FI128690B - A sound attenuator, an arrangement and a method for attenuating noise transmission along a ventilating duct - Google Patents

Abstract

The invention relates to a sound attenuator for attenuating noise transmission along a ventilating duct (2). The sound attenuator (1) comprising a sound attenuating member (3) and a fastening part (4). The sound attenuating member (3) is plate-shaped comprising a lower edge part (6) and an upper edge part (7), and the lower edge part (6) is attached to the fastening part (4) such that the sound attenuating member (3) protrudes outwards from the fastening part (4), and when the sound attenuator (1) is in an installed position inside the ventilating duct (2) the sound attenuating member (3) is parallel with the ventilating duct (2) and the fastening part (4) covers the installing opening (8) of the sound attenuator (1) in the ventilating duct (2), and the ventilating duct (2) surrounding the sound attenuator (1) forms the support structure to the sound attenuator (1). The invention relates also to an arrangement and a method for attenuating noise transmission along a ventilating duct.

Description

A SOUND ATTENUATOR, AN ARRANGEMENT AND A METHOD FOR ATTENUATING NOISE TRANSMISSION ALONG A VENTILATING DUCT FIELD OF THE INVENTION

[0001] The invention relates to a sound attenuator, an arrangement and a method for attenuating noise transmission along a ventilating duct, and par- ticularly to attenuating airborne noise transmission.

BACKGROUND OF THE INVENTION

[0002] Noise and vibration control in buildings is essential as noise lev- els affect hearing, concentration and productivity when working in an office build- ingorin a factory. The noise generated inside a building comprises airborne noises and structure-borne noises. The airborne noise travels typically through windows and doors and/or is transmitted through ventilation pipe systems. The problem with office buildings, hotels and residential buildings is the transmission of air- borne noise from one room to another room through ventilation pipe systems. Ex- amples of airborne noises are people carrying on a conversation or radio.

[0003] It is known to use separate silencers attached between two parts of pipes. The fitting of a silencer between pipes is time consuming. As the whole airflow flows through the silencer containing sound absorbing filling the si- lencer is greater in size than the pipes it connects. Both the inner and outer diame- tersofthesilencer are bigger than the corresponding diameters in the pipes. There- fore, the silencers set restrictions to the space utilization and they may need a sep- arate encapsulating or even a dropped ceiling. There is a need for a compact sound attenuator, which is space saving and easy to install.

[0004] A previously known silencer is disclosed in WO 2011/141639 < 25 Al and a ventilation duct component with a hatch for accessing an inside of the N ventilation duct is previously known from WO 88/03244A1, for instance.

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N BRIEF DESCRIPTION OF THE INVENTION I [0005] An object of the present invention is to provide a sound attenu- - ator, an arrangement and a method to overcome the above problems. The objects 3 30 of the invention are achieved by a sound attenuator, an arrangement and a method & which are characterized by what is stated in the independent claims 1, 11 and 15. > The preferred embodiments of the invention are disclosed in the dependent claims.

[0006] The invention is based on the idea of a sound attenuator for at-

tenuating noise transmission along a ventilating duct. The sound attenuator com- prising a sound attenuating member and a fastening part. The sound attenuating member is plate-shaped comprising a lower edge part and an upper edge part, and the lower edge partis attached to the fastening part such that the sound attenuat- ing member protrudes outwards from the fastening part. When the sound attenu- ator is in an installed position inside the ventilating duct the sound attenuating member is parallel with the ventilating duct and the fastening part covers the in- stalling opening of the sound attenuator in the ventilating duct, and the ventilating duct surrounding the sound attenuator forms the support structure to the sound attenuator.

[0007] Another aspect of the invention is an arrangement for attenuat- ing noise transmission along a ventilating main duct, the arrangement comprising the sound attenuator. The ventilating main duct comprises a branch duct. The sound attenuator is positioned parallel with the ventilating duct. The sound atten- — uator is positioned in front of the opening of the branch duct at a distance apart, and the length of the sound attenuating member in the longitudinal direction of the sound attenuator exceeds the diameter of the opening. The sound attenuating member extends to the inner surface of the uppermost part of the ventilating main duct.

