GB2122256A - Silencing in ventilation ducts - Google Patents
Silencing in ventilation ducts Download PDFInfo
- Publication number
- GB2122256A GB2122256A GB08312060A GB8312060A GB2122256A GB 2122256 A GB2122256 A GB 2122256A GB 08312060 A GB08312060 A GB 08312060A GB 8312060 A GB8312060 A GB 8312060A GB 2122256 A GB2122256 A GB 2122256A
- Authority
- GB
- United Kingdom
- Prior art keywords
- silencer
- unperforated
- air stream
- perforated
- sheet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
- F24F13/24—Means for preventing or suppressing noise
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N1/00—Silencing apparatus characterised by method of silencing
- F01N1/24—Silencing apparatus characterised by method of silencing by using sound-absorbing materials
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Exhaust Silencers (AREA)
- Duct Arrangements (AREA)
- Building Environments (AREA)
Abstract
Each of the sections of sound- absorbing material, e.g. mineral wool, forming a wall covering and/or a baffle extending in the direction of air flow in a rectangular or circular duct (Figs. 1 and 3) is covered by unperforated material 6, e.g. sheet metal, at its upstream and downstream end regions 4 and 5 and an intermediate portion 7 is uncovered or covered by expanded or perforated sheet metal with an aperture area of at least 20%. The sections of material may each have a length L equal to one quarter of the wave length of the sound frequency to be most silenced. <IMAGE>
Description
SPECIFICATION
Silencer
The invention relates to a silencer or noise suppressor intended for ventilation ducts or ventilation apparatus, and comprises porous elements, e.g. of mineral wool, serving as resistive sound-absorbent units, said elements being arranged as wall cladding or baffles swept over by the stream of air in a duct or apparatus casing.
Previously known silencers of this kind have generally not had completely satisfactory lowfrequency damping. Silencers of other kinds, e.g.
diaphragm absorbers, afford better low-frequency damping and are known to the art, but silencers of the former kind are often to be preferred for various reasons.
The object of the invention is therefore to provide a silencer of the kind described in the introduction, which has improved low-frequency damping, although its high-frequency damping is sufficient to meet the requirements made for ventilation plant.
The desired result is obtained by the silencer being given the characterizing features disclosed in the following claim 1.
Two embodiments of the invention are described in detail below with reference to the accompanying drawing, whereon
Fig. 1 illustrates a silencer intended for a ventilation duct with a rectangular duct crosssection,
Fig. 2 illustrates a baffle incorporated in the silencer of Fig. 1,
Fig. 3 illustrates a further silencer intended for a ventilation duct having a circular cross-section.
The silencer illustrated in Fig. 1 comprises six porous elements 1 and 2, arranged as baffles in a casing constituting an ordinary ventilation duct with rectangular cross-section. The casing is usually made from sheet steel. The porous material in the baffles is suitably mineral wool.
In the embodiment illustrated in Fig. 1, the silencer is assembled with three rows of baffles, each row including two baffles placed end to end.
The rows are oriented in the through-flow direction of the air stream. The baffles 2 are swept by the air stream while the baffles 1 are placed adjacent mutually opposing duct walls and are only swept by the air stream on one side.
The construction of a baffle will be more closely seen from Fig. 2. Each baffle may have its upstream and downstream ends 4 and 5, surrounded by substantially unperforated sheet material 6, preferably sheet metal, extending a distance along the side surfaces of the baffle in the path of the air stream. The porous material of the baffle is thus left uncovered along an intermediate portion 7, which is unclad or (not illustrated in Fig. 2) covered by a perforated material.
Expanded metal, perforated metal sheet or the like, with at least 20% aperture area may be used for such perforated material.
The substantially unperforated material 6 extends suitably over about 2/3 of the porous element length L in the flow direction of the air stream or in the direction of sound propagation.
The intermediate portion 7 should be substantially central along the distance L.
It is also suitable that the distance L is selected to be 1/4 of the wavelength of the low frequency which is intended to be more heavily dampened than what the absorber enables per se.
As will also be seen from Fig. 2, the baffle is
made from a porous element in the form of a
straight, parallelepipedic body having at either
end an unperforated sheet 6 covering the end wall of the element and folded around the edges thereof to extend a distance along its sides swept
by the air stream. The portions of the sheet 6 situated on the sides of the element are shown to
be flat, with their terminating edges defining the
intermediate free portion 7 of the element
oriented substantially at right angles to the long
edges of the sheets along the sides of the
element.
