US2043416A - Process of silencing sound oscillations - Google Patents

Process of silencing sound oscillations Download PDF

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US2043416A
US2043416A US71458234A US2043416A US 2043416 A US2043416 A US 2043416A US 71458234 A US71458234 A US 71458234A US 2043416 A US2043416 A US 2043416A
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sound
oscillations
microphone
loudspeaker
process
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Lueg Paul
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Lueg Paul
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16LPIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L55/00Devices or appurtenances for use in, or in connection with, pipes or pipe systems
    • F16L55/02Energy absorbers; Noise absorbers
    • F16L55/033Noise absorbers
    • F16L55/0333Noise absorbers by means of an active system
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N1/00Silencing apparatus characterised by method of silencing
    • F01N1/06Silencing apparatus characterised by method of silencing by using interference effect
    • F01N1/065Silencing apparatus characterised by method of silencing by using interference effect by using an active noise source, e.g. speakers
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/301Computational
    • G10K2210/3011Single acoustic input
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/301Computational
    • G10K2210/3044Phase shift, e.g. complex envelope processing
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/321Physical
    • G10K2210/3216Cancellation means disposed in the vicinity of the source
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/321Physical
    • G10K2210/3217Collocated sensor and cancelling actuator, e.g. "virtual earth" designs
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/50Miscellaneous
    • G10K2210/508Reviews on ANC in general, e.g. literature

Description

Patented June 9, 1936 PROCESS OF SILENCING SOUND OSCILLA TIONS Paul Lueg, Kirchstrasse, Germany Application March 8, 1934, Serial No. 714,582 In Germany January 27, 1933' 4 Claims.

In the known processes of silencing sound oscillations the silencing is effected by subjecting these oscillations to a displacement of phases, but in these processes only the source of the oscillations is used to cause the displacement of phases, so that the superposition of phasestakes place in a purely mechanical manner.

The present invention does away with these drawbacks and relates to a process of silencing sound oscillations especially of a disturbing nature, which can be employed independently of the source of oscillation. According to the present invention the sound oscillations, which are to be silenced are taken in by a receiver and reproduced by a reproducing apparatus in the form of sounds having an opposite phase. The means of carrying out said processes consist preferably of electrical apparatus and the reception is efiected by amicrophone, by which the acoustic oscillations are transformed into electric ones. The microphone is connected over an amplifier with a reproducing apparatus (loudspeaker). The phase opposition can be efiected by several means. In case for instance of only one single tune moving in one well defined direction (in a pipe for instance) the phase opposition can be efieeted in a very simple manner by adjusting the distance between the microphone and the producing apparatus. In this case the microphone is preferably placed between the sound source and the reproducing apparatus causing the sound oscillations to meet first the microphone and then the reproducing apparatus. Consequently two difierent kinds of oscillations are present in the reproducing apparatus, the one representing the sound oscillation of the tune, moving with normal soundvelocity, the other representing a wave advanced with respect to the first wave by electrical means between the microphone and the reproducing apparatus and reproduced by the reproducing apparatus. The phase opposition can be efiected by suitably adjusting the distance between themicrophone and the reproducing apparatus.

In order to silence acoustic vibrations of any shape within a certain range, the microphone and loudspeaker are suitably placed close to each other in such a way that the oscillations coming from a certain point will meet the microphone a silencing of the noise is effected within the range of the reproducer. Preferably one side of the loudspeaker diaphragm is used for it, whereas the other side is silenced.

It is to be understood of course that in the 5 same way several receiving and reproducing apparatus can be used working either in a single way or in connection with each other.

Sometimes it will be necessary not to silence all the noise oscillations but only a part of them. This will be the case when for instance disagreeable secondary (stray) noises (see further below) for instance in theaters, concert halls, etc. have to be avoided. In the same way is this the case in ofiices in which the disagreeable noise of the type writing machines has to be silenced. This can be efiected in a very simple way in accordance with the invention by taking in well defined frequencies of the sound oscillations, by displacing the phases and reproducing same thereupon.