[0008] Another aspect of the invention is a method for attenuating noise transmission along a ventilating main duct and in the method the ventilating main duct comprises a branch duct. A plate-shaped sound attenuator is inserted inside the ventilating main duct, the sound attenuator is positioned parallel with the ventilating main duct to allow fluid flowing along the ventilating main duct to flow between the outer surface of the sound attenuator and the inner surface of the o main duct on both sides of the sound attenuator and locating the sound attenuator AN in front of the opening of the branch duct at a distance apart, and the sound atten- > uator extends from the inner surface of the lowermost part to the inner surface of = the uppermost part of the ventilating main duct. N 30 [0009] An advantage of the sound attenuator, the arrangement and the E method for attenuating noise transmission along a ventilating duct is that the < sound attenuator is compact and the arrangement is space saving and easy to in- 3 stall. | BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figure 1 shows a side view of a sound attenuator; Figure 2 shows a front view of a sound attenuator; Figures 3a) and 3b) show a front view of a sound attenuator; Figure 4 shows a top view of a sound attenuating member; Figure 5 shows a top view of an arrangement for attenuating noise transmission along a ventilating main duct; Figure 6 shows a top view of an arrangement for attenuating noise — transmission along a ventilating main duct; Figure 7 shows a front view of the arrangement for attenuating noise transmission shown in Figure 6; Figure 8 shows a top view of an arrangement for attenuating noise transmission along a ventilating main duct.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Figure 1a side view of a sound attenuator. The sound attenuator 1 attenuates noise transmission along a ventilating duct 2. The sound attenuator 1 comprises a sound attenuating member 3 and a fastening part 4. The sound atten- — uating member 3 comprises sound absorbing material 5. The sound absorbing ma- terial 5 preferably forms an unbroken attenuating plate. The sound attenuating member 3 is plate-shaped comprising a lower edge part 6 and an upper edge part 7 and the lower edge part 6 is attached to the fastening part 4 such that the sound attenuating member 3 protrudes outwards from the fastening part 4. When the sound attenuator 1 is in an installed position inside the ventilating duct 2 the sound N attenuating member 3 is parallel with the ventilating duct 2 and the fastening part N 4 covers the installing opening 8 of the sound attenuator 1 in the ventilating duct S 2. The ventilating duct 2 surrounding the sound attenuator 1 forms the support N structure to the sound attenuator 1. E 30 [0012] The lower edge part 6 is attached to the fastening part 4 by s means of welding, soldering, gluing or using screws or rivets. | | x [0013] In Figure 1 is presented a fastening part 4 for a circular ventilat- © ing duct, where the fastening part 4 comprises a shape of a circular arc. For a rec- N tangular ventilating duct the shape of the fastening part 4 is flat. The shape of the sound attenuating member 3 is rectangular in Figures.

[0014] In an embodiment, the corners of the upper egde part 7 of the sound attenuating member 3 are chamfered to easier the installation through the installation opening.

[0015] In an embodiment, the fastening part 4 comprises a sealing 9 to seal the connection between the installing opening 8 of the ventilating duct 2 and the fastening part 4. The sealing 9 surrounding the fastening part 4 is shown in Figures 2 and 3a)-b).

[0016] In an embodiment, the fastening part 4 comprises means for forming a releasable connection between the fastening part 4 and the ventilating duct 2.

[0017] In an embodiment, the fastening part 4 comprises an access door into the ventilating duct 2. Figure 1 shows a handle 10 attached to the fas- tening part 4 to its outer surface forming part of the outer surface of the ventilating duct 2 when installed.

[0018] In an embodiment, the access door is subsequently installable on circular or rectangular ventilating duct 2. The subsequent installation can be made by providing an installation opening 8 into the ventilating duct 2 where the size of the opening 8 corresponds the size of the fastening part 4 forming the access door into the ventilating duct 2.

