WO1987003948A1 - Device for reducing duct-carried air-borne sound - Google Patents
Device for reducing duct-carried air-borne sound Download PDFInfo
- Publication number
- WO1987003948A1 WO1987003948A1 PCT/SE1985/000540 SE8500540W WO8703948A1 WO 1987003948 A1 WO1987003948 A1 WO 1987003948A1 SE 8500540 W SE8500540 W SE 8500540W WO 8703948 A1 WO8703948 A1 WO 8703948A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sound
- section
- casing
- cross
- passageway
- Prior art date
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/02—Energy absorbers; Noise absorbers
- F16L55/033—Noise absorbers
- F16L55/0336—Noise absorbers by means of sound-absorbing materials
Definitions
- This invention relates to a device for damping air-borne sound carried by a duct, comprising a casing enclosing a duct and a certain amount of sound absorbing material attached in said casing in such a manner, that at least partially a free lomgitudinal passageway is formed, which is enclosed by a surface constituting the internal defin ⁇ ing surface, or corresponding surface, for the sound absorbing material.
- a great number of sound attenuators of different designs are commercially available.
- One usual type of sound atten ⁇ uators consists of a cylindric duct, the walls of which are covered with porous absorbent. At both ends of the duct area transitions and stubs to connecting ducts are mounted, and possibly also a perforated inner pipe is mounted to protect the sound absorbing porous material against erosion.
- the aforesaid sound reducing devices are called pipe or duct sound attenuat- ors ⁇
- Examples of applications, for which this type of sound attenuator normally is used are ventilation installations, exhaust circuits for internal combustion engines and compressed air installations.
- the sound attenuator types at present available yield a low attenuat ⁇ ion within this frequency range and.. due to sound attenuat ⁇ or geometry and absorbent properties., reach their attenuat ⁇ ion maximum at substantially higher frequencies.
- For obtaining the necessary attenuation either a greater thickness of the absorbent material or a greater total length of the sound attenuator is required. This conflicts with the space requirements in buildings and other struct ⁇ ures.
- the present invention has the object to propose a duct sound attenuator without the aforesaid deficiencies.
- the invention is characterized in that the defining surface is assembled of at least three surfaces of convex shape tow ⁇ ard the passageway, which so abut each other that the pass ⁇ ageway has star-shaped cross-section with at least three points.
- FIG. 1 shows a portion of a duct provided with the sound attenuating device according to the invention
- Fig. 2 is a section along the line II-II in Fig. 1
- Fig. 3 shows an embodiment, at which the star shape is hexagonal, and the casing of the duct has six sides. Dashed lines des ⁇ ignate a variant thereof with a cylindric casing.
- Fig. 4 shows another embodiment with a square casing
- Fig. 5 shows a further embodiment thereof.
- Figs. 6-8 show variants where the duct casing has cylindric shape, and the longitud ⁇ inal passageway has different star shapes.
- Fig. 1 shows a portion of a duct provided with the sound attenuating device according to the invention
- Fig. 2 is a section along the line II-II in Fig. 1
- Fig. 3 shows an embodiment, at which the star shape is hexagonal
- the casing of the duct has six sides. Dashed lines
- FIG. 1 is a perspective view of a length unit of a duct with a surrounding casing 1 of sheet metal.
- bodies 2 of sound absorbing material are inserted in the duct.
- Each of the bodies 2 has the cross-sectional shape of a quadrant where the radius corresponds to half the side of the square cross-section of the casing. Due to the fact that the curved surfaces face inward with the convex surface, a star-shaped passageway 3 is formed within the duct.
- the passageway 3 extends integral through the duct, and the end pieces of the sound absorbing material 2 can be rounded so that sitesa line shape faces to the afflux direction for the air through the passageway 3.
- This configuration of sound damping body within the sheet metal casing 1 is especially suitable from a manufacturing point of view, because each body of sound absorbing material is manufactured in a simple manner of a homogenous cylinder of sound absorbing material which is cut open longitudinally so that the quadrants in cross-section are obtained.
- the embodiment described is particularly advantageous, because the sound absorbing material has great thickness and the distance between covered surfaces is small.