Fig. 3 illustrates a silencer with an exterior,
unperforated, cylindrically shaped casing 8, e.g. of
metal sheet, and a perforated tube 9 placed in the
casing and coaxial therewith to serve as a
passage for the air stream. The space between the casing 8 and the tube 9 is in this case filled with the circularly shaped porous element 3 only
constituting wall cladding. Here, the intermediate
portion 7, described in conjunction with figures 1
and 2 for the first embodiment, consists of the
perforated portion of the tube 9. This perforated
portion can be restricted by the remainder of the
tube upstream and downstream of the portion 7
being unperforated, or by the tube being
perforated for the whole of its length by having its
walls screened off by substantially unperforated
material upstream and downstream of the portion
7.In the latter case, this unperforated material
may suitably be the ends of adjoining ducts or
stub ends thrust into the tube 9.
The silencer described above in conjunction
with a pair of embodiments affords, by reason of
the partial enclosure using the substantially
unperforated sheet-like material 6, a combination
of resistive and reactive damping. The result of
this is substantially improved low-frequency silencing without unfavourably large reduction of
the high-frequency silencing.
Claims
1. A silencer or noise suppressor intended to
afford improved low-frequency damping, and
adapted for ventilation ducts or ventilation
apparatus, said silencer comprising one or more
porous elements (1-3), e.g. of mineral wool,
serving as resistive sound absorbers and arranged
in a duct or apparatus casing, solely as wall
cladding or as baffles swept over by the air
stream, characterized in that one or more of the
porous elements (1-3) has its upstream and
downstream ends (4 and 5) surrounded by
substantially unperforated sheet-like material (6),
preferably metal sheet, each element having an
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (8)
1. A silencer or noise suppressor intended to
afford improved low-frequency damping, and
adapted for ventilation ducts or ventilation
apparatus, said silencer comprising one or more
porous elements (1-3), e.g. of mineral wool,
serving as resistive sound absorbers and arranged
in a duct or apparatus casing, solely as wall
cladding or as baffles swept over by the air
stream, characterized in that one or more of the
porous elements (1-3) has its upstream and
downstream ends (4 and 5) surrounded by
substantially unperforated sheet-like material (6),
preferably metal sheet, each element having an intermediate portion (7) on one or more of its surfaces extending along the path of the air stream, said portion (7) having a free surface, or one covered by a perforated material, such that reactive damping is also obtained.
2. Silencer as claimed in claim 1, characterized in that the intermediate portion 7 is covered by perforated sheet metal, expanded metal or the like, with at least 20% perforation area.
3. Silencer as claimed in claim 1 or 2, characterized in that the substantially unperforated, sheet-like material (6) extends over about 2/3 of the length (L) of the porous element (1-3) in the flow direction of the air stream, or in the direction of sound propagation, and in that the intermediate portion (7) is substantially central in relation to the length (L) of the porous element (1~3).
4. Silencer as claimed in claim 3, characterized in that the length (L) of the porous element (1-3) is about 1/4 of the wave length of the low frequency which is intended to be more heavily dampened than what is enabled by the porous element per se.
5. Silencer as claimed in any of claims 1-4, in the case where these porous elements (1, 2) comprise right parallelepipedic bodies serving as baffles, characterized in that the substantially unperforated sheet-like material (6) at either end of the respective porous element (1, 2) consists of a metal sheet covering the end wall of the element (1, 2) and folded round the edges of this end wall to extend along the sides of the element swept over by the air stream.
6. Silencer as claimed in claim 5, characterized in that each of the end wall sheets (6) is flat along the side of the element swept by the air stream, and terminates substantially square to said intermediate portion (7).
7. Silencer as claimed in claim 5 or 6, characterized in that the porous elements (1, 2) are arranged one after the other in rows, end wall to end wall.
8. Silencer as claimed in any of claims 1-4 in the case where the porous element (3) has the shape of a hollow right cylindrical body which solely has a wall cladding function, and is arranged between an outer, unperforated casing (8) and a perforated tube (9) concentric with the casing (8) and constituting a passage for the air stream, characterized in that only a portion of the tube (9), constituting said intermediate portion (7), is perforated, whereas the remainder thereof is unperforated, or in that said tube (9) is perforated for its entire length, but upstream and downstream of said intermediate portion (7) said tube has its walls screened by substantially unperforated material, such as stub ends or ends of adjoining ducts thrust into said tube (9).
