EP0327617A1 - Ameliorations relatives a des systemes de reduction de bruit - Google Patents

Ameliorations relatives a des systemes de reduction de bruit

Info

Publication number
EP0327617A1
EP0327617A1 EP88905991A EP88905991A EP0327617A1 EP 0327617 A1 EP0327617 A1 EP 0327617A1 EP 88905991 A EP88905991 A EP 88905991A EP 88905991 A EP88905991 A EP 88905991A EP 0327617 A1 EP0327617 A1 EP 0327617A1
Authority
EP
European Patent Office
Prior art keywords
filter
feedback loop
gain
region
microphone
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
EP88905991A
Other languages
German (de)
English (en)
Other versions
EP0327617B1 (fr
Inventor
Robert Christopher Twiney
Anthony John Salloway
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 Defence Systems Ltd
Original Assignee
Plessey Overseas Ltd
Siemens Plessey Electronic Systems Ltd
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
Priority claimed from GB878717043A external-priority patent/GB8717043D0/en
Priority claimed from GB878717042A external-priority patent/GB8717042D0/en
Priority claimed from GB878717040A external-priority patent/GB8717040D0/en
Application filed by Plessey Overseas Ltd, Siemens Plessey Electronic Systems Ltd filed Critical Plessey Overseas Ltd
Priority to AT88905991T priority Critical patent/ATE82083T1/de
Publication of EP0327617A1 publication Critical patent/EP0327617A1/fr
Application granted granted Critical
Publication of EP0327617B1 publication Critical patent/EP0327617B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • G10K11/17853—Methods, e.g. algorithms; Devices of the filter
    • 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
    • G10K11/1781—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 characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
    • G10K11/17821—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 characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the input signals only
    • G10K11/17825—Error signals
    • 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
    • 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
    • G10K11/17885—General system configurations additionally using a desired external signal, e.g. pass-through audio such as music or speech
    • 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
    • G10K2210/1081—Earphones, e.g. for telephones, ear protectors or headsets
    • 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
    • G10K2210/3028—Filtering, e.g. Kalman filters or special analogue or digital filters
    • 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
    • G10K2210/3039—Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain
    • 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
    • G10K2210/3045—Multiple acoustic inputs, single acoustic output

