GB2149614A - Active noise reduction apparatus - Google Patents

Active noise reduction apparatus Download PDF

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Publication number
GB2149614A
GB2149614A GB08427375A GB8427375A GB2149614A GB 2149614 A GB2149614 A GB 2149614A GB 08427375 A GB08427375 A GB 08427375A GB 8427375 A GB8427375 A GB 8427375A GB 2149614 A GB2149614 A GB 2149614A
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noise reduction
loudspeakers
signal processor
active noise
reduction apparatus
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GB2149614B (en
GB8427375D0 (en
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Philip Arthur Nelson
Stephen John Elliot
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UK Secretary of State for Defence
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UK Secretary of State for Defence
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    • 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
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17853—Methods, e.g. algorithms; Devices of the filter
    • G10K11/17854—Methods, e.g. algorithms; Devices of the filter the filter being an adaptive 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
    • G10K11/1787—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
    • 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
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3011—Single acoustic input
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3023—Estimation of noise, e.g. on error signals
    • G10K2210/30232—Transfer functions, e.g. impulse response
    • 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
    • G10K2210/3025—Determination of spectrum characteristics, e.g. FFT
    • 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
    • G10K2210/3032—Harmonics or sub-harmonics
    • 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
    • G10K2210/3046—Multiple acoustic inputs, multiple acoustic outputs
    • 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
    • G10K2210/3049—Random noise used, e.g. in model identification
    • 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
    • G10K2210/3219—Geometry of the configuration
    • 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
    • G10K2210/503—Diagnostics; Stability; Alarms; Failsafe

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

Active noise reduction apparatus for reducing noise in a cabin (1), or other enclosed space, generated by an external source, wherein the noise has a fundamental frequency f0 and harmonically related frequencies f1 to fn, includes a plurality of loudspeakers (2a, 2b, 2c) and microphones (3a, 3b, 3c, 3d) distributed over the enclosed space, source frequency measurement means for measuring the frequency f0, and a signal processor (6) connected to receive and analyse input signals from the microphones and from the source frequency measurement means, and wherein the signal processor is arranged to output signals f0 to fn in antiphase with the input signals so as to minimise sound pressure levels in the enclosed space. <IMAGE>

