EP0516695B1 - Systeme de reduction de bruit - Google Patents

Systeme de reduction de bruit Download PDF

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Publication number
EP0516695B1
EP0516695B1 EP91904859A EP91904859A EP0516695B1 EP 0516695 B1 EP0516695 B1 EP 0516695B1 EP 91904859 A EP91904859 A EP 91904859A EP 91904859 A EP91904859 A EP 91904859A EP 0516695 B1 EP0516695 B1 EP 0516695B1
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EP
European Patent Office
Prior art keywords
signal
noise
control system
sensor
adaptive filter
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Expired - Lifetime
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EP91904859A
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German (de)
English (en)
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EP0516695A1 (fr
Inventor
Colin Fraser Ross
Andrew John Langley
Graham Paul Eatwell
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Noise Cancellation Technologies Inc
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Noise Cancellation Technologies Inc
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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
    • G10K11/1783—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
    • G10K11/17837—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 retaining part of the ambient acoustic environment, e.g. speech or alarm signals that the user needs to hear
    • 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
    • G10K11/17875—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
    • G10K11/17879—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
    • G10K2210/10—Applications
    • G10K2210/108—Communication systems, e.g. where useful sound is kept and noise is cancelled
    • 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
    • G10K2210/10—Applications
    • G10K2210/121—Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
    • 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
    • G10K2210/3018—Correlators, e.g. convolvers or coherence calculators
    • 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
    • G10K2210/511—Narrow band, e.g. implementations for single frequency cancellation

