EP0649129B1 - Method for active acoustic sound compensation in hollow car-bodies - Google Patents

Method for active acoustic sound compensation in hollow car-bodies Download PDF

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Publication number
EP0649129B1
EP0649129B1 EP94114135A EP94114135A EP0649129B1 EP 0649129 B1 EP0649129 B1 EP 0649129B1 EP 94114135 A EP94114135 A EP 94114135A EP 94114135 A EP94114135 A EP 94114135A EP 0649129 B1 EP0649129 B1 EP 0649129B1
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Prior art keywords
sound
digital filter
unit
adaptive digital
sensor signal
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German (de)
French (fr)
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EP0649129A2 (en
EP0649129A3 (en
Inventor
Raymond Dr. Freymann
Rainer Beer
Dieter Dr. Guicking
Marcus Dr. Bronzel
Wolfgang Dr. Böhm
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Bayerische Motoren Werke AG
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Bayerische Motoren Werke AG
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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
    • G10K11/17855—Methods, e.g. algorithms; Devices for improving speed or power requirements
    • 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
    • G10K2210/128—Vehicles
    • G10K2210/1282—Automobiles
    • 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
    • G10K2210/3017—Copy, i.e. whereby an estimated transfer function in one functional block is copied to another block
    • 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
    • G10K2210/3028—Filtering, e.g. Kalman filters or special analogue or digital filters
    • 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

