EP2485504B1 - Generation of quiet areas within the listener zone of multi-channel playback systems - Google Patents
Generation of quiet areas within the listener zone of multi-channel playback systems Download PDFInfo
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- EP2485504B1 EP2485504B1 EP20110153510 EP11153510A EP2485504B1 EP 2485504 B1 EP2485504 B1 EP 2485504B1 EP 20110153510 EP20110153510 EP 20110153510 EP 11153510 A EP11153510 A EP 11153510A EP 2485504 B1 EP2485504 B1 EP 2485504B1
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- 230000015572 biosynthetic process Effects 0.000 description 9
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- 230000005404 monopole Effects 0.000 description 3
- 238000009877 rendering Methods 0.000 description 3
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
- H04S7/30—Control circuits for electronic adaptation of the sound field
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2203/00—Details of circuits for transducers, loudspeakers or microphones covered by H04R3/00 but not provided for in any of its subgroups
- H04R2203/12—Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
- H04S2420/11—Application of ambisonics in stereophonic audio systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
- H04S2420/13—Application of wave-field synthesis in stereophonic audio systems
Definitions
- the present invention relates to the reproduction of an acoustic wave field in a listener zone by means of several loudspeakers, and more particularly to the formation of a wave-free section within the listener zone.
- the derivation of the control functions in Higher-Order Ambisonics is done by explicitly solving the underlying physical problem.
- the speakers are characterized by a circular or spherical continuous distribution of typically models acoustic monopoles that are assigned a weighting function.
- the integral equation following from this approach can be solved by the representation of the relevant acoustic fields in the form of spherical harmonics.
- Higher-order Ambisonics allows, in principle, the exact reconstruction of almost any sound field within the secondary source distribution.
- the continuous distribution of monopoles is realized by a spatially discrete distribution of a finite number of loudspeakers.
- spectral division Spectral Division Method SDM, see for example J. Ahrens and S. Spors. Sound field reproduction using planar and linear arrays of loudspeakers. IEEE Transactions on Audio, Speech and Language Processing, 18 (8): 2038 - 2050, November 2010 , doi: 10.1109 / TASL.2010.2041106) represents in principle a transfer of the higher-order Ambisonics approach to planar and linear geometries.
- SDM the underlying physical problem, formulated as an integral equation, is explicitly solved. The solution is achieved by the transition into the spatial spectral range by means of a spatial Fourier transformation. As with Higher-Order Ambisonics, the speaker drive functions in this range are calculated by spectral division.
- the propagation function (Green's function) of the loudspeakers is needed. After back transformation of the control function from the spectral range to the local area, this is then available for implementation.
- the thick black ring indicates the arrangement of the loudspeakers, which in the example shown are thus arranged in a circle around the listener zone.
- the desired wave field is a plane wave that is displayed on the left side of the listener zone.
- On the right is a small ring in which the sound field is suppressed.
- the location of the quiet zones in the listener zone or the arrangement of the loudspeakers should be subject to as few restrictions as possible.
- the object of the invention is achieved by in the method and a device according to claims 1 and 8, respectively.
- the invention provides a method for reproducing an acoustic wave field in a listener zone by means of several loudspeakers.
- Applying a spatial window function, such as a rectangular function, to the wave field to be rendered defines a wave-free section in the listener zone in which the wave field is suppressed. This can be done for example by a multiplication of the target sound field with the window function, this corresponds to a spatial convolution in the spatial frequency range.
- the determination of the drive signals may be performed by a higher order Ambisonics method or a spectral division method.
- the desired wave field is bandlimited to increase the quality of the suppression of the sound field in the corresponding area of the listener zone.
- the invention provides a corresponding device for reproducing an acoustic wave field in the listener zone, wherein the wave field is suppressed in one or more predetermined sections of the listener zone.
- the loudspeakers may be arranged on an open contour, in particular a line, or else on a contour surrounding the listener zone, that is to say for example on a circle or a rectangle.
- All methods of multi-channel acoustic reproduction systems use a pre-defined mixing matrix which maps the source signals to particular loudspeaker signals to produce a desired auditory impression.
- the derivation of the control functions in Higher-Order Ambisonics and SDM is done by explicitly solving the underlying physical problem.