In the specification only the outstanding features of the process are stated and the means of the process may be modified by a more refined working out of the problem. The electric reception and the transforming of the acoustic oscillations have the advantage of an extraordinarily exact reproduction, so that a much more exact and more sudden silencing of the oscillations can be obtained than by the mechanical process. The process on the whole'can be employed in solid as well as in liquid and in gaseous sound carriers.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example preferred embodiments of the inventive idea.

In the drawing:--

Figure 1 illustrates diagrammatically means of silencing a single linear sound wave.

Figure 2 illustrates diagrammatically a plurality of sound waves and means for silencing or damping the same.

Figure 3 is a diagram illustrating the sound waves.

Figure 4 illustrates diagrammatically means for silencing spatial sound waves.

Figure 1 illustrates a simple device by means of which a single predetermined tone which comes from a predetermined direction is silenced or damped within a pipe T. This sound or tone is actually a sine-like sound wave and is to be silenced or damped by a sound Wave having an opposite phase. This sound of opposite phase is produced simply by adjusting the distance between the microphone M, which is built into the pipe T and the sound reproducing device or loudspeaker L. The microphone is situated between the source of the sounds and the loudspeaker. Therefore, the sound waves s arriving from the point A first strike the microphone andthen the loudspeaker. The sound wave received by the microphone is transmitted electrically with the assistance of the amplifier E to the loudspeaker. Naturally this electrically transmitted sound wave is advanced in relation to the sound wave s which moves with a normal velocity of sound.

The extent of this advancement of the electrically transmitted sound wave can be conveniently adjusted by adjusting the distance between the microphone and the loudspeaker. It is easily possible to determine and regulate the distance between the microphone and the loudspeaker in such manner that the sound wave s which is electrically reproduced by the loudspeaker has an opposite phase from the original natural sound wave 8 Therefore, due to this creation'of a sound wave having an opposite phase, the two sound waves will silence each other or dampen each other.

Figure 2 shows a sound source A which, for

instance, is situated in open space, so that it emits sound waves traveling in all directions. In that case the microphone M and the loudspeaker L are both placed at the same distance from the source A and are electrically interconnected by means of an amplifier V. 7, Sound waves (11 and an produced by the source A strike the microphone M and the loudspeaker L, respectively. The sound wave in striking the microphone M is reproduced by the loudspeaker L in an opposite phase. This changing of the phase may be accomplished by several well known methods, for instance, by changing the poles of the loudspeaker L, or by providing a transformer (not shown) between the loudspeaker L and the microphone M. The sound waves produced by the sound source A are silenced around the loud.- speaker L by sound waves having an opposite phase produced by the loudspeaker L.

The sound waves which-do not have a sine-like form, 1. e., noises, may be represented by the irregular curve G G, which is shown in Figure 3. Naturally an exact phase opposition cannot be produced by shifting a sound wave of this type by 180, since the two halves of the curve are entirely different one from the other. In that case the phase opposition is produced by the following means. In my present invention, I employ the principle that an ordinary oscillating membrane of a loudspeaker provided with fiat surfaces oi. the type employed in the usual surface loudspeaker, creates thickenings and thinnings of the air when a sound is reproduced. In the example illustrated in Figure 4, the noise emerging from the point A reaches the microphone M situated at a distance a from the point A. The microphone M transmits this noise electrically to the loudspeaker in such manner that an opposite wave is produced, such as shown in Figure 3. This means that each time when a thickening of the air meets the microphone the loudspeaker answers by a corresponding thinning of the air and vice versa.

Due to this arrangement, phase opposition is produced within the space B, mainly in the direction of the arrow B.

