US3776364A - Noise reduction apparatus and method - Google Patents

Noise reduction apparatus and method Download PDF

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Publication number
US3776364A
US3776364A US00248676A US3776364DA US3776364A US 3776364 A US3776364 A US 3776364A US 00248676 A US00248676 A US 00248676A US 3776364D A US3776364D A US 3776364DA US 3776364 A US3776364 A US 3776364A
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conduit
tubular member
acoustic energy
outlet
duct
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Doeren R Van
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Donaldson Co Inc
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Donaldson Co Inc
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    • 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
    • F01N1/02—Silencing apparatus characterised by method of silencing by using resonance
    • F01N1/04—Silencing apparatus characterised by method of silencing by using resonance having sound-absorbing materials in resonance chambers
    • 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
    • F01N1/003—Silencing apparatus characterised by method of silencing by using dead chambers communicating with exhaust gas flow passages
    • 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
    • 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

Definitions

  • the apparatus includes a directional acoustic coupler comprising first and second side-by-side conduits having coupling elements in a common wall thereof.
  • the first conduit carries the fluid and acoustic energy.
  • the coupling elements couple a pre-selected portion of the energy from the first conduit into the second conduit without disturbing the flow of fluid.
  • the second conduit is provided with sound absorbing material.
  • a pair of symmetrical acoustic couplers are used as phase shifters in .a noise cancellation circuit.
  • a single coupler is designed to reflect the acoustic energy back toward the source without restricting the flow of fluid. This invention has particular utility in the field of exhaust silencing. I
  • This invention relates generally to apparatus and method for reducing noise carried by a moving fluid
  • the article discloses a 'coupler having a thick center wall through which'the coupling elements extend, as opposed to the very thin center wall of the present invention.
  • the author describes an application of the coupler as a device for direct measurement of the acoustical reflection coefficient of materials. No mention is made of utilizing a di rectional acoustic coupler in any form of sound attenuation system. Further, neither of the articles makes any reference to the separation or disposal of acoustic energy being carried by a moving fluid stream as for example, the noise being carried by exhaust gases-being dischargedfrom an engine.
  • Directional couplers have long been used in waveguide systems to couple electromagnetic energy from one waveguide to another. Because of the importance of radar systems and microwave communication systems employing waveguide transmission elements, directional couplers for use in such systems have been highly developed.
  • an acoustic coupler is used to transfer or couple acoustic energy from a conduit, through coupling elements into a separate chamber provided with sound absorbing material. The acoustic energy is coupled into the chamber while minimally affecting the free flow of gases through the conduit.
  • a passive cancellation system is designed for use as an engine exhaust silencer, for example, the cancellation of noise can be achieved without causing any restriction to the free flow of exhaust gases through the system.
  • the capabilities of directional acoustic couplers are used to reflect sound waves back toward the source without restricting flow of gases through the coupler.
  • those concerned with designing apparatus forattenuating noise being carried by a duct' or conduit are provided with a completely new technique for accomplishing their mission.
  • the acoustic directional couplers can be used either alone or in combination with other mufflers or silencers.
  • FIG. 1 is a schematic side view in section of a sym metrical, two-element directional acoustic coupler
  • FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1;
  • FIG. 3 shows a system for attenuating engine exhaus noises, employing a Odb coupler
  • FIG. 4 is a schematic diagram of a passive cancellation system employing apair of Odb couplers
  • FIG. 5 is a similar passive cancellation system employing one 3d!) coupler and one 0db coupler;
  • FIG. 6 is a similar passive cancellation system employing two 3db couplers
  • FIG. 7 shows a single 3db coupler designed to act as a noise reflection device
  • FIG. 8 shows the use of a Odb coupler designed to act as a noise reflection device.
  • FIG. 1 i i a basic form of acoustic directional coupler 10 that will be used in the various systems described herein.
  • Coupler l0 includes a first tubular member or conduit 11 having an inlet port 1 and an outlet port 3, mounted in a side-b y-side, generally parallel relationship with a second tubular member or conduit 12 having opposite open end ports 2 and 4.
  • Conduits 11 and 12 may be of arbitrary, different cross-sectional shapes. When conduits 11 and 12 are identical in area and shape, the coupler is referred to as a symmetrical coupler.
  • Conduits 11 and 12 are joined for a selected distance by a common, relatively thin wall 13 having at least a pair of coupling elements 14 andl5 therein.
  • common wall 13 may be relatively flat to provide sufficient common wall space for the coupling elements 14 and 15. Whether or not this is necessary will depend upon the size of coupling elements required.