- the suppression of the wave field in certain zones can be interpreted as a multiplication of the original desired field with certain spatial window functions that suppress the sound field in certain areas.
- this spatial multiplication is a spectral convolution and the spatial suppression is therefore done by a suitable spectral spread of the spatial spectrum of the reproduced spatial signal.
- the synthesized sound field can be understood as the result of a spatial convolution integral.
- P x ⁇ ⁇ ⁇ - ⁇ ⁇ D x 0 ⁇ ⁇ ⁇ G ⁇ x - x 0 . ⁇ d x 0 .
- D represents the drive function of the secondary sources
- the synthesized sound field corresponds to the desired sound field.
- the quality of the suppression of the sound field in a certain area depends on the spatial aliasing frequency of the playback system and the cut-off frequency of the reproduced material, because only the spectral components of the reproduced material, which are below the aliasing frequency of the system can be selectively suppressed.
- a band limitation of the material to be reproduced can be used to avoid spatial aliasing.
- the mixing matrix on the reproduction side is determined frequency-selectively on the basis of the desired wave field, the position of the recording system and the geometry of the reproduction system.
- a linear loudspeaker array is discussed, wherein the interception zone with two virtual lines, which are perpendicular to the array, should be divided into three areas. In one area, conventional flat wave reproduction should be based on the spectral division method. In the two other areas in which the recording system can be located, the wave field should be suppressed.
- the desired wave field is a multiplication of the plane waves with the spatial rectangular function or another suitable window function.
- the method of spectral division is used. This method requires an expression for both the desired wave field and Green's function in the spatially transformed region for linear array geometries. by means of the Fourier transformation along a reference line on which the reproduction should be exact.
- the driving functions in the spatial spectral range are the result of element-wise division of the spectrum of the desired field by the spectrum of Green's function.
- the thus determined spectra of the drive functions can be transformed back into the spatial domain by means of an inverse Fourier transformation.
- Fig. 1 is the result of a simulation of the presented method and shown in Fig. 2 you can see the energy distribution of the wave field.
- Fig. 3 the energy distribution is reproduced when the quiet zone, ie the wave-free section, divides the display area into two areas.
- Array geometries that enclose the audience space in two dimensions, such as rectangular arrays, allow two-dimensional suppression of the field.
- An example of this is in Fig. 4 shown.
- the procedure for carrying out the method according to the invention is similar to that described above.
- the main difference is that the window function here is two-dimensional.
- the spatially limited wave field is in the spectral range a two-dimensional convolution of the desired field with the spatially transformed window function.
- the in Fig. 4 Wave field shown a superposition of plane waves, wherein in the synthesis of the individual plane waves, the desired resting area was explicitly considered.
- the driving functions of the speakers for the in. Fig. 4 The plane waves shown were determined by means of the aforementioned method of spectral division.
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Description
Die vorliegende Erfindung betrifft die Wiedergabe eines akustischen Wellenfelds in einer Zuhörerzone mittels mehrerer Lautsprecher, und insbesondere die Ausbildung eines wellenfreien Abschnitts innerhalb der Zuhörerzone.The present invention relates to the reproduction of an acoustic wave field in a listener zone by means of several loudspeakers, and more particularly to the formation of a wave-free section within the listener zone.
Neben den bekannten stereophonischen Verfahren zur Schallwiedergabe gewinnen Verfahren, die eine physikalische Rekonstruktion eines beliebigen Wellenfeldes anstreben, in Forschung und Praxis an Bedeutung. Von besonderem Interesse sind Verfahren, die eine analytische Berechnung des Ansteuerungssignals für die Lautsprecher ermöglichen. Dies ist unter anderem bei der Wellenfeldsyntlzese und Higher-Order Ambisonics der Fall. Diese beiden Verfahren haben das gemeinsame Ziel, ein Wunschfeld in einem ausgedehnten Gebiet zu synthetisieren, so dass ein räumlicher Eindruck in einem, verglichen mit konventionellen stereophonischen Verfahren, relativ großen homogenen Zuhörerbereich hervorgerufen wird. Idealerweise umfasst der Zuhörerbereich die gesamte Fläche, die von den Lautsprechern umgeben ist.In addition to the known stereophonic methods for sound reproduction, methods aiming at a physical reconstruction of any wave field are gaining in importance in research and practice. Of particular interest are methods that allow analytic calculation of the drive signal for the speakers. This is the case, among others, with the Wellenfeldsyntlzese and Higher-Order Ambisonics. These two methods have the common goal of synthesizing a desired field in a broad area, so as to create a spatial impression in a relatively large homogeneous listening area compared to conventional stereophonic methods. Ideally, the listener area covers the entire area surrounded by the speakers.
