EP0530523B1 - Active silencer with improved method of selecting coefficient sequence - Google Patents
Active silencer with improved method of selecting coefficient sequence Download PDFInfo
- Publication number
- EP0530523B1 EP0530523B1 EP92113366A EP92113366A EP0530523B1 EP 0530523 B1 EP0530523 B1 EP 0530523B1 EP 92113366 A EP92113366 A EP 92113366A EP 92113366 A EP92113366 A EP 92113366A EP 0530523 B1 EP0530523 B1 EP 0530523B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- coefficient sequence
- noise
- coefficient
- predetermined
- noise signal
- 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.)
- Expired - Lifetime
Links
Images
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1785—Methods, e.g. algorithms; Devices
- G10K11/17857—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
- G10K11/1781—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
- G10K11/17813—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 acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
- G10K11/17819—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 acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms between the output signals and the reference signals, e.g. to prevent howling
-
- 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
- G10K11/17853—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
- G10K11/17881—General system configurations using both a reference signal and an error signal the reference signal being an acoustic signal, e.g. recorded with a microphone
-
- 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
- G10K2210/3012—Algorithms
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/30—Means
- G10K2210/301—Computational
- G10K2210/3045—Multiple acoustic inputs, single acoustic output
-
- 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
-
- 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
Definitions
- the present invention relates to silencing apparatus, and particularly to an active silencer for eliminating noise of a rotating machine such as a blower, an engine and the like.
- An active silencer is one for suppressing noise of a rotating machine such as a blower, an engine and the like.
- the active silencer suppresses noise by emitting sound wave of the same amplitude with phase shift of 180° from the noise from silencing sounding means to cause sound wave interference.
- Fig. 4 shows its basic structure.
- a noise signal sequence u (n) detected by a noise detection microphone 3 inside a duct is subjected to convolution operation of the following expression (1) with a predetermined coefficient sequence h (i) in an adaptive digital filter 4.
- the operation result y (n) is outputted to a speaker 6 as a silencing signal.
- N designates the number of taps of the digital filter.
- the coefficient sequence h (i) of the adaptive digital filter 4 is adjusted so that the silencing error becomes minimum by a coefficient control portion (not shown) according to a silencing error signal e (n) at a reference point detected by a silencing error detecting microphone 5.
- the sound emitted from the speaker 6 may be fed back to the noise detecting microphone 3 to cause howling. Also, with noise coming from outside into the silencing error detecting microphone 5, mis-adjustment of the coefficient sequence h (i) may take place also to cause howling.
- a method is used in which acoustic feedback, effects of external noise and the like are reduced by enhancing the directivity with a microphone array.
- a noise detecting microphone 3 and a silencing error detecting microphone 5 are provided at equal distances with respect to a speaker, and a difference of respective detection signals is obtained by a subtracter 7 and used as an input signal u (n) of an adaptive digital filter to cancel acoustic feedback.
- the coefficient sequence h (i) when performing coefficient updating with the LMS algorithm which is widely used as an adaption algorithm of coefficient of the adaptive digital filter 4, the coefficient sequence h (i) gradually diverge if an input signal corresponds to a narrow band, resulting in a possibility of occurrence of overflow.
- the overflow of coefficient sequence h (i) causes degradation of silencing accuracy and occurrence of howling.
- Prior art document GB-A-2 154 830 discloses an attenuation system of sound waves.
- this system when sound waves are intentionally attenuated by using destructive interference, temporal changes sometimes cause less than optimum performance, and the transfer function of a signal processing device driving a sound generator from a sound detector is modified at intervals as a result of sequential measurements of the transfer function between the sound detector and a further sound detector downstream from the generator.
- a data processor calculates the required transfer function and causes a data processor to vary the coefficients of a digital filter comprising the processing device.
- prior art document EP-A-0 071 947 discloses an apparatus for reducing vibrations of a stationary induction apparatus.
- a vibration is detected and a vibration applying force capable of suppressing the detected vibrations is applied to the stationary induction apparatus by at least one vibration applying device, in which the phase and amplitude of the vibration applying force of the vibration applying device are successively and repeatedly adjusted so as to decrease the sum of squares of the respective amplitudes of vibration detected by vibration sensors.
- a calculation for obtaining the sum of squares of the detected amplitudes of vibration and the control of the phase and amplitude of the vibration applying force based upon the calculated sum of squares may be carried out in accordance with a programm stored in a microcomputer.
