GB2126837A - Noise suppression - Google Patents

Noise suppression Download PDF

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Publication number
GB2126837A
GB2126837A GB08322281A GB8322281A GB2126837A GB 2126837 A GB2126837 A GB 2126837A GB 08322281 A GB08322281 A GB 08322281A GB 8322281 A GB8322281 A GB 8322281A GB 2126837 A GB2126837 A GB 2126837A
Authority
GB
United Kingdom
Prior art keywords
noise
signal
aircraft
suppression system
sensing
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.)
Granted
Application number
GB08322281A
Other versions
GB8322281D0 (en
GB2126837B (en
Inventor
Henry William Groves
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.)
BAE Systems PLC
Original Assignee
British Aerospace PLC
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 British Aerospace PLC filed Critical British Aerospace PLC
Priority to GB08322281A priority Critical patent/GB2126837B/en
Publication of GB8322281D0 publication Critical patent/GB8322281D0/en
Publication of GB2126837A publication Critical patent/GB2126837A/en
Application granted granted Critical
Publication of GB2126837B publication Critical patent/GB2126837B/en
Expired legal-status Critical Current

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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
    • G10K11/1787—General system configurations
    • G10K11/17879—General system configurations using both a reference signal and an error signal
    • G10K11/17883—General system configurations using both a reference signal and an error signal the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
    • 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/106—Boxes, i.e. active box covering a noise source; Enclosures
    • 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
    • G10K2210/108—Communication systems, e.g. where useful sound is kept and noise is cancelled
    • G10K2210/1082—Microphones, e.g. systems using "virtual" 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/121—Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
    • 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
    • G10K2210/123—Synchrophasors or other applications where multiple noise sources are driven with a particular phase relationship
    • 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
    • G10K2210/1281—Aircraft, e.g. spacecraft, airplane or helicopter
    • 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
    • G10K2210/50—Miscellaneous
    • G10K2210/511—Narrow band, e.g. implementations for single frequency cancellation

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

A noise suppression system e.g. for an aircraft includes sensing means M for sensing generally periodic noise generated by the powerplant 3 of the aircraft, a transducer 7/8 associated with the powerplant to producing a signal indicative of the period of the noise generated, and means for delaying the noise signal generated by the sensing means M by an interval equivalent to a whole number of periods, the delayed signal being inverted and supplied to sound producing means L, whereby the noise in the cabin is reduced. The system is also stated to be of use in airport buildings or bus terminals in which case the transducer 7/8 is replaced by a variable frequency oscillator under manual or automatic control. <IMAGE>

