WO1991015666A1 - Silencieux pour automobile a une seule cavite - Google Patents

Silencieux pour automobile a une seule cavite Download PDF

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Publication number
WO1991015666A1
WO1991015666A1 PCT/US1991/001398 US9101398W WO9115666A1 WO 1991015666 A1 WO1991015666 A1 WO 1991015666A1 US 9101398 W US9101398 W US 9101398W WO 9115666 A1 WO9115666 A1 WO 9115666A1
Authority
WO
WIPO (PCT)
Prior art keywords
noise
audio
cancellation
volume
duct
Prior art date
Application number
PCT/US1991/001398
Other languages
English (en)
Inventor
John J. Cain
Dennis Barnes
David Dye
Original Assignee
Active Noise And Vibration Technologies, Inc.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Active Noise And Vibration Technologies, Inc. filed Critical Active Noise And Vibration Technologies, Inc.
Priority to EP91906617A priority Critical patent/EP0542749B1/fr
Priority to DE69128352T priority patent/DE69128352T2/de
Publication of WO1991015666A1 publication Critical patent/WO1991015666A1/fr

Links

Classifications

    • 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
    • F01N1/16—Silencing apparatus characterised by method of silencing by using movable parts
    • F01N1/20—Silencing apparatus characterised by method of silencing by using movable parts having oscillating or vibrating movement
    • 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
    • F01N1/06—Silencing apparatus characterised by method of silencing by using interference effect
    • F01N1/065—Silencing apparatus characterised by method of silencing by using interference effect by using an active noise source, e.g. speakers
    • 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
    • F01N1/16—Silencing apparatus characterised by method of silencing by using movable parts
    • F01N1/22—Silencing apparatus characterised by method of silencing by using movable parts the parts being resilient walls
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical
    • G10K2210/3227—Resonators
    • G10K2210/32272—Helmholtz resonators