[0019] In an embodiment, a length of the sound attenuating member L1 comprises substantially a length of the fastening part L2 or less in the longitudinal direction x of the sound attenuator 3. The dimensioning of the sound attenuating member 3 to correspond the size on the installation opening 8 allows a faster in- stallation as itis not needed to pivot the sound attenuator 3 during the installation.

[0020] In an embodiment, the upper edge part 7 comprises resilient re- o silient material 11. An example of a resilient material 11 is aresilient sealant tape, AN which is attached to the upper surface of the upper edge part 7. A resilient material > 11 may also be provided inside the ventilating duct 2 attached to the inner surface = of the uppermost part of the ventilating duct 2. It is also possible to provide the N 30 resilient material 11 both in the sound attenuating member 3 and in the ventilating E duct 2. The resilient material 11 (shown in Figure 1, for instance) provides flexibil- < ity to the sound attenuating member 3 thus allowing a quick installation. The resil- = ient material 11 also acts as an attachment member 12 between the upper edge = part 7 of the sound attenuating member 3 and the ventilating duct 2 providing a N 35 — close-fitting connection.

[0021] In an embodiment the upper edge part 7 comprises an attach- ment member 12 for connecting the sound attenuating member 3 with an inner surface of the ventilating duct 2. The attachment member 12 is a resilient member, a resilient sealant tape, a magnet, a sealing or a friction surface, for instance. The 5 attachment member 12 prevents the movement of the upper egde part 7 of the sound attenuating member 3 in the radial and in the length direction of the venti- lating duct 2.

[0022] In the embodiments shown in Figures 3a) and 3b) the upper edge part 7 comprises an extension part 13 providing a support surface for the at- tachment member 12, and the support surface is wider than the thickness s of the sound attenuating member 3. In Figure 3a) the extension part comprises 13 sound absorbing material 5. In Figure 3b) the extension part 13 comprises same material as a stiffening frame structure 14 of the sound attenuating member 3, e.g. plastics, sheet metal or aluminium. The upper part of the extension part 13 is folded to form a substantially horizontal support surface for the attachment member 12. In the Figures 3a) and 3b) the attachment member 12, e.g. a resilient sealant tape, is placed onto the support surface. The attachment member 12 may also be attached to the inner surface of the ventilating duct 2.

[0023] Figure 4 shows a top view of a sound attenuating member 3. The sound attenuating member 3 comprises a stiffening frame structure 14. The stiff- ening frame structure 14 comprises a frame plate 15 and sound absorbing material 5 is attached to both sides of the frame plate 15. The sound absorbing material 5 may ne planar, comprise dents or conical parts. The sound absorbing material 5 preferably forms an attenuating plate which is quick and easy to install to the stiff- ening frame structure 14. o [0024] In a further embodiment, in Figure 4 the ends of the frame plate AN are forming the side edges 16 of the sound attenuating member 3. The frame plate > 15 comprises a wedge-shape, e.g. diamond shape, at the side edges 16 of the sound = attenuating member 3. In an installed position the side edges 16 of the sound at- N 30 — tenuating member 3 are in upright position in the ventilating duct 2 and the air E flow inside the ventilating duct hits the side edge 16 of the sound attenuating mem- < ber 3. The air flow is denoted with arrows in Figure 4. The wedge-shaped side = edges 16, e.g. diamond-shaped, act as air deflectors. = [0025] In an embodiment a ventilating duct element comprises the N 35 sound attenuator 1 installed into it.

[0026] Figure 5 shows a top view of an arrangement for attenuating noise transmission along a ventilating main duct 2. The arrangement comprises the sound attenuator 1 described and shown in Figures 1-4. The ventilating duct 2 comprises at least one branch duct 17. At the location of the opening of the branch duct 18 the air flowing in the ventilating duct 2 is divided into two parts, one part flows along the ventilating duct 2 and another part flows along the branch duct 17. The air flow is denoted with arrows in Figure 5. The sound attenuator 1 is posi- tioned parallel with the ventilating duct 2. The plate-shaped sound attenuating member 1 is positioned such that the lower edge 6 and upper edge 7 are parallel with the axial axis of the ventilating duct 2. The fastening part 4 of the sound atten- uator 3 is connected with a releasable connection to the ventilating duct 2. The ven- tilating duct 2 surrounding the sound attenuator 1 forms the support structure to the sound attenuator 1.