Die physikalische Basis beider Verfahren beruht auf der Annahme einer kontinuierlichen Verteilung von Schallquellen um den zu beschallenden Zuhörerbereich. Die praktische Realisierung durch eine endliche Anzahl von räumlich diskreten Lautsprechern muss explizit berücksichtigt werden. Im Folgenden wird kurz auf die Theorie von Higher-Order Ambisonics und der Wellenfeldsynthese eingegangen, wobei die wiedergegebenen Quellen der auditiven Szene als virtuelle Quellen und die zur Wiedergabe verwendeten Lautsprecher als Sekundärquellen bezeichnet werden.The physical basis of both methods is based on the assumption of a continuous distribution of sound sources around the audience area to be sounded. The practical realization by a finite number of spatially discrete loudspeakers must be explicitly considered. In the following, the theory of Higher-Order Ambisonics and Wave Field Synthesis will be briefly discussed, with the reproduced sources of the auditory scene as virtual sources and the speakers used for reproduction as secondary sources.
Die Herleitung der Ansteuerungsfunktionen bei Higher-Order Ambisonics erfolgt durch die explizite Lösung des zugrundeliegenden physikalischen Problems. Dazu werden die Lautsprecher durch eine kreis- oder kugelförmige kontinuierliche Verteilung von typischerweise akustischen Monopolen modelliert, die mit einer Gewichtungsfunktion belegt sind. Die aus diesem Ansatz folgende Integralgleichung kann durch die Darstellung der relevanten akustischen Felder in Form von sphärischen Harmonischen gelöst werden. Higher-Order Ambisonics ermöglicht im Prinzip die exakte Rekonstruktion eines nahezu beliebigen Schallfeldes innerhalb der Sekundärquellenverteilung. In der Praxis wird die kontinuierliche Verteilung von Monopolen jedoch durch eine räumlich diskrete Verteilung einer endlichen Anzahl von Lautsprechern realisiert. Ein Überblick über Higher-Order Ambisonics kann beispielsweise der Arbeit von
Das Verfahren der spektralen Division (Spectral Division Method SDM, siehe beispielsweise
Die physikalische Grundlage der Wellenfeldsynthese beruht qualitativ auf dem Huygens-Fresnel'schen Prinzip und quantitativ auf den Rayleigh Integralen (siehe beispielsweise
Wie bei Higher-Order Ambisonics und SDM geht auch die Theorie der Wellenfeldsynthese von einer räumlich kontinuierlichen Verteilung der Sekundärquellen aus. In der Praxis werden jedoch räumlich diskrete Verteilungen von Lautsprechern verwendet. Diese räumliche Diskretisierung führt zu einer Reihe von Artefakten im Zuhörerbereich.As with Higher-Order Ambisonics and SDM, the theory of wave field synthesis assumes a spatially continuous distribution of secondary sources. In practice, however, spatially discrete distributions of loudspeakers are used. This spatial discretization leads to a number of artifacts in the audience.
Für einige Anwendungen kann es interessant sein, eine Ruhezone innerhalb eines Zielbeschallungsbereichs, also der Zuhörerzone, vorzusehen, oder auch die Wiedergabe in einem begrenzten Bereich umgeben von einer Ruhezone. Beispielhaft seien folgende mögliche Anwendungen genannt:
- 1 Wiedergabe in einem begrenzten Bereich umgeben von einer Ruhezonen. Zum Beispiel in einem Büro, Wohnzimner, etc.
- 2 Konstruktion von akustisch getrennten Bereichen, um verschiedene Inhalte in einem physikalisch offenen Gebiet so wiederzugeben, dass sich die Inhalte nicht vermischen. Zum Beispiel für die Wiedergabe von Stereosignalen ohne die Verwendung von Kopfhörern.