Definitions

  • This invention relates to systems for reducing the level of acoustic noise fields within ear-defenders or earphone structures worn by personnel (e.g., pilots, vehicle drivers, military personnel) in high noise environments.
  • personnel e.g., pilots, vehicle drivers, military personnel
  • Known active noise reduction (ANR) systems for reducing the acoustic noise field in ear-defenders comprise noise pick-up microphones and noise-canceling sound generators (usually known as loudspeakers) mounted within the internal cavities or enclosures of the respective ear-defenders.
  • the noise pick-up microphones produce electrical signal outputs in response to the acoustic noise fields within the cavities and these signal outputs are phase inverted, filtered and amplified in a feedback loop and fed to the noise-canceling sound generators which produce noise- canceling acoustic signals of substantially the same amplitude but of opposite phase to the acoustic noise field waveforms.
  • the design considerations underlying such ANR systems are described in "Some design considerations for earphone active noise reduction systems", Twiney et al., Vol. 2, pp.95-102, Proc. Spring Conference, 1985, York, Institute of Acoustics.
  • a further problem which occurs is that due to the imperfect transfer functions of both the microphone and generator, the total bandwidth for feedback signals having an appropriate phase is limited, being bounded by regions in which positive feedback occurs. It is usual to employ in feedback systems in general a lowpass first order filter operating at a high frequency in order to stabilize the loop. However such first order low pass filters are not appropriate for filtering out sound energy frequencies in ANR systems because of the large phase changes which occur in the cut-off regions which give rise to problems of positive feedback and signal enhancement. IT was previously thought, as appears from the article referred to above, that electronic processing to overcome problems in ANR systems had limited application because of the causal relation between amplitude and phase response of electronic filters.
  • the present invention provides in a first aspect an active noise reduction system comprising :- a noise-canceling sound generator, a microphone acoustically coupled to said generator, a feedback loop connected between the microphone and the generator, the feedback loop including loop stabilisation means for filtering and inverting the phase of the microphone signal and means for amplifying the microphone signal, and the feedback loop further including high pass frequency filter means for filtering out low frequency sound energy from high pressure sound pulses arising from buffets at low frequency.
  • this aspect of the invention is based on the recognition that the major part of sound energy in high pressure pulses is present at low frequencies say below 100 Hz and thus the provision of low frequency filter means in the feedback loop can reduce a major part of the sound energy in the pulses.
  • Such further filter means is conveniently referred to as an anti-buffet filter (ABF).
  • ABF anti-buffet filter
  • Said further filter means may be used in conjunction with a voltage limiting means, which prevents the generator from being overdriven by amplification of high pressure sound pulses.
  • a voltage limiting means may comprise a non-linear amplifier or zener diode arrangement.
  • the present invention provides an active noise reduction system comprising: - a noise cancelling sound generator, a microphone acoustically coupled to said generator, and a feedback loop connected between said microphone and said generator, wherein said feedback loop comprises: loop stabilisation means for inverting the phase of microphone signals and filtering the microphone signals, and means for amplifying the phase inverted and filtered signals; and, further filter means coupled between the phase inverting means and the amplifying means for increasing loop gain and/or adjusting phase shift by predetermined amounts within one or more predetermined frequency bands.
  • the further filter means is conveniently termed an anti-enhancement filter (AEF).
  • AEF anti-enhancement filter
  • This further aspect of the invention is based on our discovery that enhancement problems caused by transducer imperfections arise in a frequency region centred at about 500 Hz where the gain decreases whereas the phase lag in this area increases to about 3 ⁇ /2.
  • a high pass filter which adjusts the gain in this region whilst providing a phase advance compensating phase shift can significantly reduce the problems of signal enhancement.
  • an active noise reduction system comprising:- a noise-cancelling sound generator, a microphone acoustically coupled to said generator, a feedback loop connected between the microphone and the generator, the feedback loop including loop stabilisation means for filtering and inverting the phase of the microphone signal and means for amplifying the microphone signal, and the feedback loop further including low pass frequency filter means for filtering out high frequency sound energy, the gain of the filter in the cut-off region having a step shape, decreasing from a relatively high constant gain region to a relatively low constant gain region in a transitional region where the gain decreases continuously from the high region to the low region.
  • phase change will be kept much smaller than that which would occur with a first order low pass filter and by careful application the ANR bandwidth can be increased whilst signal enhancement kept to acceptable levels.
  • Figure 1 is a schematic diagram of an active noise reduction system according to the present invention
  • FIG. 2 is a circuit diagram of a preferred anti-buffet (ABF)filter
  • Figure 3 is a graph of the ABF characteristics
  • Figure 4 is a circuit diagram of a preferred anti-enhancement filter (AEF), and Figure 5 is a graph of the filter characteristics;