[0027] The sound attenuator 1 is positioned in front of the opening of the branch duct 18 at a distance apart. The sound attenuating member 3 of the sound attenuator 1 is crosswise in front of the opening of the branch duct 18, and the sound absorbing material 5, e.g. the attenuation plate, faces the opening of the branch duct 18. The length Li of the sound attenuating member 3 in the longitudi- nal direction x of the sound attenuator 1 exceeds the diameter of the opening of the branch duct 18. The sound attenuating member 3 extends from the fastening part 4 to the inner surface of the uppermost part of the ventilating duct 2. The sound attenuator 1 forms a partition wall into the ventilating duct 2 at a location where the ventilation duct 2 branches.

[0028] The sound attenuator 1 attenuates airborne noise transmission from one room to another room along a ventilating duct 2 where the one and the another rooms have a connection with each other through branch ducts 17 of the o ventilating duct 2 extending to the one and the another rooms. Examples of air- O borne noises are people carrying on a conversation or radio. The arrangement for > attenuating noise transmission along a ventilating main duct is advantageous in = office buildings, hotels and residential buildings comprising a plurality of rooms N 30 connected to a ventilating duct 2 through a plurality of branch ducts 17. At least E part of the office rooms of an office building, guest rooms of a hotel and rooms in < an apartment of a residential building are connected to a ventilating duct, e.g. main = ventilating duct, through a plurality of branch ducts. The arrangement is advanta- = geous in absorbing voice. N 35 [0029] The size of the sound attenuator 1 does not exceed the inner dimensions of the ventilation duct 2 where it is used. Thus, it does not effect on space utilization and does not need a separate encapsulating or a dropped ceiling.

[0030] The ventilating duct 2 can be the main duct supplying air to in- terior spaces as shown in Figure 5 or the ventilating duct can be the main duct ex- tracting air from interior spaces. In case of the main duct is extracting air then the air flow direction in Figure 5 is from the branch duct into the ventilating main duct and the air flows join in the ventilating main duct. The air flow in the ducts and branches is created my means of a mechanical ventilation, i.e. forced ventilation, comprising air handling units, for example. The size of a branch duct and a venti- lating main duct may be equal, or the branch duct may be smaller in size.

[0031] In an embodiment, the length L; of the sound attenuating mem- ber 3 in the longitudinal direction x of the sound attenuator 1 comprises the branch duct 17 inner diameter multiplied by 1,1 ... 2.

[0032] In the embodiments presented in Figures 6-8, the ventilating duct 2 comprises two branch ducts 17, and the arrangement attenuates airborne — noise transmission from a first branch to a second branch along the ventilating duct

2.

[0033] Figure 6 shows a top view of an arrangement for attenuating noise transmission along a ventilating duct 2. In the embodiment the two branch ducts 17 are located on the opposite sides of the ventilating duct 2. The openings of the two branch ducts 18 are substantially facing each other and the sound atten- uator 1 is positioned between the openings of the branch ducts 18. The sound at- tenuator 1 is preferably installed in the middle axis of the ventilating duct 2 to form substantially similar flow channels on both sides of it.