Definitions

  • the present invention relates to sound muffling devices, particularly those of the type used in connection with tubes or ducts which emit sounds which one wishes to silence such as, for example, the exhaust pipes of internal combustion engines.
  • a combination of both high pass and low pass acoustic filters may be used to achieve the elimination of noise.
  • the elimination of noise may be viewed as generally involving the cancellation of the alternating flow of gases, representing sound transmission, while not impeding the steady flow of gas out from the exhaust system which is necessary in order to discharge spent combustion products.
  • mufflers have volumes in the range of six to eight times the piston displacement of the engine and may contain baffles with or without holes.
  • a primary aspect of their operation involves the cancellation of sound waves by interference, usually involving breaking the waves into two parts which follow different paths and meet again out of phase before leaving the muffler.
  • Another important aspect is that exhaust back pressure must be minimized in any muffler design, insofar as an increase of only one psi in back pressure decreases the maximum power output of an engine by about 2.5%. About 1% of this loss is due to additional work being expended by the engine to exhaust the gases. The balance of the loss is due to the effects of increased gas pressure on volumetric efficiency.
  • a degree of noise suppression is usually obtained by lining the ducts on at least two non-opposite walls with an efficient sound- absorbing material for a distance of three to six meters from both the inlet and the outlet. Where, due to the length of available duct, this is insufficient, additional noise suppression may be provided by introducing baffles into the duct and covering the baffles with sound-absorbing materials.
  • baffle filter systems may be obtained if we consider a quarter wavelength resonant cavity.
  • a cavity known as a Helmholz cavity is a chamber closed at one end and open at the other. Because it is a quarter wavelength in length, sounds entering the open end of the chamber pass through the chamber and are reflected back to the open end of the chamber with a phase delay of one-half a wavelength.
  • the half wavelength delay is caused because the time of transit of the acoustic disturbance through the chamber includes a forward transmission path of one-quarter wavelength and a reflected transmission back to the open end of an additional quarter wavelength.
  • the result is a half wavelength or 180° phase shift in the output of the cavity with respect to the sound passing over the top of the cavity.
  • the signals are phase shifted with respect to each other by 180 degrees, and because, for a first approximation, we can assume that during the emission of a particular sound, the amplitude and frequency of one wavelength of the sound is substantially identical to the amplitude and frequency of the next wavelength produced by the source. Thus, a given undulation corresponding to one wavelength is exactly cancelled by the prior undulation of the sound which one wishes to cancel. Naturally, this is only true for sound having the particular frequency which results in a quarter wavelength relationship between the Helmholz cavity and the sound. However, if the frequency is not far removed from the resonant frequency of cancellation, the cancellation effect will still " occur to a substantial extent.
  • Such prior art mufflers are constructed of sheet metal. More particularly, such mufflers comprise an outer shell or casing made of sheet metal and a sheet metal baffle structure secured within the casing. A path for the conduction of combustion gases and attendant acoustic disturbances is provided in the muffler adjacent the various noise absorbing cavities.
  • the invention is intended to provide a remedy. It solves the problem of how to muffle noises in a duct, such as an engine exhaust or air-conditioning duct with a simple, durable and effective device.
  • This configuration integrates a mixing diameter with an integral microphone for improved cancellation over a wider frequency range than previous attempts.
  • back pressure problems are minimized thus resulting in good fuel efficiency and minimal exhaust of pollutants into the air.
  • the same is achieved through the use of a single or multiply chambered dynamic cavity driven by an electro-
  • SUBSTITUTESHEET mechanical actuator which, effectively, generates an acoustic signal used to cancel noise in the duct.
  • the inventive muffler cavity is based upon the use of a so-called ported enclosure or symmetrically loaded system. This type of enclosure is characterized by the use of a closed rear volume, together with a front volume coupled to a radiating tuned port.
  • This novel tuned design utilizes a single circular port driven by multiple speakers which surround the exhaust pipe to provide improved cancellation.
  • Integrated into the port design is a mixing chamber surrounded by a circular sensing microphone. With the proper components and cavity volume and port selection high efficiency cancellation can be achieved over a 50 to 300 Hz frequency range.
  • a single circular port is used with multiple speakers as opposed to an array of individual ports from multiple speakers arranged around the exhaust outlet.
  • a preferred embodiment avoids locating the microphone and anti-noise port a distance away from each other for acoustic mixing in air with limited high frequency results.
  • the inventive system brings all of the components together at the exhaust port producing a higher degree of cancellation with higher frequency response than previous designs.
  • engine or other exhaust noise is introduced into a mixing region with an acoustic cancellation signal where they are caused to cancel each other.
  • a ring-shaped microphone array is disposed around the noise source and the acoustic cancellation signal, which is produced by the actuator, to generate an error signal proportional to the degree to which cancellation has not occurred. This error signal is then used to control the signal produced by the actuator.
  • Sensing of the sound pressure within the tubular member is done with one or more microphones where the output of the multiple microphones are combined by averaging of their individual outputs. Noise due to turbulence and other essentially random factors is cancelled through the use of a plurality of sound-sensing points.
  • a plurality of such sound-sensing points is achieved through the use of a tubular member with a plurality of sound-sensing holes disposed along its length.
  • This tubular member is disposed concentrically with and downstream from the emission point of sound exiting the mixing region and downstream of and concentric with the acoustic output of the actuator.
  • Figure 1 is a top plan view in cross section of an engine muffler constructed in accordance with the present invention
  • Figure 2 is a view along lines 2-2 of Figure 1
  • Figure 3 is a view along lines 3-3 of Figure 1 showing the construction of the muffler in cross section
  • Figure 4 is a transverse cross-sectional view of the muffler illustrated in Figure 1 along the lines 4-4 of Figure 1
  • Figure 5 is a detail along lines 5-5 of Figure 2 illustrating the construction of a microphone assembly useful in conjunction with the muffler of Figure 1
  • Figure 6 is a cross-sectional view along lines 6-6 of Figure 2 illustrating the placement of a microphone within the microphone assembly
  • Figure 7 is a block diagram of the inventive system
  • Figure 8 is a diagrammatic view of an aerodynamic microphone design
  • Figure 9 is a diagrammatic representation of an alternative embodiment of the inventive muffler system
  • Figure 10 is a view along lines 10-10 of Figure 9 illustrating the outside appearance of the muffler system of Figure 9.
  • Outer casing 12 comprises a cylindrical member 14, a forward end cap 16 and a rear end cap 18.
  • Cylindrical member 14, forward end cap 16 and rear end cap 18 are made of a relatively inexpensive material such as plastic which is selected for mechanical strain and durability under a wide range of temperatures and other environmental factors as would be experienced by a muffler positioned at the bottom of an automobile.
  • the exhaust pipe 20 is mounted within casing 12, being supported in forward end cap 16 by an insulative annular member 22.
  • the exhaust pipe 20 is made of steel, stainless steel or any other suitable material having a thickness sufficient to result in mechanical integrity.
