EP0040462A1 - Electroacoustical audible noise reducing apparatus - Google Patents

Electroacoustical audible noise reducing apparatus Download PDF

Info

Publication number
EP0040462A1
EP0040462A1 EP81300660A EP81300660A EP0040462A1 EP 0040462 A1 EP0040462 A1 EP 0040462A1 EP 81300660 A EP81300660 A EP 81300660A EP 81300660 A EP81300660 A EP 81300660A EP 0040462 A1 EP0040462 A1 EP 0040462A1
Authority
EP
European Patent Office
Prior art keywords
electroacoustical
acoustical
transducing means
electroacoustical transducing
noise
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.)
Withdrawn
Application number
EP81300660A
Other languages
German (de)
French (fr)
Inventor
Amar G. Bose
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.)
Bose Corp
Original Assignee
Bose 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 Bose Corp filed Critical Bose Corp
Publication of EP0040462A1 publication Critical patent/EP0040462A1/en
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • 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
    • G10K11/00—Methods 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
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods 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
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17857—Geometric disposition, e.g. placement of microphones
    • 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
    • G10K11/00—Methods 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
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods 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
    • G10K11/1787—General system configurations
    • G10K11/17875—General system configurations using an error signal without a reference signal, e.g. pure feedback
    • 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
    • G10K2210/10—Applications
    • G10K2210/112—Ducts
    • 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
    • G10K2210/10—Applications
    • G10K2210/128—Vehicles
    • G10K2210/1282—Automobiles
    • G10K2210/12822—Exhaust pipes or mufflers
    • 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
    • G10K2210/301—Computational
    • G10K2210/3011—Single acoustic input
    • 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
    • G10K2210/301—Computational
    • G10K2210/3013—Analogue, i.e. using analogue computers or circuits
    • 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
    • G10K2210/3217—Collocated sensor and cancelling actuator, e.g. "virtual earth" designs