Description

SPECIFICATION Improvements in or relating to active noise reduction The present invention relates to active noise reduction and particularly, though not exclusively, relates to active noise reduction in aircraft cabins.
Many current propeller-driven civil aircraft operate with very high noise levels in the passenger cabins. In many cases, particularly in long range aircraft, it is desirable to make cabin noise reductions of at least 14 dBA.
Significant aircraft cabin noise reductions have been achieved by providing a double fuselage wall, by using dynamic sound absorbers, by engine synchrophasing, and by lining the cabin with acoustic pads. In, for example the Fokker F27 aircraft, the provision of a double cabin wall, acoustic padding, and the use of dynamic absorbers reduces the cabin sound level from about 92 dBA to 85 dBA. However, the weight penalty incurred in the F27 to achieve this reduction is 168 kg. Reductions of about 5 dBA have been obtained by syncrophasing the engines of the Lockheed P3C aircraft.
A method of active noise reduction by generating sound waves which are in antiphase with ambient noise waves is described by B Chaplin in "The Chartered Mechanical Engineer" of January 1983. Generally, such methods of active noise reduction are only effective in l-dimensional acoustic systems where plane waves are produced in a rectangular section duct. There has been some progress in the art of achieving noise reduction by producing zero pressure fluctuation at a point in an enclosed volume. However such systems do not produce an overall significant reduction in noise levels in the volume.
The present invention provides active noise reduction apparatus for use in cabins or other enclosed volumes for reducing noise throughout all, or a substantial part of, the enclosed volume.
According to the present invention active noise reduction apparatus for reducing noise in a cabin, or other enclosed space, generated by an external source wherein the noise has a fundamental frequency fO and harmonically related frequencies f, to fnl includes a plurality of loudspeakers and microphones distributed over the enclosed space, source frequency measurement means for measuring the frequency fO, and a signal processor connected to receive and analyse input signals from the microphones and from the source frequency measurement means, and wherein the signal processor is arranged to output signals fO to fn in antiphase with the input signals so as to minimise sound pressure levels in the enclosed space.
The number of microphones may exceed the number of loudspeakers used in order to ensure noise control over all parts of the cabin. For maximum reduction of the noise throughout the volume, some of the microphones are placed near to the loudspeakers, and some microphones are placed near to the sections of the cabin wall which are vibrating and which are contributing most to the noise inside the cabin. Some of the loudspeakers may be placed close to parts of the cabin wall which are most strongly vibrating.
The signal processor may be controlled by a microprocessor which is programmed to determine the Fourier coefficients of the signals from the microphones and the source frequency measurement means at frequencies fO to fn and add the squares of the coefficients and determine the sum S of the mean square values and to adjust Fourier coefficients of signals output to the loudspeakers by minimising the value of S.
Alternately, the signal processor may be controlled by a microprocessor which is programmed to establish transfer impedances relating the response of the microphones to the output of the loudspeakers at each of the frequencies fO to fn, wherein the transfer impedances are represented by coefficients in a set of simultaneous equations which are solved by the microprocessor by matrix inversion.
Alternatively, the signal processor may be controlled by a microprocessor arranged to determine a feedback gain matrix for controlling the sound field in the enclosed space by generating test signals which are output periodically to the loudspeakers. The feedback gain matrix may be implemented by a set of programmable digital filters by solving a matrix Ricatti equation.
Embodiments of the invention will be be described, by way of example only, with reference to the drawings of which, Figure 1 is a graph which relates to the sound field in an idealised, cuboid, passenger cabin of a typical twin-engined turbo-prop aircraft.
Figure 2 shows a circuit of an active noise reduction apparatus in accordance with the invention.
Figure 3 shows a signal processor and microprocessor which form part of the embodiment of Figure 2.
Figure 4 shows a signal processor and microprocessor which form part of a second embodiment of the invention.
A known twin-engined turbo-prop aircraft has a passenger cabin which can be represented by a cuboid with the following approximate dimension: Length= 14m Width = 2.5 m Height = 2.0 m The aircraft is found to have a fundamental excitation frequency at its cruising speed with a propeller speed of 14,200 rpm of 88 Hz.
Figure 1 shows the sound field in the cabin of this aricraft as a superposition of its normal modes.
The modes of vibration for the cabin over a range of frequencies are given in the following table.
TABLE 1 frHz) Nx Ny Nz 84 0 1 4 86 0 0 7 86 1 0 0 87 1 0 1 89 1 0 2 Figure 2 shows an active noise reduction apparatus for reducing noise having a fundamental frequency f0 and harmonically related frequencies f, to fn in an enclosed cabin 1, shown as a chain-dotted cuboid. The cabin contains a set of microphones 3a, 3b, 3c, 3dand a set of loudspeakers 2a, 2b, 2c distributed over the space within the cabins. Signals from the microphones are input via amplifiers 4 on lines 9 to a signal processor 6 controlled by a microprocessor 8. Reference signals at the fundamental frequency f0 from a tachometer 12 are input to the signal processor on a line 7. Outputs from the signal processor 6 are input via amplifiers 5 to the loudspeakers 2.The signal processor is arranged to determine the Fourier coefficients, an, bnl of the input microphone signals at frequencies fO, fi, f,. Figure 3 shows the microprocessor 8 and signal proessor 6 of Figure 2 and indicates the Fourier coefficient evaluation part of the signal processor and associated input data lines 10 to the microprocessor, and output data lines 11 from the microprocessor to an output signal synthesizer part of the signal processor. The microprocessor adds the squares of the coefficients an, bn and calculates the sum, S, of the mean square values of the periodic signals detected by the microphones 3. The Fourier coefficients of the signals output to the loudspeakers are adjusted by the microprocessor to minimise the sum, S.A control algorithm for minimising the sum, S, of the mean squares employs the method of steepest descent. Thus the partial derivative of this sum with respect to each of the Fourier coefficients of the output signals is evaluated by making small changes in the values of these coefficients and sensing the resulting change in the sum. The values of the partial derivatives are then used to determine the changes in the outputs to the loudspeakers necessary to converge on the minimum value of the sum. The above process is continuously repeated during operation of the processors.
