US3920095A - Free flow sound attenuating device and method of using - Google Patents

Free flow sound attenuating device and method of using Download PDF

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Publication number
US3920095A
US3920095A US438736A US43873674A US3920095A US 3920095 A US3920095 A US 3920095A US 438736 A US438736 A US 438736A US 43873674 A US43873674 A US 43873674A US 3920095 A US3920095 A US 3920095A
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recited
sound
foraminous
attenuator
high frequency
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US438736A
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English (en)
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Raymond C Clark
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Technetics Corp
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Brunswick Corp
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Priority to US438736A priority Critical patent/US3920095A/en
Priority to CA218,185A priority patent/CA1042809A/en
Priority to GB3056/75A priority patent/GB1501441A/en
Priority to JP50013283A priority patent/JPS50127031A/ja
Priority to FR7503061A priority patent/FR2260059B1/fr
Priority to DE19752504132 priority patent/DE2504132A1/de
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Assigned to TECHNETICS CORPORATION reassignment TECHNETICS CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BRUNSWICK CORPORATION
Assigned to HOUSEHOLD COMMERCIAL FINANCIAL SERVICES, INC. reassignment HOUSEHOLD COMMERCIAL FINANCIAL SERVICES, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: TECHNETICS CORPORATION, A CORP. OF IL
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Assigned to TECHNETICS CORPORATION reassignment TECHNETICS CORPORATION RELEASE OF SECURITY INTEREST Assignors: FIRST SOURCE FINANCIAL SOURCE LLP
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    • 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
    • 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