What I claim is:

1. In combination, means receiving sound oscillations travelling in the air and means reproducing sound oscillations within the field of action of the first-mentioned sound oscillations and causing them to travel substantially-in the same direction as that of the first-mentioned sound oscillations, the second-mentioned sound oscillations having an opposite phase in relation to the first-mentioned sound oscillations, whereby the received sound oscillations are silenced within the.

range of the reproduced sound oscillations.

- 2. A process of silencing sound oscillations comprising receiving a sound wave travelling through the air, causing said sound wave to produce electricaloscillations, and transforming said electrical oscillations into a sound wave having an opposite phase to the received sound wave and travelling through the air substantially in the direction of the received sound wave, whereby the received sound wave is silenced within the range of the second-mentioned sound wave. 1

3. In combination, a microphone for receiving a sound wave travelling through the air in substantially one direction, an amplifier electrically connected with said microphone, and means electrically connected with said amplifier for transforming electrical oscillations caused by said sound wave into another sound wave traveling through the air'substantially in the same direction as-the received sound wave, the distance between said microphone and said means being adjustable to cause a mutual elimination of the two sound waves within the field of action of the received sound wave.

4. In combination with a source of sound waves travelling through the air; a microphone adapted to receive sound waves emitted by said source and situated at a certain distance from said source, and a loudspeaker electrically connected with said microphone and situated at the same distance from said source, said loudspeaker producing sound waves having an opposite phase to the received sound waves and travelling through the air substantially in the same direction as the received sound waves, whereby the receivedsound waves are eliminated within the field of action of the sound waves produced by the loudspeaker.

PAUL LUEG.

US2043416A 1933-01-27 1934-03-08 Process of silencing sound oscillations Expired - Lifetime US2043416A (en)

