the thermall insulating properties -of the sound ab- sprbsng regions.. Hence, the applicant has realized a need to- improve said panel in order to provide art optimized balance between sound absorption and Interference with the .operation of TABS,

S SUMMARY Of THE INVENTION

it is thus an. object of the present invention to provide

According to the present invention, the above-mentioned and other objects are fulfilled by a panel to be mounted on a surface inside a^: building, said panel comprising:

10 a substantially rigid frame,

a front cover placed on said frame and being configured io face away from said su face onto which the panel is to be mounted,

one or more sound-abserfoing elements placed within said frame in such .a _. way that a first air gap is forhied between the on or more, sound absorbing elements and the I S surface when the panel is. mounted on said surface, and a second air gap is formed between the one or more sound absorbing elements and the front coven wherein the panel further comprises a first air passage between the first and second air gap and means for providing a airstream through said first air passage.

20 During use, t e: surface onto which the panel is mounted will: cool (or heat) the air in the first air gap down to substantially the same temperature as the surface itself, and by providing means for providing an airsiream through the first air passage, this coo! air will be transported to the second air gap and therefore coos the front cover (and the one or more sound absorbing elements). Hereby the front cover of the pane! will

25 achieve the same temperature as the surface {e.g. celling) onto which the panel is mounted. Therefore, the comfort experienced in a room wherein the inventive panel is mounted will^', not b impaired, because the temperature conditions tha exist on the^' surface onto which the panel is mounted are "rnovecf to the front cover of the panel. Hereby is thus achieved a sound absorbing panel, which is thermal iy transparent. This

30 is a tremendous advantage in buildings which are -employed with thermally activated building systems (TA8S), such as cooling of a ceiling. Hitherto, if has bee virtually impossible to provide satisfactory sound dampening Is such rooms due to the thermal insulating properties of conventional sound absorbing panels, which thereby has lead to less satisfactory: solutions, such as using carpets o the floors in order to at least

35 suppress ack-sc tter g of sound the floor,: In a preferred embodiment of the panel according to the invention, the one or ^'more sound absorbing elements are box shaped. Hereby is achieved a rather practical solution, especially suitable for building several panels . together to form one larger unit. In an embodiment of the panel according to. the invention, the sound absorbing elements are manufactured from mineral fibers such as glass or stone ool, but -could be made from melamine foam, .glass- textile,, cellulose (paper) based materials, ceramic substances or other porous materials. The sound absorbing elements could also be membrane or perforated materials, working as membrane, or resonance absorbers.

In a further preferred embodiment of the .panel according to the invention the dimensions of the one or more sound absorbing elements are chosen according to the lowest frequency at which substantial sound absorption shall take place, in a further preferred embodiment of the panel according to the invention the thickness of the one or more, .sound absorbing elements is in the range of 20 mm to 100 mm, which has proven to be especially good in absorbing uodesired noise and its reverberations in the audible frequency range. In a preferred embodiment of the- anel according to the invention, the front cover is a sheet of flexible material, e.g. woven textile material. Preferably, the front cover is ten- sioned rega dless of fo instance changes in the temperature -and humidity of the surrounding environment and aging effect of the front cover material itself. in a -further preferred embodiment of the panel according to: the invention, the front cover Is of a material or structure whic allows air to diffuse through it, whereby heat exchange between the surface onto which the panel is mounted and the surrounding environment is further enhanced due to exchange of heat through air transport. The frame of the panel^'- may in yet another embodiment further comprise an aperture in each of the ends of the frame that are furthest away from the first air passage between the irst and second air gap, said apertures being placed on said frame for allowing air to flow from the surroundings of the panel directly Into the -first air gap for compensation of .the ajr which diffuses out of the second air gap through the front cover.

Advantageously, the first air passage Is placed in the center of the panel. Preferably, the panel has an elongated shape with a longitudinal axis, which. Is longer than its transversal axis. The panel ma have any of the following: shapes: bo shaped, oval shaped or -elliptical shaped,

In a further preferred embodimen he panel further comprises a second and third add tional air passage between the- first and -second air gap,, each of said second and third air passages being placed at the respective, end of the pane! that is furthest away from the first air passage. Hereby a forced air circulation may be achieved, wherein air is forced through the first air passage from the first or second air gap, and further through the two second and third air passages towards the first air passage again. Hereby the flow of air would be forced to substantially travel along all th surface of the sound absorbing demerits, as well as the back, side of the front cover, whereby a very efficient cooling of the front cover (and one or more: sound absorbing elements) is achieved.