Definitions

  • the present invention relates in general to reducing audible noise and more particularly concerns novel apparatus and techniques for using an active electroacoustical system to significantly reduce audible noise with relatively compact and reliable apparatus.
  • U.S. Patent No. 2,043,416 As an example of active methods to reduce unwanted audible noise reference is made to U.S. Patent No. 2,043,416. More recent approaches involve open and closed loop systems. In one open loop system a noise source within a given surface may have a number of microphones just inside the surface and a number of loudspeakers just outside the surface. The microphones pick up the noise at the surface to provide a signal that is amplified and delivered to the loudspeakers with substantially the same intensity but opposite phase as the noise passing across the surface to effectively reduce the noise perceived by an observer remote from the surface.
  • a closed loop system may use a microphone near the observer coupled to a nearby loudspeaker through signal processing electronics for receiving the audible noise from a distant source and providing a signal from the loudspeaker of opposite phase, thereby tending to reduce the noise level perceived by the listener.
  • signal processing electronics for receiving the audible noise from a distant source and providing a signal from the loudspeaker of opposite phase, thereby tending to reduce the noise level perceived by the listener.
  • electroacoustical audible noise reducing apparatus for a source of audible noise having significant audible spectral components in a predetermined frequency range below 500Hz, comprises a first electroacoustical transducing means for transducing an input electrical signal into a corresponding audible signal; an acoustical combining means for combining the audible noise from the source with the audible signal from the first electroacoustical transducing means; a second electroacoustical transducing means responsive to the acoustical signal at the output of acoustical combining means for providing an electrical signal representative thereof; controlled amplifying means responsive to the latter electrical signal for providing an amplified electrical signal to the first electroacoustical transducing means; the acoustical combining means and the first and second electroacoustical transducing means being closely spaced and separated from each other by less than a half wavelength at the highest frequency of the predetermined frequency range, whereby, in the
  • the invention thus provides improved apparatus and techniques for reducing audible noise, and over a relatively large region.
  • the acoustical combining means comprises a duct
  • the second electroacoustical transducing means is located in the duct and the duct is formed with an opening intermediate its ends coupled to the first electroacoustical transducing means.
  • the apparatus forms a closed loop that tends to minimize the intensity of the acoustical signal output from the duct outlet.
  • the source of audible noise and first and second electroacoustical transducing means are separated from each other by a distance less than a half wavelength at the frequencies of interest to be attenuated.
  • a source of audible noise 11 is combined, in an acoustical combining means 13, with an audible signal from a source 14 to provide a reduced noise level at output 12.
  • the source 14 typically comprises an acoustical transducing means for transducing an input electrical signal into a corresponding acoustical signal.
  • Controlled amplifying means 16 amplifies this signal and energizes the source of audible signal 14 to provide an audible signal.
  • Acoustical combining means 13 combines the noise signal with the audible signal of substantially the same waveform but opposite phase from the audible noise provided by source 11 thereby significantly to reduce the audible noise level on output 12.
  • the total undesired noise power radiated into the environment by the combination of sources 11 and 14 in the frequency range where attenuation occurs is significantly less throughout a region of volume significantly larger than the volume occupied by the source of audible noise 11, the acoustical combining means 13, the source of audible signal 14 and the second electroacoustical transducing means 15.
  • these elements are separated from each other by a distance less than a half wavelength at the highest frequency of interest to be attenuated, typically a frequency that is of the order of 500 Hz or less.
  • FIG. 2 there is shown a combined block-schematic-pictorial representation of an electroacoustical exhaust silencer for an engine 11 which comprises the noise source, characterized by appreciable noise reduction with compact structure without loading the engine, thereby allowing the engine to operate more efficiently as compared with an engine exhausting through a conventional passive exhaust silencer system.
  • the exhaust pipe 21 may be formed with a T-section 22 having a short stem 23 having an end opening covered by an electroacoustical transducer 14.
  • Microphone 15 between the section 22 and outlet 12 of the exhaust pipe 21 provides an electrical signal to controlled amplifying means 16 representative of the acoustical signal just inside the outlet 12 for amplification by controlled amplifying means 16 to energize loudspeaker 14 with a signal tending to reduce the audible noise from outlet 12 through the use of known negative feedback techniques.
  • Controlled amplifying means 16 preferably includes frequency selective apparatus for transmitting signals within a low audio frequency range, such as 10 to 500 Hertz, thus embracing the spectrum of significant levels of audible noise energy which are to be reduced and which are received at the inlet to the exhaust pipe 21 from the engine, and thus helping to maintain system stability.
  • a portion of the exhaust pipe 21 functions as the acoustical combining means 13.
  • T-joint 22 is as close to the outlet as practical but sufficiently far from the microphone 15 so that the acoustic wave is essentially plane where the microphone 15 is located.
  • Stem 23 is preferably as short as practical. The distance between transducers 14 and 15 should be less than a half wavelength at the highest , noise frequency to be reduced.
  • the maximum span across the duct or pipe is preferably less than a quarter wavelength at the highest noise frequency to be reduced and if circular in section the pipe preferably has a diameter less than a sixth of the wavelength.
  • the system exemplified by the electroacoustical muffler of Figure 2 is characterized by significant structural features which allow the distance of the noise source from the transducers to be relatively free from criticality because the noise energy from the source and the transducer providing the noise-bucking field is confined by the structure and released to the outside environment through a limited aperture in this case the inlet of the exhaust pipe.
  • the same system could be used in a ventilating duct.
  • the unconfined system exemplified by a compressor, and including a loudspeaker and microphone preferably has these three elements in close proximity with the microphone preferably midway between the compressor and loudspeaker providing the noise-bucking field to reduce the noise energy radiated by the system.
  • the principles of the invention may have many applications, but are especially useful where the audible noise energy sought to be attenuated is in the low frequency range. Thus, it may be used to reduce the low frequency noise present in air ducts or provided by compressors or other motors.
  • audibly perceptible noise reduction of compressors or motors may be achieved according to the invention with the first and second electroacoustical transducing means located within a half wavelength of the compressor or motor comprising the noise source, a microphone being preferably midway between each noise source and a loudspeaker or other transducer providing the noise-bucking field.
  • the invention may also be used in combination with passive devices capable of significantly reducing audible noise at higher frequencies.