  • the exhaust pipe 20 is made thick enough to withstand the expected degree of corrosion during the life of the automobile without losing the required strength.
  • muffler 10 When installed, it is contemplated that muffler 10 will be secured to the underside of the automobile and that exhaust 20 is also secured to the automobile. Insofar as it is connected to the exhaust of the engine, the end 24 of exhaust pipe 20 • is held in position by a plurality of radial support members 26, 28, 30 and 32. Radial support members 26-32 are secured between exhaust pipe 20 and mixing chamber pipe 36, by being welded or otherwise suitably attached to both of these members. In accordance with the preferred embodiment, mixing chamber pipe 34 and support members 26-32 are all made of steel, or stainless steel or other suitable materials. Likewise, exhaust pipe 20, radial support members 26-32, and mixing chamber pipe 36 may be made of stainless steel in view of the resistance of this material to long exposures of high temperatures and the various combustion products created during the operation of the internal combustion engine.
  • mixing chamber pipe 34 (which may also be made of plastic) is securely mounted within rear end cap 18 by being securely attached or jam-fitted in a circular hole 36 within end cap 18.
  • additional support is provided by a pair of transverse radial support members 38 and 40, as illustrated in Figure 4.
  • the transverse radial support members are made of material similar to that of support members 26-32.
  • transverse radial support members 38 and 40 and radial support members 30 and 32 are made of triangular shaped pieces of relatively thick sheet metal in order to provide support when forces are applied to the muffler structure in the direction parallel to the axis of symmetry of exhaust pipe 20.
  • a cylindrically- shaped layer of heat insulative material 42 which is disposed around exhaust pipe 20. Typically, this is insulating fiberglass wrap, header wrap, or an isolating air cavity.
  • An acoustical chamber 44 is defined by a pair of inner planar walls 46 and 48, actuators 50 and 52 and a forward wall 54 with a circular concentric hole 56 in its center. On the edge of the chamber opposite the forward wall 54 is a rear wall member 58. Rear wall member 58 and forward wall 54 are both made of synthetic material such as that of outer casing 12.
  • wall 54 defines a chamber 60 which is filled with sound deadening material such as fiberglass 62 in order to change the equivalent cavity volume and improve and simplify the acoustical properties of the acoustical chamber 44.
  • rear wall member 58 defines a pair of chambers 64 and 66 which are filled with acoustic deadening material such as fiberglass 68 and 70 which again change the equivalent volume and simplify the operation of acoustical chamber 44 by preventing random oscillations and resonances from interfering with the operation of the muffler.
  • a tubular microphone assembly 72 is provided at the end of mixing chamber pipe 4.
  • a mixing chamber 74 ( Figure 1) is defined at the end of mixing chamber pipe 34.
  • a plurality of holes 76 are defined by a circular tubular member 78.
  • holes 76 are equispaced along the circumference of member 78 and one such hole 76 is illustrated in detail in Figure 5.
  • four microphones are also equispaced within the circumference of member 78.
  • Microphone assembly 72 is secured to the end of mixing chamber pipe 34 using any suitable means such as rivets, adhesive, or the like. The electrical output of these multiple microphones are combined (averaged) using a mixing circuit to provide a composite residual error signal.
  • microphones 80 and 82 are illustrated by the enlarged detailed diagram of Figure 6. Here microphone 80 is shown embedded in the sidewall 86 of circular tubular member 78. Microphones 80 and 82 may be positioned at a variety of angular positions depending upon whether one wishes to route the microphone cable 88 on the inside or outside of the device.
  • the noise generated by exhaust pipe 20 and actuators 50 and 52 is detected by tubular microphone assembly 72 which generates an error signal which is sent to a cancellation signal generator 90.
  • the cancellation signal generator in turn, generates a cancellation signal which is coupled to actuators 50 and 52.
  • a cancellation signal generator such as that marketed by several companies today may be used.
  • an acoustical chamber 44 which is substantially completely closed except for an annular output duct region 92 defined between exhaust pipe 20 and mixing chamber pipe 34, is provided.
  • the acoustic energy generated by actuators 50 and 52 is transformed into a concentric source which is concentric with the noise output of exhaust pipe 20.
  • These two concentric sources are mixed together in mixing region 94 where, in the ideal case, because successive undulations are substantially completely out of phase with each other and of equal magnitude, they add together and cancel each other resulting in zero noise at the output of the exhaust system adjacent microphone assembly 72. It has been found that a mixing region 94 on the order of ten centimeters in diameter and three centimeters in length is sufficient to achieve an acceptable degree of cancellation in an automobile muffler system.
  • a drip hole with a short, small diameter tube 96 is provided at the bottom of the muffler, as illustrated in Figure 4.
  • an additional drip hole 98 adjacent to the tube microphone assembly 72 it may also be desirable to put an additional drip hole 98 adjacent to the tube microphone assembly 72. From a practical standpoint, such drip holes will not affect the performance of the system in any substantial matter from an acoustic standpoint.
  • the tubular ring microphone system disclosed above is both durable and has excellent performance characteristics.
  • the microphones 80 and 82 are protected from the environment by being positioned within circular tubular member 78.
  • the microphone is protected from weather and heat effects.
  • the use of numerous holes 76 in circular tubular member 78 results in numerous individual inputs to the microphones and has the result of acoustically averaging random noise, thus drastically reducing wind and exhaust turbulence effects.
  • the tubular configuration with the multiple microphones produces a residual error signal which is the integrated-averaged error as measured along the perimeter of the ring. For a dynamic muffler measuring this error at the zone of cancellation produces a symmetrical cancellation zone that is optimum.
  • the tubular microphone assembly 72 is constructed from an insulating tubular material such as plastic tube. This creates a thermally insulating medium to protect the microphone.
  • the tubular material is perforated at regular intervals, corresponding to 30-50 holes per wavelength at the highest frequency of interest (i.e., 0.44 meters separation between holes corresponding to 600 Hz) .
  • the hole size needs to be small, typically around 0.062 meters. The hole size and number of holes can be varied to adjust the amount of sound pickup.
  • the plastic tube of the microphone assembly protects the microphones by surrounding them with a captive thermally insulating air medium.
  • the use of open holes at the exhaust outlet provides an accurate means of sound transmission without directly exposing the microphone elements to the corrosive and hot exhaust gases.
  • An alternative configuration is to cover the perforations in the tubular member with thin (.001") Kapton (TM) tape.
  • TM Kapton
  • a bumper 104 may accommodate the inventive muffler 110.
  • an exhaust pipe 120 may feed its output to a mixing chamber 174 which, in turn, receives the acoustic output of a pair of actuators 150 and 152. Additional advantage may be obtained by providing an annular membrane 106 to receive the output of actuators 150 and 152 and couple that output generally in the directions indicated by arrows 108 while isolating the actuators from the environment. While an illustrative embodiment of the invention has been described above, it is, of course, understood that various modifications will be apparent to those of ordinary skill in the art. Such modifications are within the spirit and scope of the invention, which is limited and defined only by the appended claims.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Silencers (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

