GB2234882A - Noise reduction system - Google Patents
Noise reduction system Download PDFInfo
- Publication number
- GB2234882A GB2234882A GB8917742A GB8917742A GB2234882A GB 2234882 A GB2234882 A GB 2234882A GB 8917742 A GB8917742 A GB 8917742A GB 8917742 A GB8917742 A GB 8917742A GB 2234882 A GB2234882 A GB 2234882A
- Authority
- GB
- United Kingdom
- Prior art keywords
- noise reduction
- generator
- microphone
- earphone
- diaphragm
- 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.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
- H04R1/1083—Reduction of ambient noise
-
- 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
- G10K11/1785—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
-
- 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
- G10K2210/3214—Architectures, e.g. special constructional features or arrangements of features
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2460/00—Details of hearing devices, i.e. of ear- or headphones covered by H04R1/10 or H04R5/033 but not provided for in any of their subgroups, or of hearing aids covered by H04R25/00 but not provided for in any of its subgroups
- H04R2460/11—Aspects relating to vents, e.g. shape, orientation, acoustic properties in ear tips of hearing devices to prevent occlusion
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)
- Signal Processing (AREA)
- Biophysics (AREA)
- Vascular Medicine (AREA)
- Animal Behavior & Ethology (AREA)
- Heart & Thoracic Surgery (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Biomedical Technology (AREA)
- Psychology (AREA)
- Otolaryngology (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
Abstract
An active noise reduction system for an earphone 1 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, and including loop stabilisation means 6, 7 for filtering and inverting the phase of a microphone signal and means 12 for amplifying the signal, the sound generator 14 being mounted within an earphone or oar defender on a partition wall 16 between a rear cavity which is closed and a front cavity which is closed only when the structure is supported against a user's ear, in which the partition wall 16 is provided with an air vent hole 9 effective to equalise air pressure across the wall such that the effect of a large acoustic pressure pulse in the front cavity will be reduced in amplitude and thereby prevented from causing significant displacement of a diaphragm of sound generator 14, the diaphragm thus being able to be driven solely by the applied electrical signals. This restrains the effects of large external pressure pulses or buffets from causing damage to the diaphragm. <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 renown 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', Tainey et al, Vol 7, part 2, pp95-102, Proc Spring Conference, 1985, York,
Institute of Acoustics.
One problem which can occur is that of large pressure pulses (buffets) which may arise inside an ear defender or earphone structure due to relative motion between the human head and the earphone or which may propagate from a device that causes large, low frequency pressure changes, for example, a gun discharge. a helicopter rotor, vehicle engine or an explosive device. These pressure pulses cause the loudspeaker diaphragm to move towards the extreme of its possible displacement. Also, the pulses create large signals in the feedback loop as a result of a high system loop gain. Thus, a diaphragm that is already considerably displaced can receive a large electrical 'anti-buffet' signal requiring appreciable diaphragm displacement in the same direction.The result is that the acoustic output will be very low and active noise reduction across the noise reduction bandwidth is reduced because the diaphragm will reach the limit of its possible physical displacement. Additionally, the feeder wire of the loudspeaker speech coil may be caused to break through metal fatigue or excessive displacement.
It is an object of the present invention to reduce the above problem by permitting the diaphragm to move only as a result of the applied electrical signals and in such a way that it is substantially unaffected by the influence of the pressure pulse.
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, the said sound generator being mounted within an earphone or ear defender structure on a partition wall between a rear cavity which is closed and a front cavity which is normally open but which is closed only when the structure is supported against a user's ear, in which the said partition wall is provided with an air vent hole effective to equalise air pressure across the wall such that the effect of a large acoustic pressure pulse in the said front cavity will be reduced in amplitude and thereby prevented from causing significant displacement of a diaphragm of said sound generator, the said diaphragm thus being able to be driven solely by the applied electrical signals.
The air vent hole may be of such a size as to pass buffet pulses having a frequency in a range up to one hundred hertz. In a different embodiment, the air vent hole may be replaced by ts o or more holes of smaller diameter arranged such that a laminar fluid flow through said holes will be achieved for a given sound pressure level.
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 drawings in which:
Figure 1 is a block diagram of the components of the noise reduction system,
Figure 2 is a graph showing the sound pressure level reduction against frequency for different numbers of inter-cavity vent holes, and,
Figure 3 is a graph showing enhancement against frequency for different numbers of vent holes.
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 low frequency filter 6, a loop filter 7 for stabilisation, an inverter 8 for inverting the phase of the microphone signal and a power amplifier 12 for amplifying the microphone signal. A speech signal may be fed into the loop along a line 18.
To maintain extended low frequency sound output (and an active noise reduction response to low frequencies) it might be thought that a perfect seal between the two cavities would be required. However, a small leak would normally be provided to allow air to flow between the cavities to allow for environmental (temperature and atmospheric pressure) changes.
