US3700069A - Wave interference silencer - Google Patents

Wave interference silencer Download PDF

Info

Publication number
US3700069A
US3700069A US145405A US3700069DA US3700069A US 3700069 A US3700069 A US 3700069A US 145405 A US145405 A US 145405A US 3700069D A US3700069D A US 3700069DA US 3700069 A US3700069 A US 3700069A
Authority
US
United States
Prior art keywords
acoustical
flow path
baffle
frequency
pipes
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.)
Expired - Lifetime
Application number
US145405A
Other languages
English (en)
Inventor
John T Rausch
William J Parker
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motors Liquidation Co
Original Assignee
General Motors Corp
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 General Motors Corp filed Critical General Motors Corp
Application granted granted Critical
Publication of US3700069A publication Critical patent/US3700069A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • F01N1/06—Silencing apparatus characterised by method of silencing by using interference effect

Definitions

  • a wave interference silencer includes a pair of coaxially disposed pipes which are separated by helical baffle and define an axial flow path through the inner pipe and an outer helical flow path between the pipes and the baffle.
  • a plurality of inwardly projecting longitudinal ribs are formed on the outer pipe to radially v space the baffle from the outer pipe and define a plu- 5 Claims, 7 Drawing Figures PATENTEDHBI 24 I972 OUTLET- INLET PRESSURE RATIO IN ENTORS.
  • FREQUENCY C [fa/21. arr
  • the present invention relates to silencing systems and, in particular, to a wave interference attenuating device for a motor vehicle exhaust line that incorpor'ates supplemental acoustical couplings for improving high frequency attenuation.
  • Exhaust systems using destructive wave interference principles have been proposed for predictably silencing the periodic noises produced by an operating motor vehicle engine throughout the entire noise spectrum of the engine.
  • such systems employ a plurality of serially connected attenuating sections which are energy and flow compensated to establish actual sound propogational velocities such that the pressure waves traveling separate acoustical paths in the device exit in phase opposition. In this manner, the pressure waves destructively acoustically interfere in a coupling volume adjacent the exit end.
  • the more prevalent construction for these devices takes the form of a pair of coaxially disposed cylindrical pipes which are separated by a helically wound baffle.
  • the center pipe defines an inner axial flow path and the bafile and the pipes define an outer helical flow path.
  • the ratio of acoustical lengths of the separate flow paths places the pressure waves one-half cycle or 180 out of phase at the exit end of the device at a predetermined fundamental frequency.
  • these flow paths constitute a conduit having a substantially frequency dependent reactance, the sound energy propagates therethrough without significant attenuation but with a phase shift which increases with frequency. The phase shift will accordingly provide repetitive transmission characteristics.
  • While such a device will produce limited attenuation on either side of the fundamental frequency and at multiples thereof, normally numerous attenuating sections are needed to obtain complete silencing throughout the noise spectrum, particularly at the lower frequencies.
  • a pair of relatively long length sections will provide the requisite low frequency attenuation and due to the aforementioned repetitive transmission characteristics also provide nominal high frequency attenuation.
  • the engine will normally produce objectionably high frequency noises which are not necessarily multiples of the frequency attenuated by these sections. Therefore, two or three relatively short sections must be provided for these frequencies.
  • five or six such sections have been considered necessary to provide the required silencing.
  • the present invention provides an improved construction wherein a low frequency attenuating section contains integrated high frequency silencing means that permit elimination of the conventional high frequency sections.
  • the subject attenuating device comprises a pair of concentrically disposed cylindrical pipes which are separated by a helical wound baffle.
  • the center pipe forms an' inner axial flow conduit.
  • the space between the pipes and the baffle forms an outer helical flow conduit.
  • the baffle establishes a differing acoustical length for the helical flow conduit to place the pressure waves traveling therethrough in phase opposition at the outlet with the pressure waves traveling through the inner conduit thereby attenuating energy at a predetermined low frequency.
  • High frequency attenuation is integrally provided in the present attenuating section by supplemental acoustical leakage paths in the outer flow conduit.
  • a plurality of inwardly projecting longitudinal ribs on the outer pipe are radially spaced from the inner surface thereof to establish a circumferential series of annular flow passages between successive turns of the outer flow conduit.
  • the radial spacing in the order of 0.005 to 0.020 inch, establishes a primarily resistive acoustical impedance which is substantially independent of frequency.
  • the leakage path comprises small diameter apertures in the baffle.
  • FIG. 1 is a plan view of a motor vehicle frame having an exhaust system incorporating a wave interference silencer made in accordance with the present invention