[0034] Figure 7 shows a front view of the arrangement for attenuating — noise transmission shown in Figure 6. The sound attenuator 1 is located in the mid- o dle axis of the ventilating duct 2 in the longitudinal direction x. The sound attenua- AN tor 1 extends between the inner surface of the lowermost part the ventilating duct > 2 and the inner surface of the uppermost part of the ventilating duct 2 dividing the = ventilating duct 2 locally into two flow channels 19. The locally formed flow chan- N 30 nels 19 provide a flow path for the air flow, and the flow path is free from the sound E attenuator 1 in the flow direction, i.e. free from sound absorbing material 5. The air < flowing in the flow channels 19 in longitudinal direction x of the ventilating duct 2 = passes by the sound attenuator 1 without passing through the sound attenuator 1. = [0035] Figure 8 shows a top view of an arrangement for attenuating N 35 noise transmission along a ventilating duct 2. In the embodiment the branch ducts 17 are arranged seguentially. The branch ducts 17 are located on the opposite sides of the ventilating duct 2 at a distance apart from each other in a longitudinal direction x of the ventilating duct, 2 and the sound attenuator 1 is positioned in front of each branch duct opening 18. In Figure 8 the sound attenuators 1 attenuate noise entering to the ventilating duct 2 from the branch ducts 17 which noise would otherwise be transmitted along the ventilating duct 2.

[0036] The arrangement for attenuating noise transmission along a ventilating main duct can comprise a ventilating duct comprising one or more ar- rangements shown in Figures 6-8 and any combination of these.

[0037] In a method for attenuating noise transmission along a ventilat- ingduct2 the ventilating duct 2 comprises a branch duct 17. A plate-shaped shaped sound attenuator 1 is inserted inside the ventilating duct 2. The sound attenuator 1 is positioned parallel with the ventilating duct 2 to allow fluid, e.g. air, flowing along the ventilating duct 2 to flow between the outer surface of the sound attenu- ator 1 and the inner surface of the ventilating duct 2 on both sides of the sound attenuator 1 and locating the sound attenuator 1 in front of the opening of the branch duct 18 at a distance apart, and extending the sound attenuator 1 from the inner surface of the lowermost part to the inner surface of the uppermost part of the ventilating duct 2.

[0038] In an embodiment of the method for attenuating noise transmis- — sion along a ventilating duct 2 the sound attenuator 1 is positioned such that the fluid, e.g. air, flowing along the ventilating duct 2 flows substantially unobstructed between the outer surface of the sound attenuator 1 and the inner surface of the ventilating duct 2 on both sides of the sound attenuator 1.

[0039] It will be obvious to a person skilled in the art that, as the tech- nology advances, the inventive concept can be implemented in various ways. The o invention and its embodiments are not limited to the examples described above AN but may vary within the scope of the claims. > [0040] Parts list: 1 a sound attenuator; 2 a ventilating duct; 3 a sound = attenuating member; 4 a fastening part; 5 sound absorbing material; 6 a lower edge N 30 part; 7 an upper edge part; 8 an installing opening; 9 a sealing; 10 a handle; 11 E resilient material; 12 an attachment member; 13 an extension part; 14 a stiffening <+ frame structure; 15 a frame plate; 16 a side edge; 17 abranch duct; 18 an opening = of a branch duct; 19 a flow channel; Li, L> a length; s thickness; x longitudinal direc- = tion.

Claims (17)

1. A sound attenuator for attenuating noise transmission along a venti- lating duct (2), the sound attenuator (1) comprising a sound attenuating member (3) and a fastening part (4), characterized in that the sound attenuating member (3) is plate-shaped comprising a lower edge part (6) and an upper edge part (7), and the lower edge part (6) is attached to the fastening part (4) such that the sound attenuating member (3) protrudes outwards from the fastening part (4), and when the sound attenuator (1) is in an installed position inside the ventilating duct (2) the sound attenuating member (3) is parallel with the ventilating duct (2) and the fastening part (4) covers the installing opening (8) of the sound attenuator (1) in the ventilating duct (2), and the ventilating duct (2) surrounding the sound attenuator (1) forms the support structure to the sound attenuator (1), and in that the upper edge part (7) comprises an attachment member (12) for con- necting the sound attenuating member (3) with an inner surface of the ventilating duct (2).

2. A sound attenuator according to claim 1, characterized in that the fastening part (4) comprises means for forming a releasable connection between the fastening part (4) and the ventilating duct (2).

3. A sound attenuator according to any of claims 1-2, character - ized in thatthe fastening part (4) comprises an access door into the ventilating duct (2).

4. A sound attenuator according to claim 3, characterized in that the access door is subsequently installable on circular or rectangular ventilat- ing duct (2).