  • Figure 6 is a circuit diagram of a low pass filter for defining an upper limit of the feedback loop bandwidth
  • Figure 7 is a graph of the low pass filter characteristics
  • Figure 8 is a circuit diagram of an ABEF combining both AEF and ABF characteristics
  • Figure 9 is a graph of the transfer functions of the ABEF of figure 8.
  • the active noise reduction system illustrated comprises a generally cup-shaped circumaural earphone structure 1 arranged to enclose the wearer's ear 2.
  • the rim of the structure 1 is cushioned against the side of the wearer's head 3 by means of a compliant ring cushion 4.
  • the earphone structure 1 embodies a small noise pick-up microphone 5, which detects the noise within the earphone adjacent to the wearer's ear 2 and provides an electrical output dependent upon the detected noise.
  • This output signal from the microphone is passed through an anti-buffet filter 6, a loop stabilisation unit 7,a low-pass filter 8, an anti-enhancement filter 10 and amplifier 12, to a noise cancelling sound generator (loudspeaker) 14 which is mounted on a baffle 16 within structure 1.
  • Loop stabilisation unit 7 includes a phase inverter 72, a loop stabilizing filter 74 for filtering out very high frequencies, and a voltage limiting circuit 76 comprising a zener diode switching arrangement for limiting high amplitude input signals.
  • Filter 6 is placed first in the feedback loop in order to minimise signal values in the loop.
  • the effect of the anti-enhancement filter is to reduce noise effects arising from imperfect transfer functions of microphone 5 and generator 14.
  • a speech signal is injected between anti-enhancement filter 10 and amplifier 12 at an input node 18.
  • the introduction of the speech signal at this point allows the speech signal to be substantially uncoloured by the loop filters.
  • the speech signals may be pre-emphasised by amplification where they may be attenuated by the ANR system.
  • the ABF 6 comprises an amplifier 20 having a negative feedback loop with a resistor Rl connected to its inverting input, which receives an input signal from a resistive/capacitive network R2, R3, Cl.
  • the non-inverting input of the amplifier is connected through a resistor R4 to ground.
  • ABF 6 The characteristics of ABF 6 are shown in Figure 3, whence it may be seen that the filter has a loss factor of about 8db up to about 100 Hz at which frequency the loss reduces continuously until at about 500Hz the filter exhibits a small gain factor.
  • phase shift introduced by the filter rises in the transitional region to a maximum at about 200 Hz. This phase shift must be taken into account when considering the overall loop stability.
  • the effect of the ABF 6 on the overall feedback loop transfer function is to attenuate the low frequency end of the function whereby noise in the frequency range up to 200Hz is severely attenuated.
  • AEF The preferred form of AEF is shown in Figure 4 as comprising two cascaded stages 20, 22, each stage comprising an amplifier 24 with a resistor Rl in a negative feedback loop and with the inverting amplifier input being connected to ground via the series combination of a resistor R2 and capacitor Cl.
  • the filter characteristics are shown in Figure 5 with the gain having an step- form, being roughly Odb up to 100 Hz and then rising to lOdb gain at 1 kHz.
  • the phase shift rises in die region in which the gain changes, having a maximum value of 25° at roughly 500 Hz.
  • the gain reduces to a minimum value at about 500 Hz whereas the phase shift in this area rises to a maximum of about more than 3 ⁇ /2.
  • the transfer functions are modified in this area to reduce phase shift and increase gain, thereby reducing signal enhancement.
  • a circuit diagram of low pass filter 8 is shown in Figure 6 as comprising a transitional second order filter including an amplifier 10 having a non-inverting input connected to a filter input via resistors Rl, R2 and a capacitor Cl coupled between the amplifier input and ground.
  • Two feedback loops are provided from the amplifier output to the non-inverting input: a first loop including a capacitor C2 and a second loop comprising resistors R3, R4, R5 and a capacitor C3 in series with a resistor R9 connected between resistors R4, R5 and ground.
  • a further feedback loop is provided comprising a resistor R7 connected between the amplifier output and the inverting amplifier input.
  • a further resistor R8 is connected between resistor R7 and ground.
  • phase shift across the filter is roughly 150° in the region below 1,000Hz and above 10,000Hz, but decreases to a minimum of about 45° in the centre of the cut-off region.
  • phase change of roughly 105° is acceptable and is much smaller than 180 degrees resulting from a second order low-pass filter.Although a second order filter is shown, the filter could be a higher or lower order if desired.
  • the filter is a second order filter comprising two filter sections connected in cascade, the filter sections being identical, (i f desired a first order filter could be employed).
  • Each filter section comprises an input port 80 coupled to the inverting input of an amplifier 82 through a resistance Rl connected in parallel with a capacitance Cl and a resistance R2.
  • the non-inverting input of the amplifier is connected to ground via a resistance R3, and the output of the amplifier 86 is connected in a negative feedback loop to the inverting input of the amplifier via a resistor R4.
  • the gain is slightly greater than Odb up to about 500 Hz and then rises to about lOdb at a frequency of 2 kHz in a transitional region between 500Hz-2kHz.
  • the phase shift changes from a constant level of about 0° to a maximum value of -30° at about 1 kHz.
  • the filters shown may be replaced by digital filters, and the elements of the feedback loop may be digitised by employing a micro-computer with appropriate routines.
  • the invention claimed is intended to cover both analog and digital systems.