- prior art document US-A-5 022 082 discloses a method for reducing a convergence time of an active acoustic attenuation system upon start-up or upon a given sensed parameter change.
- the weights of an adaptive filter model coefficient weight vector are started at or changed to values which are closer to the converged value than an initial or present nonconverged value is to the converged value.
- the filter model converges in a shorter time as the weights change and are updated from their starting or changed value to the converged value.
- the present invention provides an active silencer as specified in claim 1.
- the active silencer includes especially first noise detecting means for detecting a noise signal of an object of noise silencing, operating means for performing operation on the basis of the detected noise signal and a predetermined coefficient sequence to produce a silencing signal, silencing means for generating sound wave on the basis of the produced silencing signal to reduce noise at a predetermined position with respect to the object of noise silencing, second noise detecting means for detecting a noise signal at the predetermined position which is changed because of activation of the silencing means, and control means for controlling the operating means so that a predetermined coefficient sequence takes a most appropriate value on the basis of average power of a detection output of the second noise detecting means or another value representing a noise level.
- control means controls the operating means so that a predetermined coefficient sequence takes the most appropriate value on the basis of average power of a detection output of the second noise detecting means or another value representing a noise level, so that the reliability is improved and howling can be prevented.
- Fig. 1 is a block diagram showing a structure of an active silencer according to one embodiment of the present invention.
- Fig. 2 is a diagram for illustrating control condition of a coefficient sequence in the active silencer of Fig. 1.
- Fig. 3 is a flow chart illustrating one example of contents of control corresponding to Fig. 2.
- Fig. 4 is a block diagram showing a basic structure of a conventional active silencer.
- Fig. 5 is a system block diagram showing a structure of one example having an object of preventing howling based on the active silencer of Fig. 4.
- Fig. 1 is a block diagram of an active silencer according to one embodiment of the present invention.
- a noise source 1 inside a container 2 such a duct having an opening 20 on its one side, and a noise detection microphone 3 is provided opposing thereto.
- a silencing error detection microphone 5 is provided at a reference point, and a silencing speaker 6 is provided at an intermediate position thereof as shown in the figure.
- a noise signal u (n) detected by the noise detection microphone 3 and converted into a digital signal in an A/D converter 9 through an amplifier 11 is transmitted to a digital signal processor (DSP) through a data bus 16.
- DSP digital signal processor
- a convolution operation designated by the above-noted expression (1) is applied to the noise signal u (n) there with a predetermined coefficient sequence h (i), and the operation result y (n) is outputted to a D/A converter 8 as a silencing signal through the data bus 16.
- a digital filter 22 of FIR (Finite Impulse Response) type for example
- a memory 23 for storing a noise signal u (n).
- the silence signal converted into an analog signal by the D/A converter 8 is outputted into the container 2 from the speaker 6 through the amplifier 12.
- the result of silencing is detected by the silencing error detecting microphone 5 and captured as a silencing error signal e (n) into the DSP 14 through an amplifier 13, an A/D converter 10 and the data bus 16.
- a coefficient sequence h (i) stored in the operating coefficient memory 21 is updated so that the silencing error signal e (n) becomes the minimum.
- silencing signal y (n) requires noise signals from the present time to N units time before, and the past data are stored in the memory 23 for storing noise signal u (n) through the data bus 16 together with a coefficient sequence h (i) which is the most appropriate for silencing.
- FIG. 2 is a diagram showing outline of a control system of coefficient sequence h (i) in the present invention along the time axis.
- a coefficient sequence in a stable operation or the most appropriate coefficient sequence which is measured in advance can be set.
- T represents a period in which coefficient sequence h (i) is updated, and t1-t10 indicate times of respective operations.
- the coefficient sequence h (i) is updated during the period T from t1 to t2 and the average power w is calculated on the basis of the silencing error signal during the period of t2 to t3, and further the coefficient sequence h (i) at that time is stored in the memory 15. Subsequently, the coefficient sequence h (i) is further updated during the period T from t3 to t4. Next, the average power w is calculated again on the basis of the silencing error signal from t4 to t5 period. If the calculated power is smaller than the previous average power, the coefficient sequence h (i) at that time is stored in the memory 15. This is for retaining the coefficient sequence most appropriate in this period.
- the coefficient sequence h (i) stored in the memory 15 at the previous time is copied into the convolution operation coefficient memory 21 connected to the DSP 14. Also, the memory for storing noise signal u (n) is cleared as needed.