The present invention requires a greater size of inter-cavity leak than this environmental leak in order to couple the cavities for possible buffet frequencies. The spectral content of vibration or rapid head movement buffet pulses can extend to frequencies as high as one hundred hertz. The air vent hole of the present invention is provided by forming a small number of vent holes 9 in the partition wall 16 supporting the loudspeaker 14. The invention thus permits the high pressure buffet pulses to be present on both sides of the loudspeaker diaphragm by the effect of inter-cavity coupling in the earphone shell.
Figure 2 is a graph which shows the sound pressure level reduction S on the vertical axis against frequency F (in hertz) on the horizontal axis. The sound pressure level reduction is significant above the marked value of zero shown as a horizontal line, whilst for frequency a value of one hundred hertz has been indicated.
The curves of Figure 2 show the results of tests made on noise reduction headsets using different numbers of holes of 3.2 millimetres in length and 0.5 millimetre diameter. The Curve A shows the result with five holes, Curve B applies to seven holes whilst Curve C applies to ten holes.
Figure 2 shows that, in this example, a small number of holes through the transducer partition wall is required in order to couple the cavities to a frequency of about one hundred hertz. A number of small holes is used in preference to a single hole in order to maintain laminar flow through the holes up to the highest sound pressure levels expected. Thus a degree of cavity coupling occurs up to the highest expected buffet amplitude levels (about 140dB sound pressure level).
Additionally, the low frequency amplitude and phase responses are maintained to the highest sound pressure levels. Thus, a consistent active noise reduction effect is achieved at low frequency irrespective of sound pressure level.
The buffet amplitude level is reduced when the earphone's front and rear cavities are coupled. The sound pressure level at buffet frequencies is inversely proportional to the cavity volume.
Consequently, the buffet pressure level without cavity coupling is inversely proportional to the front cavity volume (VF). When the cavities are coupled, the sound pressure level is inversely proportional to the front (VF) and rear (VR) cavity volumes.
Therefore the reduction in buffet amplitude is proportional to the front cavity volume and inversely proportional to the total volume VF
VF + VR
This reduction in buffet levels can be very significant (of the order of 10dB) which is extremely important in preventing the electrical buffet signals from exceeding the dynamic range of the active noise reduction system, thus resulting in intermittent noise reduction operation.
The use of one or more holes between headphone cavities, to maintain laminar flow and hence to maintain invariant amplitude and phase responses to high sound pressure levels has been investigated previously and it has been disclosed partly in the pending European Patent Application No. 87300610.0. The required dimensions (length and radius) of each hole depend on the maximum sound pressure level to be encountered in the system.To maintain laminar flow, Reynolds condition must be satisfied:
r3 pp
< < Reynolds number 4n 21 where r is the radius of the hole
p is the pressure difference across the hole n is the viscosity of the fluid medium
1 is the length of the hole
p is the density of the fluid
From Reynolds condition, it can be seen that to maintain laminar flow up to a high sound pressure level, a long length, small radius hole is required.
The number of holes required to couple the cavities depends on the cavity volumes, thickness of the transducer plate (hole length) and the hole radius.
A fluid leak through a hole will obey Poiseuille's law: sr4 p
V= 8 1 where V is the volume rate of fluid flow.
It can be seen that once the required hole size for laminar flow has been determined, one or more holes are introduced to obtain the required fluid flow and hence a degree of inter-cavity coupling up to a frequency of about one hundred hertz.
The number of holes introduced and hence the degree of cavity coupling provided has to be weighed against the effect on two less beneficial factors: a) Enhancement (the generation of sound which constructively
interferes with the original noise to produce a higher sound
pressure level than with the system inactive) should be at a
low frequency. As the dimensions of the inter-cavity leak are
increased, the enhancement frequency increases due to the
change in the loudspeaker's amplitude and phase responses.
b) Sound generation, which occurs during doffing and donning of
the headset due to the loudspeaker's change in amplitude and
phase responses, should be kept to a minimum.
The above factors depend not only on the acoustic design of the headset, but also on the characteristics of the electronic filters of the noise reduction system.
With the appropriate number (one or more) of intercavity holes, the cavities can be coupled at buffet frequencies resulting in lower amplitude buffet pulses. The loudspeaker diaphragm will remain central with a high degree of coupling or it will remain closer to the central position with a lower degree of cavity coupling for the duration of the pressure pulse and it will respond to the applied electrical signal. As a consequence of the reduced diaphragm displacement, active noise reduction across the noise reduction bandwidth is maintained and the expected lifetime of the loudspeaker is able to be extended due to a reduced tendency to straining of the feeder wires for the loudspeaker speech coil. The linearity of the system can be maintained to very low frequencies and to the maximum generated sound pressure level capability.
