GB2234881A - Noise reduction system - Google Patents

Noise reduction system Download PDF

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Publication number
GB2234881A
GB2234881A GB8917741A GB8917741A GB2234881A GB 2234881 A GB2234881 A GB 2234881A GB 8917741 A GB8917741 A GB 8917741A GB 8917741 A GB8917741 A GB 8917741A GB 2234881 A GB2234881 A GB 2234881A
Authority
GB
United Kingdom
Prior art keywords
noise reduction
headset
microphone
generator
feedback loop
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
GB8917741A
Other versions
GB8917741D0 (en
GB2234881B (en
Inventor
John Leslie Norman
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.)
Plessey Co Ltd
BAE Systems Electronics Ltd
Original Assignee
GEC Marconi Ltd
Plessey Co Ltd
Marconi Co 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
Application filed by GEC Marconi Ltd, Plessey Co Ltd, Marconi Co Ltd filed Critical GEC Marconi Ltd
Priority to GB8917741A priority Critical patent/GB2234881B/en
Publication of GB8917741D0 publication Critical patent/GB8917741D0/en
Publication of GB2234881A publication Critical patent/GB2234881A/en
Application granted granted Critical
Publication of GB2234881B publication Critical patent/GB2234881B/en
Anticipated expiration legal-status Critical
Expired - Fee Related 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
    • G10K11/1783—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
    • G10K11/17833—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F11/00—Methods or devices for treatment of the ears or hearing sense; Non-electric hearing aids; Methods or devices for enabling ear patients to achieve auditory perception through physiological senses other than hearing sense; Protective devices for the ears, carried on the body or in the hand
    • A61F11/06—Protective devices for the ears
    • A61F11/14—Protective devices for the ears external, e.g. earcaps or earmuffs
    • A61F11/145—Protective devices for the ears external, e.g. earcaps or earmuffs electric, e.g. for active noise reduction
    • 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
    • G10K11/1783—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
    • G10K11/17833—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
    • G10K11/17835—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels using detection of abnormal input 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
    • G10K11/1785—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
    • 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
    • G10K2210/3011—Single acoustic input

Landscapes

  • Acoustics & Sound (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Biophysics (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Animal Behavior & Ethology (AREA)
  • Biomedical Technology (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Psychology (AREA)
  • Otolaryngology (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Headphones And Earphones (AREA)

Abstract

An active noise reduction system for an earphone or ear defender, the system comprising a noise reduction sound generator 14, a microphone 5 acoustically coupled to said generator, a feedback loop connected between the microphone and generator, the feedback loop including loop stabilisation means for filtering and inverting the phase of a microphone signal and means for amplifying the microphone signal, in which the headset includes disabling means arranged for automatically disabling the said system at any time when the headset has been displaced from its working position on a user's head. This prevents a high ambient noise level from damaging the sound generator whenever the device has been removed from the user's head. The disabling means may be a microswitch or an overload protection circuit. <IMAGE>