- the coefficient sequence h (i) is updated and similar processings are continuously performed thereafter. Furthermore, check is always made for an abnormal value which exceeds a prescribed value of an input/output signal and overflow in operation processing during the coefficient updating period.
- the coefficient sequence h (i) saved in the memory 15 at the previous time is called during the time of t8 to t9 and copied into the convolution operation coefficient memory 21, and the memory 23 for storing noise signal u (n) is cleared to zero.
- Fig. 3 is one example representing the above-described silencing process flow in a flow chart.
- a noise signal u (n) and an error signal e (n) are inputted into the DSP 14 (step S101).
- a coefficient sequence h (i) is updated (step S102).
- step S103 presence or absence of overflow is examined.
- a silencing signal y (n) is calculated by the convolution operation (step S104).
- the calculated silencing signal y (n) is checked as to whether it is inside a range of prescribed values or not (step S105).
- the silencing signal y (n) is within the range of prescribed values, it is outputted to the speaker 6 (step S106).
- the average power w in the T period immediately before is calculated on the basis of the error signal e (n) (step S108).
- a check is made as to whether the average power w has increased as compared to the previous time or not (step S109).
- the coefficient sequence h (i) is retained in the memory 15 (step S110).
- step S103 When there is an overflow in step S103, when the silencing output y (n) is out of the range of prescribed values in step S105, or when the average power w is increased than the previous time in step S109, the most appropriate coefficient sequence h (i) retained in the memory 15 is called and the memory for storing noise signal u (n) is cleared (step S111).
- step S112 When the time counter which counts time T relating to the series of updating and calculation of the average power w is cleared (step S112), and when the time counter does not attain the time T in the process of step S107, the flow returns to step S101.
- the most appropriate coefficient sequence h (i) is retained such as a coefficient sequence in a stable silencing operation or an obtained coefficient sequence which is measured in advance.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
- Exhaust Silencers (AREA)
Description
Claims (5)
- An active silencer for reducing noise at a predetermined position by emitting a sound wave with an opposite phase to the noise for noise reduction of an object to be silenced, comprising:first detecting means (3) for detecting a noise signal of the object to be silenced;second detecting means (5) for detecting a noise signal at said predetermined position for every predetermined period;sound wave generating means (6, 14) for producing said sound wave by multiplying the noise signal detected by said first detecting means (3) by a coefficient updated for every predetermined period;comparing means (14) for comparing a value representing a noise level calculated on the basis of said detected noise signal detected by said first detecting means and a value representing a noise level of a previous time; andcoefficient storing means (15) responsive to an output by said comparing means (14) indicating that said calculated representing value is smaller than the previous representing value for storing the coefficient used at that point,
said coefficient storing means (15) copies the previous representing value into a convolution operation coefficient memory (21) connected to said comparing means (14), if said calculated representing value is larger than the previous representing value for retaining a coefficient sequence most appropriate. - The active silencer according to claim 1, characterized in that said sound wave generating means comprises updating means (14) for changing a coefficient sequence used as a predetermined coefficient sequence for every predetermined period,said convolution operation coefficient memory (21) stores said predetermined coefficient sequence and, when the coefficient sequence is changed by said updating means (14), storing said changed coefficient sequence in place of the predetermined coefficient sequence already stored, andnoise signal storing means (23) store a noise signal detected by said first detecting means (3).
- The active silencer according to claim 2, characterized in that said updating means replaces the predetermined coefficient sequence stored in said convolution operation coefficient memory (21) with a most appropriate coefficient sequence stored in said convolution operation coefficient memory (21) under a predetermined condition.
- The active silencer according to claim 3, characterized in that said predetermined condition is met when at least one of conditions is met, said conditions including, when the value representing the noise level calculated on the basis of the noise signal detected by said second detecting means (5) is equal to or larger than the value representing the noise level at the previous time, when said predetermined coefficient sequence overflows, when said produced silencing signal is out of a predetermined range, when a noise signal detected by said first detecting means (3) exceeds a prescribed value and when a noise signal detected by said second detecting means (5) exceeds a prescribed value.