Definitions

  • the present invention is directed to a sound and noise attenuating device for use with flowing gas systems.
  • the invention is directed to a free flow sound attenuating device wherein the sound attenuated encompasses both low and high frequency sound and to a sound attenuating device for use particularly with flowing gases of single phase.
  • single phase it is meant flow comprising substantially I percent gaseous state with little or none of the flow in a liquid state.
  • low frequency frequencies 500 Hz or less, middle frequency being defined as between 500 Hz and 1000 Hz, and high frequency any frequency above lOOO Hz.
  • the device may be used for intake and exhaust gas flow systems such as mufflers and resona tors for internal combustion engines.
  • a low frequency attenuator it is generally meant those known in the art such as a Helmholtz type resonator, a single or multi-dimensional baffle system, retroverted systems, or expansion chambers.
  • high frequency attenuator it is meant those known in the art as attenuating frequencies above I000 Hz, one example being the use of quarter-wave standing wave; cavities which are closed with acoustically absorptive foraminous material. It is noted that best results are obtained of the low frequency attenuator used is of the Helmholtz type and the high frequency attenuator is of the quarter-wave standing wave type.
  • foraminous conduit any conduit having porosity such that the flow resistance across the conduit wall is properly selected relative to the acoustical impedance of the gas and sound pressure level entering the conduit.
  • the flow resistance may be uniform or non'uniform along the conduit length, a uniform distribution being preferable because of its lower manufacturing cost.
  • Free flow or straight through sound attenuating devices are known in the art, and by free flow it is meant those devices where the flowing gas passage is direct and open with minimal back pressure developed as compared to devices where the flowing gas must pass through a multi-directional baffle system, retroverted systems, or through expansion chambers.
  • Prior art devices have used resonators of the Helmholtz type separately or in combination with baffled systems for attenuating sound in exhaust gas flows for internal combustion engines, blower duct systems, fuel burning systems, etc.
  • the art also discloses using a single Helmholtz resonator for tuning out a specific frequency or multiple resonators for tuning out a multiple of frequencies, such that sound accompanying such gas flows have sound removed by the action of certain frequencies resonating in the Helmholtz chamber. Whether single or multiple resonators are used the sound attenuation is dependent on the frequency characteristics of the single resonator or the sum of the frequency characteristics for multiple resonators.
  • the present invention has as one object and advantage, the provision of a sound attenuation device that because of the operative association of the foraminous conduit with the low frequency attenuator, the size, weight and complexity found with prior art structures are eliminated and a very simple free flow device can be defined.
  • the device of the present invention accomplishes this by permitting several attenuating functions to take place in close proximity resulting in a synergistic sound attenuation characteristic.
  • Another object of this invention is to provide a sound attenuator which is simple in structure, easier to manufacture and easier to maintain than devices heretofore known in the art.
  • the device of the present invention is lower in cost and more durable in operation than prior art devices having equivalent sound pressure level and attenuation characteristics.
  • the structure of the present invention provides an improvement over them in its utilization of a central foraminous tube which may have an internal layer of metal flbers having a special coating.
  • the coating applied will depend on the function it is to serve one example being a material in an oxidized or unoxidized state resistant to corrosive substances that may be present in the flowing gas.
  • the foraminous tube operating in conjunction with a low frequency resonator also permits greater decibel attenuation in the high frequency resonator, heretobefore not known in the art or expected.
  • FIG. I shows a schematic of the basic structure of the sound attenuating device in accordance with this invention.
  • FIG. 2 is a section of FIG. 1 taken along lines 1-];
  • FIG. 3 is a graph detailing the improvement in sound attenuation by the unit shown in FlG. l;
  • FIG. 4 shows a first alternate embodiment to that shown in FIG. I;
  • FIG. 5 is a graph detailing the sound attenuation by the attenuator shown in FIG. 4;
  • FIG. 6 shows a second alternate embodiment to that in FIG. 1;