- 3 Minimieren des Einflusses des Raumes, in dem die Wiedergabe stattfinden soll. Eine Möglichkeit dies zu erzielen ist, die Reflektion an den Wänden zu verhindern, indem die Energie des Schallfeldes nahe den Wänden minimiert wird.
- 4 Unterdrückung des Schallfeldes in einem Ort, in dem sich ein Aufnahmesystem befindet, um Rückkopplungseffekte zu unterdrücken.
- 1 Play in a limited area surrounded by quiet areas. For example in an office, living room, etc.
- 2 Construction of acoustically separated areas to render different contents in a physically open area so that the contents do not mix. For example, for the playback of stereo signals without the use of headphones.
- 3 Minimizing the influence of the room in which the playback is to take place. One way to do this is to prevent reflection on the walls by minimizing the energy of the sound field near the walls.
- 4 Suppression of the sound field in a location where a recording system is located to suppress feedback effects.
Ansätze zur Erzeugung von Ruhezonen, (acoustic contrast control) sind zum Beispiel aus dem Dokument von
Auch existieren auf Higher-Order Ambisonics basierende Verfahren. So wird in
Es ist eine Aufgabe der vorliegenden Erfindung, die Einschränkungen des Standes der Technik auszuräumen und ein verbessertes Verfahren und eine Vorrichtung zur Unterdrückung des Schallfeldes in bestimmten Bereichen der Zuhörerzone, die auch als Ruhezonen bezeichnet werden, bei gleichzeitiger Synthetisierung eines wiederzugebenden Feldes in einem Zielbereich ― also außerhalb der Ruhezonen ― bereitzustellen. Die Lage der Ruhezonen in der Zuhörerzone bzw. die Anordnung der Lautsprecher soll hierbei möglichst wenigen Einschränkungen unterliegen. Die Aufgabe der Erfindung wird durch im Verfahren bzw. eine Vorrichtung gemäß der Ansprüche 1 bzw. 8 gelöst.It is an object of the present invention to overcome the limitations of the prior art and an improved method and apparatus for suppressing the sound field in certain areas of the listener zone, also referred to as quiet zones, while synthesizing a field to be displayed in a target area - ie outside the quiet zones - provide. The location of the quiet zones in the listener zone or the arrangement of the loudspeakers should be subject to as few restrictions as possible. The object of the invention is achieved by in the method and a device according to
Mit der Erfindung wird ein Verfahren zur Wiedergabe eines akustischen Wellenfelds in einer Zuhörerzone mittels mehrerer Lautsprecher bereitgestellt. Durch Anwenden einer räumlichen Fensterfunktion, beispielsweise einer Rechteckfunktion, auf das wiederzugebende Wellenfeld wird ein wellenfreier Abschnitt in der Zuhörerzone definiert, in dem das Wellenfeld unterdrückt wird. Dies kann beispielsweise durch eine Multiplikation des Zielschallfeldes mit der Fensterfunktion geschehen, dies entspricht einer räumlichen Faltung im räumlichen Frequenzbereich.The invention provides a method for reproducing an acoustic wave field in a listener zone by means of several loudspeakers. Applying a spatial window function, such as a rectangular function, to the wave field to be rendered defines a wave-free section in the listener zone in which the wave field is suppressed. This can be done for example by a multiplication of the target sound field with the window function, this corresponds to a spatial convolution in the spatial frequency range.
Um das sich so ergebende gewünschte Wellenfeld mit den Lautsprechern wiedergeben zu können, werden entsprechende Lautsprecher- Ansteuerungssignale bestimmt und dieseTo be able to reproduce the resulting desired wave field with the speakers, corresponding loudspeaker drive signals are determined and these
Ansteueruxagssignale den Lautsprechern zugeführt. Das Bestimmen der Ansteuerungssignale kann durch ein Higher-Order-Ambisonics-Verfahren oder ein Verfahren der spektralen Division durchgeführt werden.. Vorzugsweise wird das gewünschte Wellenfeld bandbegrenzt, um die Güte der Unterdrückung des Schallfeldes in dem entsprechenden Bereich der Zuhörerzone zu erhöhen.Ansteueruxagssignale supplied to the speakers. The determination of the drive signals may be performed by a higher order Ambisonics method or a spectral division method. Preferably, the desired wave field is bandlimited to increase the quality of the suppression of the sound field in the corresponding area of the listener zone.