Definitions

  • This invention relates generally to the selective attenuation of noise where tonal noises are attenuated more than broadband (random) noises. More specifically the tones may be produced by one or more sources of noise each of which generate noise at a fundamental frequency and possibly harmonic frequencies.
  • the tones reach a region where they provide a disturbance and reduce the ability of a person to hear other sounds which are generally of a more random nature (eg speech signals).
  • the invention relates to an active noise control system which provides more attenuation of the tonal noises than of the random sounds in the region and does not require a signal link to the source or sources of tonal noise.
  • tonal noise includes narrow-band random noise, and noise includes vibration.
  • Headsets which selectively cancel the noise produced by a single rotating machine are known (Chaplin - GB2104754), but these require a link, by cable or ultrasonic/infrared transmission, to the source of repetitive noise in order to generate a trigger signal.
  • the system requires one link per machine. This link or links can be inconvenient - if they are cable they restrict the movement of the wearer and if they are by transmission they may be unreliable as the wearer moves into regions where the transmission is obscured.
  • GB2104754 describes the possibility of using a local microphone to obtain a signal to drive a phase-locked loop to generate a trigger signal but admits that this will only be effective when the repetitive noise is particularly regular. As described his method will not be able to deal with multiple sources of tonal noise.
  • an active control system for attenuating tonal noise more than broadband noise affecting a listening region comprising:
  • the sensor means may conveniently comprise a first sensor in the listening region for producing the first said signal and a second sensor, which may or may not be in the listening region, for producing the second signal.
  • the processing in the processing means may include cross-correlating the effectively delayed signal (or signals derived therefrom, or from which the said signals are themselves derived and which may itself be modified by filtering) and the monitor signal (or signals derived therefrom, or from which the said signals are themselves derived and which may itself be modified by filtering).
  • the processing in the processing means may include calculating the cross spectrum between the effectively delayed signal (or signals derived therefrom, or from which the said signals are themselves derived and which may itself be modified by filtering) and the monitor signal (or signals derived therefrom, or from which the said signals are themselves derived and which may itself be modified by filtering).
  • the said signal related at least in part to the uncontrolled sound in the listening region where selective attenuation is required may be obtained from a sensor located close to the listening region where selective attenuation is required.
  • the said signal related at least in part to the uncontrolled sound in the listening region where selective attenuation is required may be obtained by subtracting the signals which drive the transducer means (or signals derived therefrom, or from which the said signals are themselves derived and which may itself be modified by filtering) from the monitor signal.
  • the delay means may effectively delay the signal it receives by actually delaying the signal it receives.
  • this delay is adjusted, by the adaptive filter which is itself responsive to the spectrum or auto-correlation of the input to the delay means, so that the sum of this delay plus any delay in the transmission process from the transducer to the sensor providing the monitor signal is greater than the correlation time of the noises to be unattenuated and shorter than the correlation time of the noises to be attenuated.
  • This means that the system is unable to attenuate noises with short duration cross-correlations (ie broadband random signals) and yet is able to attenuate noises with long duration cross-correlations.
  • the effective delay is realised by the use of narrow band filters in series with the adaptive filter, said narrow band filters being adapted to reject signals at frequencies other than the tonal frequencies to be attenuated.
  • These narrow-band filters can be fixed or tunable so that the centre frequencies can be adjusted to correspond to the frequencies of the tones to be cancelled and their bandwidth adjusted to include these tonal noises, the narrow-band filters being adjusted by the adaptive filter which is itself responsive to the spectrum or auto-correlation of the input to the delay means.
  • the adaptive filter can include one or more parallel adaptive filter sections each of which has a characteristic at least partly determined by minimising the cross-correlation between its input and the monitor signals.
  • the delay means includes narrow-band filters the individual filter outputs are fed one to each of the parallel adaptive filter sections of the adaptive filter.
  • Each adaptive filter section may be a jth order finite impulse response filter where the coefficients are adjusted with a gradient descent algorithm.
  • a separate sensor is used to produce the signal for input to the delay means, advantageously that sensor is positioned so that it is insensitive to the noise produced by the transducers or the effect of the transducers on the signal it produces is reduced by electronic subtraction.
  • the system may be incorporated in a headset or ear defender. Either one system would be used or alternatively two systems would be used so that the quietened region generally includes one or both ears.
  • the sensors providing the monitor signal could be any transducer that can be used to infer the unsteady pressure at a point located close to each ear, for example, a microphone located close to each ear.