Definitions

  • the invention relates to a device for active acoustic sound compensation of noise in the cavities of a motor vehicle with a sensor which supplies a sensor signal which essentially corresponds to the noise and whose output is connected to an input of an adaptive digital filter unit, and with a sound generator connected downstream of the adaptive digital filter unit to generate a compensation sound.
  • Such a device is known for example from US 4,677,676.
  • This known device represents an acoustic system in a cavity, in which an input sound is detected at the entrance of the cavity by means of a microphone and is fed to a control system which contains, for example, an adaptive digital filter (ADF).
  • ADF adaptive digital filter
  • the control system analyzes the input sound to produce a compensation sound that is emitted into the cavity via a loudspeaker.
  • the compensation sound also called anti-sound, is formed in such a way that it counteracts the input sound, so that the input sound is at least almost canceled out.
  • the time period for generating an optimum compensation sound signal in the adaptive digital filter unit for canceling the input sound or interference sound is to be shortened.
  • An amplitude smoothing unit is interposed between the output of the sensor, which detects, for example, the sound disturbances introduced into the body as an input signal and emits a corresponding sensor signal, and the input of the control system or the adaptive digital filter unit, for each frequency component of the input signal or sensor signal produces essentially the same amplitude.
  • the background of this solution of the task according to the invention is that in the state of the art the adaptive digital Filter unit frequency components of the sensor signal are initially evaluated as a function of their amplitude if, for example, stochastic gradient methods are used as control algorithms. As a result, the evaluation time for recognizing those frequency components of the sensor signal that have a lower amplitude than other frequency components is extended.
  • the sensor signal is preprocessed in such a way that the adaptive digital filter unit, similar to a white noise, receives a frequency-wideband signal with approximately the same amplitudes in the entire frequency range. This is necessary because the stochastic gradient methods usually used in the adaptive digital filter (for example least mean square LMS methods) usually only converge very slowly with input signals that do not have a flat spectrum.
  • the amplitude smoothing unit essentially forms the inverse, preferably time-dependent, auto-correlation function of the sensor signal.
  • the amplitude smoothing unit initially uses adaptive system recognition to form a model of the auto-correlation function of the sensor signal that is time-dependent due to the possible unsteadiness.
  • This model which contains the statistical signal properties, is transferred to a filter.
  • the sensor signal weighted with this filter is subtracted from the current sensor signal.
  • the amplitude smoothing unit thus essentially includes the determination of the inverse, time-dependent Autocorrelation function.
  • FIG. 1 shows a device according to the invention with the representation of an amplitude smoothing unit which includes the inversion of the autocorrelation function.
  • the sensor signal x 1 which arises, for example, from bumps on the road 7 and is transmitted to vehicle cavities, such as in particular the motor vehicle interior 6, via vehicle vibration systems, leads to a noise x 2 in the motor vehicle interior 6 as shown here.
  • This interference sound x 2 is to be suppressed or extinguished by the active acoustic sound compensation device according to the invention.
  • an input interference signal or sensor signal x 1 correlated to the interference noise x 2 is formed by means of a sensor S1, for example from the acceleration signals at axle or body points or from acoustic signals measured at the location of the interference noise x 2 .
  • This sensor signal x 1 is connected to an amplitude smoothing unit 1.
  • the output of the adaptive digital filter unit 4 leads to a loudspeaker L.
  • the loudspeaker L and a sound pickup S2, the output of which is fed back to the adaptive digital filter unit 4, are located itself inside a cavity, here in the vehicle interior 6, ie inside the passenger compartment of a vehicle.
  • a filtered-X circuit known per se can additionally be used, for example.
  • the output signal x ′ of the amplitude smoothing unit 1 is connected to a multiplication point via a correction unit 5.
  • the output of the multiplication point leads to a control input of the adaptive digital filter unit 4.
  • the output of the sound sensor S2 is also connected to the multiplication point.
  • the sensor signal x 1 detected by the sensor S1 is first inverted in the amplitude smoothing unit 1 with reference to the amplitude.
  • An inverse autocorrelation function is formed with which the sensor signal x 1 is weighted and passed on to the adaptive digital filter unit 4.
  • the amplitude smoothing unit 1 contains a recognition unit 3 and a model unit 2.
  • the recognition unit 3 the autocorrelation function, in particular time-dependent, is first recognized and copied to the model unit 2, whereupon the amplitude smoothing is carried out in particular by the model unit 2.
  • the recognition unit 3 contains, for example, the statistical signal properties that are transmitted to the model unit 2, which can be a filter.
  • the sensor signal x 1 weighted with the model unit 2 is subtracted from the current sensor signal x 1 , which results in the amplitude-smoothed output signal x 'of the amplitude smoothing unit 1 from the sensor signal x 1 .
  • the adaptive digital filter unit 4 converges very quickly for all frequency components of the output signal x 'of the amplitude smoothing unit 1 in order to generate a compensation signal x L which is transmitted via the loudspeaker L as compensation sound k for broadband suppression of the interference sound x 2 in the cavity or Vehicle interior 6 is emitted.
  • a residual noise e can occur between the compensation noise k and the noise x 2 .
  • This residual sound e is detected by the sound pickup S2, multiplied by the output signal x ′ of the amplitude smoothing unit 1 corrected via the correction unit 5 and fed back to the adaptive digital filter unit 4.
  • the residual sound e is minimized over a broadband range by the amplitude smoothing unit 1 according to the invention for leveling the amplitudes of the frequency components of the sensor signal x 1 , since the faster evaluation time of the adaptive digital filter unit 4 also reduces the sound component of the residual sound e, which in known systems due to the convergence properties of the adaptives Digital filter unit 4 and the associated longer evaluation time cannot be compensated for.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)

Description

Die Erfindung betrifft eine Vorrichtung zur aktiven akustischen Schallkompensation eines Störschalls in Hohlräumen eines Kraftfahrzeuges mit einem Sensor, der ein dem Störschall im wesentlichen entsprechendes Sensorsignal liefert und dessen Ausgang mit einem Eingang einer Adaptiven Digitalen Filtereinheit verbunden ist, und mit einem der Adaptiven Digitalen Filtereinheit nachgeschalteten Schallgeber zur Erzeugung eines Kompensationsschalls.The invention relates to a device for active acoustic sound compensation of noise in the cavities of a motor vehicle with a sensor which supplies a sensor signal which essentially corresponds to the noise and whose output is connected to an input of an adaptive digital filter unit, and with a sound generator connected downstream of the adaptive digital filter unit to generate a compensation sound.