Description

NOISE REDUCTION SYSTEM This invention relates to a noise reduction system. It relates particularly to a system for reducing the level of an acoustic noise field within an ear defender or earphone structure intended to be worn by a person (for example, a pilot, vehicle driver or factory worker) in a high noise environment.
A known active noise reduction (ANR) system for reducing the acoustic noise field in an ear defender comprises a pick-up microphone and a noise-reduction sound generator (which usually takes the form of a loudspeaker) mounted within the internal cavity or enclosure of the respective ear defender. The noise pick-up microphone produces an electrical signal output in response to the acoustic noise field within the cavity and the signal output is phase inverted. filtered and amplified in a feedback loop. The output is then fed to the noise-reduction sound generator which produces noise-reduction acoustic signals of substantially the same amplitude but of opposite phase to the acoustic noise field waveform.An outline of such a system is given in 'Some transducer design considerations for earphone active noise reduction systems', Twiney et al, Vol 7, part 2, pp95-102, Proc Spring Conference, 1985, York, Institute of Acoustics.
One problem which can occur is that of excessive low frequency excursions of the loudspeaker diaphragm which take place when the noise reduction system is operating in a high noise environment at a time when it is not being worn on a user's head. In normal use, an earshell opening of the headset will be sealed by the presence of the user's head. The high ambient noise level is reduced by the headset's passive attenuation and noise reduction occurs from very low frequencies. Thus the resulting internal headset noise level is within the dynamic range of the system and excessive loudspeaker diaphragm displacements are not caused at any frequency.
When the headset is not being worn by a user, the ear shell opening will be unsealed. The noise reduction headset senses the ambient noise level and the system, which under these conditions may now be unstable, produces large amounts of sound enhancement (noise generation with the system active). This sequence of events increases the sound pressure level over a large low frequency bandwidth where active noise reduction could have been achieved in the sealed headset situation. Thus, the resulting very high low frequency noise levels sensed by the system gives rise to very large low frequency loudspeaker diaphragm excursions which can cause damage to or even failure of the loudspeaker.
According to the present invention, there is provided an active noise reduction system for an earphone or ear defender, the system comprising a noise reduction sound generator, a microphone.
acoustically coupled to said generator, a feedback loop connected between the microphone and generator, the feedback loop including loop stabilisation means for filtering and inverting the phase of a microphone signal and means for amplifying the microphone signal, in which a noise reduction headset includes disabling means arranged for automatically disabling the said system at any time when the headset has been displaced from its working position on a user's head.
The disabling means may be a mechanical microswitch. In a different embodiment, the disabling means is an electronic overload protection circuit.
The invention also comprises an active noise reduction headset comprising an ear defender or earphone incorporating the abovementioned noise reduction system.
By way of example, a particular embodiment of the invention will now be described with reference to the accompanying drawing, in which: Figure 1 is a block diagram of the components of the noise reduction system, and, Figure 2 is a circuit diagram showing the components of the overload protection circuit.
The arrangement depicted in Figure 1 shows an earphone shell 1 supported against the ear 2 of a user with the user's head 3 being in contact with a sealing pad 4 of the earphone shell. The internal construction of the shell 1 includes a partition wall 16 which divides the volume enclosed into a rear and a front cavity. A loudspeaker 14 is mounted in an opening in the partition wall 16.
The active noise reduction system comprises the loudspeaker 14, a microphone 5 acoustically coupled to said loudspeaker, a feedback loop connected between the microphone and the loudspeaker, the feedback loop including a loop filter 7 for stabilisation, an inverter 8 for inverting the phase of the microphone signal, an overload protection device 10 and a power amplifier 12 for amplifying the microphone signal. A speech signal may be fed into the loop along a line 18.
The present invention allows the headset system to operate when worn on the head but it disables the system when it is removed from the head in a high noise environment. This action can be achieved by the overload protection device 10 in one of several alternative ways: In one embodiment, a microswitch is incorporated which senses whether the headset is being worn by detecting the force exerted by the headband securing the earphone to the head. If the force is large, the headset is recognised as being worn and the noise reduction loop is not disconnected by the microswitch. Thus, the noise reduction system can function only when the headset is positioned on the user's head.
In a second embodiment, an additional electronic circuit is included to detect if the headset is being worn. The principle of operation is that if the high sound pressure level of the ambient noise is detected, then the system is disabled and if the lower sound pressure level of the actively and passively reduced ambient noise is detected, the system is enabled. The noise level is detected in a frequency band centred at a frequency where neither enhancement nor reduction occurs with the active noise reduction system operating when the headset ear shell opening is in an unsealed condition.
Figure 2 depicts the overload protection circuit in greater detail.
Part of the main feedback loop of the active noise reduction system is shown located between the terminals A and B. The switching components are located in the lower part of the Figure.
The signal is initially introduced at an input terminal A and it passes through a band pass filter stage C and a level sensitive detector stage D. If the signal level at this point is found to be too high, the noise reduction action is disabled by operation of a muting transistor E stage.
The muting stage serves to appreciably reduce the strength of the signals being fed to the input amplifier 12. With the knowledge of the noise field and the passive and active attenuation characteristics of the headset, a threshold level for the most suitable noise reduction operation can be determined.
The foregoing description of an embodiment of the invention has been given by way of example only and a number of modifications may be made without departing from the scope of the invention as defined in the appended claims. For instance, it is not essential that the sound generator should be a moving-coil electromagnetic loudspeaker, in a different embodiment the sound generator could be a piezoelectric or electrostatic loudspeaker.