  • the sensors providing the signal as input to the first circuit means could be one microphone located on or near the top of the headset or alternatively one close to the back of the shell of one or both earpieces, and in the further alternative no sensor is required specifically to generate this signal, the signal being derived from the monitor signal as described herein.
  • the transducer may be any device capable of generating unsteady pressure fluctuations, for example a loudspeaker.
  • the transducers may be mounted close to the ear so as to influence the unsteady pressure in the region around one or both ears, for example, the transducers may be mounted in the shell of one or both earpieces.
  • the headset can be of an open-backed type to allow the easy entry of desirable speech signals.
  • the headset may be part of a communications headset where desirable sounds are reproduced through the loudspeakers.
  • an effectively delayed and adaptive filter generally of the form described herein may be incorporated in the speech receiving microphone channel in order to attenuate the background tonal noises picked up by the microphone.
  • Figure one shows a sensor, 1, which produces a signal representative of the sound in region 2.
  • This signal, 3, is delayed in a first circuit means, 4, and the resultant signal fed via an adaptive filter, 5, to a transducer, 6, which generates sound to interfere with the sound in the region 2.
  • the coefficients of the adaptive filter, 5, are adjusted by a second circuit means, 26, in accordance with an adaptive algorithm, described below, which uses monitor signal, 7, from a sensor, 8, in the region to be controlled, 2, and the input, 9, to the adaptive filter, 5.
  • the first circuit means, 4, is adapted by the first adaption unit means, 10, in accordance with the spectrum or auto-correlation of the signal, 3.
  • the delay is adjusted so that it is greater than the correlation time of the sound that is to be left unattenuated and yet less than the correlation time of the sound to be attenuated. This delay may be made to depend upon frequency where some frequency selectivity is required.
  • the adaptive algorithm of the second circuit means 26 is any adaptive algorithm which adjusts the adaptive filter in order to minimise the correlation between the filter's input and the monitor signal. These may be of the frequency domain type which involve calculating cross-spectra or the time domain type which involve cross-correlating. Many algorithms of this type are described in WIDROW & STEARNS 'adaptive signal processing'. One such time domain algorithm is described below:
  • the input signal, 9, is denoted by u(t) and the output of the adaptive filter section, 5, is denoted by y(t).
  • u(t) the output of the adaptive filter section
  • y(t) the output of the adaptive filter section
  • the signals are in sampled digital form having been converted by an analogue to digital converter either before or after the delay unit.
  • the sampled version of the input and output are represented as u(k) and y(k) where k represents the time instant.
  • the signals will be converted back to analogue form after the adaptive filter, 5.
  • the output y(k) is related to the input by where b(i) represents the ith coefficient of the filter.
  • the output of sensor, 8, the monitor signal, is w(k) and this comprises two components v(k), the uncontrolled noise, and the component due to the transducer, 6. where c represents the effect of the transducer characteristic.
  • the noise in the region to be controlled is minimised by adapting the coefficients b(i) using a gradient descent algorithm (for its derivation see WIDROW & STEARNS 'adaptive signal processing' published 1985 by prentice hall).
  • b j+1 (i) b j (i) - ⁇ r(k-i) w(k)
  • b j+1 (i) is the next update of the filter coefficient b j (i).
  • r(k-i) w(k) can be interpretted as a single sample estimate of the cross-correlation between the two sugnals r and w.
  • N can be any number.
  • One particular novel feature of this invention is the ability of the circuit means, 11, to reduce the tonal noise more than the broadband random noise. This feature is now explained.
  • the adaptive filter section described above will drive the correlation (for positive time lags) between its input and the monitor signal to zero by adjusting the coefficients of the filter so that a cancelling noise is produced to eliminate any noise which contributes to the correlation between the two. By introducing a delay into the input signal there will no longer be any correlation between the two (for positive time lags) for broadband noises with shorter correlation times than the delay and thus the adaptive filter section will do nothing.
  • FIG. 5a shows a typical cross-correlation of the input to the first circuit means and monitor signal when their sensors are close together and receiving broadband noise.
  • Figure 5b shows the typical cross-correlation when their sensors are receiving a narrow-band (tonal) sound.
  • D shifts the cross-correlation so that the origin is at the point marked D. Since the adaptive filter is only able to control the sounds with a significant level of cross-correlation to the right of the origin only the narrow-band signal will be controlled. If the system receives a combination of many noises it will eliminate all those with a cross-correlation beyond the point D and so it will eliminate all tones.
  • the signal, 3, is not contaminated with noises received by its sensor, 1, from the transducer, 6.
  • This may be achieved by making the sensor, 1, directional so that it is insensitive to sounds from the transducer, or by positioning it so that it is insensitive, or by providing an additional filter which takes the transducer signal as an input and whose output is used to subtract the effect of the transducer from the sensor signal in a manner similar to that described for eliminating the effect of the transducer produced noise on the monitor signal.