In a practical embodiment of the panel according to the invention, each of the second and third air passages are provided as a gap between the frame and the one or more sound absorbing elements. Hereby is ensured that the air will flow over substantially all of the inner side of the. front cover, whereby a more effective temperature exchange with, said front cover Is achieved.

In an alternative- -embo iment of the panel according to the Invention, the first air passage is placed adjacent to the frame of the panel, the panel further comprising, a se- oond ai passage between the first and second air gaps, said second air passage being provided adjacent to the part of the frame, which is furthest away from the first air passage.

I a: preferred embodiment of the panel, the frame completely surrounds the edges of the panel. He eby if is. possible to tension the front cover by its -attachment to the frame.

In s further preferred embodiment of the panel according to the Invention,, the first air gap, which is defined by the distance between the one or more sound absorbing -ele~ meets and the surface whe the panel is mounted on said surface, is 10 mm to 25 mm wide. In a further-preferred, embodiment of the pane! according; to the invention, the second air gap is-, which is defined by- the distance: between the. om or mom sound absorbing elements and the front cover, is 8 mm to 15 mm wide.

Preferably, the speed of the airsiream through the first air passage is adjusted, so that a m ni um of energy is used, stili achieving a temperature in the second air gap dose to that of the .-surface thai the pane! is mounted on. In a further preferred embodiment of the panel according to the invention, the means for providing the airstream through said first air passage is a fan placed- in or adjacent to the first air passage. Such a fan may be connected to the power grid in a normal .way, e.g. via a transformer .fcu^'iiiiht©- the panel A fan is low in energy consumption and ^•may be virtually silent, whereby the- sound environment of the- room In which the in- ventive panel i used is not impaired by the application of a fan as means for providing said airstream through the first air passage. A specially built fan. may be used or an off- the-shelf fan, such as those used for -cooling various parts of -a computer may be used. The fan may be configured to operate at a fixed, predefined, effect.

In a further preferred embodiment of the pane! according to the invention, the pane! comprises means (e.g. two temperature sensors) for monitoring the temperature difference between the air in the two air gaps. in a further preferred embodiment of the panel according to the invention, the panel further comprises two temperature sensors placed adjacent to or on the same side of the- one or more sound absorbing elements, at two different distances from t e -first air passage In the direction of flow of air, said temperature sensors being connected to a controller, which controller is operative!y connected to the fan. Hereby the- temperature difference between the two air gaps is monitored in a very praetieal way, because if the temperature of the front cover (and sound absorbing elements) and the surface has been evened out, then there will be substantially no difference ih the two 'measurements. The difference in the temperature measurements can therefore be used- to control the fan.

Hence, in a farther .embodiment, of the pane! according to- the invention, the controller is configured to compare th temperature measurements from the two temperature sensors and regulate the operation of the fan in dependence of th numerical value of said comparison.- Said comparison could e.g. be the calculation of a ratio.

However in a further -embodiment of the pane! according to the invention, said com- 5 parise is a calculation of the difference (e.g. the numerical difference! of the temperature measurements from the two temperature sensors, and wherein the fan is regulated in such a- wa that

- the .airstrea.ni. through the first air passage between the first and second air ga is increased if said difference is above a predefined threshold value, or

O - the airsfream through the first air passage between the first and second air gap is decreased if said difference is below said predefined threshold value,

In an alternative embodiment of the panel according to the invention, said comparison i a calculation of -the numerical difference of the temperature measurements from the S two temperature sensors, and wherein the fan is. regulated in such a way. that

- the fan is turned on or kepi on if said difference is above a predefined threshold value, or

- the fan is turned off or kept off if said difference is below said predefined threshold^ value.:

0

Hereby a power saving mode of operation is achieved, wherein the fan ^"is onl -operating- hen needed.