The above described embodiment is applicable to steady periodic sound field control, such as the control of cabin noise in a propeller driven aircraft where the level and fundamental frequency of the sound field remains relatively constant for long periods.
In a further embodiment which employs similar hardware to that shown in Figure 2, a microprocessor controls signal outputs to a set of loudspeakers such that initially each loudspeaker sequentially transmits a test signal in the absence of noise in the enclosed cabin. The microphone signals resulting from the test signal transmissions are recorded in the microprocessor and a transfer impedance matrix relating to signal from each microphone to the signal input to each loudspeaker is generated by the microprocessor. Signals from the microphones which include periodic noise in the cabin are then recorded.If the number of microphones and the number of loudspeakers is the same then the signals necessary to be input to the loudspeakers to produce a zero, or very low, signal at each of the microphones are determined from the product of the inverse of the impedance matrix and a vector representing the level of undesirable sound at each microphone. If the number of loudspeakers and microphones differ then the signals to be input to the loudspeakers form the signal processors are determined from a generalised inverse of the transfer impedance matrix to ensure that the sum of the squares of the pressure amplitudes at the microphones is minimised. If the level of undesirable sound changes, the outputs to the loudspeakers may be changed by switching off the loudspeakers for a short period while new levels of undesirable sound detected by the microphones are recorded.
Alternatively the residual pressure at each of the mirophones, which remains after the initial estimate of the inputs to the loudspeakers calculated above has been applied, may be multiplied by the inverse of the impedance matrix to generate a correction to the loudspeaker inputs. The correction is added to the loudspeaker signals previously calculated and the sum applied to the loudspeakers to further rduce the sum of the squares of the pressures at the microphones. The correction process may then be repeated to further reduce the microphone signals iteratively. This procedure may be necessary if either some error exists in the measured elements of the transfer impedance matrix, or the acoustic conditions in the cabin are slowing changing.
A signal processor 40 of a further embodiment of the invention is shown in Figure 4. The signal processor 40 is connected via lines to a microprocessor 42 and a series of microphones and loudspeakers (not shown) in the same way as the signal processor 6 in the embodiment of Figure 2. This embodiment using the signal processor 40 employs automatic closed loop control and the microprocessor 42 is arranged to determine a feedback gain matrix necessary to provide optimum control of an enclosed sound field. The microprocessor 42 generates test signals from the loudspeakers to establish the dynamic properties of the system to be controlled expressed in state variable form. The microprocessor then determines the form of the feedback gain matrix which is implemented by programmable digital filters all to a34 by solving a matrix Ricatti equation.
An alternative method of quickly controlling the outputs to the loudspeakers in order to minimise the sum of the mean squared pressures at the microphones is to use an adaptive digital filter. The basis of the method is the 'Widrow LMS' algorithm described in 'Proceedings of the IEEE, V0163 page 1692, 1975, entitled "Adaptive noise cancellation: Principles and applications". The algorithm must be significantly extended to enable it to be used in this application. Firstly, the error minimised by the algorithm must be the sum of the mean squared outputs of all the microphones rather than a single signal described in the above reference.Secondly, to align the reference signal, which would typically be an impulse train synchronised with the fundamental excitation frequency, with each of the error signals, the reference signal must be passed through an array of digital filters which compensate for the transfer functions between the relevant loudspeaker input and each microphone output. This is to form an unbiased estimate of the gradient of the total error with respect to each of the filter coefficients upon which the LMS algorithm depends.
Suppose a sampled Finite Impulse Response (FIR) representation of the transfer function between the m-th loudspeaker and the f -th micropone is C,m(n), the electical input to the m-th loudspeaker is Vsm and the electrical output from the f -th microphone is zero Also let the sample FIR representation of the transfer function between the reference signal, x(n), and each of the t-th microphones be a,(n). Then by superposition
where it is assumed that there are M loudspeakers. the total error is defined as
where L is the total number of microphones.
The rate of change of this total error with respect to the i-th coefficient of an adaptive FIR filter connected between the reference signal and the m-th loudspeaker is
Also
and substituting into the equation for Ve, above, we have
This is equal to the reference signal x (n) delayed by i samples and passed through the filter C,m(k);; this signal may be represented by
Thus
The basis of the LMS algorithm is the method of steepest descents, which, when applied to the i-th coefficient of the adaptive filter feeding the m-th loudspeaker, becomes
where hm(i) is the initial estimate of the filter coefficient, and hm(i) is an improved estimate of the optimum value of that coefficient to minimise the total error. 8 is a convergence parameter.One method of implementing this in practice is to use an instantaneous estimate of the gradient and update all of the filter coefficients for every new sample received, thus
where ffi = 2, and hm(i) is now the i-th filter coefficient feeding the m-th loudspeaker at a time corresponding to the n-th sample, and hm(i) is the same coefficient at the previous, (n-1 )-th, sample.
The above method may be achieved in practice either by using digital filters, or as a program which is run on a fast microcomputer such as those especially designed for digital signal processing (for example, the Texas Instruments TMS 320, NEC Microcomputers Ltd., FPD 77P20 or American Micrnsystems Inc S2811).
The elements of each of the filters represented as C6rn(n) may be found by a number of methods using the results of experiments performed in the cabin. The frequency decomposition method described above could be used for example. Alternatively the elements of these filters can also be determined using adaptive filtering, by feeding an excitation signal to each loudspeaker in turn and adaptively adjusting the coefficients of a number of filters to minimise the difference between each microphone outut and the respective filter output.
Thus the above method consists of determining the elements of the FIR approximation to the transfer functions between each loudspeaker and each microphone, C,m(n), usually in a separate initial experiment in the cabin. Then the reference signal is passed through a separate bank of adaptive filters which feed each of the loudspeakers. Each element of each of these filters is updated every sample by a value proportional to the sum of the products of each of the microphone outputs with the delayed reference passed through the filter representing the transfer function between the loudspeaker being considered and each microphone.