Eine derartige Vorrichtung ist beispielsweise aus der US 4 677 676 bekannt. Diese bekannte Vorrichtung stellt ein akustisches System in einem Hohlraum dar, bei dem am Eingang des Hohlraums mittels eines Mikrofons ein Eingangsschall erfaßt wird, der an ein Regelsystem, das beispielsweise ein Adaptives Digitales Filter (ADF) enthält, zugeführt wird. Das Regelsystem analysiert den Eingangsschall, um einen Kompensationsschall zu erzeugen, der über einen Lautsprecher in den Hohlraum abgegeben wird. Der Kompensationsschall, auch Antischall genannt, wird derart gebildet, daß er dem Eingangsschall entgegenwirkt, so daß der Eingangsschall zumindest nahezu ausgelöscht wird. Da eine vollständige Auslöschung des Eingangsschalls durch den Kompensationsschall aufgrund von Ungenauigkeiten und Zeitverzögerungen im Regelsystem oder in den verwendeten Sensoren bzw. Schallgebern meist nicht erreicht wird, wird der Restschall im Hohlraum erfaßt und ebenfalls dem Reglersystem zugeführt. Durch diese Rückführung des Restschalls wird eine Korrektur im Reglersystem vorgenommen, die zu einer besseren Unterdrückung des Eingangsschalls führt als ohne Rückführung des Restschalls. Jedoch bleiben Ungenauigkeiten im Regelsystem, insbesondere durch die zur Analyse des Eingangsschalls erforderliche Zeit, weiter bestehen.Such a device is known for example from US 4,677,676. This known device represents an acoustic system in a cavity, in which an input sound is detected at the entrance of the cavity by means of a microphone and is fed to a control system which contains, for example, an adaptive digital filter (ADF). The control system analyzes the input sound to produce a compensation sound that is emitted into the cavity via a loudspeaker. The compensation sound, also called anti-sound, is formed in such a way that it counteracts the input sound, so that the input sound is at least almost canceled out. Because a complete annihilation If the input sound is mostly not reached by the compensation sound due to inaccuracies and time delays in the control system or in the sensors or sounders used, the residual sound in the cavity is detected and also fed to the control system. This feedback of the residual sound results in a correction in the control system, which leads to better suppression of the input sound than without feedback of the residual sound. However, inaccuracies in the control system remain, in particular due to the time required to analyze the input sound.

Es ist Aufgabe der Erfindung, eine Vorrichtung zur aktiven akustischen Schallkompensation mit einer Adaptiven Digitalen Filtereinheit als Reglersystem zu schaffen, bei dem der durch zu lange Auswertezeiten in der Adaptiven Digitalen Filtereinheit bedingte Restschall zwischen dem Eingangsschall und dem Kompensationsschall minimiert wird. Insbesondere soll die Zeitdauer zur Erzeugung eines zur Auslöschung des Eingangsschalls bzw. Störschalls optimalen Kompensationsschallsignals in der Adaptiven Digitalen Filtereinheit verkürzt werden.It is an object of the invention to provide a device for active acoustic sound compensation with an adaptive digital filter unit as a control system, in which the residual sound between the input sound and the compensating sound caused by too long evaluation times in the adaptive digital filter unit is minimized. In particular, the time period for generating an optimum compensation sound signal in the adaptive digital filter unit for canceling the input sound or interference sound is to be shortened.

Diese Aufgabe wird durch die kennzeichnenden Merkmale des Patentanspruchs 1 gelöst.
Zwischen dem Ausgang des Sensors, der z.B. die in die Karosserie eingeleiteten Schall-Störungen als Eingangssignal erfaßt und ein entsprechendes Sensorsignal abgibt, und dem Eingang des Regelsystems bzw. der Adaptiven Digitalen Filtereinheit wird eine Amplitudenglättungseinheit zwischengeschaltet, die für jeden Frequenzanteil des Eingangssignals bzw. Sensorsignals im wesentlichen die gleiche Amplitude erzeugt.This object is achieved by the characterizing features of patent claim 1.
An amplitude smoothing unit is interposed between the output of the sensor, which detects, for example, the sound disturbances introduced into the body as an input signal and emits a corresponding sensor signal, and the input of the control system or the adaptive digital filter unit, for each frequency component of the input signal or sensor signal produces essentially the same amplitude.