Weiterhin stellt die Erfindung eine entsprechende Vorrichtung zur Wiedergabe eines akustischen Wellenfelds in der Zuhörerzone bereit, wobei das Wellenfeld in einem oder mehreren vorbestimmten Abschnitten der Zuhörerzone unterdrückt wird. Hierbei können die Lautsprecher auf einer offenen Kontur, insbesondere einer Linie, oder auch auf einer die Zuhörerzone umgebenden Kontur, also beispielsweise auf einem Kreis oder einem Rechteck, angeordnet sein.Furthermore, the invention provides a corresponding device for reproducing an acoustic wave field in the listener zone, wherein the wave field is suppressed in one or more predetermined sections of the listener zone. In this case, the loudspeakers may be arranged on an open contour, in particular a line, or else on a contour surrounding the listener zone, that is to say for example on a circle or a rectangle.
Die Erfindung wird im Folgenden unter Bezugnahme auf die beigefügten Figuren näher beschrieben. Es zeigen:
-
Fig. 1 eine Simulation der Wiedergabe einer ebenen Welle umgeben von einer ruhigen Zone; -
Fig. 2 die Energieverteilung des inFig. 1 . gezeigten Schallfeldes (in dB); -
Fig. 3 die Energieverteilung des inFig. 1 gezeigten Schallfeldes, wenn das Wellenfeld nur in einem bestimmten Gebiet unterdrückt werden soll (in dB); -
Fig. 4 eine Simulation der Wiedergabe einer ebenen Welle umgeben von einer ruhigen Zone bei rechteckiger Arraygeometrie; und -
Fig. 5 ein mit dem im Stand der Technik bekannten Ambisonics- Verfahren wieder gegebenes Schallfeld.
-
Fig. 1 a simulation of the reproduction of a plane wave surrounded by a quiet zone; -
Fig. 2 the energy distribution of inFig. 1 , shown sound field (in dB); -
Fig. 3 the energy distribution of inFig. 1 shown sound field, if the wave field is to be suppressed only in a certain area (in dB); -
Fig. 4 a simulation of the reproduction of a plane wave surrounded by a quiet zone with rectangular array geometry; and -
Fig. 5 a sound field reproduced with the Ambisonics method known in the art.
Alle Verfahren der mehrkanaligen akustischen Wiedergabesysteme verwenden eine vordefinierte Mischmatrix, die die Quellensignale auf bestimmte Lautsprechersignale abbildet, um einen gewünschten Höreindruck hervorzurufen. Die Herleitung der Ansteuerungsfunktionen bei Higher-Order Ambisonics und SDM erfolgt durch die explizite Lösung des zugrundeliegenden physikalischen Problems.All methods of multi-channel acoustic reproduction systems use a pre-defined mixing matrix which maps the source signals to particular loudspeaker signals to produce a desired auditory impression. The derivation of the control functions in Higher-Order Ambisonics and SDM is done by explicitly solving the underlying physical problem.
Die Unterdrückung des Wellenfeldes in bestimmten Zonen kann interpretiert werden als eine Multiplikation des ursprünglichen Wunschfeldes mit bestimmten räumlichen Fensterfünktionen, die das Schallfeld in bestimmten Gebieten unterdrücken. Im räumlichen Spektralbereich betrachtet, ist diese räumliche Multiplikation eine spektrale Faltung und die räumliche Unterdrückung geschieht daher durch eine geeignete spektrale Spreizung des räumlichen Spektrums des wiederzugebenden räumlichen Signals.The suppression of the wave field in certain zones can be interpreted as a multiplication of the original desired field with certain spatial window functions that suppress the sound field in certain areas. Considered in the spatial spectral range, this spatial multiplication is a spectral convolution and the spatial suppression is therefore done by a suitable spectral spread of the spatial spectrum of the reproduced spatial signal.