In a further preferred embodiment -of the panel according to the invention, the surface5 onto which the pan©! is to be mounted forms part of a thermally activated building system. Due to the forced airsfream between the first and second air gaps, the sound absorbing element will not functio as thermally- insulating, thereby making the panel according to the invention especially: suitable for being used in connection with TABS, e.g. a water cooled roof or ceiling.

0

In a further embodiment of the panel according to the invention, the surface onio which the panel Is to be mewted-fs a ceiling or a. wail.

In a further embodiment of the panel according to -the. invention, said controller is fur-5 thermare operatively connected to the thermally activated building system. BREJF. DESCRIPTION OF THE DRAWI GS

A further understanding of the nature and advantages of the present indention may be realized y reference to h remaining portions of the specification and- the drawings. In the following, preferred embodiments of the invention are explained in more detail with reference to the drawings, wherein

Fig. 1 shows an embodiment of a panel^' according to the invention,

Fig. 2 shows a cross section of the embodiment of the panel illustrated^' in- R0. 1 , ig , 3 shows a further embodiment of a panel-according to the invention,

Fig, 4 shows a further embodiment of a pane! according to the invention,

Fig; 5 shows a further embodiment of a panel according to the invention, and

Fig. 6 shows a cross section of a further -embodiment of a panel according to the

invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter wit reference to the- accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may., however, be embodied in different forms and should not be construed as limited to the - embodiments -set forth, herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and wi!i fully convey the scope of the invention to those skilled in the art. L ke reference numerals refer to ilke elements: throughout.. Like elements will, thus, not be described In detail with respect to the description of each figure.

Referring to Fig, i and 2, which show a panel 2 according: to the invention as seen from above (Fig. 1), and as seen from the side (Fig. 2), In Fig. 2, the panel .is mounted on a ceiling 6 inside a uilding. The illustrated panel 2 comprises a substantially rigid frame 4, a front- cove 8 placed on said frame 4 and being configured to face- away from said surface (e.g.. ceiling 8} onto which the panel 2 is to be- mounted. The panel 2 also -comprises a sound absorbing element 10_: placed within said frame- 4 in such a way that a first -air gap 12 is formed between the sound absorbing element 10. and the ceiling 8 when th panel 2 is mounted on said celling 8, and a second air gap 14 is formed between the sound absorbing element 10 and: the front cover 8. The illustrated panel further comprises a tan 16 placed in a first air passage 18 between the first air ga 12 and the second air gap 14, The fan 16 is. configured for providing an airstream through said first air passage 18. The fan 18 may be connected to the power grid in a norma! way e.g. via a transformer built into the panel 2. Sn the illustrated embodiment the frrst air passage 18 is placed in the center of the pane! 2.

The panei 2 shown In Fig. 1 and Fig. 2 further comprises a second and third additional air passage 20, 22 between the first and second air gap 12, 14, each of said second and third air passages 20, 22. being provided as a gap between the frame 4 and the absorbing elements 10, Hereby, a forced air circulation may be achieved, wherein a r is forced through the firs! air passage 18 from the first air gap 12, and further through the two second and third: air passages 20, 22 towards the first air passage 18 again as indicated by the arrows. Hereby, the flow of air would be forced to substantially travel along ail the surface of the sound absorbing element 10 as well as the back side of the front cover 8, whereby a very efficient cooling of the front cover 8 (and sound absorb- ing eiement 10) is achieved if the ceiling 6 is cooled by for example a TABS, By placing the second and third air passages 20, 22 as a gap between the frame 4 and sound absorbing element 10 at the. ends of the pane! 2 that are. furthest away from the first air passage 1:8, it is ensured that the air wili flow over substantially all of the inner side of th front cover 8„ whereby a more effective temperature exchange with said front cover 8 is achieved

During se, the ceiling © will cool the air in the first air gap 12 down to substantially the Sams- temperature as the ceil ing 8 .itself, and by providing a fan 16 for providing airstream through the first air passage 18, this cool air will be transported to the se- eond air ga 14 and therefore cool the front cover 8 (and the sound absorbing eiement 10}_> Hereby the front cover 8 of the panel 2 will; achieve the same temperature as the ceiling S, onto which the panel 2 m mounted. Therefore, the comfort experienced id a room wherein the inventive panel .2 is mounted will not be impaired, because the temperature .conditions,- which ^'exist on the surface (ceiling 6) onto which the panel 2 is mounted, are "moved" to the front cover S of the panel 2, Hereby is therefore achieved a sound absorbing panel 2, which Is thermally transparent. This is a tremendous advantage in. buildings thai are employed with thermally activated building systems (TABS), -such as cooling of a ceiling 6. Hitherto, it has been virtually impossible to provide satisfactor sound dampening in such rooms due. to the thermal Insulating prop- erties of conventional sound absorbing panels, which thereb has lead to less satis- factory solutions, such as using carpets on the floors in order to at least suppress back-scattering of sound the floor.