Claims (6)

CLAIMS:
1. An active noise reduction system for an earphone or ear defender, the system comprising a noise reduction sound generator, a microphone acoustically coupled to said generator, a feedback loop connected between the microphone and generator, the feedback loop including loop stabilisation means for filtering and inverting the phase of a microphone signal and means for amplifying the microphone signal, in which a noise reduction headset includes disabling means arranged for automatically disabling the said system at any time when the headset has been displaced from its working position on a user's head.
2. A system as claimed in Claim 1, in which the said disabling means is a mechanical microswitch.
3. A system as claimed in Claim 1 in which the said disabling means is an electronic overload protection circuit.
4. An active noise reduction system substantially as hereinbefore described, with reference to the accompanying drawing.
5. An active noise reduction headset, comprising a ear defender or earphone and a noise reduction system according to any one of Claims 1 to 4.
6. An active noise reduction headset, substantially as hereinbefore described, with reference to Figure 1 or 2 of the accompanying drawing.
GB8917741A 1989-08-03 1989-08-03 Noise reduction system Expired - Fee Related GB2234881B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8917741A GB2234881B (en) 1989-08-03 1989-08-03 Noise reduction system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8917741A GB2234881B (en) 1989-08-03 1989-08-03 Noise reduction system

Publications (3)

Publication Number Publication Date
GB8917741D0 GB8917741D0 (en) 1989-09-20
GB2234881A true GB2234881A (en) 1991-02-13
GB2234881B GB2234881B (en) 1993-09-15

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Family Applications (1)

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2681717A1 (en) * 1991-09-23 1993-03-26 Sogelec Sarl Audio-visual device fitted with a cell for detecting the position of the headset
WO1994009480A2 (en) * 1992-10-21 1994-04-28 Lotus Cars Limited Adaptive control system
WO1995000946A1 (en) * 1993-06-23 1995-01-05 Noise Cancellation Technologies, Inc. Variable gain active noise cancellation system with improved residual noise sensing
EP1189480A2 (en) * 2000-09-14 2002-03-20 König, Florian Meinhard Headset with earpiece and mouthpiece
GB2479672A (en) * 2006-04-01 2011-10-19 Wolfson Microelectronics Plc Noise reduction system for earphones controlled by detected head movement
GB2484722A (en) * 2010-10-21 2012-04-25 Wolfson Microelectronics Plc Control of a noise cancellation system according to a detected position of an audio device
US8320974B2 (en) 2010-09-02 2012-11-27 Apple Inc. Decisions on ambient noise suppression in a mobile communications handset device
US8391530B2 (en) 2009-01-16 2013-03-05 Sennheiser Electronic Gmbh & Co. Kg Helmet and apparatus for active noise suppression
US8515089B2 (en) 2010-06-04 2013-08-20 Apple Inc. Active noise cancellation decisions in a portable audio device
WO2013022981A3 (en) * 2011-08-08 2013-09-12 Qualcomm Incorporated Electronic devices for controlling noise
US9099077B2 (en) 2010-06-04 2015-08-04 Apple Inc. Active noise cancellation decisions using a degraded reference
DE102016008274A1 (en) 2016-07-07 2017-02-02 Daimler Ag Sound system for a car and method for controlling a sound system
WO2023033973A1 (en) * 2021-08-30 2023-03-09 Bose Corporation Broad spectrum instability detection and mitigation
PL442201A1 (en) * 2022-09-05 2024-03-11 Centralny Instytut Ochrony Pracy - Państwowy Instytut Badawczy Electronic system for transmitting sound to the hearing protector

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2160070A (en) * 1984-05-12 1985-12-11 Plessey Co Plc Sound reproduction system
GB2172470A (en) * 1985-03-16 1986-09-17 Plessey Co Plc Improvements relating to noise reduction arrangements