  • Figure 2 shows a similar layout to figure 1 but with a different internal layout for the circuit means 11.
  • the signal, 3, from the sensor, 1, is fed to one or more narrow-band filters in a first circuit means, 12, whose outputs, 16, are fed one to each of the parallel adaptive filter sections of the adaptive filter, 14.
  • the output of all of the parallel sections are combined to form the drive to the transducer, 6.
  • the adaption of the individual parallel adaptive filter sections of the adaptive filter, 14, is accomplished by the second circuit means, 15, in response to the monitor signal 7 and each of the narrow-band filter outputs 16.
  • the second circuit means uses the adaptive algorithm described above where the coefficients of each of the parallel adaptive filter sections are adapted in accordance with the corresponding input and the monitor signal.
  • the narrow-band filters in a first circuit means, 12, are either fixed or tunable. In the case when they are fixed there are a sufficient number of them, closely spaced in frequency, so that a tonal signal of any frequency in the range of interest will pass through one of them.
  • this first circuit When a tonal noise is fed to this first circuit means with a bandwidth smaller than the bandwidth of the narrow-band filters there will be an output from one of the filters which is a delayed (and thus phase-shifted) version of the input. Because the cross-correlation of the sensor and monitor signals will have a long correlation time, despite the delay introduced by the filter, this output will have a correlation (for positive time lags) with the monitor signal and thus the corresponding parallel adaptive filter section of the adaptive filter, 14, will be adapted to produce an output signal to attenuate the tonal noise.
  • this first circuit When a broadband signal is fed to this first circuit means which has a bandwidth much larger than the bandwidth of the narrow-band filter some output will be generated at each of the filters in the bandwidth of the original signal, but the outputs will be delayed versions of the input (delayed by a time corresponding to the reciprocal of the bandwidth of the narrow-band filters) and because of the short correlation time of the original broadband signal this (effectively) delayed signal will have little cross-correlation with the monitor signal and thus the parallel adaptive filter sections will produce little output and the noise will be unattenuated.
  • the narrow-band filters may be tunable in order to minimise the complexity of the system by reducing the number of narrow-band filters.
  • the narrow-band filters would be continually adjusted by the first adaption unit 13 in order to maintain their centre frequency close to the frequency of the corresponding tone. Their bandwidth would be adjusted to ensure that it was greater than the tone being attenuated and yet not too broad to let broadband signals through with insufficient delay. This processing being done automatically.
  • Figure 3 shows how the sensor signal may be derived from the sensor, 8, in the region to be controlled, 2.
  • the output, 17, from the circuit means, 11, which in this figure is identical to that shown in figure 1, is fed to a filter 18.
  • the characteristic of this filter is adjusted to correspond to the transfer function between signal 17 and signal 7. This is identical to the filter c(i) used in the first adaption unit 6.
  • the output of filter 18 is subtracted from the monitor signal 7 to provide an equivalent signal 3.
  • the characteristic of the filter 18 may be updated in order to maintain it as an accurate representation of the transfer function.
  • Figure 4 shows the equivalent circuit where the input to the first circuit means and monitor signals are derived from the same sensor for the circuit means 11 which uses narrow-band filters.
  • Figure 6 shows the system incorporated in a ear defender.
  • the ear defender may be of the open-backed type to allow the desired sounds to reach the ear unimpeded.
  • the sensor, 1, generating the input to the first circuit means is a microphone mounted on the shell of the earpiece, 19 and the sensor, 8, generating monitor signals is a microphone contained in the earpiece close to the ear.
  • the transducer, 6, is a loudspeaker incorporated in the shell of the earpiece.
  • Figure 7 shows a system where one microphone 22, is used to provide the input to the first circuit means for both circuits 11.
  • Figure 8 shows the embodiment in which there is no separate sensor to provide an input to the first circuit means (and the input is derived from the monitor signals as described hereinbefore).
  • An additional input can be fed to one or each of the loudspeakers carrying desirable communication signals for the wearer and these signals will be converted into sounds for the wearer to hear. These sounds will be unaffected by the citcuit means, 11.
  • a microphone would be attached to the headset to receive the wearer's speech.
  • the effective delay can be achieved by introducing a delay into the signal either before, during or after adaptive filtering or any combination thereof.
  • some or all of the delay introduced by device 4 can be incorporated in the filter 5 or achieved by a discrete device located between the filter 5 and the transducer 6.
  • the second circuit 76 must of course be adjusted accordingly.
  • cross correlation of two signals is referred to in the foregoing specification and the following claims and this expression is defined as follows: the cross correlation (c) of two digitally sampled signals r(i) and w(i) (where the offset between the two signals to be cross correlated is n ), is given by: where N can be any number, and as indicated above n is the number of sampling points by which one signal is offset from the other.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Noise Elimination (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)