The front cover 8 is a sheet of flexible material, e.g. woven textile, material. Preferably, the front caver 8 is tensioned regardless of for instance changes in the; temperature and humidity of the surrounding environment and aging effect of the front cover -material Itself. The frame 4 completely surrounds the edges of the pane! 2. Hereby it is possible to tension the front cover 8 by it attachment to the frame 4. The illustrated sound absorbing element 10 is substantially box shaped, Hereby ^'is achieved a rather practical solution,, especially suitable for building several panels £ together to^" form one larger unit The sound absorbing element 10 is preferably manufactured from mineral fibers such as glass or stone wool, but could be made from raeiarnine foam.,, glass textile, cellulose (paper) based . materials, ceramic substances or other porous materials. The sound absorbing elements could also be membranes or perforated materials, working as membrane or resonance absorbers. The thickness of the sound absorbing element 10 is- preferably in the range of 20 mm to 100 mm, which has proven, to- be especially good in absorbing noise and reverberations in the frequency range of 300 Hz to 3500 Hz.

In ihe illustrated embodiment; the first ai gap 12, which is defined by the distance between the sound absorbing element 10 and the ceiling- 6, is approximately 10 mm to 25 mm wide, the secon air ga 14, which is defined by the distance between he sound absorbing element 10 and the front 8 cover, is 8 mm to 15 mm wide,

Preferably, the speed of the airstrea.m throug the first air passage 18 is adjusted, so that a minimum of energy is used, still achieving a temperature in_. the second air gap close to that of the su face that the pane! is mounted on.. Fig. 3 shows another embodiment of a panel 2 according to the invention:. The illustrated panel 2 comprises two temperature sensors 24, 26 for monitoring the temperature differenc between the air in the two air gaps 12 and 14. The two temperature sensors 24, 26 are placed on the same side, of the sound absorbing element 10 at two different distances- from th first ai passag 18 in the direction of flow of air (as iUus- trated by the arrows). The temperature sensors 24, 26 are connected to a controller 28, which controller 28 is operatively connected to the fan 16. Hereby the temperature difference between the two air gaps 12, 14 is monitored^" in a very practical way, because, if the temperature of t e front cave 8 and the eeliing 6 has been evened out then there n be substantially no differe ce in the two measurements, the difference in the temperature measurements can therefore be used to^••control the fan 16.

In one embodiment of. the .pane! 2 -according to the invention, the controller 28 calculates the difference {e.g. the numerical: difference) of the temperature measurements from the two temperature sensors 24, 26, and regulates the fan 16 in such a way thai

- the airsiream through the first air passage 18 betw e the first and second air gap 12, 1 is increased f said difference is above a predefined threshold value, or

- the alfsfrearn through the first air passage I S between the first and second air gap 12, 14 is decreased I said difference is below said predefined threshold value.

In another -embodiment of the panel 2 according to the invention, the controller .28 calsuiafes the difference (e.g. the numerical difference} of the temperature measurements from the two temperatur sensors 24, 28, and controls the fan 18 in- such a way that

- the fan. 16 is turned on or kept on if said difference is above a predefined threshold value, or

- the fan 16 is turned off or kept off if said difference. Is below said predefined threshold

Hereby a power saving mode of operation is achieved, wherein the fan 16 is only operating: when needed.

In a further embodiment of the pane! Z. according to the invention, said control ier may be operativeiy connected to a thermally activated building system.

Fig. 4 shows an alternativ embodiment; of a panel 2 according to the inventio having an elliptical shape.