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2160070A (en) * 1984-05-12 1985-12-11 Plessey Co Plc Sound reproduction system
GB2172470A (en) * 1985-03-16 1986-09-17 Plessey Co Plc Improvements relating to noise reduction arrangements

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2681717A1 (en) * 1991-09-23 1993-03-26 Sogelec Sarl Audio-visual device fitted with a cell for detecting the position of the headset
WO1994009480A2 (en) * 1992-10-21 1994-04-28 Lotus Cars Limited Adaptive control system
WO1994009480A3 (en) * 1992-10-21 1994-06-09 Lotus Car Adaptive control system
US5768124A (en) * 1992-10-21 1998-06-16 Lotus Cars Limited Adaptive control system
WO1995000946A1 (en) * 1993-06-23 1995-01-05 Noise Cancellation Technologies, Inc. Variable gain active noise cancellation system with improved residual noise sensing
EP1189480A2 (en) * 2000-09-14 2002-03-20 König, Florian Meinhard Headset with earpiece and mouthpiece
EP1189480A3 (en) * 2000-09-14 2003-11-05 König, Florian Meinhard Headset with earpiece and mouthpiece
GB2479672A (en) * 2006-04-01 2011-10-19 Wolfson Microelectronics Plc Noise reduction system for earphones controlled by detected head movement
GB2479672B (en) * 2006-04-01 2011-11-30 Wolfson Microelectronics Plc Ambient noise-reduction control system
US8391530B2 (en) 2009-01-16 2013-03-05 Sennheiser Electronic Gmbh & Co. Kg Helmet and apparatus for active noise suppression
US8515089B2 (en) 2010-06-04 2013-08-20 Apple Inc. Active noise cancellation decisions in a portable audio device
US9099077B2 (en) 2010-06-04 2015-08-04 Apple Inc. Active noise cancellation decisions using a degraded reference
US9330654B2 (en) 2010-06-04 2016-05-03 Apple Inc. Active noise cancellation decisions in a portable audio device
US8600454B2 (en) 2010-09-02 2013-12-03 Apple Inc. Decisions on ambient noise suppression in a mobile communications handset device
US8320974B2 (en) 2010-09-02 2012-11-27 Apple Inc. Decisions on ambient noise suppression in a mobile communications handset device
US9749737B2 (en) 2010-09-02 2017-08-29 Apple Inc. Decisions on ambient noise suppression in a mobile communications handset device
US8831238B2 (en) 2010-10-21 2014-09-09 Wolfson Microelectronics Plc Noise cancellation system
GB2484722B (en) * 2010-10-21 2014-11-12 Wolfson Microelectronics Plc Noise cancellation system
GB2484722A (en) * 2010-10-21 2012-04-25 Wolfson Microelectronics Plc Control of a noise cancellation system according to a detected position of an audio device
CN103827959A (en) * 2011-08-08 2014-05-28 高通股份有限公司 Electronic devices for controlling noise
WO2013022981A3 (en) * 2011-08-08 2013-09-12 Qualcomm Incorporated Electronic devices for controlling noise
CN103827959B (en) * 2011-08-08 2016-01-13 高通股份有限公司 For the electronic installation of control noises
US9495952B2 (en) 2011-08-08 2016-11-15 Qualcomm Incorporated Electronic devices for controlling noise
DE102016008274A1 (en) 2016-07-07 2017-02-02 Daimler Ag Sound system for a car and method for controlling a sound system
WO2023033973A1 (en) * 2021-08-30 2023-03-09 Bose Corporation Broad spectrum instability detection and mitigation
PL442201A1 (en) * 2022-09-05 2024-03-11 Centralny Instytut Ochrony Pracy - Państwowy Instytut Badawczy Electronic system for transmitting sound to the hearing protector

Also Published As

Publication number Publication date
GB8917741D0 (en) 1989-09-20
GB2234881B (en) 1993-09-15

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Legal Events

Date Code Title Description
730A Proceeding under section 30 patents act 1977
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20040803