  • FIG. 7 shows a section of the structure in FIG. 6 taken along lines I-l;
  • FIG. 8 shows a third alternate embodiment of the sound attenuation device of the present invention.
  • FIG. 9 shows an embodiment of the central tube used in the present invention, sectioned along its centerline
  • FIG. 10 shows a second embodiment of the central tube of the present invention, sectioned along its centerline
  • FIG. 11 shows a third embodiment of the central tube of the present invention, sectioned along its centerline
  • FIG. 12 shows a fourth embodiment of the central tube of the present invention, sectioned along its centerline
  • FIG. 13 is a cross sectional view of another embodiment of this invention.
  • FIG. 14 is a cross sectional view of another embodiment of this invention.
  • FIG. 15 is a cross sectional view of another embodiment of this invention.
  • FIG. I6 is a cross sectional view of another embodiment of this invention.
  • the basic features of the preferred embodiment of this invention comprise (l) a foraminous conduit surrounded by (2) a housing having in series after the inlet end (3) a low frequency attenuator operatively associated with the conduit and (4) a high frequency attenuator operatively associated with the conduit end positioned after the low frequency attenuator to enhance the effectiveness of the high frequency attenuator by providing lower resistance to the high frequency sound entering the high frequency attenuator due to the absence of low frequency sound entering the high frequency attenuator.
  • FIG. I shows a schematic of a section of a sound attenuator according to the present invention.
  • the attenuator 8 has a central conduit 10 having an inlet end 12 and outlet end 13 which outlet and inlet end can be connected to conventional intake or exhaust pipes according to the particular application.
  • the attenuator 8 has a high frequency attenuator 8A and a low frequency Hz attenuator portion 88.
  • the low frequency attenuator may be a baffle system 8C, a multi-dimensional baffle system 8D, a retroverted system 8E, and an expansion chamber system 8F, shown in FIGS. 13-16 respectively, and used as desired.
  • the low frequency attenuators of FIGS. 13-16 do not prevent the high frequency portions from being flowed through.
  • the central conduit 10 is generally described as a foraminous tube, meaning a tube having a preselected flow resistance such that the pressure drop across the wall of the conduit is selected to match the impedance of the flowing fluid. That is. it is necessary that the conduit not be totally impervious to a flow of gas.
  • the choice of material for the conduit may be made of a number of materials some examples being. laminated screen structure. perforated tube, metal fiber web, knitted fiber or wire material. compacted fiber. foamed metals or non-metals, glass fiber. plastic fiber. porous ceramics or combinations thereof. However. it is noted that the choice of material for the conduit will be related to its particular application.
  • conduit strucutres may be used depending on the physical characteristics of the gas flow, four structures are shown as example in FIGS. 9, 10, II and 12.
  • FIG. 9 shows a tubular section 48 made of perforate plate having a plurality of holes 49. These holes may all have s similar or different diameters.
  • FIG. 10 shows a tubular metal structure section 50 made of metal fiber web or mesh structure.
  • which web and mesh structures may be produced by processes known in the art as described in U.S. Pat. No. 3.505.038; 3,127,668 and 3,469,297 each of which is incorporated by reference.
  • the mesh and web structures can be made of metal fiber made in accordance with the descriptions given in U.S. Pat. No. 3.394.2l3; 3.505.038; 3,505,039; 3,698,863; 3.379.000 and 3.277.550 each of which is also herein incorporated by reference. It is also possible to provide chopped fibers useful in the tubular structure in accordance with U.S. Pat. No. 3,504,516.
  • the above listed patents being owned by the assignee of the present invention.
  • coated metal fibers in accordance with U.S. Pat. No. 3.698.863 and 3,505,038.
  • Other ways of producing the fibers and fiber webs for the tube of this invention are known in the prior art and such other references are not excluded by the citing of the above references which are given as example only.
  • tubular structure made of fiber web or mesh as described above is desirable to other structures, since it has been found that this structure provides the greatest amount of frictional losses for optimum sound absorption.
  • FIG. II shows a tube made of a screen-like material 51 which may be used either separately or in combination with the tube shown in FIG. 9, the controlling factor being whether the outer shell 11 (See FIG. I of the structure has sufficient rigidity to provide support for the screen-like tube.