Landscapes

  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Electroluminescent Light Sources (AREA)
  • Gas-Filled Discharge Tubes (AREA)
  • Exhaust Silencers (AREA)
  • Noise Elimination (AREA)
  • Networks Using Active Elements (AREA)

Abstract

Systèmes de réduction de bruit actifs. Afin de surmonter les problèmes, existant dans un système de réduction de bruit, de tremblements sonores à basse fréquence et d'intensification des signaux causée par des fonctions de transfert imparfaites d'un générateur de sons annulant le bruit et d'un microphone, un ou plusieurs filtres passe-haut destinés à réduire les signaux à basse fréquence sont montés dans une boucle de rétroaction, entre le générateur de sons et le microphone. Un filtre passe-bas est prévu pour allonger la bande passante du système, mais n'introduit pas de déphasages excessivement grands.
EP88905991A 1987-07-20 1988-07-20 Ameliorations relatives a des systemes de reduction de bruit Expired - Lifetime EP0327617B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88905991T ATE82083T1 (de) 1987-07-20 1988-07-20 Anordnungen zur stoerschall-verminderung.

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB8717042 1987-07-20
GB878717043A GB8717043D0 (en) 1987-07-20 1987-07-20 Noise reduction systems
GB878717042A GB8717042D0 (en) 1987-07-20 1987-07-20 Noise reduction systems
GB8717043 1987-07-20
GB8717040 1987-07-20
GB878717040A GB8717040D0 (en) 1987-07-20 1987-07-20 Noise reduction systems

Publications (2)

Publication Number Publication Date
EP0327617A1 true EP0327617A1 (fr) 1989-08-16
EP0327617B1 EP0327617B1 (fr) 1992-11-04

Family

ID=27263515

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88905991A Expired - Lifetime EP0327617B1 (fr) 1987-07-20 1988-07-20 Ameliorations relatives a des systemes de reduction de bruit

Country Status (6)

Country Link
EP (1) EP0327617B1 (fr)
AT (1) ATE82083T1 (fr)
AU (1) AU608041B2 (fr)
CA (1) CA1299725C (fr)
DE (1) DE3875717T2 (fr)
WO (1) WO1989000746A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2569954A4 (fr) * 2010-05-14 2015-11-25 Creative Tech Ltd Circuit de réduction de bruit doté d'une fonction de contrôle

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5091954A (en) * 1989-03-01 1992-02-25 Sony Corporation Noise reducing receiver device
KR100231219B1 (ko) * 1990-01-19 1999-11-15 오오가 노리오 이어폰 장치
US5276740A (en) * 1990-01-19 1994-01-04 Sony Corporation Earphone device
US5224168A (en) * 1991-05-08 1993-06-29 Sri International Method and apparatus for the active reduction of compression waves
AU6127494A (en) * 1993-01-29 1994-08-15 Active Noise And Vibration Technologies, Inc. Earpiece for active noise cancelling headset
DE69424419T2 (de) * 1993-06-23 2001-01-04 Noise Cancellation Technologies, Inc. Aktive lärmunterdrückungsanordnung mit variabler verstärkung und verbesserter restlärmmessung
AT403417B (de) * 1995-04-25 1998-02-25 Fritz Dr Paschke Schallfiltervorrichtung
US5675658A (en) * 1995-07-27 1997-10-07 Brittain; Thomas Paige Active noise reduction headset
CN1427988A (zh) * 2000-03-07 2003-07-02 新西兰商史莱柏Dsp公司 有源噪声抑制系统
US8054992B2 (en) 2006-04-24 2011-11-08 Bose Corporation High frequency compensating
US8077874B2 (en) 2006-04-24 2011-12-13 Bose Corporation Active noise reduction microphone placing
DE102009005302B4 (de) 2009-01-16 2022-01-05 Sennheiser Electronic Gmbh & Co. Kg Schutzhelm und Vorrichtung zur aktiven Störschallunterdrückung
US8085946B2 (en) 2009-04-28 2011-12-27 Bose Corporation ANR analysis side-chain data support
US8345888B2 (en) * 2009-04-28 2013-01-01 Bose Corporation Digital high frequency phase compensation
US11164554B2 (en) 2020-03-06 2021-11-02 Bose Corporation Wearable active noise reduction (ANR) device having low frequency feedback loop modulation

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4061875A (en) * 1977-02-22 1977-12-06 Stephen Freifeld Audio processor for use in high noise environments
US4654871A (en) * 1981-06-12 1987-03-31 Sound Attenuators Limited Method and apparatus for reducing repetitive noise entering the ear
ZA825676B (en) * 1981-08-11 1983-06-29 Sound Attenuators Ltd Method and apparatus for low frequency active attennuation
DE3133107A1 (de) * 1981-08-21 1983-03-10 Michael 5440 Mayen Hofmann Persoenlicher schallschutz
GB2172769B (en) * 1985-03-21 1988-07-06 Topexpress Ltd Improvements in acoustic attenuation
GB8517716D0 (en) * 1985-07-13 1985-08-21 Plessey Co Plc Noise reduction arrangements

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8900746A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2569954A4 (fr) * 2010-05-14 2015-11-25 Creative Tech Ltd Circuit de réduction de bruit doté d'une fonction de contrôle

Also Published As

Publication number Publication date
DE3875717T2 (de) 1993-03-18
WO1989000746A1 (fr) 1989-01-26
AU608041B2 (en) 1991-03-21
CA1299725C (fr) 1992-04-28
EP0327617B1 (fr) 1992-11-04
AU2071688A (en) 1989-02-13
DE3875717D1 (de) 1992-12-10
ATE82083T1 (de) 1992-11-15

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