Claims (6)

1. Active noise reduction apparatus for reducing noise in a cabin, or other enclosed space, generated by an external soucre, wherein the noise has a fundamental frequency f0 and harmonically related frequencies f, to fnl includes a plurality of loudspeakers and microphones distributed over the enclosed space, source frequency measurement means for measuring the frequency f0, and a signal processor connected to receive and analyse input signals from the microphones and from the source frequency measurement means, and wherein the signal processor is arranged to output signals f0 to fn in antiphase with the input signals so as to minimise sound pressure levels in the enclosed space.
2. Active noise reduction apparatus as claimed in claim 1 wherein the signal processor is controlled by a microprocessor which is programmed to determine the Fourier coefficients of the signals from the mirophones and the source frequency measurement means at frequencies f0 to fn and add the squares of the coefficients and determine the sum S of the mean square values and to adjust Fourier coefficients of signals output to the loudspeakers by minimising the value of S.
3. Active noise reduction apparatus as claimed in claim 1 wherein the signal processor is controlled by a microprocessor which is programmed to establish transfer impedances relating the response of the microphones to the output of the loudspeakers at each of the frequencies f0 to fn, wherein the transfer impedances are represented by coefficients in a set of simultaneous equations which are solved by the micro-processor by matrix inversion.
4. Active noise reduction apparatus as claimed in claim 1 wherein the signal processor is controlled by a microprocessor arranged to determine a feedback gain matrix for controlling the sound field in the enclosed space by generating test signals which are output periodically to the loudspeakers.
5. Active noise reduction apparatus as claimed in claim 4 wherein the feedback gain matrix is implemented by a set of programmable digitial filters by solving a matrix Ricatti equation.
6. Active noise reduction apparatus substantially as described herein with reference to the drawings.
GB08427375A 1983-10-31 1984-10-30 Active noise reduction apparatus Expired GB2149614B (en)