- the quare casing, relative to a cylindric one, provides a greater effective sound attenuator volume without requir ⁇ ing more space for the attenuator in the building.
- the quarter-segmental tube-shaped bodies of sound absorbing material increase the effective absorbent thickness, decrease the distance between covered surfaces and yield ' a positive effect, due to the fact that the sound wave penetrates the absorbent material from the outside inward and not, as at conventional sound attenuators, from the inside outward. (The sound wave meets a decreasing area when it penetrates the absorbent material according to the present invention, while at conventional sound atten ⁇ uator designs the area is increasing).
- Fig. 3 shows a variant of the invention.
- the casing 4 in this case has hexagonal cross-section, and the bodies 5 of sound absorbing material are six in number and have subst ⁇ antially parabola shape with the point directed inward.
- the passageway 7 has star shape with six points.
- the casing is of cylindric shape as indicated by the dashed lines 8.
- Fig. 4 shows a further embodiment where the easing 1 has square cross-section.
- the passageway 9 has star shape with four points.
- the defining surface 10 facing to the passage ⁇ way 9 consists of a quadrant of a cylindric plastic foil with the convex side facing inward the passageway 9.
- the plastic foil can be perforated for air transmission, and alternative materials to the plastic foils can be used.
- the object of the plastic foil is to protect the body 11 of the sound absorbing material and to maintain its shape.
- Fig. 5 shows a further embodiment, where the casing for the duct has square cross-section.
- the sound absorbing bodies 12 here have the shape of a cylinder quadrant with great wall thickness whereby an air gap 13 is obtained in each corner of the duct.
- the passageway 14 has star shape with four points in the same way as at the embodim ⁇ ent shown in Fig. 4.
- Fig. 6 shows a duct defined by a circular casing 15.
- the passageway l ⁇ has star shape with four points, and the surface defining the sound absorbing bodies 17 toward the passageway is assembled of two surface planes 18 and 19 meeting angularly to the interior of the passageway.
- the defining surface for the absorbent body 17 hereby also is given convex-shaped configuration.
- Fig. 7 shows a variant of the embodiment according to Fig. 6 with a circular casing 15.
- the passageway 20 here has star shape with three points, and the defining surfaces for the absorbent bodies 21 have the cross-sectional shape of arcs.
- Fig. 8 shows another variant of the embodiment according to Figs. 6 and 7 with a circular casing 15.
- the passageway 22 has star shape with four points, and the absorbent bodies 23 have defining surfaces which face inward and have arc-shaped cross-section.
- the bodies of sound absorbing porous material shall be hom ⁇ ogenous and be manufactured so that a flow resistance is obtained which is homogenous or increases toward the corner points.
- the mounting can be carried out, for example, by glueing the bodies on the casing inside, and the casing can be manufactured, for example, of sheet metal.
- the bodies can be manufactured, for example, by compression moulding mineral or glass wool, which has been given suit ⁇ ably adapted density and flow resistance by choQsigg--a suitable amount of starting material. If desired, several sound attenuators according to the invention can be stacked one upon the other or be mounted laterally so that the desired total cross-section dimension is obtained.
- the mineral wool bodies in the attenuators can be given in the end areas a suitable aero ⁇ dynamic configuration, as already mentioned above.
- the sound reduction can be calculated according to the Sabine duct attenuation formula
- the outer duct is square, with the side 200 mm.
- U 0,628.
- A 0,0086.
- U/A 73.
- the attenuation is 6,87 dB.
- At increased thickness of the absorbent material primarily the low frequency attenuation is improved. Also the value of a, thus, is influenced by the absorbent geometry according to the pres ⁇ ent invention.