  • FIG. 2 is an enlarged fragmentary cross sectional view of the silencer shown in FIG. 1;
  • FIG. 3 is a view taken along line 33 of FIG. 2;
  • FIG. 4 is an enlarged cross sectional view of a portion of FIG. 3 showing the acoustical and fluid leakage paths between the baffle and the outer pipe;
  • FIG. 5 is a view taken along line 5--5 of FIG. 4;
  • FIG. 6 is a view similar to FIG. 5 showing an alternate form of the acoustical and fluid leakage paths.
  • FIG. 7 is a graph showing the relationship of the outlet-inlet pressure ratio versus frequency in a device having acoustical and fluid leakage paths.
  • FIG. 1 there is shown a motor vehicle frame 10 on which there is mounted an internal combustion engine 12 having a pair of exhaust conduits 14.
  • an internal combustion engine 12 having a pair of exhaust conduits 14.
  • exhaust gases are discharged from the exhaust manifolds to an exhaust line 16 including a crossover pipe 18.
  • the exhaust line 16 comprises a catalytic convertor 20 and low frequency wave interference silencers or attenuating sections 22, 24.
  • the convertor 20 and the attenuating section 22, 24 are acoustically coupled in series by coupling conduits 25, 26.
  • a tailpipe extension 28 is connected to the outlet end of the attenuating section 24 and constitutes the exhaust end of the system.
  • the above components from the exhaust manifold 14 to the tailpipe extension 28 form an acoustical line through which heated exhaust gases and the resultant 5 pressure waves flow as products of combustion .from the engine 12.
  • the engine 12 generates pressure pulses and sound waves in the exhaust line 16 having plural frequencies which are a function of engine speed.
  • the attenuating sections 22 and 24 provide broad band attenuation throughout the noise spectrum of the engine.
  • the catalytic convertor which is used in an exhaust emission system, additionally provides an inherent high frequency attenuation and accordingly, supplements the sections 22 and 24.
  • the convertor 20 is conventional in construction and forms no part of the present invention other than performing the aforementioned high frequency supplemental attenuation.
  • the attenuating sections 22 and 24 have section lengths for providing attenuation at select low frequencies.
  • the section 22 is designed to have fundamental attenuating frequency around 25 Hz.
  • the section 24 will be designed to have a fundamental attenuating frequency for around 40 Hz. Additionally, the sections will provide attenuation at multiples of this fundamental frequencies. Except for their lengths, the sections 22, 24 are identical in construction and further details will be given with reference to the attenuating section 22.
  • the attenuating section 22 comprises a cylindrical inner pipe 30 and a cylindrical outer pipe 32, which are separated by a helically wound baffle 34.
  • the inner pipe 30 forms a flow conduit or axial flow path 36.
  • the outer pipe 32, the inner pipe 30, and the baffle 34 establish an outer flow conduit or helical flow path 38.
  • the flow paths 36 and 38 are acoustically coupled in parallel between an inlet 40 defined by the coupling 25 at the upstream end of the attenuating section and an outlet 41 defined by the coupling 26 at the downstream end thereof.
  • the flow paths 36 and 38 form acoustical sound transmission paths having reactances substantially the same as a straight pipe.
  • the reactance due to the compliance of the flowing gas, increases with frequency. Additionally acoustical energy propagates through the flow paths without appreciable loss, but with phase shift which increases with frequency.
  • the present invention improves upon this construction by providing supplemental acoustical couplings between adjacent or spaced sections of the outer flow path 38 to provide increased attenuation at the higher frequencies.
  • the helical baffle 34 is attached to the inner pipe 30 at its inner diameter and has an outer diameter slightly smaller than the inner diameter of the outer pipe 32.
  • Four circumferentially spaced inwardly projecting ribs 42 extend longitudinally along the inner surface of the outer pipe 32.
  • the ribs 42 have apexes 44, as shown in FIG. 4, which engage the outer surface of the baffle 34 to radially space the inner surface of the outer pipe 32 from the outer surface of the baffle 34.
  • the ribs 42 thus establish narrow annular acoustical and fluid leakage paths or passages between the baffle 34 and the outer pipe 32. Accordingly, parallel acoustical couplings are provided by the leakage paths 46 between adjacent turns of the flow path 38.
  • the leakage paths 46 are quite restrictive and in the preferred embodiment the baffle 34 and the pipe 32 have a clearance between 0.005 and 0.020 inch. This sizing will provide a primarily restrictive impedance which is substantially independent of frequency. As shown in FIG. 6, an alternate form of restrictive leakage can be generated by making apertures or perforations in baffle 34.
  • the outlet-inlet pressure ratio in the outer flow path 38 has a low frequency peak 50 around Hz, and a substantially reduced and constant ratio in the higher frequency region 52.
  • the high frequency ratio is in the order of0.l to 0.01.
  • the dividing of the flow and the basic attenuation due to the flow passages 46 provides a substantial and inherent attenuation at frequencies above Hz. Therefore, we have found that broad band attenuation throughout the noise spand of the attenuation can be provided by two basic sections.