  • conduits 11 and 12 can be thin-walled steel tubing welded together in a side-by-side relationship with wall 13 thus being a double wall.
  • coupling elements 14 and 15 are openings in the wall 13. If desired, and if the application permits, the coupling elements can be membrane covered openings. The membranes will vibrate under the influence of acoustic energy to thereby couple the energy from one conduit to the other.
  • conduit 11 should be designedto provide a relatively unrestricted flow path for the exhaust gases.
  • the couplers l0 usually transfer either one-half power or full power.
  • the coupling notations in db give the negative of the acoustic power at port 4 relative to the power incident at port 1 in decibels.
  • the notation Odb indicates a complete transfer of power from one conduit to the other.
  • the notation 3db indicates a transfer of one-half of the power. Therefore,
  • Coupler 10 is directional in that ideally, for a wave incident on port 1, no energy could be coupled from the incident port 1 to the auxiliary port 2. All of the acoustic energy leaves ports, 3 and 4 in amounts depending upon the coupling ratio. For an acoustic directional coupler, it is desirable to have a low level of energy coupled out port 2 and a low reflection coefficient looking into port 1. The ratio of the coupled level in port 4 to that in port 2 in decibels is defined to be the directivity of the coupler. For symmetric couplers, it can be shown that a high directivity is equivalent to a low input reflection coefficient. A high directivity within a band of frequencies is achieved by spacing the coupling openings one-quarter wave length apart at the center frequency.
  • the coupler be capable of transferring power effectively over a wide band of frequencies in the range of audible sound. It is also desirable that the directivity be high so that most efficient use can be made of the coupled energy. Unsymmetrical directional couplers are also applicable to some of the systems discussed herein.
  • FIG. 3 discloses a form of muffler in which the inlet port 1 of a duct 17 is connected to an engine exhaust port 18. The exhaust gases pass freely through duct 17 for discharge from port 3. Noise within a predetermined frequency range is coupled into a chamber 19 (corresponding to conduit 12) through a plurality of coupling elements (openings 20) in the common wall between duct 17 and chamber 19.
  • the coupling openings 20 are designed to provide full power (Odb) coupling over a relatively wide range of frequencies. Adjacent pairs of openings are spaced apart one-quarter wave length for the selected frequency. The openings will then couple energy with a high degree of directionality and a low input reflection coefficient over a band of frequencies centered on the selected frequency. Further, the sizes of the holes are tapered from the ends toward the middle, with the largest openings being in the middle to prevent abrupt coupling thereby minimizing impedance discontinuities and reducing reflection.
  • a sound absorbing material 21 such as fiberglass is placed in chamber 19 to absorb the noise being coupled therein.
  • the ends of chamber 19 (corresponding to ports 2 and 4) are closed.
  • the acoustic energy is coupled into a side conduit or chamber where it can be absorbed without influencing the flow path through duct 17 followed by the exhaust gases.
  • several absorption-type filters like that shown in FIG. 3, each designed for a particular frequency can be connected in series to effectively cover a wider frequency range.
  • a number of these absorption-like filters can be connected in series, with each filter covering very effectively a rather narrow range of frequencies, to thereby cover in total a relatively wide frequency range without causing any sub stantial restriction to the flow of exhaust gases through the duct 17.
  • the absorption-type filter shown in FIG. 3 can also be connected for use in combination with'standard muffler systems.
  • a low-reflection absorption-type filter has the advantage of isolating the absorbing action from the engine and from the exhaust gas flow'path. This allows realization of'the maximum reflection coefficients of reflective (reactive) devices, such as conventional mufflers, irrespective of their location in the exhaust system, so long as the absorption filter is between the reflective device and the engine.
  • a practical Odb coupler will remove over percent of the acoustic energy (transmitted power reduced by 10db) over some band of frequencies, and over 99 percent of the energy (transmission reduced by 20:11)) over a narrower band.
  • a laboratory model has given l0db reduction over a 370Hz band for a design frequency of 800Hz (a 46 percentband width) and 20db reduction over al00I-Iz band (12.5 percent band width).
  • the test also showed that over the frequency range from 7OOI-Iz to 1,000Hz, the amplitude reflection coefficient looking into port 1 was less than 0.08.
  • a practical Odb coupler can be designed as a very low reflection device.
  • a very useful inherent property of symmetrical acoustic couplers is that the wave leaving port 4 lags in phase 90 with respect to the wave leaving port3.
  • the acoustic energy leaving port 4 will be 90 out of phase with respect to the remaining acoustic energy leaving port 3.
  • a symmetrical acoustic coupler can thus be used as a phase shifter.
  • FIG. 4 discloses one configuration for achieving a relative phase shift for internal cancellation.
  • the exhaust gases and acoustic noise from the engine enter the inlet of a first conduit 25 which is provided at its outlet end with a Y-junction 26.
  • 'Y-junction 26 divides at least the sound energy (but not necessarily the exhaust gases) into two generally equal parts for separate transmission through second conduit means 27 and third conduit means 28.