- a sound attenuator according to the present invention substantially improves the sound reduction, especially in the low frequency range, provided that the free flow area is maintained constant and the flow resistance for the new absorbent geometry is optimized.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
- Exhaust Silencers (AREA)
- Pipe Accessories (AREA)
- Duct Arrangements (AREA)
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8406282A SE447413B (en) | 1984-12-11 | 1984-12-11 | Noise muffler for reducing conduit borne air noise |
EP86900679A EP0261105A1 (en) | 1984-12-11 | 1985-12-20 | Device for reducing duct-carried air-borne sound |
PCT/SE1985/000540 WO1987003948A1 (en) | 1984-12-11 | 1985-12-20 | Device for reducing duct-carried air-borne sound |
NO88880116A NO880116L (en) | 1984-12-11 | 1988-01-12 | DEVICE FOR REDUCTION OF CHANNELABLE AIR SOUND. |
FI881922A FI881922A (en) | 1984-12-11 | 1988-04-22 | LJUDDAEMPARE FOER REDUCERING AV KANALBURET LUFTLJUD. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8406282A SE447413B (en) | 1984-12-11 | 1984-12-11 | Noise muffler for reducing conduit borne air noise |
PCT/SE1985/000540 WO1987003948A1 (en) | 1984-12-11 | 1985-12-20 | Device for reducing duct-carried air-borne sound |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1987003948A1 true WO1987003948A1 (en) | 1987-07-02 |
Family
ID=26658834
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1985/000540 WO1987003948A1 (en) | 1984-12-11 | 1985-12-20 | Device for reducing duct-carried air-borne sound |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0261105A1 (en) |
FI (1) | FI881922A (en) |
NO (1) | NO880116L (en) |
SE (1) | SE447413B (en) |
WO (1) | WO1987003948A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0487481A1 (en) * | 1990-11-20 | 1992-05-27 | Valmet Paper Machinery Inc. | Absorptive sound attenuator, in particular for air ducts in paper mills |
EP0754901A1 (en) * | 1995-07-21 | 1997-01-22 | Robert Alan Gladden | Noise attenuators, their manufacture, and their use for noise attenuation in ducts |
WO2011141639A1 (en) | 2010-05-12 | 2011-11-17 | Jeven Oy | Attenuating section for sound attenuator in air conditioning duct and sound attenuator for air conditioning duct |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2620169A1 (en) * | 1976-05-07 | 1977-11-10 | Gruenzweig Hartmann Glasfaser | Sound damper for ventilation pipes - has parallel rigid pipe sections made from mineral fibres with plastic-rubber dispersion forming abrasive resistant coat |
-
1984
- 1984-12-11 SE SE8406282A patent/SE447413B/en not_active IP Right Cessation
-
1985
- 1985-12-20 EP EP86900679A patent/EP0261105A1/en not_active Withdrawn
- 1985-12-20 WO PCT/SE1985/000540 patent/WO1987003948A1/en not_active Application Discontinuation
-
1988
- 1988-01-12 NO NO88880116A patent/NO880116L/en unknown
- 1988-04-22 FI FI881922A patent/FI881922A/en not_active Application Discontinuation
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2620169A1 (en) * | 1976-05-07 | 1977-11-10 | Gruenzweig Hartmann Glasfaser | Sound damper for ventilation pipes - has parallel rigid pipe sections made from mineral fibres with plastic-rubber dispersion forming abrasive resistant coat |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0487481A1 (en) * | 1990-11-20 | 1992-05-27 | Valmet Paper Machinery Inc. | Absorptive sound attenuator, in particular for air ducts in paper mills |
US5260523A (en) * | 1990-11-20 | 1993-11-09 | Valmet Paper Machinery, Inc. | Absorptive sound attenuator, in particular for air ducts in paper mills |
EP0754901A1 (en) * | 1995-07-21 | 1997-01-22 | Robert Alan Gladden | Noise attenuators, their manufacture, and their use for noise attenuation in ducts |
WO2011141639A1 (en) | 2010-05-12 | 2011-11-17 | Jeven Oy | Attenuating section for sound attenuator in air conditioning duct and sound attenuator for air conditioning duct |
Also Published As
Publication number | Publication date |
---|---|
FI881922A0 (en) | 1988-04-22 |
SE8406282D0 (en) | 1984-12-11 |
FI881922A (en) | 1988-04-22 |
NO880116D0 (en) | 1988-01-12 |
NO880116L (en) | 1988-01-12 |
SE8406282L (en) | 1986-06-12 |
EP0261105A1 (en) | 1988-03-30 |
SE447413B (en) | 1986-11-10 |
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