  • the first section 22 has a fundamental frequency of around 25 Hz and having a section length of about 64 inches.
  • the second section 24 has a fundamental frequency of around 40 Hz and a section length of about 40 inches length.
  • the high frequency noises from the engine will be attenuated by flow passages with the characteristics outlined above.
  • a wave interference attenuating device comprising: means defining first and second flow paths having frequency dependent acoustical reactances, said second flow path having an inlet and an outlet acoustically coupled in parallel with the first flow path, said flow paths having conduits differing in acoustical lengths for placing sound waves traveling therethrough in phase opposition at said outlet; acoustical fluid leakage means between spaced sections of said second flow path having a frequency independent acoustical resistance, said leakage means providing parallel acoustical couplings between said spaced sections for attenuating the sound waves flowing through the second flow path without an appreciable phase shift thereby producing a reduced acoustical pressure at said outlet.
  • a wave interference attenuating device having a pair of conduits acoustically coupled in parallel between an inlet and an outlet, one of the conduits including bafile means having multiple turns which defines a helical flow path and establishes differing acoustical lengths between the conduits so as to place the sound waves traveling through the conduits in phase opposition at the outlet wherein said helical flow path has a substantially frequency dependent reactance
  • acoustical and fluid leakage paths in the baffle means acoustically connecting successive turns of said helical flow path to provide parallel acoustical couplings, said leakage paths having frequency independent acoustical resistances whereby said leakage paths are effective upon increasing frequency to attenuate acoustical energy flowing through said helical flow path thereby producing a reduced acoustical pressure at said outlet such that a portion of the acoustical energy from the other of said conduits flows reversely through said leakage paths for additional attenuation.
  • a broad band wave interference device comprising: a cylindrical inner pipe; a cylindrical outer pipe concentrically disposed with respect to said inner pipe; a helical baffle between said pipes, said baffle being connected to one of said pipes and having a clearance with respect to the other of said pipes, said pipes forming an inner axial flow path through inner pipe and an outer helical flow path between said pipes and said baffle, said helical flow path having an acoustical reactance substantially dependent on frequency; inlet means and outlet means fluidly and acoustically coupling said flow paths in parallel; connecting means structurally connecting said other of said pipes to said baffle and forming annular acoustical leakage passages between spaced sections of said helical flow path, said passages having an acoustical resistance substantially independent of frequency and being effective upon increasing sound wave frequencies for attenuating sound waves flowing through said helical flow path thereby producing reduced acoustical pressure at said outlet means.
  • a broad band wave interference device comprising: a cylindrical inner pipe having an axial flow path; a cylindrical outer pipe concentrically disposed with respect to said inner pipe; a multiple turn helical baffle between said pipes, said baffle being connected to said inner pipe and having a diametral clearance with respect to said outer pipes, said pipes and said baffle forming outer flow paths having multiple turns and a substantially frequency dependent acoustical reactance; an inlet and an outlet fluidly and acoustically coupling said flow paths in parallel; a plurality of longitudinally extending inwardly projecting ribs formed on the outer pipe, said ribs engaging said baffle and forming annular acoustical leakage passages between adjacent turns of said outer flow path, said passages having a substantially frequency independent acoustical resistance and being effective upon increasing frequency to attenuating sound waves flowing through said outer flow path thereby producing reduced acoustical pressure at said outlet such that a portion of the acoustical energy from the axial flow path flows up
  • a broad band wave interference silencer comprising: a cylindrical inner pipe; a helical baffle connected to the inner pipe; a cylindrical outer pipe concentrically disposed with respect to said inner pipe and connected to said bafile, said pipes forming an inner axial flow path through inner pipe and an outer helical flow path between said pipes and said baffle, said helical flow path having an acoustical reactance substantially dependent on frequency; inlet means and outlet means fluidly and acoustically coupling said flow paths in parallel; acoustical and fluid leakage apertures formed in said baffle establishing acoustical couplings between spaced sections of said helical flow path having an acoustical resistance substantially independent of frequency, said apertures being efiective upon increasing sound wave frequencies for attenuating sound waves flowing through said helical flow path thereby producing reduced acoustical pressure at said outlet means and a pressure imbalance between said flow paths whereby a portion of the acoustical energy from the axial flow path is conducted up