  • Connected. in series with second conduit means 27 are a pair of Odb acoustic couplers 10.
  • the couplers 10 are shown schematically, but the construction of each is generally the same as shown in FIG. 1.
  • the port numbering system is also the same.
  • Ports 2 and 3 of each coupler 10 are blocked off and may contain absorbers so that both the gases and sound energy enter port 1 and leave port 4. Because these are symmetrical 0db couplers, all of the acoustic energy incident on port 1 of each coupler leaves the coupler through port 4 shifted in phase by minus 90 relative to port 3.
  • the sound waves leaving port 4 of the downstream coupler are made to be 180 out of phase with respect to the sound waves in third conduit means 28 by properly adjusting the length of conduit means 28.
  • the out of phasesound waves in conduit means 27 and 28 are recombined at a downstream Y-junction 29,
  • conduit means 27 and 28 which leads to a single outlet conduit 30. If the system is designed so that the sound waves in conduit means 27 and 28 are of equal amplitude, they will recombine and cancel each other at the Y-junction 29. Thus, in a perfectly designed system, for a particular frequency range, no audible sound would leave port 30. The sound waves cancel in the sense that they are reflected back toward the source from the Y-junction 29 and are eventually dissipated as heat. However, it can be seen that the exhaust gases are free to flow through the system without restriction. In a practical system, the sound waves being propagated through conduit means 27 will suffer a phase change merely from traveling a distance through the various conduits. In like manner, some phase change will occur to the sound waves passing through conduit means 28.
  • conduit means 28 should therefore be adjusted so that there is a net 180 phase difference between the waves recombining at the Y-junction 29 and so that the rates of change of phase with frequency of the two conduits is as close to being equal as possible.
  • the Y-junction 26 is designed to split the sound energy into substantially equal halves.
  • the exhaust gas flow is not necessarily split into two equal parts. Depending upon their relative restrictions to gas flow, a portion of the gas will flow through conduit means 27 and the remaining portion will flow through conduit means 28 but these gas flows will be recombined at Y-junction 29 for common discharge through outlet conduit 30.
  • FIG. discloses another form of cancellation system utilizing one symmetrical 3db coupler and one symmetrical 0db coupler.
  • this system all of the exhaust gas flow and sound energy enters port 1 of the 3db coupler.
  • Port 2 is blocked off and may contain absorbers.
  • the coupler has imposed a 90 phase lag on the energy leaving port 4 relative to that leaving port 3.
  • the sound energy and gases leaving port 4 enter port 1 of the ()db coupler.
  • Ports 2 and 3 of the 0db coupler are blocked. All of the energy entering port 1 of the Odb coupler leaves port 4, shifted in phase a total of minus 180".
  • the out of phase sound waves are again recombined for cancellation at the downstream Y-junction. Adjustments in conduit length are required for achieving the 180 relative phase and nearly equal phase slopes.
  • FIG. 6 Another system for achieving internal cancellation is shown in FIG. 6.
  • One component is carried to a recombination point 31 without shifting its phase.
  • the other component is transmitted thorugh a pair of 3db couplers in series to obtain a minus 180 phase shift.
  • the component to be shifted enters port 1 of the first 3db coupler and leaves port 2 thereof. Ports 3 and 4 are blocked.
  • Ports 3 and 4 are blocked.
  • essentially all of the energy entering port 1' eventually leaves port 2 with a relative phase of minus 90 relative to the outgoing wave at port 1.
  • the operation is as follows. Two symmetrical 3db directional couplers connected end-to-end result in a Odb coupler having the required 90 phase property of symmetrical couplers.
  • FIGS. 4-6 are meant to be representative of the sys 'tems employing acoustic couplers as phase shifters to provide internal noise cancellation. It is not intended that these three figures represent the only ways in which internal cancellation can be achieved by using shown schematically with the same port numbering system being retained.
  • the exhaust gases and noise enter port 1.
  • ports 3 and 4 are connected by a curved conduit 32 permitting the free flow of gases and sound waves between ports 3 and 4.
  • Port 2 is left open and represents the exhaust discharge opening.
  • the exhaust gases are provided with a uniform, unrestrictedgas flowfrom port 1 through port 3, conduit '32, port 4 and port 2.
  • the two numerals (1.0) at port 1 represent unit amplitude acoustic waves propagating into and out of the filter, thus the case of perfect reflection is shown.
  • the numeral (0.0) at port 2 indicates that no sound energy within the design frequency band leaves port 2.
  • a 3db coupler is used in the bandstop filter of FIG. 7;
  • the starting point isthe realization that two 3d! couplers connected end-to-end comprise a composite 0db coupler. If the conduits connecting the two Sdb couplers are crossed so that port 3 of the first connects to port 2 of the second, and so on, then the composite coupler will have all its energy appearing at port 3. Then, realize that if ports 4 and 3 of the first coupler are connected to togetherer, the same situation results but all the acoustic energy is now propagating out of port 1 (the image of port 3 of the composite crossconnected coupler). Thus, connecting ports 3 and 4 of a symmetrical 3db coupler as shown results in a reflective, bandstop filtering device.