Système de suppression de bruit destiné à être utilisé dans des moteurs à combustion interne et suffisamment petits pour être utilisés dans des applications automobiles. Un générateur de bruit d'annulation ainsi que des hauts-parleurs actuateurs (50, 52) produisent un bruit destiné à se combiner avec le bruit du moteur et à annuler ce dernier lequel est porté dans les gaz d'échappement dans un conduit à chambre de mélange (34). Le bruit obtenu quittant le conduit à chambre de mélange (34) est mesuré par un réseau de microphones tubulaire circulaire (72) destiné à réguler le générateur de bruit.
PCT/US1991/001398 1990-04-09 1991-02-26 Silencieux pour automobile a une seule cavite WO1991015666A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP91906617A EP0542749B1 (fr) 1990-04-09 1991-02-26 Amortissement du bruit
DE69128352T DE69128352T2 (de) 1990-04-09 1991-02-26 Schalldämpfervorrichtung

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US50736690A 1990-04-09 1990-04-09
US507,366 1990-04-09

Publications (1)

Publication Number Publication Date
WO1991015666A1 true WO1991015666A1 (fr) 1991-10-17

Family

ID=24018364

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1991/001398 WO1991015666A1 (fr) 1990-04-09 1991-02-26 Silencieux pour automobile a une seule cavite

Country Status (5)

Country Link
EP (1) EP0542749B1 (fr)
AU (1) AU7572191A (fr)
CA (1) CA2039745C (fr)
DE (1) DE69128352T2 (fr)
WO (1) WO1991015666A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5325438A (en) * 1993-02-01 1994-06-28 At&T Bell Laboratories Active noise-cancellation system for automotive mufflers
WO1995002238A1 (fr) * 1993-07-07 1995-01-19 Leistritz Ag & Co. Abgastechnik Attenuateur de bruit actif
EP0674097A1 (fr) * 1994-02-22 1995-09-27 ELECTRONIC SOUND ATTENUATION S.p.A. Silencieux actif de gaz d'échappement
EP0817166A1 (fr) * 1992-05-01 1998-01-07 Fujitsu Ten Limited Dispositif antibruit
FR3005993A1 (fr) * 2013-05-23 2014-11-28 Dcns Systeme de silencieux actif pour ligne d'echappement d'un moteur diesel notamment de plateforme navale