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Cited By (64)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2431862A (en) * 1946-03-26 1947-12-02 Sperry Prod Inc Means for supersonic inspection
US2516776A (en) * 1946-08-07 1950-07-25 Bell Telephone Labor Inc Electroacoustic system and means
US2611035A (en) * 1950-01-31 1952-09-16 Rca Corp Noise-canceling microphone
US2694868A (en) * 1943-08-03 1954-11-23 Edwin M Mcmillan Echo repeater
US2776020A (en) * 1955-02-09 1957-01-01 Gen Electric Noise reducing system for transformers
US2783008A (en) * 1951-07-28 1957-02-26 Jr Albert G Bodine Acoustical boundary layer control for aerodynamic bodies
US2966549A (en) * 1954-04-02 1960-12-27 Lawrence J Fogel Apparatus for improving intelligence under high ambient noise levels
US2972018A (en) * 1953-11-30 1961-02-14 Rca Corp Noise reduction system
US2983790A (en) * 1953-04-30 1961-05-09 Rca Corp Electronic sound absorber
US3044570A (en) * 1957-04-08 1962-07-17 Watts Ltd Cecil E Loudspeakers
US3071752A (en) * 1958-01-02 1963-01-01 Strasberg Murray Interference reduction apparatus
US3229429A (en) * 1960-04-27 1966-01-18 Conrad Ivan Willard Secure conference systems
US3308425A (en) * 1965-09-03 1967-03-07 Vector Cable Company Depth sensitive transducer
US3685610A (en) * 1970-02-26 1972-08-22 Messerschmitt Boelkow Blohm Noise reduction for propellers
US3826870A (en) * 1970-03-20 1974-07-30 Quest Electronics Corp Noise cancellation
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
US4109108A (en) * 1976-10-01 1978-08-22 National Research Development Corporation Attenuation of sound waves in ducts
DE2712534A1 (en) * 1977-03-22 1978-09-28 Sound Attenuators Ltd Active sound attenuation using secondary wave - has stored programme used to obtain signal representing secondary wave
EP0040462A1 (en) * 1980-05-16 1981-11-25 Bose Corporation Electroacoustical audible noise reducing apparatus
US4473906A (en) * 1980-12-05 1984-09-25 Lord Corporation Active acoustic attenuator
US4805733A (en) * 1987-07-07 1989-02-21 Nippondenso Co., Ltd. Active silencer
US4989252A (en) * 1988-09-30 1991-01-29 Kabushiki Kaisha Toshiba Silencer
US5040156A (en) * 1989-06-29 1991-08-13 Battelle-Institut E.V. Acoustic sensor device with noise suppression
US5088575A (en) * 1990-09-13 1992-02-18 Nelson Industries, Inc. Acoustic system with transducer and venturi
DE4033269A1 (en) * 1990-10-19 1992-04-23 Gillet Heinrich Gmbh Schalldaempferanlage for motor vehicles
US5117642A (en) * 1989-12-18 1992-06-02 Kabushiki Kaisha Toshiba Low noise refrigerator and noise control method thereof
US5127235A (en) * 1989-12-18 1992-07-07 Kabushiki Kaisha Toshiba Low noise refrigerator and noise control method thereof
DE4130559A1 (en) * 1991-09-10 1993-03-25 Calsonic Corp Silencing system with expansion chamber formed in main pipe - incorporates combination of active and passive reflecting surfaces in pipes of different dia.
US5255321A (en) * 1990-12-05 1993-10-19 Harman International Industries, Inc. Acoustic transducer for automotive noise cancellation
EP0611089A2 (en) * 1993-02-11 1994-08-17 DIGISONIX, Inc. Active acoustic control system matching model reference
US5355417A (en) * 1992-10-21 1994-10-11 The Center For Innovative Technology Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
US5475761A (en) * 1994-01-31 1995-12-12 Noise Cancellation Technologies, Inc. Adaptive feedforward and feedback control system
US5488666A (en) * 1993-10-01 1996-01-30 Greenhalgh Technologies System for suppressing sound from a flame
US5662136A (en) * 1995-09-11 1997-09-02 Defense Research Technologies, Inc. Acousto-fluidic driver for active control of turbofan engine noise
DE19702390A1 (en) * 1997-01-24 1998-07-30 Audi Ag wind Tunnel
US6461144B1 (en) * 1999-05-07 2002-10-08 Alstom (Switzerland) Ltd Method of controlling thermoacoustic vibrations in a combustion system, and combustion system
US6622647B2 (en) 2001-06-26 2003-09-23 Depoy Martin L. Active noise cancellation for a torpedo seeker head
US6671224B1 (en) * 2002-08-26 2003-12-30 Schlumberger Technology Corporation Active reduction of tool borne noise in a sonic logging tool