Claims (20)

  1. Système de commande actif pour atténuer sélectivement un bruit tonal d'une manière plus importante qu'un bruit à large bande affectant une zone d'écoute (2), comportant :
    des moyens (6) formant transducteur pour produire des sons dans la zone d'écoute (2) qui interfèrent avec le bruit existant dans cette région pour entraîner au moins une suppression partielle dudit bruit,
    des moyens de détection comportant un détecteur (8) situé dans la zone d'écoute (2), lesdits moyens de détection délivrant un premier signal (7) en rapport avec le bruit (atténué) résiduel existant dans la zone, et un second signal (3) qui en rapport au moins en partie avec le bruit qui affecterait la zone d'écoute (2) en l'absence d'atténuation sélective,
    des moyens de traitement de signaux (11) pour traiter les premier et second signaux (ou des signaux dérivés de ceux-ci),
       caractérisé en ce que
    les premier et second signaux sont tous deux représentatifs à la fois du bruit tonal et du bruit à large bande,
    les moyens de traitement de signaux comportent un filtre adaptatif (5), qui reçoit un signal dérivé au moins du second signal (3) et produit des signaux pour commander les moyens (6) formant transducteur, et des moyens de circuit (26) pour ajuster la caractéristique adaptative du filtre afin de minimiser la corrélation existant entre l'entrée (9) du filtre et le premier signal (7),
    les moyens de traitement de signaux (11) comportent des moyens pour soustraire du second signal (3), avant d'envoyer ledit signal vers le filtre adaptatif (5), une partie quelconque dudit signal (3) qui est due à l'effet des moyens (6) formant transducteur, et
    des moyens (4) pour introduire un retard effectif dans le trajet du second signal (3) ou d'un signal quelconque dérivé de celui-ci formé à travers le filtre adaptatif (5) jusqu'aux moyens (6) formant transducteur, le retard efficace plus le retard acoustique entre les moyens formant transducteur et le détecteur dans la zone d'écoute étant supérieur au temps de corrélation du bruit à ne pas atténuer, de sorte que les moyens formant transducteur peuvent agir pour produire des sons destinés à atténuer le bruit tonal d'une manière plus importante que le bruit à large bande.
  2. Système de commande actif selon la revendication 1, caractérisé en ce que les moyens de détection comportent le détecteur (8) destiné à produire le premier signal (7) et un second détecteur (1) destiné à produire le second signal (3).
  3. Système de commande actif selon la revendication 2, caractérisé en ce que le second détecteur (1) est aussi situé dans la zone d'écoute.
  4. Système de commande actif selon la revendication 2, dans lequel le second détecteur (1) est placé dans une zone qui n'est pas affectée par le son émis par le transducteur.
  5. Système de commande actif selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le retard est appliqué au signal (7) qui doit être envoyé vers le filtre adaptatif (5).
  6. Système de commande actif selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le retard est incorporé dans le filtre adaptatif (5).
  7. Système de commande actif selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le retard est appliqué au signal (3) à appliquer pour commander les moyens formant transducteur.
  8. Système de commande actif selon l'une quelconque des revendications 1 à 7, caractérisé en ce que les moyens de traitement (26) servent à produire une corrélation croisée entre le premier signal (7) ou un signal dérivé de celui-ci, et le signal (9) appliqué au filtre adaptatif (ou un signal dérivé de celui-ci ou dont est déduit ledit signal appliqué au filtre adaptatif et qui peut être modifié lui-même par filtrage).
  9. Système de commande actif selon l'une quelconque des revendications 1 à 8, caractérisé en ce que les moyens de traitement (26) servent à calculer le spectre croisé du premier signal (7) ou d'un signal dérivé de celui-ci, et du signal (9) appliqué au filtre adaptatif (ou un signal dérivé de celui-ci ou dont est dérivé ledit signal appliqué au filtre adaptatif et qui peut être modifié lui-même par filtrage).
  10. Système de commande actif selon l'une quelconque des revendications précédentes, caractérisé en ce que le retard efficace est réalisé par l'utilisation de filtres à bande étroite (12), montés en série avec le filtre adaptatif, lesdits filtres à bande étroite étant adaptés pour supprimer les signaux de fréquences autres que les fréquences tonales à atténuer.
  11. Système de commande actif selon la revendication 10, caractérisé en ce qu'un ensemble de filtres à bande étroite (12), montés en parallèle, est utilisé.
  12. Système de commande actif selon l'une quelconque des revendications précédentes, caractérisé en ce que le signal appliqué sur le filtre adaptatif (5) est rendu insensible aux moyens (6) formant transducteur en utilisant une combinaison du second signal (3) (ou d'un signal dérivé de celui-ci) et du signal envoyé vers les moyens (6) formant transducteur (ou d'un signal dérivé de celui-ci ou dont il est dérivé) ou du premier signal (ou d'un signal dérivé de celui-ci).
  13. Casque d'écoute, écouteur ou protection auditive active qui incorpore le système de commande actif selon l'une quelconque des revendications 1 à 12, caractérisés en ce que le bruit tonal au niveau de l'oreille de l'auditeur est réduit de manière plus importante que le bruit aléatoire.
  14. Casque d'écoute, écouteur ou protection auditive active selon la revendication 13, caractérisés en ce qu'un système de commande séparé est appliqué à chacune des unités couvrant les oreilles.
  15. Casque d'écoute, écouteur ou protection auditive active selon la revendication 13 ou 14, dans lesquels le détecteur ou les détecteurs (1, 8) est ou sont un microphone ou des microphones positionné(s) sur la bande de support des écouteurs du casque d'écoute ou à l'extérieur du boîtier des moyens formant transducteur.
  16. Casque d'écoute, écouteur ou protection auditive active selon l'une quelconque des revendications 13, 14 ou 15, lorsque celles-ci sont rattachées à la revendication 4, caractérisés en ce que, pour chaque oreille, un détecteur (8) unique est utilisé.
  17. Casque d'écoute, écouteur ou protection auditive active selon l'une quelconque des revendications 13 à 16, caractérisés en ce que les moyens (6) formant transducteur sont montés de manière à se trouver proches des oreilles de l'utilisateur, lorsqu'en utilisation.
  18. Casque d'écoute, écouteur ou protection auditive active selon l'une quelconque des revendications 13 à 16, caractérisés en ce que chacun des moyens (6) formant transducteur est monté dans une cavité fermée, formée par une coque (19) recouvrant complètement l'oreille.
  19. Casque d'écoute, écouteur ou protection auditive active selon la revendication 18, caractérisés en ce que les propriétés du matériau constituant la coque (19) sont choisies de manière à favoriser la transmission du son dans un plage de fréquences sélectionnée.
  20. Casque d'écoute, écouteur ou protection auditive active selon l'une quelconque des revendications 13 à 19, lorsque celles-ci sont rattachées à la revendication 8, caractérisés en ce que la corrélation croisée est calculée sur un échantillon unique ou sur plusieurs échantillons, directement ou de manière récursive.
EP91904859A 1990-02-21 1991-02-20 Systeme de reduction de bruit Expired - Lifetime EP0516695B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB909003938A GB9003938D0 (en) 1990-02-21 1990-02-21 Noise reducing system
GB9003938 1990-02-21
PCT/GB1991/000265 WO1991013429A1 (fr) 1990-02-21 1991-02-20 Systeme de reduction de bruit