Enhancement can be arranged to occur at a low frequency where its effect will not be significant due to the low sensitivity of the human ear. However, if enhancement occurs at too high a frequency, active noise reduction will be reduced at higher frequencies where the noise reduction is required to minimise the dB(A) value in a high noise environment (for example, use in a noisy vehicle).
Figure 3 is a graph which shows the enhancement value E in dB on the vertical axis against frequency F (in hertz) on the horizontal axis. An enhancement value of zero has been indicated by a horizontal line.
For the graph of Figure 3, the dimensions of the holes present are the same as those of Figure 2, and the references A to C for the relevant numbers of holes also correspond. The curves show that as the volume of fluid flow through the vent hole is allowed to increase, the enhancement effect similarly increases in frequency.
The preferred vent arrangement between the cavities is one of between one and ten holes, each hole being of 3.2 millimetres in length and 0.5 millimetres diameter. The number of holes required for a particular headset application will depend on the front and rear cavity volumes and the characteristics of the electronic filters in the noise reduction system and of other acoustic components within the system
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)
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, the said sound generator being mounted within an earphone or ear defender structure on a partition wall between a rear cavity which is closed and a front cavity which is normally open but which is closed only when the structure is supported against a user's ear, in which the said partition wall is provided with an air vent hole effective to equalise air pressure across the wall such that the effect of a large acoustic pressure pulse in the said front cavity will be reduced in amplitude and thereby prevented from causing significant displacement of a diaphragm of said sound generator, the said diaphragm thus being able to be driven solely by the applied electrical signals.
2. A system as claimed in Claim 1, in which the said air vent hole is of such size as to pass buffet pulses having a frequency in a range up to one hundred hertz.
3. A system as claimed in Claim 1 or 2, in which the said air vent hole is replaced by two or more holes of smaller diameter arranged such that a laminar fluid flow through said holes will be achieved for a given sound pressure level.
4. An active noise reduction system substantially as hereinbefore described, with reference to any one of the accompanying drawings.
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 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8917742A GB2234882B (en) | 1989-08-03 | 1989-08-03 | Noise reduction system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8917742A GB2234882B (en) | 1989-08-03 | 1989-08-03 | Noise reduction system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8917742D0 GB8917742D0 (en) | 1989-09-20 |
| GB2234882A true GB2234882A (en) | 1991-02-13 |
| GB2234882B GB2234882B (en) | 1994-01-12 |
Family
ID=10661088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8917742A Expired - Fee Related GB2234882B (en) | 1989-08-03 | 1989-08-03 | Noise reduction system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2234882B (en) |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995000946A1 (en) * | 1993-06-23 | 1995-01-05 | Noise Cancellation Technologies, Inc. | Variable gain active noise cancellation system with improved residual noise sensing |
| EP0801785A1 (en) * | 1994-05-02 | 1997-10-22 | Noise Cancellation Technologies, Inc. | Industrial headset |
| GB2360165A (en) * | 2000-03-07 | 2001-09-12 | Central Research Lab Ltd | A method of improving the audibility of sound from a loudspeaker located close to an ear |
| WO2002080615A2 (en) * | 2001-03-30 | 2002-10-10 | Think-A-Move, Ltd. | Ear microphone apparatus and method |
| US6647368B2 (en) | 2001-03-30 | 2003-11-11 | Think-A-Move, Ltd. | Sensor pair for detecting changes within a human ear and producing a signal corresponding to thought, movement, biological function and/or speech |
| WO2004100607A1 (en) * | 2003-05-09 | 2004-11-18 | Widex A/S | Hearing aid system, a hearing aid and a method for processing audio signals |
| US7502484B2 (en) | 2006-06-14 | 2009-03-10 | Think-A-Move, Ltd. | Ear sensor assembly for speech processing |
| US7983433B2 (en) | 2005-11-08 | 2011-07-19 | Think-A-Move, Ltd. | Earset assembly |
| US8571227B2 (en) | 2005-11-11 | 2013-10-29 | Phitek Systems Limited | Noise cancellation earphone |
| US8666085B2 (en) | 2007-10-02 | 2014-03-04 | Phitek Systems Limited | Component for noise reducing earphone |