  • An equivalent form for the screenlike material would be a highly perforated tube or mat structure tubular in shape and having an external diameter approximately equal to the internal diameter of the tube.
  • FIG. 12 shows a preferred embodiment of the present invention comprising a conduit 10, wherein a conduit 52 (in accordance with the conduit shown in FIG. 9) has ports 53 of similar diameter shown large for purposes of illustration. It also has metal. organic or ceramic fibers 54 provided on the internal surface thereof. the fibers having a protective coating of oxidation-catalyst such as nickel. platinum. aluminum oxide. copper oxide. etc.
  • FIG. I and FIG. 2 whatever the form of the central conduit used. it is surrounded by and secured to an inner wall 21 closing cavities 19. with an outer shell ll enclosing this inner wall except for the inlet and outlet ends projecting a short distance for easy attachment to the device with which it will be used.
  • the foraminous portion of conduit is foraminous only for that portion of the conduit associated with cavities I9, this being indicated between points c and b.
  • the remaining portions of conduit 10 being non-porous to fluid flow except for ports 15.
  • the outer shell I1 is of a conventional nature, one example being sheet metal.
  • the flowing gas having concomitant sound to be attcnuatcd enters the sound attenuator 8 at the inlet end l2.
  • the gas comes into contact with low frequency Helmholtz resonator ports which use chamber 17 for resonating. Although it was defined earlier in the specification what is generally accepted as definition for low, middle, and high frequency, the cut-off range for low, medium and high frequency is relative and will depend upon the application.
  • the gas stream then passes by annular high frequency, quarter wavelength depth tuned cavities 19 which communicate with the central tube through the tube's foraminous wall 20.
  • the alpha character a indicates the depth of the quarter wavelength cavity.
  • FIG. 3 is a graph plotting attenuation of sound power in db verses frequency of the sound with the area under the curves representing the amount of sound absorbed. If for example the low frequency resonator was tuned, by appropriate adjustment of chamber volume 17 and port diameter l5 well known in the art, to 250 Hz the response curve would be that designated by lines L. A high frequency resonator line duct will have the typical curve shown as line H, usually tuned somewhere above 1000 Hz.
  • a reduction of IO decibels (db) in sound power level is equivalent to reducing the sound power level to one-tenth of the original level.
  • This one improvement of the invention and it is significant in that none of the prior art structures have disclosed or suggested this possibility.
  • the improvement is believed to be the result of the elimination of low frequency sound from interacting with the foraminous tube and thereby enhancing the effectiveness of the tube at high frequencies.
  • the wall of the foraminous conduit provides a certain resistance to the flow of high frequency sound to resonant cavities 19. This resistance is increased if low frequency sound is present along with the high frequency sound. There is a further increase in resistance at the wall of the tube if the low frequencies are at high sound pressure levels.
  • the acoustical impedance of fluid gases can range between 3 400 cgs, rayls, the following given as example only with impedance values for other gases available in standard reference books:
  • the high frequencies pass through a low resistance wall, establish standing waves and are attenuated.
  • the high frequencies can then be attenuated with greater efficiency in the high frequency resonators which is the improvement shown as curve I in FIG. 3. If the low frequencies were present with the high when encountering chambers 19, the low frequencies would cause the tube wall to exhibit a high resistance.
  • the high resistance of the wall however will prevent the high frequencies from entering chambers I9 efficiently and thereby result in lower attenuation, which is the curve H in FIG. 3.
  • FIG. 4 Another embodiment of the attenuator shown in FIG. I is that shown in FIG. 4 which is identical to the attenuator in FIG. I, but which has in addition a middle frequency Helmholtz attenuator indicated by chamber 18. Tube 10 communicates with chamber 18 by ports I6 to attenuate the middle frequency generally designated in the art as between 500 and 800 Hz.
  • the response of this attenuator is shown in FIG. 5 where line H-I would be expected according to the teachings of the prior art and where line H is the improvement according to the structure of the present invention.
  • frequencies of 0 to 500, 500-1000 Hz and 1000 Hz and above were used in defining the low, medium and high frequency ranges respectively.