Hintergrund dieser erfindungsgemäßen Lösung der Aufgabe ist, daß beim Stand der Technik die Adaptive Digitale Filtereinheit Frequenzanteile des -Sensorsignals zunächst in Abhängigkeit von ihrer Amplitude bewertet, wenn beispielsweise stochastische Gradientenverfahren als Regelalgorithmen verwendet werden. Dadurch verlängert sich die Auswertezeit zur Erkennung derjenigen Frequenzanteile des Sensorsignals, die gegenüber anderen Frequenzanteilen eine geringere Amplitude aufweisen. Mit der erfindungsgemäßen Vorrichtung wird das Sensorsignal derart vorverarbeitet, daß die Adaptive Digitale Filtereinheit, ähnlich einem weißen Rauschen, ein frequenzbreitbandiges Signal mit im gesamten Frequenzbereich in etwa gleichen Amplituden erhält. Dies ist notwendig, da die im Adaptiven Digitalen Filter üblicherweise verwendeten stochastischen Gradientenverfahren (beispielsweise Least-Mean-Square LMS-Verfahren) bei Eingangssignalen, die kein flaches Spektrum besitzen, gewöhnlich nur sehr langsam konvergieren.The background of this solution of the task according to the invention is that in the state of the art the adaptive digital Filter unit frequency components of the sensor signal are initially evaluated as a function of their amplitude if, for example, stochastic gradient methods are used as control algorithms. As a result, the evaluation time for recognizing those frequency components of the sensor signal that have a lower amplitude than other frequency components is extended. With the device according to the invention, the sensor signal is preprocessed in such a way that the adaptive digital filter unit, similar to a white noise, receives a frequency-wideband signal with approximately the same amplitudes in the entire frequency range. This is necessary because the stochastic gradient methods usually used in the adaptive digital filter (for example least mean square LMS methods) usually only converge very slowly with input signals that do not have a flat spectrum.

Eine vorteilhafte Weiterbildung der Erfindung ist der Gegenstand des Patentanspruchs 2.
Erfindungsgemäß bildet die Amplitudenglättungseinheit im wesentlichen die inverse, vorzugsweise zeitabhängige Autokorrelationsfunktion des Sensorsignals.An advantageous further development of the invention is the subject matter of patent claim 2.
According to the invention, the amplitude smoothing unit essentially forms the inverse, preferably time-dependent, auto-correlation function of the sensor signal.

Beispielsweise bildet die Amplitudenglättungseinheit dabei zunächst mittels adaptiver Systemerkennung ein Modell der aufgrund der möglichen Instationarität zeitabhängigen Autokorrelationsfunktion des Sensorsignals. Dieses Modell, das die statistischen Signaleigenschaften beinhaltet, wird in ein Filter übertragen. Das mit diesem Filter gewichtete Sensorsignal wird von dem momentanen Sensorsignal subtrahiert. Dadurch ergibt sich am Ausgang der Amplitudenglättungseinheit ein Signal, das als Filterung des Sensorsignals mit seiner inversen zeitabhängigen Autokorrelationsfunktion betrachtet werden kann. Die Amplitudenglättungseinheit beinhaltet somit im wesentlichen die Bestimmung der inversen, zeitabhängigen Autokorrelationsfunktion. Durch diese erfindungsgemäße Vorrichtung wird eine breitbandige Nivellierung der Frequenzanteile des Sensorsignals besonders einfach erreicht, da dazu bereits bekannte, beispielsweise elektronische Bauteile eingesetzt werden können.For example, the amplitude smoothing unit initially uses adaptive system recognition to form a model of the auto-correlation function of the sensor signal that is time-dependent due to the possible unsteadiness. This model, which contains the statistical signal properties, is transferred to a filter. The sensor signal weighted with this filter is subtracted from the current sensor signal. This results in a signal at the output of the amplitude smoothing unit, which can be viewed as filtering the sensor signal with its inverse time-dependent autocorrelation function. The amplitude smoothing unit thus essentially includes the determination of the inverse, time-dependent Autocorrelation function. With this device according to the invention, broadband leveling of the frequency components of the sensor signal is achieved particularly easily, since already known, for example electronic, components can be used for this purpose.