  • FIG. 8 illustrates how a Odb coupler is used as a bandstop filter. In this case, all of the ports are open, except port 4, which is blocked. Because this is a 01111 coupler,
  • any odd quarter wave length coupler will be highly directional.
  • the spacing of the coupling elements may be one-quarter wave length or any odd multiple thereof.
  • a spacing of three quarter-wave lengths may be needed when attempting to directionally couple high frequency acoustic energy. At high frequencies,
  • Apparatus for separating acoustic energy in the form of waves from a moving fluid comprising:
  • a duct adapted to carry said fluid and said acoustic energy
  • said duct and chamber are formed by first andsecond generally parallel, tubular members'each having opposite open ends to permit free fluid flow theiethrough, wherein substantially all of the acoustic energy being coupled into the second tubular member from the first tubular member continues to travel in the same direction in the second tubular member but undergoes aphase shift of during the coupling process, wherein said'coupling elements are sized to couple approximately one-half of the acoustic energy from said first tubular member to said second tubular member, and further including means for'conveying fluid from the fluid outlet end of said first tubular member to the adjoining end of the second tubular member for free passage of fluid through said first tubular member in one direction and through said second tubular member in the opposite direction, said acoustic energy being reflected back to its source as a result of a series of coupling actions and phase shifts between said tubular members in both directions.
  • said coupling elements are designed to couple substantially all of said acoustic energy into said chamber, said acoustic energy undergoing a phase shift of 90 during the coupling process, wherein a second muffler apparatus is connected to an outlet of said chamber to provide an additional .phase shift of 90, and wherein means are provided to combine the resultant sound wave shifted inphase by with an equal amount of the original acoustic energy to provide cancellation thereof.
  • a muffler system comprising:
  • means including second'and third conduit means connected to a discharge outlet of said first conduit for dividing at least the acousticenergy therein into two generally equal parts for separate transmission through said second and third conduit means;
  • said second conduit means including directional acoustic coupling means for imposing a 180 phase shift on the sound waves being transmitted therethrough;
  • first and second tubular members are generally parallel members, and wherein said inlet and said outlet are on opposite ends of said members.
  • each coupler comprises a first tubular member having an inlet and a second tubular member having an outlet, said members being mounted in a side-by-side relationship with a wall therebetween, and wherein a plurality of coupling ele ments are provided in said wall to couple approximately one-half of the acousticenergy being carried bysaid first tubular member into said second tubular member.
  • first and second tubular members are generally parallel mem-- bers, and wherein said inlet of one member is disposed adjacent said outlet of the other member.
  • each coupler comprises a first tubular member and a second tubular member mounted in a side-by-side relationship with a wall therebetween, wherein a plurality of coupling elements are provided ,in said wall to couple acoustic energy from said first tubular member into said second tubular member, wherein an inlet of the first tubular member of the first coupler is connected to the discharge outlet of said first conduit, an outlet of said first tubular member is connected to said third conduit means, and an outlet of said second tubular member of the first coupler is connected to said second conduit means, said coupling openings of said first coupler being sized to transfer approximately one-half of the acoustic energy in said first tubular member into said second tubular member thereof, and wherein the second coupler has an inlet of the first tubularv member thereof and an outlet of the second tubular member thereof connected in said second conduit means, and
  • An engine exhaust muffler comprising:
  • a second conduit mounted in a side-by-side, generally parallel relationship with said first conduit, and having an inlet and an outlet in reverse positions with respect to said first conduit;
  • conduitmeans connecting said outlet of said first conduit to said inlet of said second conduit to provide anexhaust flow path in one direction through said first conduit and in the opposite direction through said second conduit;
  • first and second conduits being separated by single wall means having at least a pair of coupling elements therein axially spaced apart a distance approximately equal to an odd multiple of onequarter of the wave length of a selected frequency of sound waves emanating from the engine;
  • An engine exhaust muffler comprising:
  • a. a first conduit having an inlet adapted to be connected to an exhaust discharge port of an engine, and an outlet;
  • conduits being separated by wall means. having at least a pair of coupling elements therein spaced apart axially a distance approximately equal to an odd multiple of one-quarter of the wave length of a selected frequency of sound waves emanating from the engine;
  • said coupling openings being sized to directionally couple substantially all of the sound energy being carried by one of said conduits into the other conduit to thereby reflect back to the engine substantially all of the sound energy emanating from the engine at said selected frequency.
  • a method of separating acoustic energy. in the form of waves from a moving fluid comprising the steps of:

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Exhaust Silencers (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
US00248676A 1972-04-28 1972-04-28 Noise reduction apparatus and method Expired - Lifetime US3776364A (en)

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JP (1) JPS4941738A (enrdf_load_stackoverflow)
AU (1) AU472372B2 (enrdf_load_stackoverflow)
CA (1) CA981130A (enrdf_load_stackoverflow)
DE (1) DE2321649C2 (enrdf_load_stackoverflow)
FR (1) FR2182463A5 (enrdf_load_stackoverflow)
GB (1) GB1431662A (enrdf_load_stackoverflow)
IT (1) IT998103B (enrdf_load_stackoverflow)
SU (1) SU576972A3 (enrdf_load_stackoverflow)

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US6082487A (en) * 1998-02-13 2000-07-04 Donaldson Company, Inc. Mufflers for use with engine retarders; and methods
US6148519A (en) * 1998-09-18 2000-11-21 Donaldson Company, Inc. Apparatus for installing a packing material in a muffler assembly; and methods thereof
US6332511B1 (en) 1999-12-07 2001-12-25 Burgess-Manning, Inc. Silencer assembly having single strand fiberglass acoustic pack material
US6354398B1 (en) 1998-02-13 2002-03-12 Donaldson Company, Inc. Mufflers for use with engine retarders; and methods
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USD581335S1 (en) * 2007-05-02 2008-11-25 Manuel P. Contreas Split flow muffler
US20100051379A1 (en) * 2008-09-02 2010-03-04 Charles Graves Enhanced Exhaust System
US20120206011A1 (en) * 2011-02-15 2012-08-16 Westinghouse Electric Company Noise and vibration mitigation system for nuclear reactors employing an acoustic side branch resonator
US20120301267A1 (en) * 2006-05-24 2012-11-29 Seleon Gmbh Conducting unit, and conducting methods
CN103696828A (zh) * 2014-01-04 2014-04-02 诸城市海得威机械有限公司 一种工程车用除高频噪声消声器
US20170030610A1 (en) * 2015-07-31 2017-02-02 Mahle International Gmbh Flow channel and heating, ventilation, or air conditioning system
US9618151B2 (en) 2015-02-26 2017-04-11 Adriaan DeVilliers Compact modular low resistance broadband acoustic silencer
CN109899132A (zh) * 2017-12-11 2019-06-18 郑州宇通客车股份有限公司 排气管后处理器及车辆
US10458589B2 (en) * 2014-08-06 2019-10-29 Aaf Ltd. Sound suppression apparatus