Abstract

The noise power perceived in an environment of volume larger than and outside a volume including a source (11) of audible noise is appreciably reduced with an active system that includes an acoustical combiner (13) that combines the noise signal to be reduced with an inversely fed back signal provided by a loudspeaker (14) energized by a controlled frequency selective amplifier (16) that amplifies spectral components to be reduced provided by a microphone (15) near the output of the acoustical combiner (13).

Description

  • The present invention relates in general to reducing audible noise and more particularly concerns novel apparatus and techniques for using an active electroacoustical system to significantly reduce audible noise with relatively compact and reliable apparatus.
  • Exposure to audible noise at significant levels not only causes discomfort and fatigue but may result in temporary and/or-permanent damage to hearing. Accordingly, to meet government-established maximum noise levels, passive techniques, such as noise-reducing enclosures, have been employed to reduce audible noise levels. While reasonably effective at high audio frequencies, attenuating low frequency audible noise passively requires considerable mass to obtain effective attenuation.
  • As an example of active methods to reduce unwanted audible noise reference is made to U.S. Patent No. 2,043,416. More recent approaches involve open and closed loop systems. In one open loop system a noise source within a given surface may have a number of microphones just inside the surface and a number of loudspeakers just outside the surface. The microphones pick up the noise at the surface to provide a signal that is amplified and delivered to the loudspeakers with substantially the same intensity but opposite phase as the noise passing across the surface to effectively reduce the noise perceived by an observer remote from the surface.
  • A closed loop system may use a microphone near the observer coupled to a nearby loudspeaker through signal processing electronics for receiving the audible noise from a distant source and providing a signal from the loudspeaker of opposite phase, thereby tending to reduce the noise level perceived by the listener. Such a system is described in 28 Journal of the Acoustical Society of America 966-972 (1956) and discloses using a specially designed loudspeaker and microphone separated by a distance of approximately one inch. This approach works only when the listener, loudspeaker, and microphone are separated by a small fraction of a wavelength of the highest frequency audible noise energy to be cancelled as attenuation is provided in only a small volume of space directly around the microphone.
  • - According to the invention electroacoustical audible noise reducing apparatus for a source of audible noise having significant audible spectral components in a predetermined frequency range below 500Hz, comprises a first electroacoustical transducing means for transducing an input electrical signal into a corresponding audible signal; an acoustical combining means for combining the audible noise from the source with the audible signal from the first electroacoustical transducing means; a second electroacoustical transducing means responsive to the acoustical signal at the output of acoustical combining means for providing an electrical signal representative thereof; controlled amplifying means responsive to the latter electrical signal for providing an amplified electrical signal to the first electroacoustical transducing means; the acoustical combining means and the first and second electroacoustical transducing means being closely spaced and separated from each other by less than a half wavelength at the highest frequency of the predetermined frequency range, whereby, in the predetermined frequency range, spectral components of noise energy in a volume of the environment, outside, and significantly larger than, the volume occupied by the source of audible noise, the first and second electroacoustical transducing means and the acoustical combining means are significantly less than corresponding components at the output of the source of audible noise.
  • The invention thus provides improved apparatus and techniques for reducing audible noise, and over a relatively large region.
  • Preferably, the acoustical combining means comprises a duct, the second electroacoustical transducing means is located in the duct and the duct is formed with an opening intermediate its ends coupled to the first electroacoustical transducing means. The apparatus forms a closed loop that tends to minimize the intensity of the acoustical signal output from the duct outlet.
  • According to another specific form of the invention, the source of audible noise and first and second electroacoustical transducing means are separated from each other by a distance less than a half wavelength at the frequencies of interest to be attenuated.
  • An example of apparatus according to the invention will now be described with reference to the accompanying drawings in which:-
    • Figure 1 is a block diagram illustrating the logical arrangement of the apparatus; and,
    • Figure 2 is a combined pictorial-schematic-block diagram illustrating the logical arrangement of the apparatus when used as an electroacoustical exhaust silencer system.