US20040122614A1 (en) * 1996-11-14 2004-06-24 Lg Electronics, Inc. Noise controller for controlling noise and method of removing noise
US20040125922A1 (en) * 2002-09-12 2004-07-01 Specht Jeffrey L. Communications device with sound masking system
US20050189165A1 (en) * 2004-02-12 2005-09-01 Mathur Gopal P. Method and apparatus for reducing acoustic noise
US20060158814A1 (en) * 2003-03-05 2006-07-20 Masaru Wasaki Noise supression circuit
US7088828B1 (en) * 2000-04-13 2006-08-08 Cisco Technology, Inc. Methods and apparatus for providing privacy for a user of an audio electronic device
US20090180635A1 (en) * 2008-01-10 2009-07-16 Sun Microsystems, Inc. Method and apparatus for attenuating fan noise through turbulence mitigation
US20090284996A1 (en) * 2008-05-15 2009-11-19 Lockheed Martin Corporation System and method of cancelling noise radiated from a switch-mode power converter
US20100028134A1 (en) * 2007-01-22 2010-02-04 Alon Slapak Quiet fan incorporating active noise control (anc)
US20100064696A1 (en) * 2006-11-03 2010-03-18 Koninklijke Philips Electronics N.V. Active control of an acoustic cooling system
US20100202633A1 (en) * 2008-01-29 2010-08-12 Korea Advanced Institute Of Science And Technology Sound system, sound reproducing apparatus, sound reproducing method, monitor with speakers, mobile phone with speakers
US20100284544A1 (en) * 2008-01-29 2010-11-11 Korea Advanced Institute Of Science And Technology Sound system, sound reproducing apparatus, sound reproducing method, monitor with speakers, mobile phone with speakers
WO2013076137A1 (en) 2011-11-25 2013-05-30 Renault S.A.S. Method and device for controlling an active noise reduction system
EP2645362A1 (en) 2012-03-26 2013-10-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Apparatus and method for improving the perceived quality of sound reproduction by combining active noise cancellation and perceptual noise compensation
US20140276276A1 (en) * 2011-10-25 2014-09-18 Ryo Kurosawa Therapeutic apparatus and therapeutic method
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US9230534B2 (en) 2010-12-29 2016-01-05 Zhongyi Xu Suppression device for outdoor noise in indoor space
US9253556B1 (en) 2013-08-29 2016-02-02 ConcealFab Corporation Dissipative system for increasing audio entropy thereby diminishing auditory perception
US9431001B2 (en) 2011-05-11 2016-08-30 Silentium Ltd. Device, system and method of noise control
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US20170198723A1 (en) * 2016-01-11 2017-07-13 Rolls-Royce North American Technologies Inc. System and method of alleviating blade flutter
US9786262B2 (en) 2015-06-24 2017-10-10 Edward Villaume Programmable noise reducing, deadening, and cancelation devices, systems and methods
US9792892B2 (en) 2014-07-15 2017-10-17 Amphenol Phitek Limited Noise cancellation system
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US9928824B2 (en) 2011-05-11 2018-03-27 Silentium Ltd. Apparatus, system and method of controlling noise within a noise-controlled volume
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Cited By (76)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2694868A (en) * 1943-08-03 1954-11-23 Edwin M Mcmillan Echo repeater
US2431862A (en) * 1946-03-26 1947-12-02 Sperry Prod Inc Means for supersonic inspection
US2516776A (en) * 1946-08-07 1950-07-25 Bell Telephone Labor Inc Electroacoustic system and means
US2611035A (en) * 1950-01-31 1952-09-16 Rca Corp Noise-canceling microphone
US2783008A (en) * 1951-07-28 1957-02-26 Jr Albert G Bodine Acoustical boundary layer control for aerodynamic bodies
US2983790A (en) * 1953-04-30 1961-05-09 Rca Corp Electronic sound absorber
US2972018A (en) * 1953-11-30 1961-02-14 Rca Corp Noise reduction system
US2966549A (en) * 1954-04-02 1960-12-27 Lawrence J Fogel Apparatus for improving intelligence under high ambient noise levels
US2776020A (en) * 1955-02-09 1957-01-01 Gen Electric Noise reducing system for transformers
US3044570A (en) * 1957-04-08 1962-07-17 Watts Ltd Cecil E Loudspeakers
US3071752A (en) * 1958-01-02 1963-01-01 Strasberg Murray Interference reduction apparatus
US3229429A (en) * 1960-04-27 1966-01-18 Conrad Ivan Willard Secure conference systems