Description

SPECIFICATION Noise suppression This invention relates to the suppression of noise of a generally periodic nature, and in particular but not exclusively to the suppression of audible noise generated by propeller driven aircraft.
In such aircraft, and particuiarly in multiengined aircraft, passengers seated within the fuselage in a zone adjacent the plane of rotation of the propellers may experience noise of sufficient magnitude to give discomfort, especially when in a multi-engined aircraft, the engines are running at slightly different speeds, thus generating a beat frequency.
In the Specification of our U.K. Patent No, 1,530,814, there is described a hearing protection device comprising a pair of headphones in the earpiece of each of which there is provided a microphone which senses the soundwaves which have propagated through the outer insulating shell and which generates signals which are amplified and inverted to drive a diaphragm in a sense to reduce the sound waves which impinge on the ear.
It is to be understood that the expression "noise" used in this Specification is to be construed broadly, without implying any limitation to the audible range of frequencies.
According to one aspect of this invention, there is provided a noise suppression system for suppressing noise of a generally periodic nature, including sensing means for sensing noise and for producing a noise signal in response to the sensed noise, delay means for delaying the noise signal by an interval substantially equal to a whole number of periods of the noise, and sound producing means supplied by the delayed noise signal in the appropriate sense to produce sound waves substantially in antiphase with the sensed noise.
Naturally, the sensing means should be arranged so that it senses unprocessed, raw noise, and thus should be remote from the sound producing means, either by its physical location, or by signal processing.
In one arrangement, the system includes an inverting amplifier which inverts and amplifies the noise signal either before or after it is delayed.
In another aspect of this invention, there is provided a noise suppression system for an aircraft for suppressing noise of a generally periodic nature caused by the aircraft powerplant, including sensing means for sensing noise and for producing a noise signal in response to the sensed noise, delay means for delaying the noise signal by an interval substantially equal to a whole number of periods of the noise, and sound producing means located in the cabin of the aircraft and supplied by the delayed noise signal in the appropriate sense to produce sound waves substantially in antiphase with the sensed noise.
Preferably, the delay means include synchronising means including a transducer associated with the power plant so as to provide a reference signal indicative of the operating speed of the powerplant. Where the system is used in a propeller driven aircraft, the transducer means may produce a signal indicative of the rate of rotation of the propeller.
In a further aspect of this invention, there is provided a method of suppressing noise of a generally periodic nature which comprises the steps of (a) sensing the noise to be suppressed and producing a representative noise signal, (b) determining the period of said noise, (c) delaying the noise signal by an internal substantially equal to a whole number of periods of said noise, and (d) supplying said delayed noise signal to sound producing means in an appropriate sense.
Further aspects of the invention will be apparent from the following description, which is made by way of example only, of a noise suppression system for an aircraft, in which reference will be made to the accompanying drawings in which: Figure 1 is a diagrammatic cross-sectional view of a multi-engined propeller driven aircraft, and Figure 2 is a block diagram illustrating the operation of one form of noise suppression system.
-Referring to Figure 1, there is shown an aircraft which includes a fuselage 1, wings 2 extending away from each side of the fuselage, each wing 2 carrying an engine 3 having a drive shaft 4 to which is secured a propeller 5. A passenger cabin 6 is defined within the fuselage, and a microphone M is located within the cabin which senses the sound waves which reach the cabin mainly in the region of the plane rotation of the propeller where the amplitude of noise is greatest. The noise within the cabin 6 is composed of engine noise and propeller noise and is thus of a generally periodic nature dependent on the rotational speed of the propeller 5, a period being repeated for each revolution of the propeller.
The microphone M produces an electrical signal in response to the sensed sound waves within the cabin. The signal so produced has impressed upon it a series of reference pulses R which are created by means of a transducer T which includes a notched wheel 7 secured to the drive shaft 4 of one of the engines 3 and a magnetic pick-up 8 to provide a pulse R on each revolution of the drive shaft 4.
The signal produced by the microphone M, together with the reference pulses R impressed thereon is presented to a signal synchroniser S which acts to delay the signal before it is presented to an inverting amplifier I which drives a loudspeaker L. The signal synchroniser S calculates the interval between successive pulses R and hence derives the notional period of the signal sensed by the microphone M; the synchroniser S then delays the signal produced by the microphone by an interval equivalent to one notional period, so that the signal fed to a loudspeaker L is substantially equivalent to, but inverted with respect to the signal produced by the microphone M.
Thus, as a period of noise is generated in the cabin by the propeller and sensed by microphone M, the previous period of noise is emitted by the loudspeaker L, but in antiphase.
The microphone M and loudspeaker L will be positioned having regard to the acoustic characteristics of the aircraft, the microphone being acoustically isolated from the loudspeaker.
The loudspeaker may be directed at or attached to the region of the fuselage through which the sound acts, or it may be directed at the region occupied by the passengers. The microphone M may be positioned near the propeller/engine. A plurality of loudspeakers and/or microphones may be used.
It will be appreciated that the above described embodiment may produce noise in antiphase irrespective of the speed of the propeller 5, the delay being controlled by the reference signal generated by the transducer T.
Further microphones M, synchronisers S inverting amplifiers I, and loudspeakers L, may be employed to counteract residual noise which remains after this treatment so that the residual noise is suppressed.
In a modification of this arrangement, for suppressing noise of a variable, but still essentially periodic nature, for example that present in an airport building or bus terminal, the transducer T may be replaced by a variable frequency oscillator or other suitable means which is used to impress a series of notional reference pulses on the signal, the interval between successive pulses being varied until the noise is suitably suppressed, the oscillator being under manual or automatic control.
The arrangements as described above may be adapted for suppressing noise in vehicles, vessels, craft or buildings where noise is generated or present.