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8203030A SE450656B (en) | 1982-05-14 | 1982-05-14 | Muffler for ventilation ducts or ventilation equipment |
Publications (3)
Publication Number | Publication Date |
---|---|
GB8312060D0 GB8312060D0 (en) | 1983-06-08 |
GB2122256A true GB2122256A (en) | 1984-01-11 |
GB2122256B GB2122256B (en) | 1985-11-13 |
Family
ID=20346812
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08312060A Expired GB2122256B (en) | 1982-05-14 | 1983-05-03 | Silencing in ventilation ducts |
Country Status (7)
Country | Link |
---|---|
DE (1) | DE3317273A1 (en) |
DK (1) | DK159669C (en) |
FI (1) | FI75415C (en) |
FR (1) | FR2526860B1 (en) |
GB (1) | GB2122256B (en) |
NO (1) | NO162931C (en) |
SE (1) | SE450656B (en) |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2267731A (en) * | 1992-06-10 | 1993-12-15 | Lancaster Glass Fibre | Sound absorber insert for an exhaust silencer. |
US5801342A (en) * | 1997-01-27 | 1998-09-01 | Lindab Ab | Double-walled structure and method and arrangement for producing the same |
WO2000003129A1 (en) * | 1998-07-10 | 2000-01-20 | Lindab Ab | Double-walled structure in a ventilation duct system |
EP0897083A3 (en) * | 1997-08-14 | 2000-03-29 | Müller-BBM GmbH | Ultrasonic sound attenuator |
US6062270A (en) * | 1997-01-27 | 2000-05-16 | Lindab Ab | Double-walled structure in a ventilation duct system |
US6167984B1 (en) | 1996-12-19 | 2001-01-02 | Abb Flakt Ab | Device and a method for sound reduction in a transport system for gaseous medium and use of the device in an exhaust system for ships |
US6543575B1 (en) | 2000-06-14 | 2003-04-08 | Lindab Ab | Double-walled structure and connection arrangement |
US8272475B2 (en) | 2008-04-30 | 2012-09-25 | Metso Paper, Inc. | Sound attenuator for low frequencies, method for manufacturing sound attenuator for low frequencies and system for attenuating low frequencies for example in air-conditioning ducts of paper mills |
WO2014076355A1 (en) | 2012-11-15 | 2014-05-22 | Wärtsilä Finland Oy | An exhaust gas noise attenuator unit for internal combustion piston engine |
JP2019132576A (en) * | 2018-01-31 | 2019-08-08 | 富士フイルム株式会社 | Silent ventilating structure |
US10458589B2 (en) | 2014-08-06 | 2019-10-29 | Aaf Ltd. | Sound suppression apparatus |
US11186126B2 (en) * | 2013-10-24 | 2021-11-30 | Bentley Motors Limited | Tyre cavity noise absorber |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3934756A1 (en) * | 1989-10-18 | 1991-04-25 | Kuehnle Kopp Kausch Ag | Noise damper for axial-flow fan - has adjacent sound absorbing chamber behind diffuser core and/or jacket transversely to flow direction |
FI91995C (en) * | 1990-11-20 | 1994-09-12 | Valmet Paper Machinery Inc | Absorptive silencer, especially for air ducts in paper mills |
EP0558472B1 (en) * | 1990-11-21 | 1998-04-08 | Sound Attenuators Limited | Improvements in attenuators |
SE511627C2 (en) * | 1997-11-03 | 1999-11-01 | Stifab Farex Ab | Muffler baffle for rectangular vents |
SE511628C2 (en) * | 1997-11-10 | 1999-11-01 | Stifab Farex Ab | Silencer with baffles for rectangular ventilation ducts |
US6073723A (en) * | 1998-06-05 | 2000-06-13 | Gallo; Anthony | Acoustic damping material |
EP3610205A1 (en) * | 2017-04-14 | 2020-02-19 | Fraunhofer Gesellschaft zur Förderung der Angewand | Splitter sound attenuator assembly comprising sound-absorbing end faces |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1350683A (en) * | 1970-04-22 | 1974-04-18 | Grassmann Isoliertechnik | Muffler for flowing gases |
GB1423986A (en) * | 1972-02-21 | 1976-02-04 | Colchester Woods | Sound attenuating units for ventilating openings |
GB1431662A (en) * | 1972-04-28 | 1976-04-14 | Donaldson Co Inc | Methods of separating acoustic energy from a flowing fluid and exhaust mufflers using same |
GB1432206A (en) * | 1973-06-29 | 1976-04-14 | Caterpillar Tractor Co | Sound attenuating engine enclosures for vehicles |
GB1556823A (en) * | 1975-07-30 | 1979-11-28 | Industrial Acoustics Co | Silencer |
GB1570074A (en) * | 1977-07-13 | 1980-06-25 | British Gas Corp | Ventilators |