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)
US145405A 1971-05-20 1971-05-20 Wave interference silencer Expired - Lifetime US3700069A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US14540571A 1971-05-20 1971-05-20

Publications (1)

Publication Number Publication Date
US3700069A true US3700069A (en) 1972-10-24

Family

ID=22512960

Family Applications (1)

Application Number Title Priority Date Filing Date
US145405A Expired - Lifetime US3700069A (en) 1971-05-20 1971-05-20 Wave interference silencer

Country Status (7)

Country Link
US (1) US3700069A (cg-RX-API-DMAC10.html)
JP (1) JPS558650B1 (cg-RX-API-DMAC10.html)
CA (1) CA953591A (cg-RX-API-DMAC10.html)
DE (1) DE2221634C3 (cg-RX-API-DMAC10.html)
FR (1) FR2138733B1 (cg-RX-API-DMAC10.html)
GB (1) GB1325837A (cg-RX-API-DMAC10.html)
IT (1) IT957829B (cg-RX-API-DMAC10.html)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888331A (en) * 1974-05-03 1975-06-10 Gen Motors Corp Power tuned wave interference silencer
US3913703A (en) * 1974-05-03 1975-10-21 Gen Motors Corp Single inner assembly wave interference silencer
US3966015A (en) * 1975-02-19 1976-06-29 General Motors Corporation Silencer element
WO1985000853A1 (en) * 1983-08-16 1985-02-28 Burstein Lincoln A Method and apparatus for fluid control and silencing of exhausting or exploding gases
US4683978A (en) * 1984-11-22 1987-08-04 Tula Silencers (Propriety) Limited Exhaust silencer
US4685534A (en) * 1983-08-16 1987-08-11 Burstein A Lincoln Method and apparatus for control of fluids
US5765997A (en) * 1995-04-29 1998-06-16 Daewoo Electronics Co., Ltd. Bubble generator for a washing machine
US6364055B1 (en) 2000-09-26 2002-04-02 Alan H. Purdy Acoustically non-resonant pipe
US20050011700A1 (en) * 2003-07-14 2005-01-20 Dadd Paul M. Devices for regulating pressure and flow pulses
US20050045419A1 (en) * 2003-08-25 2005-03-03 Michael Choi Noise attenuation device for a vehicle exhaust system
US20050045418A1 (en) * 2003-08-25 2005-03-03 Michael Choi Noise attenuation device for a vehicle exhaust system
US20050153035A1 (en) * 2004-01-12 2005-07-14 Winterlab Limited Presentation board for freezing meat product
US20070034444A1 (en) * 2005-08-15 2007-02-15 Mk Seiko Co., Ltd. Reflecting plate type silencer pipe
US20070107982A1 (en) * 2005-11-17 2007-05-17 Sullivan John T Flow-through sound-cancelling mufflers
CN107002544A (zh) * 2015-02-26 2017-08-01 金基训 引擎配管流速增大装置及其加工方法
CN107476863A (zh) * 2016-06-07 2017-12-15 东北林业大学 具有节能减排功效的汽车复合式消声器系统
US20190162350A1 (en) * 2017-11-30 2019-05-30 General Electric Company Inline fluid damper device
US20200043456A1 (en) * 2018-08-03 2020-02-06 Boston University Air-transparent selective sound silencer using ultra-open metamaterial
US11549414B1 (en) * 2019-11-07 2023-01-10 Phillip M. Adams Sound attenuator apparatus and method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2620169B1 (fr) * 1987-09-09 1990-07-20 Glaenzer Spicer Sa Partie de ligne d'echappement, notamment pour moteur a combustion interne