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FR2543342B1 (fr) * 1983-03-21 1986-10-17 Centre Techn Ind Mecanique Dispositif anechoique attenuateur de bruit pour canalisations de liquides ainsi que procede et circuit l'utilisant pour mesurer l'energie emise par un equipement hydraulique
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US3946558A (en) * 1973-08-06 1976-03-30 Beekhuis Jr William H Exhaust system and method
US4038820A (en) * 1973-12-25 1977-08-02 Yamaha, Hatsudoki Kabushiki Kaisha Two-cycle engine wave interference muffler means
US4420750A (en) * 1979-03-30 1983-12-13 Sharp Kabushiki Kaisha Alphanumeric visual display of the matrix type
US4819428A (en) * 1986-02-27 1989-04-11 Alfa Romeo Auto S.P.A. Exhaust system for an internal combustion engine
US5123501A (en) * 1988-10-21 1992-06-23 Donaldson Company, Inc. In-line constricted sound-attenuating system
US5493080A (en) * 1993-03-05 1996-02-20 Ab Volvo External arrangement for damping sounds in a pipe system
US6082487A (en) * 1998-02-13 2000-07-04 Donaldson Company, Inc. Mufflers for use with engine retarders; and methods
US6354398B1 (en) 1998-02-13 2002-03-12 Donaldson Company, Inc. Mufflers for use with engine retarders; and methods
US6148519A (en) * 1998-09-18 2000-11-21 Donaldson Company, Inc. Apparatus for installing a packing material in a muffler assembly; and methods thereof
US6332511B1 (en) 1999-12-07 2001-12-25 Burgess-Manning, Inc. Silencer assembly having single strand fiberglass acoustic pack material
US20030136117A1 (en) * 2000-06-09 2003-07-24 Volvo Lastvagnar Ab Regeneration of a filter by the use of a tone generator
US7174707B2 (en) * 2000-06-09 2007-02-13 Volvo Lastvagnar Ab Regeneration of a filter by the use of a tone generator
WO2005097244A1 (en) * 2004-04-05 2005-10-20 Breas Medical Ab Ventilator for supplying breathable gas to a patient, and a noise reduction method for said ventilator
FR2878894A1 (fr) * 2004-12-08 2006-06-09 Faurecia Sys Echappement Volume d'echappement
WO2006061489A1 (fr) * 2004-12-08 2006-06-15 Faurecia Systemes D'echappement Volume d'echappement
US7527125B2 (en) * 2006-02-23 2009-05-05 J. Eberspaecher Gmbh & Co. Kg Muffler for an exhaust system
US20070205045A1 (en) * 2006-02-23 2007-09-06 Sascha Leng Muffler for an exhaust system
US20120301267A1 (en) * 2006-05-24 2012-11-29 Seleon Gmbh Conducting unit, and conducting methods
USD581335S1 (en) * 2007-05-02 2008-11-25 Manuel P. Contreas Split flow muffler
US20100051379A1 (en) * 2008-09-02 2010-03-04 Charles Graves Enhanced Exhaust System
US20120206011A1 (en) * 2011-02-15 2012-08-16 Westinghouse Electric Company Noise and vibration mitigation system for nuclear reactors employing an acoustic side branch resonator
US8393437B2 (en) * 2011-02-15 2013-03-12 Westinghouse Electric Company Llc Noise and vibration mitigation system for nuclear reactors employing an acoustic side branch resonator
CN103696828A (zh) * 2014-01-04 2014-04-02 诸城市海得威机械有限公司 一种工程车用除高频噪声消声器
US10458589B2 (en) * 2014-08-06 2019-10-29 Aaf Ltd. Sound suppression apparatus
US9618151B2 (en) 2015-02-26 2017-04-11 Adriaan DeVilliers Compact modular low resistance broadband acoustic silencer
US20170030610A1 (en) * 2015-07-31 2017-02-02 Mahle International Gmbh Flow channel and heating, ventilation, or air conditioning system
CN109899132A (zh) * 2017-12-11 2019-06-18 郑州宇通客车股份有限公司 排气管后处理器及车辆

Also Published As

Publication number Publication date
CA981130A (en) 1976-01-06
JPS4941738A (enrdf_load_stackoverflow) 1974-04-19
DE2321649A1 (de) 1973-11-15
IT998103B (it) 1976-01-20
DE2321649C2 (de) 1981-09-17
AU472372B2 (en) 1976-05-20
FR2182463A5 (enrdf_load_stackoverflow) 1973-12-07
SU576972A3 (ru) 1977-10-15
GB1431662A (en) 1976-04-14
AU5459773A (en) 1974-10-17

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