In der Zeichnung ist ein Ausführungsbeispiel der Erfindung dargestellt. Sie zeigt eine erfindungsgemäße Vorrichtung mit der Darstellung einer Amplitudenglättungseinheit, die die Invertierung der Autokorrelationsfunktion beinhaltet.In the drawing, an embodiment of the invention is shown. It shows a device according to the invention with the representation of an amplitude smoothing unit which includes the inversion of the autocorrelation function.

Das Sensorsignal x1, das beispielsweise durch Unebenheiten auf der Fahrbahn 7 entsteht und über Fahrzeug-Schwingungssysteme an Fahrzeughohlräume, wie insbesondere den Kraftfahrzeuginnenraum 6, übertragen wird, führt wie hier dargestellt im Kraftfahrzeuginnenraum 6 zu einem Störschall x2. Dieser Störschall x2 soll durch die erfindungsgemäße aktive akustische Schallkompensationsvorrichtung unterdrückt bzw. ausgelöscht werden.The sensor signal x 1 , which arises, for example, from bumps on the road 7 and is transmitted to vehicle cavities, such as in particular the motor vehicle interior 6, via vehicle vibration systems, leads to a noise x 2 in the motor vehicle interior 6 as shown here. This interference sound x 2 is to be suppressed or extinguished by the active acoustic sound compensation device according to the invention.

Hierzu wird mittels eines Sensors S1 ein dem Störschall x2 korreliertes Eingangsstörsignal bzw. Sensorsignal x1, beispielsweise aus den Beschleunigungssignalen an Achsoder Karosseriepunkten oder aus am Ort des Störschalls x2 gemessenen akustischen Signalen, gebildet. Dieses Sensorsignal x1 ist mit einer Amplitudenglättungseinheit 1 verbunden. Der Ausgang der Amplitudenglättungseinheit 1, der das vorverarbeitete Sensorsignal x' liefert, führt zu dem Eingang der Adaptiven Digitalen Filtereinheit 4.For this purpose, an input interference signal or sensor signal x 1 correlated to the interference noise x 2 is formed by means of a sensor S1, for example from the acceleration signals at axle or body points or from acoustic signals measured at the location of the interference noise x 2 . This sensor signal x 1 is connected to an amplitude smoothing unit 1. The output of the amplitude smoothing unit 1, which supplies the preprocessed sensor signal x ′, leads to the input of the adaptive digital filter unit 4.

Der Ausgang der Adaptiven Digitalen Filtereinheit 4 führt zu einem Lautsprecher L. Der Lautsprecher L und ein Schallaufnehmer S2, dessen Ausgang an die Adaptive Digitale Filtereinheit 4 zurückgeführt ist, befinden sich im Inneren eines Hohlraumes, hier im Fahrzeuginnenraum 6, d.h. innerhalb der Fahrgastzelle eines Fahrzeugs.The output of the adaptive digital filter unit 4 leads to a loudspeaker L. The loudspeaker L and a sound pickup S2, the output of which is fed back to the adaptive digital filter unit 4, are located itself inside a cavity, here in the vehicle interior 6, ie inside the passenger compartment of a vehicle.