US4287962A (en) * | 1977-11-14 | 1981-09-08 | Industrial Acoustics Company | Packless silencer |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2513946C2 (en) * | 1975-03-29 | 1981-11-26 | Gebrüder Trox, GmbH, 4133 Neukirchen-Vluyn | Splitter silencer |
DE3202078A1 (en) * | 1982-01-23 | 1983-08-04 | IT - Isoliertechnik und Schallschutz GmbH, 4830 Gütersloh | Silencer |
-
1982
- 1982-05-14 SE SE8203030A patent/SE450656B/en not_active IP Right Cessation
-
1983
- 1983-05-03 GB GB08312060A patent/GB2122256B/en not_active Expired
- 1983-05-09 FR FR8307681A patent/FR2526860B1/en not_active Expired
- 1983-05-09 FI FI831586A patent/FI75415C/en not_active IP Right Cessation
- 1983-05-11 DE DE19833317273 patent/DE3317273A1/en active Granted
- 1983-05-13 NO NO831722A patent/NO162931C/en not_active IP Right Cessation
- 1983-05-13 DK DK214483A patent/DK159669C/en not_active IP Right Cessation
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1350683A (en) * | 1970-04-22 | 1974-04-18 | Grassmann Isoliertechnik | Muffler for flowing gases |
GB1423986A (en) * | 1972-02-21 | 1976-02-04 | Colchester Woods | Sound attenuating units for ventilating openings |
GB1431662A (en) * | 1972-04-28 | 1976-04-14 | Donaldson Co Inc | Methods of separating acoustic energy from a flowing fluid and exhaust mufflers using same |
GB1432206A (en) * | 1973-06-29 | 1976-04-14 | Caterpillar Tractor Co | Sound attenuating engine enclosures for vehicles |
GB1556823A (en) * | 1975-07-30 | 1979-11-28 | Industrial Acoustics Co | Silencer |
GB1570074A (en) * | 1977-07-13 | 1980-06-25 | British Gas Corp | Ventilators |
US4287962A (en) * | 1977-11-14 | 1981-09-08 | Industrial Acoustics Company | Packless silencer |
Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2267731A (en) * | 1992-06-10 | 1993-12-15 | Lancaster Glass Fibre | Sound absorber insert for an exhaust silencer. |
US6167984B1 (en) | 1996-12-19 | 2001-01-02 | Abb Flakt Ab | Device and a method for sound reduction in a transport system for gaseous medium and use of the device in an exhaust system for ships |
US6062270A (en) * | 1997-01-27 | 2000-05-16 | Lindab Ab | Double-walled structure in a ventilation duct system |
US5911457A (en) * | 1997-01-27 | 1999-06-15 | Lindab Ab | Method for producing a double-walled structure |
US5881442A (en) * | 1997-01-27 | 1999-03-16 | Lindab Ab | Apparatus for making a double-walled structure |
US5801342A (en) * | 1997-01-27 | 1998-09-01 | Lindab Ab | Double-walled structure and method and arrangement for producing the same |
EP0897083A3 (en) * | 1997-08-14 | 2000-03-29 | Müller-BBM GmbH | Ultrasonic sound attenuator |
WO2000003129A1 (en) * | 1998-07-10 | 2000-01-20 | Lindab Ab | Double-walled structure in a ventilation duct system |
US6543575B1 (en) | 2000-06-14 | 2003-04-08 | Lindab Ab | Double-walled structure and connection arrangement |
US8272475B2 (en) | 2008-04-30 | 2012-09-25 | Metso Paper, Inc. | Sound attenuator for low frequencies, method for manufacturing sound attenuator for low frequencies and system for attenuating low frequencies for example in air-conditioning ducts of paper mills |
WO2014076355A1 (en) | 2012-11-15 | 2014-05-22 | Wärtsilä Finland Oy | An exhaust gas noise attenuator unit for internal combustion piston engine |
US11186126B2 (en) * | 2013-10-24 | 2021-11-30 | Bentley Motors Limited | Tyre cavity noise absorber |
US10458589B2 (en) | 2014-08-06 | 2019-10-29 | Aaf Ltd. | Sound suppression apparatus |
JP2019132576A (en) * | 2018-01-31 | 2019-08-08 | 富士フイルム株式会社 | Silent ventilating structure |
Also Published As
Publication number | Publication date |
---|---|
DE3317273C2 (en) | 1991-04-11 |
FI75415C (en) | 1988-06-09 |
FI75415B (en) | 1988-02-29 |
DK159669B (en) | 1990-11-12 |
DE3317273A1 (en) | 1983-11-17 |
NO162931B (en) | 1989-11-27 |
SE450656B (en) | 1987-07-13 |
DK159669C (en) | 1991-04-15 |
FR2526860A1 (en) | 1983-11-18 |
NO162931C (en) | 1990-03-07 |
FI831586A0 (en) | 1983-05-09 |
DK214483A (en) | 1983-11-15 |
SE8203030L (en) | 1983-11-15 |
GB2122256B (en) | 1985-11-13 |
DK214483D0 (en) | 1983-05-13 |
NO831722L (en) | 1983-11-15 |
FI831586L (en) | 1983-11-15 |
GB8312060D0 (en) | 1983-06-08 |
FR2526860B1 (en) | 1989-06-16 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PE20 | Patent expired after termination of 20 years |
Effective date: 20030502 |