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE7353C (de) * L. V. BERND in Wiener Neustadt Schnellwaage zum Abwägen von Getreide
GB460148A (en) * 1934-07-19 1937-01-18 Zygmunt Wilman Improvements relating to exhaust gas mufflers
US2185489A (en) * 1934-07-19 1940-01-02 Wilman Zygmunt Muffler
US2468454A (en) * 1944-05-10 1949-04-26 Bell Telephone Labor Inc Acoustic wave filter with resistive termination, including side branch chamber
FR1087417A (fr) * 1953-07-29 1955-02-23 Silencieux pour amortir les bruits de pulsation des gaz d'un moteur et procédé de fabrication
US3113635A (en) * 1959-03-31 1963-12-10 Bolt Beranek & Newman Apparatus for silencing vibrational energy
US3209858A (en) * 1963-06-25 1965-10-05 Walker Mfg Co Muffler having depressed channel forming tuning passages
US3235003A (en) * 1963-06-04 1966-02-15 Cloyd D Smith Spiral flow baffle system
US3370673A (en) * 1964-09-02 1968-02-27 Walker Mfg Co Exhaust system with serially-connected mufflers
US3393767A (en) * 1967-06-28 1968-07-23 Travis B. Monk Combustion engine muffler

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE7353C (de) * L. V. BERND in Wiener Neustadt Schnellwaage zum Abwägen von Getreide
GB460148A (en) * 1934-07-19 1937-01-18 Zygmunt Wilman Improvements relating to exhaust gas mufflers
US2185489A (en) * 1934-07-19 1940-01-02 Wilman Zygmunt Muffler
US2468454A (en) * 1944-05-10 1949-04-26 Bell Telephone Labor Inc Acoustic wave filter with resistive termination, including side branch chamber
FR1087417A (fr) * 1953-07-29 1955-02-23 Silencieux pour amortir les bruits de pulsation des gaz d'un moteur et procédé de fabrication
US3113635A (en) * 1959-03-31 1963-12-10 Bolt Beranek & Newman Apparatus for silencing vibrational energy
US3235003A (en) * 1963-06-04 1966-02-15 Cloyd D Smith Spiral flow baffle system
US3209858A (en) * 1963-06-25 1965-10-05 Walker Mfg Co Muffler having depressed channel forming tuning passages
US3370673A (en) * 1964-09-02 1968-02-27 Walker Mfg Co Exhaust system with serially-connected mufflers
US3393767A (en) * 1967-06-28 1968-07-23 Travis B. Monk Combustion engine muffler