Zur Kompensation der elektroakustischen Übertragungsstrecke zwischen dem Ausgang der Adaptiven Digitalen Filtereinheit 4 und dem Schallaufnehmer S2 kann beispielsweise zusätzlich eine an sich bekannte Filtered-X-Schaltung verwendet werden. Dazu ist das Ausgangssignal x'der Amplitudenglättungseinheit 1 über eine Korrektureinheit 5 mit einer Multiplizierstelle verbunden. Der Ausgang der Multiplizierstelle führt an einen Kontrolleingang der Adaptiven Digitalen Filtereinheit 4. Mit der Multiplizierstelle ist weiterhin der Ausgang des Schallaufnehmers S2 verbunden.To compensate for the electroacoustic transmission path between the output of the adaptive digital filter unit 4 and the sound pickup S2, a filtered-X circuit known per se can additionally be used, for example. For this purpose, the output signal x ′ of the amplitude smoothing unit 1 is connected to a multiplication point via a correction unit 5. The output of the multiplication point leads to a control input of the adaptive digital filter unit 4. The output of the sound sensor S2 is also connected to the multiplication point.

Das vom Sensor S1 erfaßte Sensorsignal x1 wird in der Amplitudenglättungseinheit 1 zunächst bezogen auf die Amplitude invertiert. Dabei wird eine inverse Autokorrelationsfunktion gebildet, mit der das Sensorsignal x1 gewichtet und an die Adaptive Digitale Filtereinheit 4 weitergeleitet wird.The sensor signal x 1 detected by the sensor S1 is first inverted in the amplitude smoothing unit 1 with reference to the amplitude. An inverse autocorrelation function is formed with which the sensor signal x 1 is weighted and passed on to the adaptive digital filter unit 4.

Dazu enthält in diesem Beispiel die Amplitudenglättungseinheit 1 eine Erkennungseinheit 3 und eine Modelleinheit 2. In der Erkennungseinheit 3 wird zunächst die Autokorrelationsfunktion, insbesondere zeitabhängig, erkannt und zur Modelleinheit 2 kopiert, woraufhin die Amplitudenglättung insbesondere durch die Modelleinheit 2 durchgeführt wird. Die Erkennungseinheit 3 enthält z.B. die statistischen Signaleigenschaften, die an die Modelleinheit 2, das ein Filter sein kann, übertragen werden. Das mit der Modelleinheit 2 gewichtete Sensorsignal x1 wird von dem momentanen Sensorsignal x1 subtrahiert, wodurch sich aus dem Sensorsignal x1 das amplitudengeglättete Ausgangssignal x' der Amplitudenglättungseinheit 1 ergibt.For this purpose, in this example the amplitude smoothing unit 1 contains a recognition unit 3 and a model unit 2. In the recognition unit 3, the autocorrelation function, in particular time-dependent, is first recognized and copied to the model unit 2, whereupon the amplitude smoothing is carried out in particular by the model unit 2. The recognition unit 3 contains, for example, the statistical signal properties that are transmitted to the model unit 2, which can be a filter. The sensor signal x 1 weighted with the model unit 2 is subtracted from the current sensor signal x 1 , which results in the amplitude-smoothed output signal x 'of the amplitude smoothing unit 1 from the sensor signal x 1 .

Das derart vorverarbeitete Sensorsignal x1 und somit das Ausgangssignal x' der Amplitudenglättungseinheit 1 zeichnet sich dadurch aus, daß sämtliche Frequenzanteile des Ausgangssignals x' im wesentlichen dieselbe Amplitude aufweisen. Die Adaptive Digitale Filtereinheit 4 konvergiert auf diese Weise sehr schnell für alle Frequenzanteile des Ausgangssignals x' der Amplitudenglättungseinheit 1, um damit ein Kompensationssignal xL zu erzeugen, das über den Lautsprecher L als Kompensationsschall k zur breitbandigen Unterdrückung des Störschalls x2 im Hohlraum bzw. Fahrzeuginnenraum 6 abgestrahlt wird.The sensor signal x 1 preprocessed in this way and thus the output signal x 'of the amplitude smoothing unit 1 is characterized in that all frequency components of the output signal x' have essentially the same amplitude. In this way, the adaptive digital filter unit 4 converges very quickly for all frequency components of the output signal x 'of the amplitude smoothing unit 1 in order to generate a compensation signal x L which is transmitted via the loudspeaker L as compensation sound k for broadband suppression of the interference sound x 2 in the cavity or Vehicle interior 6 is emitted.