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009045999A1 (de) * 2009-10-26 2011-04-28 J. Eberspächer GmbH & Co. KG Fahrzeugheizsystem
DE102013005147A1 (de) 2013-03-26 2014-10-02 Mann + Hummel Gmbh Aktive Schalldämpfereinrichtung für eine Brennkraftmaschine
DE102014001786A1 (de) 2013-03-26 2014-10-02 Mann + Hummel Gmbh Aktive Schalldämpfereinrichtung für eine Brennkraftmaschine
DE102014001721A1 (de) 2013-03-26 2014-10-02 Mann+Hummel Gmbh Aktive Schalldämpfereinrichtung für eine Brennkraftmaschine
DE102015212041A1 (de) * 2015-06-29 2016-12-29 Mahle International Gmbh Gasführende Einrichtung

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3712412A (en) * 1971-11-18 1973-01-23 Environeering Sound suppressing system
US3936606A (en) * 1971-12-07 1976-02-03 Wanke Ronald L Acoustic abatement method and apparatus
US4044203A (en) * 1972-11-24 1977-08-23 National Research Development Corporation Active control of sound waves
US4177874A (en) * 1977-04-01 1979-12-11 Agence Nationale De Valorisation De La Recherche (Anvar) Active acoustic sound absorber device
US4527282A (en) * 1981-08-11 1985-07-02 Sound Attenuators Limited Method and apparatus for low frequency active attenuation
US4665549A (en) * 1985-12-18 1987-05-12 Nelson Industries Inc. Hybrid active silencer
WO1989007701A1 (fr) * 1988-02-19 1989-08-24 Noise Cancellation Technologies, Inc. Systeme actif d'attenuation sonore pour systemes d'echappement d e moteur et analogue

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3789166A (en) * 1971-12-16 1974-01-29 Dyna Magnetic Devices Inc Submersion-safe microphone
GB2204916B (en) * 1987-05-19 1991-10-16 British Gas Plc A silencer

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3712412A (en) * 1971-11-18 1973-01-23 Environeering Sound suppressing system
US3936606A (en) * 1971-12-07 1976-02-03 Wanke Ronald L Acoustic abatement method and apparatus
US4044203A (en) * 1972-11-24 1977-08-23 National Research Development Corporation Active control of sound waves
US4177874A (en) * 1977-04-01 1979-12-11 Agence Nationale De Valorisation De La Recherche (Anvar) Active acoustic sound absorber device
US4527282A (en) * 1981-08-11 1985-07-02 Sound Attenuators Limited Method and apparatus for low frequency active attenuation
US4665549A (en) * 1985-12-18 1987-05-12 Nelson Industries Inc. Hybrid active silencer
WO1989007701A1 (fr) * 1988-02-19 1989-08-24 Noise Cancellation Technologies, Inc. Systeme actif d'attenuation sonore pour systemes d'echappement d e moteur et analogue

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0542749A4 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0817166A1 (fr) * 1992-05-01 1998-01-07 Fujitsu Ten Limited Dispositif antibruit
US5325438A (en) * 1993-02-01 1994-06-28 At&T Bell Laboratories Active noise-cancellation system for automotive mufflers
WO1994017761A1 (fr) * 1993-02-01 1994-08-18 At & T Corp. Systeme actif de suppression de bruit pour silencieux de vehicules automobiles
WO1995002238A1 (fr) * 1993-07-07 1995-01-19 Leistritz Ag & Co. Abgastechnik Attenuateur de bruit actif
US5677958A (en) * 1993-07-07 1997-10-14 Leistritz Ag & Co Abgastechnik Active sound damper
EP0674097A1 (fr) * 1994-02-22 1995-09-27 ELECTRONIC SOUND ATTENUATION S.p.A. Silencieux actif de gaz d'échappement
FR3005993A1 (fr) * 2013-05-23 2014-11-28 Dcns Systeme de silencieux actif pour ligne d'echappement d'un moteur diesel notamment de plateforme navale

Also Published As

Publication number Publication date
CA2039745A1 (fr) 1991-10-10
DE69128352T2 (de) 1998-06-10
AU7572191A (en) 1991-10-30
DE69128352D1 (de) 1998-01-15
EP0542749A4 (en) 1994-05-25
CA2039745C (fr) 2001-06-12
EP0542749B1 (fr) 1997-12-03
EP0542749A1 (fr) 1993-05-26

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