  • the particular frequencies generated by a sound source will vary with style, size, etc. of the application.
  • the frequencies necessary and useful in the above structures will vary.
  • the maximum efficiency of the attenuator of the present invention will thus depend upon the exact frequency characteristics of the sound source. Utilizing this data the frequencies to be used for tuning the low, medium and high resonators can be calculated by standard formulae as described in The Theory of Sound," by John William Strut, Baron Rayleigh, published in 1894 and republished by Dover Publications, Inc. in I945.
  • the effect of the Helmholtz resonators used in this invention is maximized by knowing the frequencies of the system to be treated. Variations in gas flow volume and sound pressure level will obviously necessitate increases or decreases in the size and design of the attenuator. However, adjustments for these parameters are well known in the art.
  • FIGS. 6 and 7 show another alternate embodiment of the present invention wherein a shell 36 surrounds and is secured to a foraminous tube 3] having an inlet 32 and outlet 38.
  • FIG. 7 more clearly shows the low frequency resonators chamber 41 communicating with the gas flow by ports 37.
  • the high frequency standing wave cavities 42 communicate with the gas flow by the porous nature ofthe tube.
  • the gases enter at inlet 32 and come in contact with a low frequency resonator chamber 41 through ports 37.
  • the gas stream flows by annular high frequency cavities 42 through the tube's foraminous wall 43, and then continues to flow and contact simultaneously a series of both low frequency resonators and high frequency standing wave cavities.
  • Every sound attenuating structure has a certain efficiency in attenuating the sound accompanying gases flowing therethrough.
  • the magnitude of sound accompanying the gas flow is directly related to the sound pressure level. If the sound pressure level is very high, an attenuator, say for example having a given amount of efficiency. may not attenuate a sufficient amount of sound to bring it to an acceptable level. Accordingly, it will be necessary to flow the gas through a second unit to further attenuate the sound.
  • the structure in FIG. 6 is for this purpose, indicating an attenuator having a plurality of single attenuators similar to that shown in FIG. I for applications where large sound pressure lev els are encountered.
  • FIG. 8 shows a third embodiment of the present invention having a double. parallel ducted structure having a shell 23 provided with an inlet 24 and outlet 25.
  • a middle frequency resonator 3I is provided and communicates with tube 27 through ports 29.
  • the resonators depending on the system on which it will be used, will be tuned in accordance with the above discussion regarding frequency design characteristics and the mesh or web structure discussed previously. This embodiment is useful for higher volumes of gas flow.
  • the depth a of the high frequency resonators is measured from the outer wall E of the foraminous material. These resonators being preferably tuned by making a an odd multiple of onequarter wave lengths of the high frequency sound. This will cause the sound pressure level at the tube wall to be substantially at zero pressure with the sound velocity being at its maximum.
  • a device for attenuating sound in a fluid flowing therefrom, the fluid having a known acoustical impedance measured in rayls comprising a housing surrounding a conduit having an inlet and an outlet. the conduit having in series after the inlet:
  • the second means having a foraminous duct in series with said conduit.
  • the duct having a preselected acoustical resistance measured in rayls substantially the same value in rayls as the impedance of the flowing fluid.
  • the first means attenuating the low frequency sound to a level sufficiently low to enable the foraminous duct to effectively function at its preselected acoustical resistance.
  • baffle system is a multi-dimensional baffle system.
  • the device as recited in claim 1 further including third means, located in series after the second means, for attenuating middle frequency sound entering the device.
  • At least one Helmholtz resonator surrounding the plurality of standing wave cavities and communicating with the foraminous duct by ports located in the conduit at those portions not communicating with the standing wave cavities.
  • a method for attenuating the level of sound in a fluid flowing through a muffler, the fluid having a known acoustical impedance measured in rayls. comprising the steps of:
  • a. providing a high frequency sound attenuator for absorbing frequencies over 1000 Hz, the attenuator having an acoustical resistance in rayls matched to the acoustical impedance of a fluid entering the muffler;