Zur Verdeutlichung des Wirkprinzips der Erfindung werden im Folgenden beispielhaft die der Synthese akustischer Wellenfelder mithilfe linearer Arrays zugrundeliegenden Gleichungen angegeben. Bei der Diskussion wird die Wiedergabe des Wellenfelds in einer Ebene beschrieben, es gilt also z=0. Die Ausdehnung des Arrays verläuft in Richtung der x-Achse.To clarify the principle of operation of the invention, the following is an example of the synthesis of acoustic wave fields using linear arrays underlying equations. In the discussion, the reproduction of the wave field is described in one plane, so z = 0. The extent of the array runs in the direction of the x-axis.
Das synthetisierte Schallfeld kann als das Ergebnis eines räumlichen Faltungsintegrals verstanden werden.
dabei stellt D die Ansteuerungsfunktion der Sekundärquellen dar und G die Green'sche Funktion, die den Ausbreitungspfad eines akustischen Monopols an der Position (x0=(x 0,y 0,z 0)) zum Punkt (x=(x,y,z))charakterisiert. Im Idealfall entspricht das synthetisiert Schallfeld dem gewünschten Schallfeld.The synthesized sound field can be understood as the result of a spatial convolution integral.
where D represents the drive function of the secondary sources and G the Green's function, which determines the propagation path of an acoustic monopole at the position (x 0 = ( x 0 , y 0 , z 0 )) to the point (x = ( x , y , z )). Ideally, the synthesized sound field corresponds to the desired sound field.
Es sei das Wunschfeld zum Beipiel eine monochromatische ebene Welle, diese ist gegeben durch die Gleichung:
eine zeitliche Fouriertransformation obiger Gleichung gefolgt von zwei räumlichen Fouriertransformationen entlang der x- und y-Achse liefern
provide a temporal Fourier transform of the above equation followed by two spatial Fourier transforms along the x and y axes
Gewünscht sei nun eine Begrenzung des Wellenfeldes auf einen Streifen, der zu dem Array senkrecht ist. Dieses kann als eine räumliche Fensterung verstanden werden. Eine mögliche Fensterfunktion ist die Rechteckfunktion. Die räumliche Fouriertransformation der Rechteckfunktion der Breite (1/a) lautet.
Insgesamt ist das gewünschte räumlich begrenzte Wellenfeld durch die folgende Faltung gegeben:
Um die Ansteuenmgsfunktionen für die Lautsprecher zu berechnen kann das Verfahren der spektralen Division verwendet werden. Diese beruht darauf, dass sich das Faltungsintegral in (G1. 1) zu einer Multiplikation im räumlichen Fourierbereich transformieren lässt. Damit kann (G1. 1) wie folgt umgeformt werden
Die Güte der Unterdrückung des Schallfeldes in einem bestimmten Gebiet hängt von der räumlichen Aliasingfrequenz des Wiedergabesystems und der Grenzfrequenz des wiedergegebenen Materials ab, weil nur die Spektralanteile des wiedergegebenen Materials, die unterhalb der Aliasingfrequenz des Systems liegen, gezielt unterdrückt werden können. Zusätzlich kann eine Bandbegrenzung des wiederzugebenden Materials eingesetzt werden um räumliches Aliasing zu vermeiden.The quality of the suppression of the sound field in a certain area depends on the spatial aliasing frequency of the playback system and the cut-off frequency of the reproduced material, because only the spectral components of the reproduced material, which are below the aliasing frequency of the system can be selectively suppressed. In addition, a band limitation of the material to be reproduced can be used to avoid spatial aliasing.
In einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens wird die Mischmatrix auf der Wiedergabeseite frequenzselektiv ausgehend von dem gewünschten Wellenfelds, der Lage des Aufnahmesystem und der Geometrie des Wiedergabesystems bestimmt. Als Anwendungsbeispiel wird ein lineares Lautsprecherarray diskutiert, wobei die Abhörzone mit zwei virtuellen Linien, die senkrecht zum Array stehen, in drei Gebiete unterteilt sein soll. In einem Gebiet soll eine konventionelle Wiedergabe ebener Wellen basierend auf dem Verfahren der spektralen Division erfolgen. In den beiden anderen Gebieten, in denen sich das Aufnahmesystem befinden kann, soll das Wellenfeld unterdrückt werden.In a preferred embodiment of the method according to the invention, the mixing matrix on the reproduction side is determined frequency-selectively on the basis of the desired wave field, the position of the recording system and the geometry of the reproduction system. As an application example, a linear loudspeaker array is discussed, wherein the interception zone with two virtual lines, which are perpendicular to the array, should be divided into three areas. In one area, conventional flat wave reproduction should be based on the spectral division method. In the two other areas in which the recording system can be located, the wave field should be suppressed.
Das Wunschwellenfeld ist eine Multiplikation der ebenen Wellen mit der räumlichen Rechteckfunktion oder einer anderen geeigneten Fensterfunktion. Für die Bestimmung der Ansteuerungsfunktionen für die Lautsprecher wird gemäß der Ausführungsform die Methode der spektralen Division eingesetzt. Dieses Verfahren benötigt bei linearen Arraygeometrien einen Ausdruck für sowohl das gewünschte Wellenfeld als auch die Green'sche Funktion im räumlich transformierten Bereich. mittels der Fouriertransformation entlang einer Referenzlinie, auf der die Wiedergabe exakt sein soll. Die Ansteuerfunktionen im räumlichen Spektralbereich sind das Ergebnis der elementweisen Division des Spektrums des Wunschfeldes durch das Spektrum der Green'schen Funktion. Die so ermittelten Spektren der Ansteuerfunktionen können mit Hilfe einer inversen Fouriertransformation in den räumlichen Bereich zurücktransformiert werden.The desired wave field is a multiplication of the plane waves with the spatial rectangular function or another suitable window function. For the determination of Driving functions for the speakers according to the embodiment, the method of spectral division is used. This method requires an expression for both the desired wave field and Green's function in the spatially transformed region for linear array geometries. by means of the Fourier transformation along a reference line on which the reproduction should be exact. The driving functions in the spatial spectral range are the result of element-wise division of the spectrum of the desired field by the spectrum of Green's function. The thus determined spectra of the drive functions can be transformed back into the spatial domain by means of an inverse Fourier transformation.
In
Arraygeometrien, die den Zuhörerraum zweidimensional einschließen, wie z.B. rechteckige Arrays, erlauben eine zweidimensionale Unterdrückung des Feldes. Ein Beispiel hierfür ist in
Das räumlich begrenzte Wellenfeld ist im Spektralbereich eine zweidimensionale Faltung des Wunschfeldes mit der räumlich transformierten Fensterfunktion. So ist beispielsweise das in
Claims (11)
- A method of reproducing an acoustic wave field in a listener zone comprising the suppression of the wave field in one or more predetermined portions of the listener zone by means of a plurality of loudspeakers, the method comprising the steps of:- determining a desired wave field in the listener zone by applying a spatial window function for forming wave-free portions on a wave field to be reproduced;- determining gating signals for the loudspeakers for generating the desired wave field in the listener zone; and- supplying the gating signals to the loudspeakers.
- The method of claim 1, wherein the wave field to be reproduced is multiplied by the spatial window function for determining the desired wave field.
- The method of claim 1, wherein a spatial convolution of the spectrum of the wave field to be reproduced with the window function in the spatial frequency area is performed for determining the desired wave field.
- The method of claim 1, wherein the wave field to be reproduced is spectrally spread for forming the wave-free portion.
- The method of any of the preceding claims, wherein the window function is a rectangular function.
- The method of any of the preceding claims, wherein the gating signals are determined by a higher-order ambisonics method or a spectral division method.
- The method of any of the preceding claims, wherein the desired wave field is bandlimited.
- A device for reproducing an acoustic wave field in a listener zone comprising the suppression of the wave field in one or more predetermined portions of the listener zone by a plurality of loudspeakers, the device comprising:- a plurality of loudspeakers;- a device for supplying gating signals to the loudspeaker for generating a desired wave field comprising a wave-free portion in the listener zone, wherein the desired wave field is formed by applying a window function to a wave field to be reproduced.
- The device of claim 8, wherein the loudspeakers are arranged on an open contour, in particular a line.
- The device of claim 8, wherein the loudspeakers are arranged on a contour surrounding the listener zone.
- The device of claim 10, wherein the loudspeakers are arranged on a circle or a rectangle.
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