  • With reference now to the drawings and more particularly Figure 1 thereof, there is shown a block diagram illustrating the logical arrangment of electroacoustical audible noise reducing apparatus according to the invention. Like elements are identified by the same reference symbols throughout the drawings. A source of audible noise 11 is combined, in an acoustical combining means 13, with an audible signal from a source 14 to provide a reduced noise level at output 12. The source 14 typically comprises an acoustical transducing means for transducing an input electrical signal into a corresponding acoustical signal. A second electroacoustical transducing means 15 for transducing an acoustic signal into a corresponding electrical signal, such as a microphone, provides an electrical signal representative of the acoustical signal at output 12. Controlled amplifying means 16 amplifies this signal and energizes the source of audible signal 14 to provide an audible signal. Acoustical combining means 13 combines the noise signal with the audible signal of substantially the same waveform but opposite phase from the audible noise provided by source 11 thereby significantly to reduce the audible noise level on output 12.
  • The result is that the total undesired noise power radiated into the environment by the combination of sources 11 and 14 in the frequency range where attenuation occurs is significantly less throughout a region of volume significantly larger than the volume occupied by the source of audible noise 11, the acoustical combining means 13, the source of audible signal 14 and the second electroacoustical transducing means 15. In a specific form of the invention these elements are separated from each other by a distance less than a half wavelength at the highest frequency of interest to be attenuated, typically a frequency that is of the order of 500 Hz or less.
  • Referring to Figure 2, there is shown a combined block-schematic-pictorial representation of an electroacoustical exhaust silencer for an engine 11 which comprises the noise source, characterized by appreciable noise reduction with compact structure without loading the engine, thereby allowing the engine to operate more efficiently as compared with an engine exhausting through a conventional passive exhaust silencer system.
  • The exhaust pipe 21 may be formed with a T-section 22 having a short stem 23 having an end opening covered by an electroacoustical transducer 14. Microphone 15 between the section 22 and outlet 12 of the exhaust pipe 21 provides an electrical signal to controlled amplifying means 16 representative of the acoustical signal just inside the outlet 12 for amplification by controlled amplifying means 16 to energize loudspeaker 14 with a signal tending to reduce the audible noise from outlet 12 through the use of known negative feedback techniques. Controlled amplifying means 16 preferably includes frequency selective apparatus for transmitting signals within a low audio frequency range, such as 10 to 500 Hertz, thus embracing the spectrum of significant levels of audible noise energy which are to be reduced and which are received at the inlet to the exhaust pipe 21 from the engine, and thus helping to maintain system stability. A portion of the exhaust pipe 21 functions as the acoustical combining means 13. Preferably T-joint 22 is as close to the outlet as practical but sufficiently far from the microphone 15 so that the acoustic wave is essentially plane where the microphone 15 is located. Stem 23 is preferably as short as practical. The distance between transducers 14 and 15 should be less than a half wavelength at the highest , noise frequency to be reduced.
  • The maximum span across the duct or pipe is preferably less than a quarter wavelength at the highest noise frequency to be reduced and if circular in section the pipe preferably has a diameter less than a sixth of the wavelength.
  • The system exemplified by the electroacoustical muffler of Figure 2 is characterized by significant structural features which allow the distance of the noise source from the transducers to be relatively free from criticality because the noise energy from the source and the transducer providing the noise-bucking field is confined by the structure and released to the outside environment through a limited aperture in this case the inlet of the exhaust pipe. The same system could be used in a ventilating duct. The unconfined system exemplified by a compressor, and including a loudspeaker and microphone preferably has these three elements in close proximity with the microphone preferably midway between the compressor and loudspeaker providing the noise-bucking field to reduce the noise energy radiated by the system.
  • The principles of the invention may have many applications, but are especially useful where the audible noise energy sought to be attenuated is in the low frequency range. Thus, it may be used to reduce the low frequency noise present in air ducts or provided by compressors or other motors. For example, audibly perceptible noise reduction of compressors or motors, may be achieved according to the invention with the first and second electroacoustical transducing means located within a half wavelength of the compressor or motor comprising the noise source, a microphone being preferably midway between each noise source and a loudspeaker or other transducer providing the noise-bucking field. The invention may also be used in combination with passive devices capable of significantly reducing audible noise at higher frequencies.