Claims (8)

1. A noise suppression system for suppressing noise of a generally periodic nature, including sensing means for sensing noise and for producing a noise signal in response to the sensed noise, delay means for delaying the noise signal by an interval substantially equal to a whole number of periods of the noise, and sound producing means supplied by the delayed noise signal in the appropriate sense to produce sound waves substantially in antiphase with the sensed noise.
2. A system according to Claim 1, wherein the system includes an inverting amplifier which inverts and amplifies the noise signal.
3. A noise suppression system for an aircraft for suppressing noise of a generally periodic nature caused by the aircraft powerplant, including sensing means for sensing noise and for producing a noise signal in response to the sensed noise, delay means for delaying the noise signal by an interval substantially equal to a whole number of periods of the noise, and sound producing means located in the cabin of the aircraft and supplied by the delayed noise signal in the appropriate sense to produce sound waves substantially in antiphase with the sensed noise.
4. A noise suppression system as claimed in Claim 3, wherein the delay means include synchronising means responsive to a reference signal generated by means of a transducer associated with the power plant, so as to provide a reference signal indicative of the operating speed of the powerplant.
5. A noise suppression system as claimed in Claim 3, adapted for use with a propeller-driven aircraft, wherein the transducer means produces a signal indicative of the rate of rotation of the propeller.
6. A noise suppression system as claimed in any of Claims 3 to 5, wherein the sensing means are located within the cabin of the aircraft.
7. A method of suppressing noise of a generally periodic nature which comprises the steps of (a) sensing the noise to be suppressed and producing a representative noise signal, (b) determining the noise signal of said noise, (c) delaying the noise signal by an interval substantially equal to a whole number of periods of said noise, and (d) supplying said delayed noise signal to sound producing means in an appropriate sense.
8. A noise suppression system substantially as hereinbefore described, with reference to and as illustrated in, any of the accompanying drawings.
GB08322281A 1982-08-19 1983-08-18 Noise suppression Expired GB2126837B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08322281A GB2126837B (en) 1982-08-19 1983-08-18 Noise suppression

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8223893 1982-08-19
GB08322281A GB2126837B (en) 1982-08-19 1983-08-18 Noise suppression

Publications (3)

Publication Number Publication Date
GB8322281D0 GB8322281D0 (en) 1983-09-21
GB2126837A true GB2126837A (en) 1984-03-28
GB2126837B GB2126837B (en) 1986-07-23

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Family Applications (1)

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987007974A1 (en) * 1986-06-23 1987-12-30 The Secretary Of State For Trade And Industry In H Aircraft cabin noise control apparatus
GB2201858A (en) * 1986-10-07 1988-09-07 Adaptive Control Ltd Active noise control
WO1990002447A1 (en) * 1988-08-17 1990-03-08 Topexpress Limited Signal processing means for sensing a periodic signal in the presence of another interfering periodic noise
WO1990003026A1 (en) * 1988-09-06 1990-03-22 Topexpress Limited Noise reduction in vehicle cabins
GB2239577A (en) * 1989-12-29 1991-07-03 Nissan Motor Active noise control system for automotive vehicle
US5111507A (en) * 1989-07-24 1992-05-05 Nissan Motor Company, Limited System for reducing noise level in vehicular cabin
GB2255256A (en) * 1991-04-12 1992-10-28 W S Atkins Engineering Science Method of and apparatus for reducing vibrations
WO1994029845A1 (en) * 1993-06-11 1994-12-22 Caterpillar Inc. Top speaker mounting for active noise cancellation
EP0667757A1 (en) * 1992-10-13 1995-08-23 WAGENFELD, Robert Active gas turbine (jet) engine noise suppression
US5455779A (en) * 1991-09-05 1995-10-03 Hitachi, Ltd. Noise reduction apparatus
US5478199A (en) * 1994-11-28 1995-12-26 General Electric Company Active low noise fan assembly
WO1996017339A1 (en) * 1994-11-30 1996-06-06 Lord Corporation Broadband noise and vibration reduction
US5967863A (en) * 1998-04-15 1999-10-19 Marchant; Gary R. Trolling motor
EP1518638A1 (en) * 2003-09-02 2005-03-30 Schwäbische Werkzeugmaschinen GmbH Machine tool with active noise reduction
EP3070708A1 (en) * 2015-03-20 2016-09-21 Yamaha Corporation Sound masking apparatus and sound masking method

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB547082A (en) * 1941-04-11 1942-08-12 George Thomas Cain Improvements in sound receiving apparatus
GB1199925A (en) * 1966-09-08 1970-07-22 Midland Transformer Company Lt Improvements in or relating to Noise Reduction
GB1304329A (en) * 1970-02-26 1973-01-24
GB1577322A (en) * 1976-05-13 1980-10-22 Bearcroft R Active attenuation of recurring vibrations
GB2104754A (en) * 1981-06-12 1983-03-09 George Brian Barrie Chaplin Method and apparatus for reducing repetitive noise entering the ear
GB2107960A (en) * 1981-10-21 1983-05-05 George Brian Barrie Chaplin Method and apparatus for cancelling vibrations