| US8929082B2 (en) | 2010-05-17 | 2015-01-06 | Thales Avionics, Inc. | Airline passenger seat modular user interface device |
| US9487295B2 (en) | 2010-11-15 | 2016-11-08 | William James Sim | Vehicle media distribution system using optical transmitters |
| US9654854B2 (en) | 2011-06-01 | 2017-05-16 | Paul Darlington | In-ear device incorporating active noise reduction |
| US9818394B2 (en) | 2009-11-30 | 2017-11-14 | Graeme Colin Fuller | Realisation of controller transfer function for active noise cancellation |
| EP3447762A1 (en) * | 2017-08-23 | 2019-02-27 | ams International AG | Noise cancellation headphone |
| CN111625905A (en) * | 2020-05-29 | 2020-09-04 | 中国航空工业集团公司西安飞机设计研究所 | High-frequency simulation method for noise in propeller aircraft cabin |
| WO2022136807A1 (en) * | 2020-12-24 | 2022-06-30 | Focal Jmlab | Audio headset with active noise reduction |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2188210A (en) * | 1986-03-21 | 1987-09-23 | Univ Southampton | Acoustic noise reduction in ear defenders |
-
1989
- 1989-08-03 GB GB8917742A patent/GB2234882B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2188210A (en) * | 1986-03-21 | 1987-09-23 | Univ Southampton | Acoustic noise reduction in ear defenders |
Cited By (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995000946A1 (en) * | 1993-06-23 | 1995-01-05 | Noise Cancellation Technologies, Inc. | Variable gain active noise cancellation system with improved residual noise sensing |
| EP0801785A1 (en) * | 1994-05-02 | 1997-10-22 | Noise Cancellation Technologies, Inc. | Industrial headset |
| EP0801785A4 (en) * | 1994-05-02 | 1999-08-04 | Noise Cancellation Tech | Industrial headset |
| GB2360165A (en) * | 2000-03-07 | 2001-09-12 | Central Research Lab Ltd | A method of improving the audibility of sound from a loudspeaker located close to an ear |
| WO2002080615A2 (en) * | 2001-03-30 | 2002-10-10 | Think-A-Move, Ltd. | Ear microphone apparatus and method |
| WO2002080615A3 (en) * | 2001-03-30 | 2003-08-07 | Think A Move Ltd | Ear microphone apparatus and method |
| US6647368B2 (en) | 2001-03-30 | 2003-11-11 | Think-A-Move, Ltd. | Sensor pair for detecting changes within a human ear and producing a signal corresponding to thought, movement, biological function and/or speech |
| US6671379B2 (en) | 2001-03-30 | 2003-12-30 | Think-A-Move, Ltd. | Ear microphone apparatus and method |
| US8036405B2 (en) | 2003-05-09 | 2011-10-11 | Widex A/S | Hearing aid system, a hearing aid and a method for processing audio signals |
| AU2003229529B2 (en) * | 2003-05-09 | 2009-09-03 | Widex A/S | Hearing aid system, a hearing aid and a method for processing audio signals |
| WO2004100607A1 (en) * | 2003-05-09 | 2004-11-18 | Widex A/S | Hearing aid system, a hearing aid and a method for processing audio signals |
| US7983433B2 (en) | 2005-11-08 | 2011-07-19 | Think-A-Move, Ltd. | Earset assembly |
| US8571227B2 (en) | 2005-11-11 | 2013-10-29 | Phitek Systems Limited | Noise cancellation earphone |
| US7502484B2 (en) | 2006-06-14 | 2009-03-10 | Think-A-Move, Ltd. | Ear sensor assembly for speech processing |
| US8666085B2 (en) | 2007-10-02 | 2014-03-04 | Phitek Systems Limited | Component for noise reducing earphone |
| US9818394B2 (en) | 2009-11-30 | 2017-11-14 | Graeme Colin Fuller | Realisation of controller transfer function for active noise cancellation |
| US8929082B2 (en) | 2010-05-17 | 2015-01-06 | Thales Avionics, Inc. | Airline passenger seat modular user interface device |
| US9487295B2 (en) | 2010-11-15 | 2016-11-08 | William James Sim | Vehicle media distribution system using optical transmitters |
| US9654854B2 (en) | 2011-06-01 | 2017-05-16 | Paul Darlington | In-ear device incorporating active noise reduction |
| EP3447762A1 (en) * | 2017-08-23 | 2019-02-27 | ams International AG | Noise cancellation headphone |
| WO2019038178A1 (en) * | 2017-08-23 | 2019-02-28 | Ams International Ag | Noise cancellation headphone |
| US11100912B2 (en) | 2017-08-23 | 2021-08-24 | Ams International Ag | Noise cancellation headphone |
| CN111625905A (en) * | 2020-05-29 | 2020-09-04 | 中国航空工业集团公司西安飞机设计研究所 | High-frequency simulation method for noise in propeller aircraft cabin |
| CN111625905B (en) * | 2020-05-29 | 2023-08-04 | 中国航空工业集团公司西安飞机设计研究所 | High-frequency simulation method for noise in cabin of propeller aircraft |
| WO2022136807A1 (en) * | 2020-12-24 | 2022-06-30 | Focal Jmlab | Audio headset with active noise reduction |
| FR3118526A1 (en) * | 2020-12-24 | 2022-07-01 | Focal Jmlab | ACTIVE NOISE CANCELING HEADPHONES |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8917742D0 (en) | 1989-09-20 |
| GB2234882B (en) | 1994-01-12 |
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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 |