Publications (2)

Publication Number Publication Date
EP0516695A1 EP0516695A1 (fr) 1992-12-09
EP0516695B1 true EP0516695B1 (fr) 1997-04-09

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EP91904859A Expired - Lifetime EP0516695B1 (fr) 1990-02-21 1991-02-20 Systeme de reduction de bruit

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EP (1) EP0516695B1 (fr)
JP (1) JPH07500677A (fr)
AT (1) ATE151554T1 (fr)
AU (1) AU639761B2 (fr)
CA (1) CA2076390C (fr)
DE (1) DE69125601T2 (fr)
GB (1) GB9003938D0 (fr)
WO (1) WO1991013429A1 (fr)

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US9818394B2 (en) 2009-11-30 2017-11-14 Graeme Colin Fuller Realisation of controller transfer function for active noise cancellation
WO2011146429A1 (fr) 2010-05-17 2011-11-24 Thales Avionics, Inc. Dispositif d'interface utilisateur modulaire de siège de passager d'une compagnie aérienne
US9487295B2 (en) 2010-11-15 2016-11-08 William James Sim Vehicle media distribution system using optical transmitters
JP5937611B2 (ja) 2010-12-03 2016-06-22 シラス ロジック、インコーポレイテッド パーソナルオーディオデバイスにおける適応ノイズキャンセラの監視制御
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Also Published As

Publication number Publication date
JPH07500677A (ja) 1995-01-19
CA2076390C (fr) 1998-07-14
AU639761B2 (en) 1993-08-05
AU7336091A (en) 1991-09-18
DE69125601T2 (de) 1997-08-14
DE69125601D1 (de) 1997-05-15
ATE151554T1 (de) 1997-04-15
CA2076390A1 (fr) 1991-08-22
WO1991013429A1 (fr) 1991-09-05
EP0516695A1 (fr) 1992-12-09
GB9003938D0 (en) 1990-04-18

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