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Exhaust Silencers (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
US438736A 1974-02-01 1974-02-01 Free flow sound attenuating device and method of using Expired - Lifetime US3920095A (en)

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Application Number Priority Date Filing Date Title
US438736A US3920095A (en) 1974-02-01 1974-02-01 Free flow sound attenuating device and method of using
CA218,185A CA1042809A (en) 1974-02-01 1975-01-20 Free flow sound attenuating device and method of using
GB3056/75A GB1501441A (en) 1974-02-01 1975-01-23 Sound attenuating devices
FR7503061A FR2260059B1 (de) 1974-02-01 1975-01-31
JP50013283A JPS50127031A (de) 1974-02-01 1975-01-31
DE19752504132 DE2504132A1 (de) 1974-02-01 1975-01-31 Vorrichtung zur daempfung des schallpegels

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US438736A US3920095A (en) 1974-02-01 1974-02-01 Free flow sound attenuating device and method of using

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US (1) US3920095A (de)
JP (1) JPS50127031A (de)
CA (1) CA1042809A (de)
DE (1) DE2504132A1 (de)
FR (1) FR2260059B1 (de)
GB (1) GB1501441A (de)

Cited By (31)

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US4371054A (en) * 1978-03-16 1983-02-01 Lockheed Corporation Flow duct sound attenuator
US5205719A (en) * 1992-01-13 1993-04-27 Copeland Corporation Refrigerant compressor discharge muffler
CN1039550C (zh) * 1993-12-11 1998-08-19 简志坚 消音器
US6558137B2 (en) 2000-12-01 2003-05-06 Tecumseh Products Company Reciprocating piston compressor having improved noise attenuation
US6571910B2 (en) 2000-12-20 2003-06-03 Quiet Storm, Llc Method and apparatus for improved noise attenuation in a dissipative internal combustion engine exhaust muffler
US6622680B2 (en) * 2000-05-17 2003-09-23 Toyoda Gosei Co., Ltd. Air intake duct and manufacturing method therefor
US6695094B2 (en) * 2001-02-02 2004-02-24 The Boeing Company Acoustic muffler for turbine engine
US20040065504A1 (en) * 2002-10-02 2004-04-08 Daniels Mark A. Absorptive/reactive muffler for variable speed compressors
US20050252716A1 (en) * 2004-05-14 2005-11-17 Visteon Global Technologies, Inc. Electronically controlled dual chamber variable resonator
US20060043236A1 (en) * 2004-09-02 2006-03-02 Campbell Thomas A Integrated axially varying engine muffler, and associated methods and systems
US20060071123A1 (en) * 2004-09-27 2006-04-06 Nguyen Phuong H Automatic control systems for aircraft auxiliary power units, and associated methods
US20060102779A1 (en) * 2004-10-26 2006-05-18 Campbell Thomas A Dual flow APU inlet and associated systems and methods
EP1685327A1 (de) * 2004-10-20 2006-08-02 Carrier Corporation Schalldämpfer für verdichter
WO2006131660A1 (fr) * 2005-06-10 2006-12-14 Faurecia Interieur Industrie Conduit de circulation d’air ayant des proprietes d’absorption acoustique
US20070102236A1 (en) * 2005-11-10 2007-05-10 Thomas Uhlemann Muffler
US20080078863A1 (en) * 2006-09-25 2008-04-03 The Boeing Company Thermally compliant APU exhaust duct arrangements and associated systems and methods
US7513119B2 (en) 2005-02-03 2009-04-07 The Boeing Company Systems and methods for starting aircraft engines
US20100224159A1 (en) * 2009-03-05 2010-09-09 Gm Global Techonolgy Operations, Inc. Engine assembly having variable intake air tuning device and tuning method
CN101975325A (zh) * 2010-10-19 2011-02-16 哈尔滨工程大学 多线谱可变频充液管道消声器
US7992676B1 (en) * 2010-07-21 2011-08-09 Mann & Hummel Gmbh Compact tuned acoustic attenuation device
WO2011100083A3 (en) * 2010-02-11 2011-11-24 Faurecia Emissions Control Technologies, Usa, Llc Plastic muffler with helmholtz chamber
US8657227B1 (en) 2009-09-11 2014-02-25 The Boeing Company Independent power generation in aircraft
US8738268B2 (en) 2011-03-10 2014-05-27 The Boeing Company Vehicle electrical power management and distribution
WO2014093215A1 (en) * 2012-12-10 2014-06-19 Eaton Corporation Resonator with liner
DE102014101144A1 (de) * 2014-01-30 2015-07-30 Smk Systeme Metall Kunststoff Gmbh & Co. Kg. Reflexionsschalldämpfer
WO2016040431A1 (en) * 2014-09-09 2016-03-17 3M Innovative Properties Company Acoustic device
WO2018234826A1 (en) * 2017-06-22 2018-12-27 The University Of Manchester APPARATUS FOR MODIFYING ACOUSTIC TRANSMISSION
US20190120414A1 (en) * 2017-10-23 2019-04-25 Hamilton Sundstrand Corporation Duct assembly having internal noise reduction features, thermal insulation and leak detection
US11578687B1 (en) * 2022-04-05 2023-02-14 Brunswick Corporation Marine engine intake manifolds having noise attenuation
US11698008B2 (en) * 2020-02-14 2023-07-11 Tenneco Automotive Operating Company Inc. Exhaust device
US20230400221A1 (en) * 2020-04-14 2023-12-14 Johnson Controls Tyco IP Holdings LLP Noise suppression apparatus for an air handling unit

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DE2947256C2 (de) * 1979-11-23 1984-09-13 Messerschmitt-Bölkow-Blohm GmbH, 8000 München Einrichtung zur Reduzierung des Auspuff- bzw. Abgaslärmes
US4601168A (en) * 1984-12-12 1986-07-22 Harris Harold L Noise and emission control apparatus
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US6684842B1 (en) * 2002-07-12 2004-02-03 Visteon Global Technologies, Inc. Multi-chamber resonator
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US2075263A (en) * 1931-10-19 1937-03-30 Maxim Silencer Co Sound attenuating device
US3113635A (en) * 1959-03-31 1963-12-10 Bolt Beranek & Newman Apparatus for silencing vibrational energy
US3362783A (en) * 1963-12-23 1968-01-09 Texaco Inc Treatment of exhaust gases
US3690606A (en) * 1968-05-27 1972-09-12 Pall Corp Anisometric compressed and bonded multilayer knitted wire mesh composites
US3734234A (en) * 1971-11-08 1973-05-22 Lockheed Aircraft Corp Sound absorption structure
US3831710A (en) * 1973-01-24 1974-08-27 Lockheed Aircraft Corp Sound absorbing panel

Cited By (59)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4371054A (en) * 1978-03-16 1983-02-01 Lockheed Corporation Flow duct sound attenuator
US5205719A (en) * 1992-01-13 1993-04-27 Copeland Corporation Refrigerant compressor discharge muffler
CN1039550C (zh) * 1993-12-11 1998-08-19 简志坚 消音器
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DE2504132A1 (de) 1975-08-14
CA1042809A (en) 1978-11-21
JPS50127031A (de) 1975-10-06
FR2260059A1 (de) 1975-08-29
FR2260059B1 (de) 1978-10-06
GB1501441A (en) 1978-02-15

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