5. A sound attenuator according to any of claims 1-4, character - o ized in that a length (Li)of the sound attenuating member (3) comprises sub- O stantially a length (L2)of the fastening part (4) or less in the longitudinal direction O (x) of the sound attenuator (1). =

6. A sound attenuator according to any of claims 1-5, character- N 30 ized inthattheupper edge part (7) comprises resilient material (11). E

7. A sound attenuator according to any of claims 1-6, character- x iz ed in thatthe upper edge part (7) comprises an extension part (13) providing 3 a support surface for the attachment member (12), and the support surface is 5 wider than the thickness(s) of the sound attenuating member (3). N 35

8. A sound attenuator according to any of claims 1-7, character- ized inthatthesound attenuating member (3) comprises a frame plate (15) and sound absorbing material (5) is attached at least to one side of the frame plate (15).

9. A sound attenuator according to claim 8, characterized in thatthe frame plate (15) comprises wedge shape at the side edges (16) of the sound attenuating member (3).

10. A ventilating duct element comprising a sound attenuator (1) ac- cording to claim 1-9.

11. An arrangement for attenuating noise transmission along a ventilat- ing duct, the arrangement comprising a sound attenuator (1) according to any of claims 1-9, characterized in that the ventilating duct (2) comprises at least one branch duct (17), the sound attenuator (19 is positioned parallel with the ven- tilating duct (2), the sound attenuator (1) is positioned in front of the opening of the branch duct (18) at a distance apart, and the length (L1) of the sound attenuat- ing member (3) in the longitudinal direction (x) of the sound attenuator (1) ex- ceeds the diameter of the opening (18) and the sound attenuating member (3) ex- tends to the inner surface of the uppermost part of the ventilating duct (2).

12. An arrangement for attenuating noise transmission along a ventilat- ing duct according to claim 11, characterized in thatthe ventilating duct (2) comprises two branch ducts (17), and the arrangement attenuates airborne noise transmission from a first branch duct (17) to a second branch duct (17) along — the ventilating duct (2).

13. An arrangement for attenuating noise transmission along a ventilat- ing main duct according to claim 12, characterized in that the branch ducts (17) are located on the opposite sides of the ventilating duct (2) and the openings of the branch ducts (18) are substantially facing each other and the sound attenuator (19 is positioned between the openings of the branch ducts (18).

o 14. An arrangement for attenuating noise transmission along a ventilat- AN ing main duct according to claim 12, characterized in that the branch > ducts (17) are located on the opposite sides of the ventilating duct (2) at a distance = apart from each other in a longitudinal direction (x) of the ventilating duct (2), and N 30 the sound attenuator (1) is positioned in front of each branch duct opening (18).

E 15. A method for attenuating noise transmission along a ventilating < duct, in the method the ventilating duct (2) comprises a branch duct (17), char - = acterized inthata plate-shaped sound attenuator (1) is inserted inside the = ventilating duct (2), the sound attenuator (1) is positioned parallel with the venti- N 35 lating duct (2) to allow fluid flowing along the ventilating duct (2) to flow between the outer surface of the sound attenuator (1) and the inner surface of the ventilat- ing duct (2) on both sides of the sound attenuator (1) and locating the sound at- tenuator (1) in front of the opening of the branch duct (18) at a distance apart, and the sound attenuator (1) extends from the inner surface of the lowermost part to the inner surface of the uppermost part of the ventilating duct (2).

16. A method for attenuating noise transmission along a ventilating duct according to claim 15, characterized in that the sound attenuator (1) is positioned such that the fluid flowing along the ventilating duct (2) flows substan- tially unobstructed between the outer surface of the sound attenuator (1) and the inner surface of the ventilating duct (2) on both sides of the sound attenuator (1).

17. Use of the arrangement for attenuating noise transmission along a ventilating duct according to any of claims 11-14 in an office building, in a hotel or a residential building comprising a plurality of rooms connected to a ventilating duct (2) through a plurality of branch ducts (17).

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