F|g., 5 shows yet another alternative embodiment of the invention,, wherein the first air passage 18 Is placed: adjacent to the frame 4 of the panel, and wherein the panel 2 only further comprises a second air passage; 30 between, th first and second air gaps, 1 , 14, said second air passage 30 being provided adjacent the part of the frame 4 that. is furthest away from the first ir passage 18. Fig. -6 shows a cross section of another embodimen of a panel 2 mounted on a ceiling 6.. The illustrated panel 2 is substantially simitar to the panel 2 illustrated in arty of the Figures 1-3. Hence, only the differences will be described. In the illustrated panel 2, the- front cover 8 is of a material or structure- that allows air to diffuse through it, as indicated by the arrows -going through the front cover 8, -whereby he t exchange between the ceiling 8 onto which the panel 2 Is mounted a d the surrounding environment is further enhanced due to exchange of heat through air transport The frame 4 of the illustrated pa el 2 further comprises an aperture 32 in each of the ends of the frame 4 that are furthest away from the first air passage 18 between the first air gap 12 and second air gap 14. These apertures 32 are placed in such a way on the frame 4 that air is allowed to flow from the surroundings of the panel 2 directly into the first air gap- 12 for compensation of the air that diffuses out of the second air gap 14 through the front cover 8.

Test results

A panel -according, to the embodiment illustrated in Fig. 1 has been tested and compared with a panel without a fan in order to assess the thermal conductivity properties in connection with a TAB celling. The tests were perforrned by the independent Ger- man- company HLR Stuttgart GmbH. The tests showed that the acoustical elements reduced the heat, transport through the- panel by 41% if no fan was present. If however a fan, ype CMP-Fan 25, from the producer onig Electronic, Diameter 12 mm, was used as shown in e.g. Fig. 1 and 2, the heat transport was onl reduced by 10%, thereby making the panel according to the Invention virtually thermally transparent.

LIST OF REFERENCE NUMBERS

In the .foi Sowing Is given a list of reference numbers that are used In the detailed description of the invention. panel,

4 frame,

e ceiling,

8 front cover,

10 acoustic element,

12 first air gap,

1 second air gap.

18 fan.

18 first air passage,

20, 30 second air passage,

22 third air passage,

24, 26 temperature sensors,

28 controller and

32 apertures in the frame

Claims

1. A panel (2) to be mounted on a surface inside a building, said _:panei. (2) comprising: a substantially rigid frame (4)

a front caver (8) placed on said frame (4 and being configured to face away from said surface onto which the panel (2) is to be mounted

one or more sound absorbing elements (10) placed within said frame (4> i such way that a first air gap {12} is formed between the on or more sound absorbing elements (10) and the surface when the panel (2) is mounted on said surface, arid a second ai gap (14) is formed between the one or more sound absorbing elements (10) and the front cover (8), wherein the panel (2) further comprises & first air passage (18) between the first and second air gap {12, 14) and means for providing an: airstream through said first air passage (18). 2. The panel (2). ccording to claim 1 _t wherein said one or more sound absorbing elements (10) ar box-shaped.

3. The panel (2) according to claim 1 or 2. wherein the. sound absorbing elements (10) are manufactured from any of the following materials: mineral fibers such as glass or stone wool, meiamJne foam, glass textile, cellulose based materials, ceramic substances, membranes: or perforated materials, working as membrane or resonance absorbers,

4. The pane! (2) according to claim 1 ,_. 2 or 3, wherein the dimensions of the one or more sound absorbing elements (10) are chose according: to the. lowest frequency at which substantial sound absorption shall fake place,

5. The panel (2) according to claim 4, wherei the thickness of the one or more sound absorbing elements (t0) is in the range of 20 mm to 100 mm, whereby noise in the audible frequency range are substantially absorbed.

6. The pane! (2) according to: any of the preceding claims, wherein the front cover (8) is a sheet of flexible materia!, e.g.. woven textile material. 7. The panel (2) according to any of the preceding claims, wherein the front cover .(8) is: of a material^' or structure that allows air to diffuse through, it.

8. The panel (2) according to claim 7, further comprising an aperture (32) In- each of the ends of the frame (4) that are furthest away from the first air passage (18} between the first and second air gap (12, 14), said apertures (32) being placed on said frame (4) for allowing; air to f ow from the surroundings of the anel (2) directly Info the first air gap (12 for compensation; of the sir that diffuses out of the; second air gap (14) through the front cover (8).