- The active silencer according to claim 3, characterized in that said updating means (14) cancels a content stored by said noise signal storing means (23) under said predetermined condition.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP196513/91 | 1991-08-06 | ||
JP3196513A JP2886709B2 (en) | 1991-08-06 | 1991-08-06 | Active silencer |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0530523A2 EP0530523A2 (en) | 1993-03-10 |
EP0530523A3 EP0530523A3 (en) | 1993-11-24 |
EP0530523B1 true EP0530523B1 (en) | 1998-03-18 |
Family
ID=16358999
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP92113366A Expired - Lifetime EP0530523B1 (en) | 1991-08-06 | 1992-08-05 | Active silencer with improved method of selecting coefficient sequence |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0530523B1 (en) |
JP (1) | JP2886709B2 (en) |
DE (1) | DE69224780T2 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB9222103D0 (en) * | 1992-10-21 | 1992-12-02 | Lotus Car | Adaptive control system |
US5475189A (en) * | 1992-11-16 | 1995-12-12 | Carrier Corporation | Condition responsive muffler for refrigerant compressors |
WO1996002910A1 (en) * | 1994-07-15 | 1996-02-01 | Noise Cancellation Technologies, Inc. | Active duct silencer kit |
JP3732167B2 (en) * | 2002-08-26 | 2006-01-05 | ティーオーエー株式会社 | Adaptive filter |
US11164554B2 (en) | 2020-03-06 | 2021-11-02 | Bose Corporation | Wearable active noise reduction (ANR) device having low frequency feedback loop modulation |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5827313A (en) * | 1981-08-11 | 1983-02-18 | Hitachi Ltd | Method of reducing oscillation of stationary electric induction apparatus |
GB8404494D0 (en) * | 1984-02-21 | 1984-03-28 | Swinbanks M A | Attenuation of sound waves |
JPH087002B2 (en) * | 1989-02-28 | 1996-01-29 | 株式会社東芝 | Silencer for cooling system |
US5022082A (en) * | 1990-01-12 | 1991-06-04 | Nelson Industries, Inc. | Active acoustic attenuation system with reduced convergence time |
-
1991
- 1991-08-06 JP JP3196513A patent/JP2886709B2/en not_active Expired - Fee Related
-
1992
- 1992-08-05 EP EP92113366A patent/EP0530523B1/en not_active Expired - Lifetime
- 1992-08-05 DE DE69224780T patent/DE69224780T2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JP2886709B2 (en) | 1999-04-26 |
DE69224780D1 (en) | 1998-04-23 |
JPH0540486A (en) | 1993-02-19 |
DE69224780T2 (en) | 1998-10-29 |
EP0530523A2 (en) | 1993-03-10 |
EP0530523A3 (en) | 1993-11-24 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5386472A (en) | Active noise control system | |
US6330336B1 (en) | Active silencer | |
US5278913A (en) | Active acoustic attenuation system with power limiting | |
EP0578212B1 (en) | Active control apparatus with an adaptive digital filter | |
JPH11305783A (en) | Active noise eliminating device | |
US5577127A (en) | System for rapid convergence of an adaptive filter in the generation of a time variant signal for cancellation of a primary signal | |
EP0530523B1 (en) | Active silencer with improved method of selecting coefficient sequence | |
EP0492680B1 (en) | Method and apparatus for attenuating noise | |
JP2923476B2 (en) | Adaptive active silencer | |
JP3058307B2 (en) | Active controller using adaptive digital filter. | |
JP3505306B2 (en) | Adaptive filter | |
JP2996770B2 (en) | Adaptive control device and adaptive active silencer | |
JPH07219559A (en) | Adaptive active noise elimination device | |
JP3544999B2 (en) | Silencer | |
JP3522018B2 (en) | Noise control device | |
JPH0619482A (en) | Method and device for active sound elimination | |
JP2989379B2 (en) | Active control device using adaptive IIR digital filter | |
JP3505337B2 (en) | Transfer function identification device and active noise elimination device | |
JPH06230789A (en) | Active noise controller | |
JPH0876774A (en) | Muffler | |
JPH0635482A (en) | Method and device for active noise elimination | |
JPH08179782A (en) | Active silencer | |
JPH09250409A (en) | Active noise controller for automobile | |
JPH09101789A (en) | Noise control device | |
JP2791510B2 (en) | Active silencer |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FR GB |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE FR GB |
|
17P | Request for examination filed |
Effective date: 19931213 |
|
17Q | First examination report despatched |
Effective date: 19960821 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
REF | Corresponds to: |
Ref document number: 69224780 Country of ref document: DE Date of ref document: 19980423 |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20020731 Year of fee payment: 11 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20020808 Year of fee payment: 11 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20020816 Year of fee payment: 11 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030805 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040302 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20030805 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040430 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |