EP0342353A2 - Arrangement for diminishing the noise level within a motor car - Google Patents

Arrangement for diminishing the noise level within a motor car Download PDF

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Publication number
EP0342353A2
EP0342353A2 EP19890106308 EP89106308A EP0342353A2 EP 0342353 A2 EP0342353 A2 EP 0342353A2 EP 19890106308 EP19890106308 EP 19890106308 EP 89106308 A EP89106308 A EP 89106308A EP 0342353 A2 EP0342353 A2 EP 0342353A2
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EP
European Patent Office
Prior art keywords
arrangement according
noise
loudspeaker
motor vehicle
arrangement
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.)
Granted
Application number
EP19890106308
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German (de)
French (fr)
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EP0342353B1 (en
EP0342353A3 (en
Inventor
R. Dr. Freymann
R. Beer
R. Schmaderer
K. Stricker
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Bayerische Motoren Werke AG
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Bayerische Motoren Werke AG
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Publication of EP0342353A2 publication Critical patent/EP0342353A2/en
Publication of EP0342353A3 publication Critical patent/EP0342353A3/en
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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
    • G10K11/17853—Methods, e.g. algorithms; Devices of the 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
    • G10K11/1781—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
    • G10K11/17823—Reference signals, e.g. ambient acoustic environment
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17857—Geometric disposition, e.g. placement of microphones
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17873—General system configurations using a reference signal without an error signal, e.g. pure feedforward
    • 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
    • G10K2210/3046—Multiple acoustic inputs, multiple acoustic outputs
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical
    • G10K2210/3216—Cancellation means disposed in the vicinity of the source
    • 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
    • G10K2210/3227—Resonators
    • G10K2210/32272—Helmholtz resonators
    • 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
    • G10K2210/509—Hybrid, i.e. combining different technologies, e.g. passive and active

Definitions

  • the invention relates to an arrangement for reducing the noise level in the interior of a motor vehicle with the features of the preamble of claim 1.
  • the invention has for its object to reduce the noise level in the interior of a vehicle in one or more frequency range (s), the frequencies of which are related to the natural cavity frequencies of the interior, by active damping of the natural cavity vibration frequencies at all locations in the vehicle interior.
  • the design of the noise sensor as a Helmholtz resonator with a microphone accommodated therein ensures stable control and suitable filtering of the recorded noise signal without a sensitive reaction to changes in the acoustic transmission behavior of the vehicle interior, which result, for example, from opening the doors, windows or sunroof .
  • the Helmholtz resonator thus acts as an acoustic filter with the advantage over conventional electronic filters that it has a very time-stable transmission behavior due to the very low filter attenuation required here.
  • the Helmholtz resonator is preferably tuned to the cavity natural frequency to be damped.
  • the damping can be done by a damping material, such as cotton, wool or the like, which is accommodated in the resonator neck or resonator volume of the Helmholtz resonator.
  • noise sensor designed according to the invention is that it can be installed very close to the loudspeaker or loudspeakers, which act as actuators in the control loop. In this way, instabilities due to feedback effects can be avoided even at high control loop gains.
  • a plurality of noise sensors with microphones accommodated in Helmholtz resonators are provided, the individual Helmholtz resonators each being matched to different natural cavity frequencies of the motor vehicle.
  • the control device can be designed very simply in the arrangement according to the invention.
  • the output signals of the noise sensors are connected in parallel, the output signal of each noise sensor being individually amplified or weakened and undergoing a phase shift.
  • the output signals of the noise sensors are then added in at least one summing amplifier and switched to the loudspeakers acting as actuators.
  • the arrangement with several noise sensors opens up the possibility of accommodating them at several locations in the vehicle interior where high sound pressures of the relevant cavity natural frequencies prevail.
  • a microphone 3 is arranged in the interior 2 of a car 1 in the driver's head area, the output signal of which is fed to a controller 4.
  • the controller 4 generates an actuating signal which is fed to a loudspeaker 5 which is also arranged in the interior, for example the loudspeaker of a radio device.
  • the sinusoidal signal in the conventional arrangement oscillates with a phase which is shifted relative to the phase of the actual signal detected by the microphone 3 such that the sound signal emitted by the loudspeaker 5 just cancels a certain frequency of the noise signal detected in the driver's head area.
  • Figure 2 shows the measured sound pressure distribution of the cavity resonance vibration with the lowest frequency of a particular motor vehicle.
  • the natural frequency of this vibration is in the order of 75 Hz for vehicles of the middle and upper class.
  • the next higher natural cavity frequency is in the range of approx. 150 Hz.
  • the numerical values for the sound pressure in decibels (db) show that the maxima of the sound pressure distribution are in the area of the front footwell (117.5 db) and in the area of the rear passenger area (113 db).
  • FIG. 3 shows a diagram with a real abscissa and an imaginary ordinate of the Nyquist stability locus of an open control loop with a profile, the implementation of which results in active damping leading to a reduction in the noise level at all locations in the vehicle interior.
  • E denotes the cavity natural frequency to be damped.
  • FIG. 4 shows schematically the structure of a simple arrangement according to the invention.
  • a noise sensor comprises a Helmholtz resonator, which is designed as a rectangular hollow body 10 with an opening 11 in a side face, and a microphone 12, which is received within the hollow body 10 and whose output signal is fed to a control device 13.
  • the control device 13 generates an actuating signal which is forwarded to a loudspeaker 14 arranged at or near the location of a sound pressure maximum (according to FIG. 2).
  • the Helmholtz resonator 10 is tuned to a specific cavity natural frequency of the respective motor vehicle to be damped, the noise level of which is to be reduced in the interior.
  • the Helmholtz resonator 10 can be embedded by a porous damping materials, such as cotton, wool or the like, are individually prepared.
  • the loudspeaker 14 is arranged in places in the interior where maximum sound pressures prevail, in the example according to FIG. 2 in the area of the rear shelf 6 or in the footwell 7, as is customary for radio loudspeakers, so that the loudspeakers which are provided anyway can be used.
  • FIG. 5 shows the filtering effect of the noise sensor with microphone 12 described in FIG. 4 in the Helmholtz resonator 10: While FIG. 5a) shows several sound pressure peaks in the range of different natural frequencies, which are detected by a simple microphone without a Helmholtz resonator, the Figure 5b) the filter effect when measured at the same location with a microphone, which is arranged according to Figure 4 in a Helmholtz resonator. This enables a targeted approach to reducing the sound pressure generated by a certain natural frequency.
  • the arrangement according to FIG. 4 is accommodated in a vehicle according to FIG. 6, for example.
  • the same reference numerals as in FIG. 4 are used in FIG. 6.
  • the noise sensor comprising the microphone 12 and the Helmholtz resonator 10 is arranged in the area of the rear shelf 6 near the rear speakers 14, which are also accommodated in this area.
  • the control device 13 has two outputs which act on the two loudspeakers 14, 14.
  • FIG. 7 shows the result of the measure according to FIG. 6, the dashed curve showing the sound pressure versus frequency without the described measures of the invention, and the solid curve showing the sound pressure in the interior versus frequency when used represent the measures according to the invention.
  • Figures 8 and 9 show arrangements with which a sound pressure reduction for several cavity natural frequencies of a vehicle is possible.
  • Four noise sensors 10a, 10b, 10c, 10d are provided with corresponding microphones 12a, 12b, 12c, 12d, which are tuned to frequencies f a , f b , f c , f d , which correspond to particularly pronounced cavity natural frequencies.
  • each sensor signal is input into a series circuit, each with an amplifier 15a to 15d, a phase shifter 16a to 16d and a filter 17a to 17d, the series circuits for the individual sensor signals lying in parallel, and in the embodiment according to FIG. 8 fed to a common summing amplifier 18 , where the sensor signals are summed and input to a power amplifier 19 for three loudspeakers 20, 21, 22.
  • the loudspeakers are arranged at various locations in the vehicle interior which are favorable for noise reduction and, as stated above, can coincide with the usual accommodation locations for the radio loudspeakers.
  • Each power amplifier 19A, 19B supplies its own group of three loudspeakers 20, 21, 22 and 23, 24, 25.
  • control device 13 can be implemented using analog or digital technology, in which case a digital computer (not shown) can take over the signal processing.
  • Characteristic of the arrangement according to FIGS. 8 and 9 is the parallel arrangement of the series circuit 15, 16, 17 for each sensor output signal. In this way, individual signal processing can be achieved in adaptation to the individual tuning of the associated noise sensor 10, 12 before the signals are combined in the summing amplifiers 18.
  • the filters 17 can comprise low-pass, high-pass, band-pass or blocking filters.
  • control device 13 is of a simple construction, as shown in FIGS. 8 and 9.

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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)

Abstract

An arrangement for diminishing the noise level within a motor vehicle comprises at least one noise sensor, at least one loudspeaker and a control device which receives the output signal of the noise sensor as an actual variable and issues an actuating signal which is fed to the loudspeaker. In order to achieve over a large frequency range an effective noise reduction which is stable with respect to changes of the acoustic transmission characteristics within the vehicle, according to the invention a microphone is mounted in a Helmholtz resonator as noise sensor and the loudspeaker or loudspeakers are arranged near to the places of maximum sound pressure of the motor vehicle cavity natural frequencies to be damped.

Description

Die Erfindung betrifft eine Anordnung zur Verminderung des Geräuschpegels im Innenraum eines Kraftfahr­zeuges mit den Merkmalen des Oberbegriffs des Anspruchs 1.The invention relates to an arrangement for reducing the noise level in the interior of a motor vehicle with the features of the preamble of claim 1.

Bei einer bekannten Anordnung dieser Art (DE-Al 31 06 029) werden mit Hilfe eines nahe dem Kopfbereich des Fahrers angeordneten Mikrofons als Geräuschsensor und eines Lautsprechers unter Verwendung eines Sinus-Generators sinusförmige Schaltsignale mit einer Frequenz erzeugt, die eine störende Frequenz im Geräuschpegel gerade aufheben soll.In a known arrangement of this type (DE-Al 31 06 029) with the help of a microphone arranged near the driver's head area as a noise sensor and a loudspeaker using a sine generator, sinusoidal switching signals are generated with a frequency that is just a disturbing frequency in the noise level should cancel.

Der Erfindung liegt die Aufgabe zugrunde, den Geräusch­pegel im Innenraum eines Fahrzeugs in einem oder mehreren Frequenzbereich(en), dessen bzw. deren Frequenzen in Zusammenhang mit den Hohlraumeigen­frequenzen des Innenraums stehen, durch aktive Dämpfung der Hohlraumeigenschwingungsfrequenzen an allen Orten des Fahrzeuginnenraums zu senken.The invention has for its object to reduce the noise level in the interior of a vehicle in one or more frequency range (s), the frequencies of which are related to the natural cavity frequencies of the interior, by active damping of the natural cavity vibration frequencies at all locations in the vehicle interior.

Zur Lösung dieser Aufgabe dienen die Merkmale des Anspruchs 1.The features of claim 1 serve to achieve this object.

Die Ausbildung des Geräuschsensors als Helmholtz-­Resonator mit einem darin untergebrachten Mikrofon gewährleistet eine stabile Regelung und geeignete Filterung des aufgenommenen Geräuschsignals ohne empfindliche Reaktion auf Veränderungen des akustischen Übertragungsverhaltens des Fahrzeuginnenraumes, die sich zum Beispiel in Folge Öffnens der Türen, der Fenster oder des Schiebedachs ergeben. Der Helmholtz-Resonator wirkt somit als akustisches Filter mit dem Vorteil gegenüber herkömmlichen elektronischen Filtern, daß er aufgrund der hier nur sehr geringen erforderlichen Filterdämpfungen ein sehr zeitstabiles Übertragungsverhalten aufweist.The design of the noise sensor as a Helmholtz resonator with a microphone accommodated therein ensures stable control and suitable filtering of the recorded noise signal without a sensitive reaction to changes in the acoustic transmission behavior of the vehicle interior, which result, for example, from opening the doors, windows or sunroof . The Helmholtz resonator thus acts as an acoustic filter with the advantage over conventional electronic filters that it has a very time-stable transmission behavior due to the very low filter attenuation required here.

Der Helmholtz-Resonator ist vorzugsweise auf die zu dämpfende Hohlraumeigenfrequenz abgestimmt. Die Dämpfung kann durch ein Dämpfungsmaterial, wie Watte, Wolle oder dergleichen erfolgen, die im Resonatorhals oder Resonatorvolumen des Helmholtz-­Resonators untergebracht ist.The Helmholtz resonator is preferably tuned to the cavity natural frequency to be damped. The damping can be done by a damping material, such as cotton, wool or the like, which is accommodated in the resonator neck or resonator volume of the Helmholtz resonator.

Ein weiterer Vorteil des erfindungsgemäß ausgebildeten Geräuschsensors besteht darin, daß er sehr nahe neben dem oder den Lautsprechern installiert werden kann, die als Stellglieder im Regelkreis wirken. Damit lassen sich auch bei hohen Regelkreisver­stärkungen Instabilitäten in Folge von Rückkopplungs­effekten vermeiden.Another advantage of the noise sensor designed according to the invention is that it can be installed very close to the loudspeaker or loudspeakers, which act as actuators in the control loop. In this way, instabilities due to feedback effects can be avoided even at high control loop gains.

Zur Geräuschminderung in einem breiten Frequenzband ist bevorzugt, wenn mehrere Geräuschsensoren mit in Helmholtz-Resonatoren untergebrachten Mikrofonen vorgesehen werden, wobei die einzelnen Helmholtz-­Resonatoren jeweils auf unterschiedliche Hohlraum­eigenfrequenzen des Kraftfahrzeuges abgestimmt sind.To reduce noise in a broad frequency band, it is preferred if a plurality of noise sensors with microphones accommodated in Helmholtz resonators are provided, the individual Helmholtz resonators each being matched to different natural cavity frequencies of the motor vehicle.

Die Regeleinrichtung läßt sich bei der Anordnung nach der Erfindung sehr einfach gestalten. Vorzugsweise liegen bei der zuletzt beschriebenen Anordnung mit mehreren Geräuschsensoren die Ausgangssignale der Geräuschsensoren in Parallelschaltung, wobei das Ausgangssignal jedes Geräuschsensors individuell verstärkt bzw. abgeschwächt wird und eine Phasen­drehung erfährt. Darauf werden die Ausgangssignale der Geräuschsensoren in mindestens einem Summier­verstärker addiert und auf die als Stellglieder wirkenden Lautsprecher geschaltet.The control device can be designed very simply in the arrangement according to the invention. Preferably in the arrangement with several noise sensors described last, the output signals of the noise sensors are connected in parallel, the output signal of each noise sensor being individually amplified or weakened and undergoing a phase shift. The output signals of the noise sensors are then added in at least one summing amplifier and switched to the loudspeakers acting as actuators.

Die Anordnung mit mehreren Geräuschsensoren eröffnet die Möglichkeit ihrer Unterbringung an mehreren Orten des Fahrzeuginnenraumes, an denen hohe Schall­drücke der betreffenden Hohlraumeigenfrequenzen herrschen.The arrangement with several noise sensors opens up the possibility of accommodating them at several locations in the vehicle interior where high sound pressures of the relevant cavity natural frequencies prevail.

Die Erfindung ist im folgenden anhand schematischer Zeichnungen an Ausführungsbeispielen mit weiteren Einzelheiten näher erläutert. Es zeigen:

  • Fig. 1 schematisch eine herkömmliche Anordnung zur Verminderung des Geräuschpegels im Innenraum eines Kraftfahrzeugs;
  • Fig. 2 die gemessene Schalldruckverteilung für die frequenzniedrigste Hohlraumresonanz­schwingung im Innenraum eines Fahrzeuges;
  • Fig. 3 die Nyquist-Stabilitätsortskurve einer gemäß der Erfindung ausgebildeten Regelein­richtung, welche eine aktive Dämpfung einer oder mehrerer Hohlraumresonanz­schwingungen eines Kraftfahrzeuges bewirkt;
  • Fig. 4 ein Teilschema einer einfachen Anordnung gemäß der Erfindung;
  • Fig. 5 eine Gegenüberstellung von Diagrammen, wobei das Diagramm nach Figur 5a den mittels eines Mikrofones erfaßten Schalldruck über der Frequenz und Figur 5b den mittels eines Geräuschsensors nach der Erfindung erfaßten Schalldruck über der Frequenz darstellen;
  • Fig. 6 eine schematische Draufsicht auf ein Kraftfahrzeug, aus der die Orte der Unter­bringung von Geräuschsensor und Lautsprechern bei einer Anordnung nach der Erfindung ersichtlich sind;
  • Fig. 7 ein Vergleichsdiagramm, welches den Verlauf des Schalldruckes über der Frequenz in einem Kraftfahrzeug ohne die Anordnung nach der Erfindung und mit einer Anordnung gemäß Figur 4 bzw. Figur 6 darstellt; und
  • Fig. 8, 9 Blockschaltbilder zweier Anordnungen gemäß der Erfindung mit jeweils vier Geräuschsensoren und mehreren Lautsprechern.
The invention is explained in more detail below with reference to schematic drawings of exemplary embodiments. Show it:
  • 1 schematically shows a conventional arrangement for reducing the noise level in the interior of a motor vehicle;
  • 2 shows the measured sound pressure distribution for the lowest-frequency cavity resonance vibration in the interior of a vehicle;
  • 3 shows the Nyquist stability locus of a control device designed according to the invention, which actively dampens one or more cavity resonance vibrations of a motor vehicle;
  • Fig. 4 is a partial schematic of a simple arrangement according to the invention;
  • 5 shows a comparison of diagrams, the diagram according to FIG. 5a representing the sound pressure versus frequency detected by means of a microphone and FIG. 5b the sound pressure versus frequency detected using a noise sensor according to the invention;
  • 6 shows a schematic plan view of a motor vehicle, from which the locations of the accommodation of the noise sensor and loudspeakers in an arrangement according to the invention can be seen;
  • 7 shows a comparison diagram which shows the course of the sound pressure over the frequency in a motor vehicle without the arrangement according to the invention and with an arrangement according to FIG. 4 or FIG. 6; and
  • 8, 9 block diagrams of two arrangements according to the invention, each with four noise sensors and several speakers.

Bei der Anordnung nach Figur 1 ist im Innenraum 2 eines PKW 1 im Kopfbereich des Fahrers ein Mikrofon 3 angeordnet, dessen Ausgangssignal einem Regler 4 zugeführt wird. Der Regler 4 erzeugt ein Stellsignal, das zu einem ebenfalls im Innenraum angeordneten Lautsprecher 5, beispielsweise dem Lautsprecher eines Radiogerätes, zugeführt wird.In the arrangement according to FIG. 1, a microphone 3 is arranged in the interior 2 of a car 1 in the driver's head area, the output signal of which is fed to a controller 4. The controller 4 generates an actuating signal which is fed to a loudspeaker 5 which is also arranged in the interior, for example the loudspeaker of a radio device.

Das bei der konventionellen Anordnung sinusförmige Signal schwingt mit einer Phase, welche gegenüber der Phase des mittels des Mikrofons 3 erfaßten Istsignals gerade so verschoben ist, daß das vom Lautsprecher 5 abgestrahlte Schallsignal eine bestimmte Frequenz des im Kopfbereich des Fahrers erfaßten Geräuschsignals gerade aufhebt.The sinusoidal signal in the conventional arrangement oscillates with a phase which is shifted relative to the phase of the actual signal detected by the microphone 3 such that the sound signal emitted by the loudspeaker 5 just cancels a certain frequency of the noise signal detected in the driver's head area.

Figur 2 zeigt die gemessene Schalldruckverteilung der Hohlraumresonanzschwingung mit der tiefsten Frequenz eines bestimmten Kraftfahrzeuges. Die Eigenfrequenz dieser Schwingung liegt bei Fahrzeugen der Mittel- und Oberklasse in der Größenordnung von 75Hz. Die nächsthöhere Hohlraumeigenfrequenz liegt im Bereich von ca. 150Hz. Die Zahlenwerte für den Schalldruck in Dezibel (db) zeigen, daß die Maxima der Schalldruckverteilung im Bereich des vorderen Fußraumes (117,5 db) und im Bereich des hinteren Fahrgastraumes (113 db) liegen.Figure 2 shows the measured sound pressure distribution of the cavity resonance vibration with the lowest frequency of a particular motor vehicle. The natural frequency of this vibration is in the order of 75 Hz for vehicles of the middle and upper class. The next higher natural cavity frequency is in the range of approx. 150 Hz. The numerical values for the sound pressure in decibels (db) show that the maxima of the sound pressure distribution are in the area of the front footwell (117.5 db) and in the area of the rear passenger area (113 db).

Figur 3 zeigt in einem Diagramm mit realer Abszisse und imaginärer Ordinate die Nyquist-Stabilitäts­ortskurve eines offenen Regelkreises mit einem Verlauf, bei dessen Verwirklichung eine aktive Dämpfung zu einer Geräuschpegelverringerung an allen Orten des Fahrzeuginnenraumes führt. Mit E ist die zu dämpfende Hohlraumeigenfrequenz bezeichnet.FIG. 3 shows a diagram with a real abscissa and an imaginary ordinate of the Nyquist stability locus of an open control loop with a profile, the implementation of which results in active damping leading to a reduction in the noise level at all locations in the vehicle interior. E denotes the cavity natural frequency to be damped.

Figur 4 zeigt schematisch den Aufbau einer einfachen Anordnung gemäß der Erfindung. Dabei umfaßt ein Geräuschsensor einen Helmholtz-Resonator, der als rechteckiger Hohlkörper 10 mit einer Öffnung 11 in einer Seitenfläche ausgebildet ist, und ein Mikrofon 12, das innerhalb des Hohlkörpers 10 aufge­nommen ist und dessen Ausgangssignal zu einer Regelein­richtung 13 geführt wird. Die Regeleinrichtung 13 erzeugt ein Stellsignal, welches zu einem am oder nahe dem Ort eines Schalldruckmaximums (gemäß Figur 2) angeordneten Lautsprecher 14 weitergeleitet wird. Der Helmholtz-Resonator 10 ist auf eine be­stimmte zu dämpfende Hohlraumeigenfrequenz des jeweiligen Kraftfahrzeugs abgestimmt, dessen Geräusch­pegel im Innenraum abgesenkt werden soll. Zum Erzeugen einer geeigneten Charakteristik kann der Helmholtz-­Resonator 10 durch Einbetten eines porösen Dämpfungs­ materials, wie Watte, Wolle oder dergleichen, individuell präpariert werden.Figure 4 shows schematically the structure of a simple arrangement according to the invention. In this case, a noise sensor comprises a Helmholtz resonator, which is designed as a rectangular hollow body 10 with an opening 11 in a side face, and a microphone 12, which is received within the hollow body 10 and whose output signal is fed to a control device 13. The control device 13 generates an actuating signal which is forwarded to a loudspeaker 14 arranged at or near the location of a sound pressure maximum (according to FIG. 2). The Helmholtz resonator 10 is tuned to a specific cavity natural frequency of the respective motor vehicle to be damped, the noise level of which is to be reduced in the interior. In order to generate a suitable characteristic, the Helmholtz resonator 10 can be embedded by a porous damping materials, such as cotton, wool or the like, are individually prepared.

Der Lautsprecher 14 ist an Orten im Innenraum ange­ordnet, an denen maximale Schalldrücke herrschen, bei dem Beispiel gemäß Figur 2 im Bereich der Hutablage 6 oder im Fußraum 7, wie für Radiolautsprecher üblich, so daß die ohnehin vorgesehenen Lautsprecher Verwendung finden können.The loudspeaker 14 is arranged in places in the interior where maximum sound pressures prevail, in the example according to FIG. 2 in the area of the rear shelf 6 or in the footwell 7, as is customary for radio loudspeakers, so that the loudspeakers which are provided anyway can be used.

Figur 5 zeigt den Filterungseffekt des anhand der Figur 4 beschriebenen Geräuschsensors mit Mikrofon 12 im Helmholtz-Resonator 10: Während in Figur 5a) mehrere Schalldruckspitzen im Bereich verschiedener Eigenfrequenzen zu erkennen sind, die durch ein einfaches Mikrofon ohne Helmholtz-Resonator erfaßt werden, zeigt die Figur 5b) den Filtereffekt bei Messung am gleichen Ort mit einem Mikrofon, das gemäß Figur 4 in einem Helmholtz-Resonator angeordnet ist. Dies ermöglicht einen gezielten Ansatz zur Minderung des durch eine bestimmte Eigenfrequenz erzeugten Schalldruckes.FIG. 5 shows the filtering effect of the noise sensor with microphone 12 described in FIG. 4 in the Helmholtz resonator 10: While FIG. 5a) shows several sound pressure peaks in the range of different natural frequencies, which are detected by a simple microphone without a Helmholtz resonator, the Figure 5b) the filter effect when measured at the same location with a microphone, which is arranged according to Figure 4 in a Helmholtz resonator. This enables a targeted approach to reducing the sound pressure generated by a certain natural frequency.

Die Anordnung nach Figur 4 ist beispielsweise gemäß Figur 6 in einem Fahrzeug untergebracht. In Figur 6 sind gleiche Bezugszeichen wie in Figur 4 verwendet. Der Geräuschsensor aus Mikrofon 12 und Helmholtz-­Resonator 10 ist im Bereich der Hutablage 6 nahe den ebenfalls in diesem Bereich untergebrachten Heck-Lautsprechern 14 angeordnet. Die Regeleinrichtung 13 hat in diesem Fall zwei Ausgänge, die auf die beiden Lautsprecher 14, 14 wirken.The arrangement according to FIG. 4 is accommodated in a vehicle according to FIG. 6, for example. The same reference numerals as in FIG. 4 are used in FIG. 6. The noise sensor comprising the microphone 12 and the Helmholtz resonator 10 is arranged in the area of the rear shelf 6 near the rear speakers 14, which are also accommodated in this area. In this case, the control device 13 has two outputs which act on the two loudspeakers 14, 14.

Figur 7 zeigt das Ergebnis der Maßnahme nach Figur 6, wobei die gestrichelte Kurve den Schalldruck über der Frequenz ohne die geschilderten Maßnahmen der Erfindung und die durchgezogene Kurve den Schall­druck im Innenraum über der Frequenz bei Anwendung der Maßnahmen nach der Erfindung darstellen.FIG. 7 shows the result of the measure according to FIG. 6, the dashed curve showing the sound pressure versus frequency without the described measures of the invention, and the solid curve showing the sound pressure in the interior versus frequency when used represent the measures according to the invention.

Die Figuren 8 und 9 zeigen Anordnungen, mit denen eine Schalldruckminderung für mehrere Hohlraumeigen­frequenzen eines Fahrzeuges möglich ist.Figures 8 and 9 show arrangements with which a sound pressure reduction for several cavity natural frequencies of a vehicle is possible.

Dabei sind vier Geräuschsensoren 10a, 10b, 10c, 10d mit entsprechenden Mikrofonen 12a, 12b, 12c, 12d vorgesehen, die auf Frequenzen fa, fb, fc, fd abgestimmt sind, welche besonders ausgeprägten Hohlraumeigenfrequenzen entsprechen.Four noise sensors 10a, 10b, 10c, 10d are provided with corresponding microphones 12a, 12b, 12c, 12d, which are tuned to frequencies f a , f b , f c , f d , which correspond to particularly pronounced cavity natural frequencies.

Die Ausgangssignale der Mikrofone 12a bis 12d werden in die wie auch in den Figuren 8 und 9 mit 13 bezeich­nete Regeleinrichtung eingegeben. Hier wird jedes Sensorsignal in eine Reihenschaltung mit jeweils einem Verstärker 15a bis 15d, einem Phasenschieber 16a bis 16d und einem Filter 17a bis 17d eingegeben, wobei die Reihenschaltungen für die einzelnen Sensor­signale parallel liegen, und bei der Ausführung nach Figur 8 einem gemeinsamen Summierverstärker 18 zugeführt, wo die Sensorsignale summiert und einem Leistungsverstärker 19 für drei Lautsprecher 20, 21, 22 eingegeben werden. Die Lautsprecher sind an verschiedenen, für die Geräuschminderung günstigen Orten im Fahrzeuginnenraum angeordnet, die sich, wie oben angegeben, mit den üblichen Unterbringungsorten für die Radiolautsprecher decken können.The output signals of the microphones 12a to 12d are input into the control device designated 13 as in FIGS. 8 and 9. Here, each sensor signal is input into a series circuit, each with an amplifier 15a to 15d, a phase shifter 16a to 16d and a filter 17a to 17d, the series circuits for the individual sensor signals lying in parallel, and in the embodiment according to FIG. 8 fed to a common summing amplifier 18 , where the sensor signals are summed and input to a power amplifier 19 for three loudspeakers 20, 21, 22. The loudspeakers are arranged at various locations in the vehicle interior which are favorable for noise reduction and, as stated above, can coincide with the usual accommodation locations for the radio loudspeakers.

Die Ausführung nach Figur 9, in der für gleiche Bauteile gleiche Bezugszeichen wie in Figur 8 verwendet sind, unterscheidet sich von der Ausführung nach Figur 8 dadurch, daß die verstärkten, phasenver­schobenen und gefilterten Sensorsignale in zwei parallel geschaltete Summierverstärker 18A und 18B mit jeweils nachgeschalteten Leistungsverstärkern 19A und 19B eingegeben werden. Jeder Leistungsver­stärker 19A, 19B versorgt eine eigene Gruppe von jeweils drei Lautsprechern 20, 21, 22 und 23, 24, 25.The embodiment according to FIG. 9, in which the same reference numerals as in FIG. 8 are used for the same components, differs from the embodiment according to FIG. 8 in that the amplified, phase-shifted and filtered sensor signals are divided into two summing amplifiers 18A and 18B connected in parallel, each with downstream power amplifiers 19A and 19B can be entered. Each power amplifier 19A, 19B supplies its own group of three loudspeakers 20, 21, 22 and 23, 24, 25.

Die Regeleinrichtung 13 kann bei allen beschriebenen Ausführungen in analoger oder digitaler Technik ausgeführt sein, wobei im letzteren Falle ein nicht gezeigter digitaler Rechner die Signalverarbeitung übernehmen kann.In all the embodiments described, the control device 13 can be implemented using analog or digital technology, in which case a digital computer (not shown) can take over the signal processing.

Charakteristisch für die Anordnung nach den Figuren 8 und 9 ist die parallele Anordnung der Reihen­schaltung 15, 16, 17 für jedes Sensorausgangs­signal. Hierdurch läßt sich eine individuelle Signal­verarbeitung in Anpassung an die individuelle Abstimmung des zugehörigen Geräuschsensors 10, 12 vor der Zusammenfassung der Signale in den Summier­verstärkern 18 erzielen.Characteristic of the arrangement according to FIGS. 8 and 9 is the parallel arrangement of the series circuit 15, 16, 17 for each sensor output signal. In this way, individual signal processing can be achieved in adaptation to the individual tuning of the associated noise sensor 10, 12 before the signals are combined in the summing amplifiers 18.

Die Filter 17 können entsprechend dem Stand der Technik Tiefpaß-, Hochpaß-, Bandpaß- bzw. Sperrfilter umfassen.According to the prior art, the filters 17 can comprise low-pass, high-pass, band-pass or blocking filters.

Auch bei Anordnung mehrerer Geräuschsensoren ergibt sich ein einfacher Aufbau der Regeleinrichtung 13, wie die Figuren 8 und 9 zeigen.Even if several noise sensors are arranged, the control device 13 is of a simple construction, as shown in FIGS. 8 and 9.

Claims (11)

1. Anordnung zur Verminderung des Geräuschpegels im Innenraum eines Kraftfahrzeugs mit mindestens einem Geräuschsensor, mindestens einem Laut­sprecher und einer Regeleinrichtung, die als Istgröße das Ausgangssignal des Geräuschsensors erhält und ein den Lautsprecher beaufschlagendes Stellsignal abgibt, dadurch gekennzeichnet, daß als Geräuschsensor ein in einem Helmholtz-­Resonator (10) untergebrachtes Mikrofon (12) verwendet ist und daß der Lautsprecher (14; 20-22;20-25) an oder nahe dem Ort maximalen Schalldruckes von zu dämpfenden Hohlraumeigenfreq­quenzen des Kraftfahrzeuges angeordnet ist.1. Arrangement for reducing the noise level in the interior of a motor vehicle with at least one noise sensor, at least one loudspeaker and a control device which receives the output signal of the noise sensor as an actual variable and emits an actuating signal acting on the loudspeaker, characterized in that a noise sensor in a Helmholtz Resonator (10) housed microphone (12) is used and that the loudspeaker (14; 20-22; 20-25) is arranged at or near the location of maximum sound pressure of cavity natural frequencies of the motor vehicle to be damped. 2. Anordnung nach Anspruch 1, dadurch gekennzeichnet, daß die Nyquist-Stabilitätsortskurve des Frequenz­gangs vom offenen Regelkreis die positive reelle Achse bei einer Frequenz schneidet, die mit der Eigenfrequenz (E) einer Hohlraumresonanz übereinstimmt.2. Arrangement according to claim 1, characterized in that the Nyquist stability locus of the frequency response from the open control loop intersects the positive real axis at a frequency which corresponds to the natural frequency (E) of a cavity resonance. 3. Anordnung nach Anspruch 1 oder 2, dadurch gekenn­zeichnet, daß mehrere Lautsprecher (20-22;20-25) im Bereich der Hutablage (6) und/oder im vorderen Fußbereich (7) angeordnet sind.3. Arrangement according to claim 1 or 2, characterized in that a plurality of loudspeakers (20-22; 20-25) are arranged in the region of the parcel shelf (6) and / or in the front region of the foot (7). 4. Anordnung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der Helmholtz-Resonator (10) auf die zu dämpfende Hohlraumeigenfrequenz abgestimmt ist.4. Arrangement according to one of claims 1 to 3, characterized in that the Helmholtz resonator (10) is tuned to the cavity natural frequency to be damped. 5. Anordnung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß ein Dämpfungsmaterial, wie Watte, Wolle oder dergleichen, im Resonatorhals oder Resonatorvolumen des Helmholtz-Resonators (10) untergebracht ist.5. Arrangement according to one of claims 1 to 4, characterized in that a damping material, such as cotton, wool or the like, is housed in the resonator neck or resonator volume of the Helmholtz resonator (10). 6. Anordnung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß der Helmholtz-Resonator (10) mit Mikrofon (12) nahe dem oder den Laut­sprechern (14;20-22;20-25) angeordnet ist.6. Arrangement according to one of claims 1 to 5, characterized in that the Helmholtz resonator (10) with microphone (12) near the one or more speakers (14; 20-22; 20-25) is arranged. 7. Anordnung nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß mehrere Geräuschsensoren mit in Helmholtz-Resonatoren (10a-10d) unter­gebrachten Mikrofonen (12a-12d) vorgesehen sind, wobei die einzelnen Helmholtz-Resonatoren jeweils auf unterschiedliche Hohlraum-Eigenfrequenzen des Kraftfahrzeugs abgestimmt sind.7. Arrangement according to one of claims 1 to 6, characterized in that a plurality of noise sensors with in Helmholtz resonators (10a-10d) housed microphones (12a-12d) are provided, the individual Helmholtz resonators each having different natural cavity frequencies Motor vehicle are matched. 8. Anordnung nach Anspruch 7, dadurch gekennzeichnet, daß die Ausgangssignale der Geräuschsensoren in Parallelschaltung liegen, wobei das Ausgangs­signal jedes Geräuschsensors in eine Reihen­schaltung aus einem Verstärker (15a-15d), einem Phasenschieber (16a-16d) und gegebenenfalls einem Filter (17a-17d) oder einer Filtereinheit (Tiefpaß, Hochpaß, Bandpaß) eingegeben wird.8. Arrangement according to claim 7, characterized in that the output signals of the noise sensors are connected in parallel, the output signal of each noise sensor in a series circuit comprising an amplifier (15a-15d), a phase shifter (16a-16d) and optionally a filter (17a- 17d) or a filter unit (low pass, high pass, band pass) is entered. 9. Anordnung nach Anspruch 7 oder 8, dadurch gekenn­zeichnet, daß die Ausgangssignale der Geräusch­sensoren in mindestens einem Summierverstärker (18;18A,18B) addiert werden.9. Arrangement according to claim 7 or 8, characterized in that the output signals of the noise sensors in at least one summing amplifier (18; 18A, 18B) are added. 10. Anordnung nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die Regeleinrichtung (13) analog arbeitet.10. Arrangement according to one of claims 1 to 9, characterized in that the control device (13) works analogously. 11. Anordnung nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die Regeleinrichtung (13) einen digitalen Rechner enthält, der die analog erfaßten und in digitale Signale gewandelten Geräuschsignale nach einem eingespeicherten Programm verarbeitet.11. Arrangement according to one of claims 1 to 9, characterized in that the control device (13) contains a digital computer which processes the analog detected and converted into digital signals noise signals according to a stored program.
EP89106308A 1988-05-18 1989-04-10 Arrangement for diminishing the noise level within a motor car Expired - Lifetime EP0342353B1 (en)

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DE3816921A DE3816921A1 (en) 1988-05-18 1988-05-18 ARRANGEMENT FOR REDUCING NOISE LEVEL IN THE INTERIOR OF A MOTOR VEHICLE
DE3816921 1988-05-18

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GB2234137B (en) * 1989-07-18 1994-01-12 Messerschmitt Boelkow Blohm A device for the detection and location of sound waves
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DE102004016689A1 (en) * 2004-04-05 2005-10-27 Volkswagen Ag Improvement of acoustic situation in passenger cabin of vehicle, comprising use of Helmholtz-resonators
DE102007032600A1 (en) * 2007-07-11 2009-01-15 Deutsches Zentrum für Luft- und Raumfahrt e.V. Apparatus and method for improving the attenuation of acoustic waves
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GB2234137B (en) * 1989-07-18 1994-01-12 Messerschmitt Boelkow Blohm A device for the detection and location of sound waves
DE4015313A1 (en) * 1990-05-12 1991-11-14 Opel Adam Ag ACTIVE NOISE REDUCTION SYSTEM FOR THE INTERIOR OF MOTOR VEHICLES
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EP0457176A3 (en) * 1990-05-12 1992-09-02 Adam Opel Aktiengesellschaft Active noise reduction system for the interior of motor vehicles
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EP0916536A3 (en) * 1997-11-13 2000-12-20 DORNIER GmbH Method for reducing the periodical pressure variations of an external stream flowing around the opening of a cavity

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EP0342353A3 (en) 1991-03-20
DE3816921A1 (en) 1989-11-30
DE58905218D1 (en) 1993-09-16

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