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GB2149614A true GB2149614A (en) 1985-06-12
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Cited By (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2191063A (en) * 1986-05-01 1987-12-02 Plessey Co Plc Active noise suppression
WO1987007974A1 (en) * 1986-06-23 1987-12-30 The Secretary Of State For Trade And Industry In H Aircraft cabin noise control apparatus
WO1988002912A1 (en) * 1986-10-07 1988-04-21 Adaptive Control Limited Active vibration control
GB2201858A (en) * 1986-10-07 1988-09-07 Adaptive Control Ltd Active noise control
EP0342353A2 (en) * 1988-05-18 1989-11-23 Bayerische Motoren Werke Aktiengesellschaft Arrangement for diminishing the noise level within a motor car
GB2223376A (en) * 1988-09-30 1990-04-04 Toshiba Kk Acoustic silencer
EP0361968A2 (en) * 1988-09-30 1990-04-04 Kabushiki Kaisha Toshiba Noise cancellor
EP0415237A2 (en) * 1989-08-31 1991-03-06 Kabushiki Kaisha Toshiba Active noise control apparatus for domestic appliance
GB2236640A (en) * 1989-08-22 1991-04-10 Volkswagen Ag A device for the active reduction in noise level of a periodically operating noise source
WO1991010226A1 (en) * 1989-12-30 1991-07-11 Noise Cancellation Technologies, Inc. Active vibration reducing system
EP0506280A2 (en) * 1991-03-27 1992-09-30 Tsudakoma Kogyo Kabushiki Kaisha Device for noise attenuation of weaving machine
US5170433A (en) * 1986-10-07 1992-12-08 Adaptive Control Limited Active vibration control
DE4228695A1 (en) * 1991-08-30 1993-03-04 Nissan Motor DEVICE FOR ACTIVE REDUCTION OF LAERM INSIDE A CLOSED ROOM
US5325437A (en) * 1991-12-27 1994-06-28 Nissan Motor Co., Ltd. Apparatus for reducing noise in space applicable to vehicle compartment
WO1994023420A1 (en) * 1993-04-07 1994-10-13 Noise Cancellation Technologies, Inc. Hybrid analog/digital vibration control system
US5384853A (en) * 1992-03-19 1995-01-24 Nissan Motor Co., Ltd. Active noise reduction apparatus
US5410604A (en) * 1991-04-16 1995-04-25 Nissan Motor Co., Ltd. System for reducing noise sounding in passenger compartment of vehicle
US5416844A (en) * 1992-03-04 1995-05-16 Nissan Motor Co., Ltd. Apparatus for reducing noise in space applicable to vehicle passenger compartment
US5426703A (en) * 1991-06-28 1995-06-20 Nissan Motor Co., Ltd. Active noise eliminating system
US5434783A (en) * 1993-01-06 1995-07-18 Nissan Motor Co., Ltd. Active control system
US5455779A (en) * 1991-09-05 1995-10-03 Hitachi, Ltd. Noise reduction apparatus
WO1996011466A1 (en) * 1994-10-06 1996-04-18 Duke University Feedback acoustic energy dissipating device with compensator
WO1996031872A1 (en) * 1995-04-04 1996-10-10 Technofirst Personal active noise cancellation method and device having invariant impulse response
WO1998022933A1 (en) * 1996-11-20 1998-05-28 Vtt Method and apparatus for attenuating sound
US5809152A (en) * 1991-07-11 1998-09-15 Hitachi, Ltd. Apparatus for reducing noise in a closed space having divergence detector
JP2590783Y2 (en) 1991-02-28 1999-02-17 株式会社トランストロン Vehicle interior noise reduction device
WO2010070561A1 (en) * 2008-12-18 2010-06-24 Koninklijke Philips Electronics N.V. Active audio noise cancelling
US8019502B2 (en) * 2002-03-28 2011-09-13 Pirelli Pneumatici S.P.A. Tyre and system for monitoring the tyre during the running of a vehicle
RU2472237C2 (en) * 2010-01-30 2013-01-10 Ман Трак Унд Бас Аг Device for noise compensation in car
WO2015084652A1 (en) * 2013-12-03 2015-06-11 Bose Corporation Active noise reduction headphone
EP2884488A1 (en) * 2013-12-16 2015-06-17 Harman Becker Automotive Systems GmbH Active noise control system

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1981001479A1 (en) * 1979-11-10 1981-05-28 Sound Attenuators Ltd The cancelling of vibrations transmitted through a fluid in a containing vessel

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1981001479A1 (en) * 1979-11-10 1981-05-28 Sound Attenuators Ltd The cancelling of vibrations transmitted through a fluid in a containing vessel