US3308425A (en) * 1965-09-03 1967-03-07 Vector Cable Company Depth sensitive transducer
US3685610A (en) * 1970-02-26 1972-08-22 Messerschmitt Boelkow Blohm Noise reduction for propellers
US3826870A (en) * 1970-03-20 1974-07-30 Quest Electronics Corp Noise cancellation
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
US4109108A (en) * 1976-10-01 1978-08-22 National Research Development Corporation Attenuation of sound waves in ducts
DE2712534A1 (en) * 1977-03-22 1978-09-28 Sound Attenuators Ltd Active sound attenuation using secondary wave - has stored programme used to obtain signal representing secondary wave
EP0040462A1 (en) * 1980-05-16 1981-11-25 Bose Corporation Electroacoustical audible noise reducing apparatus
US4473906A (en) * 1980-12-05 1984-09-25 Lord Corporation Active acoustic attenuator
US4805733A (en) * 1987-07-07 1989-02-21 Nippondenso Co., Ltd. Active silencer
US4989252A (en) * 1988-09-30 1991-01-29 Kabushiki Kaisha Toshiba Silencer
US5040156A (en) * 1989-06-29 1991-08-13 Battelle-Institut E.V. Acoustic sensor device with noise suppression
US5117642A (en) * 1989-12-18 1992-06-02 Kabushiki Kaisha Toshiba Low noise refrigerator and noise control method thereof
US5127235A (en) * 1989-12-18 1992-07-07 Kabushiki Kaisha Toshiba Low noise refrigerator and noise control method thereof
US5088575A (en) * 1990-09-13 1992-02-18 Nelson Industries, Inc. Acoustic system with transducer and venturi
DE4033269A1 (en) * 1990-10-19 1992-04-23 Gillet Heinrich Gmbh Schalldaempferanlage for motor vehicles
US5255321A (en) * 1990-12-05 1993-10-19 Harman International Industries, Inc. Acoustic transducer for automotive noise cancellation
DE4130559A1 (en) * 1991-09-10 1993-03-25 Calsonic Corp Silencing system with expansion chamber formed in main pipe - incorporates combination of active and passive reflecting surfaces in pipes of different dia.
US5347585A (en) * 1991-09-10 1994-09-13 Calsonic Corporation Sound attenuating system
US5355417A (en) * 1992-10-21 1994-10-11 The Center For Innovative Technology Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
EP0611089A2 (en) * 1993-02-11 1994-08-17 DIGISONIX, Inc. Active acoustic control system matching model reference
EP0611089A3 (en) * 1993-02-11 1995-10-11 Digisonix Inc Active acoustic control system matching model reference.
US5488666A (en) * 1993-10-01 1996-01-30 Greenhalgh Technologies System for suppressing sound from a flame
US5475761A (en) * 1994-01-31 1995-12-12 Noise Cancellation Technologies, Inc. Adaptive feedforward and feedback control system
US5662136A (en) * 1995-09-11 1997-09-02 Defense Research Technologies, Inc. Acousto-fluidic driver for active control of turbofan engine noise
US20040122614A1 (en) * 1996-11-14 2004-06-24 Lg Electronics, Inc. Noise controller for controlling noise and method of removing noise
DE19702390A1 (en) * 1997-01-24 1998-07-30 Audi Ag wind Tunnel
US6155111A (en) * 1997-01-24 2000-12-05 Audi Ag Wind tunnel with air vibration phase cancellation
US6461144B1 (en) * 1999-05-07 2002-10-08 Alstom (Switzerland) Ltd Method of controlling thermoacoustic vibrations in a combustion system, and combustion system
US7088828B1 (en) * 2000-04-13 2006-08-08 Cisco Technology, Inc. Methods and apparatus for providing privacy for a user of an audio electronic device
US6622647B2 (en) 2001-06-26 2003-09-23 Depoy Martin L. Active noise cancellation for a torpedo seeker head
US6671224B1 (en) * 2002-08-26 2003-12-30 Schlumberger Technology Corporation Active reduction of tool borne noise in a sonic logging tool
US20040125922A1 (en) * 2002-09-12 2004-07-01 Specht Jeffrey L. Communications device with sound masking system
US20060158814A1 (en) * 2003-03-05 2006-07-20 Masaru Wasaki Noise supression circuit
US7423520B2 (en) 2003-03-05 2008-09-09 Tdk Corporation Noise suppressing circuit
US20050189165A1 (en) * 2004-02-12 2005-09-01 Mathur Gopal P. Method and apparatus for reducing acoustic noise
US7267196B2 (en) * 2004-02-12 2007-09-11 The Boeing Company Method and apparatus for reducing acoustic noise
US20100064696A1 (en) * 2006-11-03 2010-03-18 Koninklijke Philips Electronics N.V. Active control of an acoustic cooling system
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