9. The panel (2) according to any of the preceding claims, wherein the first air passage (18) is placed in the center of the panel (2).

10. The panel (2) according to any of the preceding claims, wherein the panel (2) has. an elongated shape, with a longitudinal axis_:. which Is longer than its transversa! axis, 11 . The panel (2) according to claim. 10,. having any of the following shapes: _.box shaped, oval shaped or elliptical shaped,

12. The panel (2) according to claim¹ 10 or further comprising second and third additional air passage (20, 22) between the first and second air gap (12, 14), each- of said Second and third air passages (20, 22) being placed at the respective end of the panel ;(2), which is furthest away from the first air passage (1.8).

13. The panel (2) according to claim 12, wherein eac of the second and third air passages (2-0, 22) is provided as a gap between the frame (4) and the one or more sound absorbing elements ( 0).

14. The panel (2) according to any of the claims 1-7, wherein the first air passage (18) is placed adjacent the frame (4): of the panel (2), the panel (2) further comprising a second air passage (30) between the first and second air gaps (12, 14), said second air passage (30) bein provided adjacent the part, of the- frame (4) which is furthest away from the first air passage. (I B).

15, The panel (2) according to. any of the preceding claims,, wherein the frame (4) completely surrounds the edges of the panel (2).

18. The panel (2) according to any of the preceding claims,, wherein the first air gap ^'{12), whic is defined by the distance between the one or more sound absorbing eleents (10) and the surface when the pane! (2) is mounted on said surface, is 1 mm to 25 mm wide.

17. The panel (2) according to my of the preceding claims, wherein the second air gap (14), which is defined by the distance between ti e one or more sound -absorbing elements (10) ami the front cover (8}, Is 8 mm to 15 mm wide. 18, The panel (2) according to any of th preceding- claims, wherein the speed of the alrstrea through the first air passage (18} is adjusted, so that a minimum of energy is used, still achieving a temperature in the second air gap close to that of the surface that the panel is mounted on, 19. The panel {2} according to any of the preceding claims, wherein the means for providing the airstream through said first air passage is a fan (16) placed in, or adjacent to, the first air passage (I S).

20. The panel (2) according to claim 19, wherein the fan (16) is configured to operate at a fixed, predefined, effect.

21. The panel (2) according to claim 19, wherein the panel (2)- further comprises two temperature sensors (24, 26) placed adjacent to, -or on, the same side of the one or more sound absorbing elements (10), at two different distances from the first air pas- sage (18) in the direction of flow, of air, said temperature sensors (24, 26) being connected to a controller (28), which controller (28) is operative^; connected to the fan (16),

22. The panel (2) according to claim 21, wherein the controller (28) is configured to compare the temperature measurements from the two temperature sensors (20, 22} and regulate the operation -of the fan (18) in dependence of the numerical value of said comparison,

23. Th panel (2) according to claim 22, wheresn said compariso is a calculation of the numerical difierence of the temperature measurernenis from the two temperature sensors (24, 26), and wherein the. fan (18)^' is- egulated^' i -such a way that - the. airstraarn through the first air passage (18) between the first^' and second air gap (12, 14} is increased if said difference is above a predefined threshold value, or

- the airstream through the first air passage (18) between the first and second air gap (12, 14} ¼ decreased; if said difference is below said predefined threshold value.

24. The panel (2) according: to claim 22, wherein said comparison is a calculation of the numerical difference of the temperature measurements from the two temperature sensors (24, 28), and wherein the fan (18) is regulated in such a way that

- the fan (16) is turned on or kept on if said difference is- above predefine threshold value, or

^■- the fan (16) is turned off er kept off if said difference is below safe! predefined threshold v lue.

25. The pane! (2) according to -any of the preceding claims,, wherein the surface onto which the panel is to- be mounted forms part of a thermally activated building system .

26. The panel (2) according to any of the preceding cl ims, wherein the surface onto which the pane! is to foe. mounted. is a- -ceiling (6) or a wall, 27. The panel (2) according to claim 2¾ when dependent on any of the claims 21-25,_. wherein said controller -^'(26) is furthermore operaiiveiy connected to the thermally activated building system.