Claims (9)

1. Electroacoustical audible noise reducing apparatus for a source (11) of audible noise having significant audible spectural components in a predetermined frequency range below 500 Hz, the apparatus having a first electroacoustical transducing means (14) for transducing an input electrical signal into a corresponding audible signal; an acoustical combining means (13) for combining the audible noise from the source (11) with the audible signal from the first electroacoustical transducing means (14); a second electroacoustical transducing means (15) responsive to the acoustical signal at the.output (12) of the acoustical combining means (13) for providing an electrical signal representative thereof; controlled amplifying means (16) responsive to the latter electrical signal for providing an amplified electrical signal to the first electroacoustical transducing means (14); the acoustical combining means (13) and the first (14) and second (15) electroacoustical transducing means being closely spaced and separated from each other by less than a half wavelength at the highest frequency of the predetermined frequency range, whereby in the predetermined frequency range, spectral components of noise energy in a volume of the environment outside, and significantly larger than, the volume occupied by the source (11) of audible noise, the first (14) and second (15) electroacoustical transducing means and the acoustical combining means (13) are significantly less than corresponding components at the output of the source of audible noise.
2. Apparatus according to claim 1, wherein the first (14) and second (15) electroacoustical transducing means are a loudspeaker and a microphone, respectively.
3. Apparatus according to claim 1 or claim 2, wherein the acoustical combining means (13) comprises a duct (21), the second electroacoustical transducing means (15) is located in the duct (21), and the duct (21) is formed with an opening intermediate its ends coupled to the first electroacoustical transducing means (14).
4. Apparatus according to claim 3, wherein the opening comprises a T-joint having a hollow stem (23) formed with an opening to which the first electroacoustical transducing means (14) is connected.
5. Apparatus according to claim 3 or claim 4, wherein the duct (21) has a cross-sectional area with a maximum span thereacross that is less than a half wavelength at the highest frequency of the predetermined frequency range, a portion (22) of the duct comprising the acoustical combining means (13), and the second electroacoustical transducing means (15) being spaced from the opening sufficiently far so that the acoustical wave in a cross-sectional plane of the duct (21) passing through the second electroacoustical transducing means (15) is substantially plane.
6. Apparatus according to any of claims 3 to 5, wherein the duct (21) is an exhaust pipe for connection to the exhaust outlet of an enging (11).
7. Apparatus according to any of claims 1 to 6, wherein the controlled amplifying means (16) includes frequency selective apparatus for attenuating signals outside a predetermined low audio frequency range that is within the frequency range of 11 to 500 Hz.
8. Apparatus according to claim 1, wherein the second electroacoustical transducing means (15) is located substantially midway between the source (11) of audible noise and the first electroacoustical transducing means (14).
9. Apparatus according to claim 8, wherein the controlled amplifying means (16) includes frequency selective apparatus for attenating signals outside a predetermined low audio frequency range that is within the frequency.
EP81300660A 1980-05-16 1981-02-18 Electroacoustical audible noise reducing apparatus Withdrawn EP0040462A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US15058180A 1980-05-16 1980-05-16
US150581 1998-09-10

Publications (1)

Publication Number Publication Date
EP0040462A1 true EP0040462A1 (en) 1981-11-25

Family

ID=22535165

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81300660A Withdrawn EP0040462A1 (en) 1980-05-16 1981-02-18 Electroacoustical audible noise reducing apparatus

Country Status (2)

Country Link
EP (1) EP0040462A1 (en)
JP (1) JPS576897A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983000580A1 (en) * 1981-08-11 1983-02-17 Chaplin, George, Brian, Barrie Method and apparatus for low frequency active attenuation
WO1983002031A1 (en) * 1981-11-26 1983-06-09 Chaplin, George, Brian, Barrie Improved method of an apparatus for cancelling vibrations from a source of repetitive vibrations