Beispielsweise durch Rundungsfehler oder durch einen sich sehr schnell ändernden Störschall x2 kann ein Restschall e zwischen dem Kompensationsschall k und dem Störschall x2 entstehen. Dieser Restschall e wird von dem Schallaufnehmer S2 erfaßt, mit dem über die Korrektureinheit 5 korrigierten Ausgangssignal x' der Amplitudenglättungseinheit 1 multipliziert und an die Adaptive Digitale Filtereinheit 4 zurückgeführt.For example, due to rounding errors or a very rapidly changing noise x 2 , a residual noise e can occur between the compensation noise k and the noise x 2 . This residual sound e is detected by the sound pickup S2, multiplied by the output signal x ′ of the amplitude smoothing unit 1 corrected via the correction unit 5 and fed back to the adaptive digital filter unit 4.

Der Restschall e wird durch die erfindungsgemäße Amplitudenglättungseinheit 1 zur Nivellierung der Amplituden der Frequenzanteile des Sensorsignals x1 breitbandig minimiert, da durch die schnellere Auswertezeit der Adaptiven Digitalen Filtereinheit 4 auch der Schallanteil des Restschalls e vermindert wird, der bei bekannten Systemen aufgrund der Konvergenzeigenschaften der Adaptiven Digitalen Filtereinheit 4 und der damit verbundenen längeren Auswertezeit nicht kompensierbar ist.The residual sound e is minimized over a broadband range by the amplitude smoothing unit 1 according to the invention for leveling the amplitudes of the frequency components of the sensor signal x 1 , since the faster evaluation time of the adaptive digital filter unit 4 also reduces the sound component of the residual sound e, which in known systems due to the convergence properties of the adaptives Digital filter unit 4 and the associated longer evaluation time cannot be compensated for.

Claims (2)

  1. A device for active acoustic compensation of an interfering sound in cavities in a motor vehicle, comprising a sensor which delivers a signal substantially corresponding to the interfering sound and whose output is connected to an input of an adaptive digital filter unit, a sound generator for generating a compensating sound being disposed downstream of the adaptive digital filter unit, characterised in that an amplitude smoothing unit (1) is interposed between the output of the sensor (S1) and the input of the adaptive digital filter unit (4) and generates substantially the same amplitude for each frequency component of the sensor signal (x1).
  2. A device according to claim 1, characterised in that the amplitude smoothing unit (1) substantially constructs the inverse autocorrelation function of the sensor signal (x1).
EP94114135A 1993-10-13 1994-09-08 Method for active acoustic sound compensation in hollow car-bodies Expired - Lifetime EP0649129B1 (en)

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DE4334942 1993-10-13
DE4334942A DE4334942A1 (en) 1993-10-13 1993-10-13 Device for active acoustic sound compensation in the cavities of a motor vehicle

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EP0649129A3 EP0649129A3 (en) 1996-02-07
EP0649129B1 true EP0649129B1 (en) 1997-12-03

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US3542954A (en) * 1968-06-17 1970-11-24 Bell Telephone Labor Inc Dereverberation by spectral measurement
SU836654A1 (en) * 1979-07-18 1981-06-07 Научно-Исследовательский Институтстроительной Физики Госстроя Cccp Noise suppression device
SU1494031A1 (en) * 1987-01-30 1989-07-15 Предприятие П/Я А-1687 Device for compensation of random acoustic oscillations in construtions and media
JPH05232969A (en) * 1992-02-19 1993-09-10 Mazda Motor Corp Vibration control device for vehicle
US5222148A (en) * 1992-04-29 1993-06-22 General Motors Corporation Active noise control system for attenuating engine generated noise
FR2701784B1 (en) * 1993-02-18 1995-05-12 Matra Sep Imagerie Inf Method and device for active vibration damping.

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DE4334942A1 (en) 1995-04-20
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EP0649129A3 (en) 1996-02-07

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