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB547082A (en) * 1941-04-11 1942-08-12 George Thomas Cain Improvements in sound receiving apparatus
GB1199925A (en) * 1966-09-08 1970-07-22 Midland Transformer Company Lt Improvements in or relating to Noise Reduction
GB1304329A (en) * 1970-02-26 1973-01-24
GB1577322A (en) * 1976-05-13 1980-10-22 Bearcroft R Active attenuation of recurring vibrations
GB2104754A (en) * 1981-06-12 1983-03-09 George Brian Barrie Chaplin Method and apparatus for reducing repetitive noise entering the ear
GB2107960A (en) * 1981-10-21 1983-05-05 George Brian Barrie Chaplin Method and apparatus for cancelling vibrations

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987007974A1 (en) * 1986-06-23 1987-12-30 The Secretary Of State For Trade And Industry In H Aircraft cabin noise control apparatus
EP0252647A1 (en) * 1986-06-23 1988-01-13 Secretary of State for Trade and Industry in Her Britannic Majesty's Gov. of the U.K. of Great Britain and Northern Ireland Aircraft cabin noise control apparatus
JPH01502973A (en) * 1986-06-23 1989-10-12 イギリス国 Aircraft cabin noise control device
US4947356A (en) * 1986-06-23 1990-08-07 The Secretary Of State For Trade And Industry In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Aircraft cabin noise control apparatus
JP2620274B2 (en) 1986-06-23 1997-06-11 イギリス国 Noise control device for aircraft cabin
GB2201858A (en) * 1986-10-07 1988-09-07 Adaptive Control Ltd Active noise control
GB2203016A (en) * 1986-10-07 1988-10-05 Adaptive Control Ltd Active sound control apparatus
WO1990002447A1 (en) * 1988-08-17 1990-03-08 Topexpress Limited Signal processing means for sensing a periodic signal in the presence of another interfering periodic noise
WO1990003026A1 (en) * 1988-09-06 1990-03-22 Topexpress Limited Noise reduction in vehicle cabins
US5111507A (en) * 1989-07-24 1992-05-05 Nissan Motor Company, Limited System for reducing noise level in vehicular cabin
GB2239577B (en) * 1989-12-29 1994-08-03 Nissan Motor Active noise control system for automotive vehicle
US5245664A (en) * 1989-12-29 1993-09-14 Nissan Motor Company, Limited Active noise control system for automotive vehicle
GB2239577A (en) * 1989-12-29 1991-07-03 Nissan Motor Active noise control system for automotive vehicle
GB2255256A (en) * 1991-04-12 1992-10-28 W S Atkins Engineering Science Method of and apparatus for reducing vibrations
GB2255256B (en) * 1991-04-12 1994-11-02 W S Atkins Engineering Science Method of and apparatus for reducing vibrations
US5455779A (en) * 1991-09-05 1995-10-03 Hitachi, Ltd. Noise reduction apparatus
EP0667757A4 (en) * 1992-10-13 1996-10-16 Robert Wagenfeld Active gas turbine (jet) engine noise suppression.
EP0667757A1 (en) * 1992-10-13 1995-08-23 WAGENFELD, Robert Active gas turbine (jet) engine noise suppression
WO1994029845A1 (en) * 1993-06-11 1994-12-22 Caterpillar Inc. Top speaker mounting for active noise cancellation
US5478199A (en) * 1994-11-28 1995-12-26 General Electric Company Active low noise fan assembly
WO1996017339A1 (en) * 1994-11-30 1996-06-06 Lord Corporation Broadband noise and vibration reduction
US5967863A (en) * 1998-04-15 1999-10-19 Marchant; Gary R. Trolling motor
EP1518638A1 (en) * 2003-09-02 2005-03-30 Schwäbische Werkzeugmaschinen GmbH Machine tool with active noise reduction
EP3070708A1 (en) * 2015-03-20 2016-09-21 Yamaha Corporation Sound masking apparatus and sound masking method

Also Published As

Publication number Publication date
GB8322281D0 (en) 1983-09-21
GB2126837B (en) 1986-07-23

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19990818