Cited By (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888331A (en) * 1974-05-03 1975-06-10 Gen Motors Corp Power tuned wave interference silencer
US3913703A (en) * 1974-05-03 1975-10-21 Gen Motors Corp Single inner assembly wave interference silencer
US3966015A (en) * 1975-02-19 1976-06-29 General Motors Corporation Silencer element
WO1985000853A1 (en) * 1983-08-16 1985-02-28 Burstein Lincoln A Method and apparatus for fluid control and silencing of exhausting or exploding gases
US4685534A (en) * 1983-08-16 1987-08-11 Burstein A Lincoln Method and apparatus for control of fluids
WO1989000237A1 (en) * 1983-08-16 1989-01-12 Roy Burstein Method and apparatus for control of fluids
US4683978A (en) * 1984-11-22 1987-08-04 Tula Silencers (Propriety) Limited Exhaust silencer
US5765997A (en) * 1995-04-29 1998-06-16 Daewoo Electronics Co., Ltd. Bubble generator for a washing machine
US6364055B1 (en) 2000-09-26 2002-04-02 Alan H. Purdy Acoustically non-resonant pipe
US20050011700A1 (en) * 2003-07-14 2005-01-20 Dadd Paul M. Devices for regulating pressure and flow pulses
US7661509B2 (en) 2003-07-14 2010-02-16 Dadd Paul M Devices for regulating pressure and flow pulses
US7131514B2 (en) 2003-08-25 2006-11-07 Ford Global Technologies, Llc Noise attenuation device for a vehicle exhaust system
US7086498B2 (en) 2003-08-25 2006-08-08 Ford Global Technologies, Llc Noise attenuation device for a vehicle exhaust system
US20050045418A1 (en) * 2003-08-25 2005-03-03 Michael Choi Noise attenuation device for a vehicle exhaust system
US20050045419A1 (en) * 2003-08-25 2005-03-03 Michael Choi Noise attenuation device for a vehicle exhaust system
US20050153035A1 (en) * 2004-01-12 2005-07-14 Winterlab Limited Presentation board for freezing meat product
US20070034444A1 (en) * 2005-08-15 2007-02-15 Mk Seiko Co., Ltd. Reflecting plate type silencer pipe
US7503426B2 (en) * 2005-08-15 2009-03-17 Mk Seiko Co., Ltd. Reflecting plate type silencer pipe
US20070107982A1 (en) * 2005-11-17 2007-05-17 Sullivan John T Flow-through sound-cancelling mufflers
US7600607B2 (en) * 2005-11-17 2009-10-13 John Timothy Sullivan Flow-through sound-cancelling mufflers
CN107002544A (zh) * 2015-02-26 2017-08-01 金基训 引擎配管流速增大装置及其加工方法
CN107002544B (zh) * 2015-02-26 2019-08-02 金基训 引擎配管流速增大装置及其加工方法
CN107476863A (zh) * 2016-06-07 2017-12-15 东北林业大学 具有节能减排功效的汽车复合式消声器系统
US20190162350A1 (en) * 2017-11-30 2019-05-30 General Electric Company Inline fluid damper device
US10808874B2 (en) * 2017-11-30 2020-10-20 General Electric Company Inline fluid damper device
US20200043456A1 (en) * 2018-08-03 2020-02-06 Boston University Air-transparent selective sound silencer using ultra-open metamaterial
US10947876B2 (en) * 2018-08-03 2021-03-16 Trustees Of Boston University Air-transparent selective sound silencer using ultra-open metamaterial
US11846217B2 (en) 2018-08-03 2023-12-19 Trustees Of Boston University Air-transparent selective sound silencer using ultra-open metamaterial
US12352190B2 (en) 2018-08-03 2025-07-08 Trustees Of Boston University Air-transparent selective sound silencer using ultra-open metamaterial
US11549414B1 (en) * 2019-11-07 2023-01-10 Phillip M. Adams Sound attenuator apparatus and method
US11988123B1 (en) 2019-11-07 2024-05-21 Phillip M. Adams Sound attenuator apparatus and method

Also Published As

Publication number Publication date
CA953591A (en) 1974-08-27
FR2138733B1 (cg-RX-API-DMAC10.html) 1973-07-13
JPS558650B1 (cg-RX-API-DMAC10.html) 1980-03-05
DE2221634C3 (de) 1979-06-21
IT957829B (it) 1973-10-20
DE2221634B2 (de) 1978-11-02
DE2221634A1 (de) 1972-11-30
GB1325837A (en) 1973-08-08
FR2138733A1 (cg-RX-API-DMAC10.html) 1973-01-05

Similar Documents

Publication Publication Date Title
US3700069A (en) Wave interference silencer
US3948349A (en) Wave interference silencer
US3913703A (en) Single inner assembly wave interference silencer
US3888331A (en) Power tuned wave interference silencer
US8083025B2 (en) Silencer provided on exhaust pipe of vehicle engine
US3212603A (en) Muffler with tuned silencing chambers
US3072214A (en) Gas blending and sound-attenuating system and apparatus
US20090014238A1 (en) Muffler
US3429397A (en) Laminated conduit and acoustic silencer
US4046219A (en) Exhaust silencer apparatus for internal combustion engine
US6595319B1 (en) Muffler
US2940538A (en) Silencer
US4172508A (en) Exhaust silencers
US3993160A (en) Silencer for a heat engine
US3744589A (en) Swirling flow muffler
US4779703A (en) Silencing device for internal combustion engine
US20200173320A1 (en) Acoustic volume in hot-end of exhaust systems
JP7125441B2 (ja) 消音器
US2922485A (en) Muffler
US3648802A (en) Gas flow baffle for wave interference silencing systems
US2150811A (en) Muffler
US2445045A (en) Sound-trapping muffler construction
US3495680A (en) Exhaust silencing system
US2928491A (en) Sound and gas-flow control unit
US2124933A (en) Muffler