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4562589A (en) * 1982-12-15 1985-12-31 Lord Corporation Active attenuation of noise in a closed structure
CH670390A5 (en) * 1987-03-31 1989-06-15 Nestle Sa
US4805733A (en) * 1987-07-07 1989-02-21 Nippondenso Co., Ltd. Active silencer
JP2579966B2 (en) * 1987-10-30 1997-02-12 株式会社日本自動車部品総合研究所 Intake system noise reduction device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2043416A (en) * 1933-01-27 1936-06-09 Lueg Paul Process of silencing sound oscillations
GB1357330A (en) * 1970-07-01 1974-06-19 Secr Defence Dynamic silencing systems
US3826870A (en) * 1970-03-20 1974-07-30 Quest Electronics Corp Noise cancellation
FR2275722A1 (en) * 1974-06-21 1976-01-16 Sound Attenuators Ltd NOISE MITIGATION PROCESS
US3936606A (en) * 1971-12-07 1976-02-03 Wanke Ronald L Acoustic abatement method and apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2043416A (en) * 1933-01-27 1936-06-09 Lueg Paul Process of silencing sound oscillations
US3826870A (en) * 1970-03-20 1974-07-30 Quest Electronics Corp Noise cancellation
GB1357330A (en) * 1970-07-01 1974-06-19 Secr Defence Dynamic silencing systems
US3936606A (en) * 1971-12-07 1976-02-03 Wanke Ronald L Acoustic abatement method and apparatus
FR2275722A1 (en) * 1974-06-21 1976-01-16 Sound Attenuators Ltd NOISE MITIGATION PROCESS

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983000580A1 (en) * 1981-08-11 1983-02-17 Chaplin, George, Brian, Barrie Method and apparatus for low frequency active attenuation
US4527282A (en) * 1981-08-11 1985-07-02 Sound Attenuators Limited Method and apparatus for low frequency active attenuation
WO1983002031A1 (en) * 1981-11-26 1983-06-09 Chaplin, George, Brian, Barrie Improved method of an apparatus for cancelling vibrations from a source of repetitive vibrations
US4566118A (en) * 1981-11-26 1986-01-21 Sound Attenuators Limited Method of and apparatus for cancelling vibrations from a source of repetitive vibrations

Also Published As

Publication number Publication date
JPS576897A (en) 1982-01-13

Similar Documents

Publication Publication Date Title
US6278786B1 (en) Active noise cancellation aircraft headset system
US5448645A (en) Active fan blade noise cancellation system
US5995632A (en) Fan noise canceller
US7043037B2 (en) Hearing aid having acoustical feedback protection
AU2004203048B2 (en) Active Noise Suppression for a Hearing Aid Device Which Can Be Worn in the Ear or a Hearing Aid Device With Otoplasty Which Can Be Worn in the Ear
US6434239B1 (en) Anti-sound beam method and apparatus
US6754355B2 (en) Digital hearing device, method and system
EP1770685A1 (en) A system for providing a reduction of audiable noise perception for a human user
US20080247560A1 (en) Audio output device
JPH0692728B2 (en) Active acoustic control system
ES2092497T3 (en) ELECTROACOUSTIC DEVICE FOR HEARING NEEDS THAT INCLUDES NOISE CANCELLATION.
WO1994002935A1 (en) Method and device for active noise reduction in a local area
US6714654B2 (en) Hearing aid operative to cancel sounds propagating through the hearing aid case
USH417H (en) Headset for ambient noise suppression
EP0040462A1 (en) Electroacoustical audible noise reducing apparatus
CA2137651C (en) Active acoustical controlled enclosure
Streeter et al. Hybrid feedforward-feedback active noise control
Sun et al. Experiments on performances of active-passive hybrid mufflers
JPH0195699A (en) Sound pressure control system
JPH0285637A (en) Electronic silencer
JP2620050B2 (en) Active noise control system speaker device
Hong et al. Applications of Active Attenuators in Controlling Low-Frequency Noise
EP1249829A3 (en) Low frequency active noise control
JPH0456499A (en) Active noise canceler
JPS58156997A (en) Active type silencer

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE DE FR GB IT LU NL

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19821030

RIN1 Information on inventor provided before grant (corrected)

Inventor name: BOSE, AMAR G.