Cited By (55)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2191063A (en) * 1986-05-01 1987-12-02 Plessey Co Plc Active noise suppression
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
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
JP2620274B2 (en) 1986-06-23 1997-06-11 イギリス国 Noise control device for aircraft cabin
WO1988002912A1 (en) * 1986-10-07 1988-04-21 Adaptive Control Limited Active vibration control
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
US5170433A (en) * 1986-10-07 1992-12-08 Adaptive Control Limited Active vibration control
EP0342353A2 (en) * 1988-05-18 1989-11-23 Bayerische Motoren Werke Aktiengesellschaft Arrangement for diminishing the noise level within a motor car
EP0342353A3 (en) * 1988-05-18 1991-03-20 Bayerische Motoren Werke Aktiengesellschaft Arrangement for diminishing the noise level within a motor car
GB2223376B (en) * 1988-09-30 1992-10-14 Toshiba Kk Silencer
EP0361968A3 (en) * 1988-09-30 1991-03-06 Kabushiki Kaisha Toshiba Noise cancellor
US5029218A (en) * 1988-09-30 1991-07-02 Kabushiki Kaisha Toshiba Noise cancellor
US4989252A (en) * 1988-09-30 1991-01-29 Kabushiki Kaisha Toshiba Silencer
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GB2223376A (en) * 1988-09-30 1990-04-04 Toshiba Kk Acoustic silencer
GB2236640A (en) * 1989-08-22 1991-04-10 Volkswagen Ag A device for the active reduction in noise level of a periodically operating noise source
GB2236640B (en) * 1989-08-22 1994-04-06 Volkswagen Ag A device for the active reduction in noise level of a periodically operating noise source
EP0415237A2 (en) * 1989-08-31 1991-03-06 Kabushiki Kaisha Toshiba Active noise control apparatus for domestic appliance
EP0415237A3 (en) * 1989-08-31 1992-06-03 Kabushiki Kaisha Toshiba Active noise control apparatus for domestic appliance
WO1991010226A1 (en) * 1989-12-30 1991-07-11 Noise Cancellation Technologies, Inc. Active vibration reducing system
JP2590783Y2 (en) 1991-02-28 1999-02-17 株式会社トランストロン Vehicle interior noise reduction device
EP0506280A2 (en) * 1991-03-27 1992-09-30 Tsudakoma Kogyo Kabushiki Kaisha Device for noise attenuation of weaving machine
US5271062A (en) * 1991-03-27 1993-12-14 Tsudakoma Kogyo Kabushiki Kaisha Device for noise attenuation of weaving machine
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US5410604A (en) * 1991-04-16 1995-04-25 Nissan Motor Co., Ltd. System for reducing noise sounding in passenger compartment of vehicle
US5426703A (en) * 1991-06-28 1995-06-20 Nissan Motor Co., Ltd. Active noise eliminating system
US5809152A (en) * 1991-07-11 1998-09-15 Hitachi, Ltd. Apparatus for reducing noise in a closed space having divergence detector
US5337365A (en) * 1991-08-30 1994-08-09 Nissan Motor Co., Ltd. Apparatus for actively reducing noise for interior of enclosed space
DE4228695A1 (en) * 1991-08-30 1993-03-04 Nissan Motor DEVICE FOR ACTIVE REDUCTION OF LAERM INSIDE A CLOSED ROOM
US5455779A (en) * 1991-09-05 1995-10-03 Hitachi, Ltd. Noise reduction apparatus
US5325437A (en) * 1991-12-27 1994-06-28 Nissan Motor Co., Ltd. Apparatus for reducing noise in space applicable to vehicle compartment
US5416844A (en) * 1992-03-04 1995-05-16 Nissan Motor Co., Ltd. Apparatus for reducing noise in space applicable to vehicle passenger compartment
US5384853A (en) * 1992-03-19 1995-01-24 Nissan Motor Co., Ltd. Active noise reduction apparatus
US5434783A (en) * 1993-01-06 1995-07-18 Nissan Motor Co., Ltd. Active control system
WO1994023420A1 (en) * 1993-04-07 1994-10-13 Noise Cancellation Technologies, Inc. Hybrid analog/digital vibration control system
US5848169A (en) * 1994-10-06 1998-12-08 Duke University Feedback acoustic energy dissipating device with compensator
WO1996011466A1 (en) * 1994-10-06 1996-04-18 Duke University Feedback acoustic energy dissipating device with compensator
WO1996031872A1 (en) * 1995-04-04 1996-10-10 Technofirst Personal active noise cancellation method and device having invariant impulse response
US5987144A (en) * 1995-04-04 1999-11-16 Technofirst Personal active noise cancellation method and device having invariant impulse response
WO1998022933A1 (en) * 1996-11-20 1998-05-28 Vtt Method and apparatus for attenuating sound
US8019502B2 (en) * 2002-03-28 2011-09-13 Pirelli Pneumatici S.P.A. Tyre and system for monitoring the tyre during the running of a vehicle
WO2010070561A1 (en) * 2008-12-18 2010-06-24 Koninklijke Philips Electronics N.V. Active audio noise cancelling
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US8948410B2 (en) 2008-12-18 2015-02-03 Koninklijke Philips N.V. Active audio noise cancelling
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GB8328997D0 (en) 1983-11-30
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