EP3058762B1 - Method for operating an arrangement of sound transducers according to the wave-field synthesis principle - Google Patents
Method for operating an arrangement of sound transducers according to the wave-field synthesis principle Download PDFInfo
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- EP3058762B1 EP3058762B1 EP14806713.5A EP14806713A EP3058762B1 EP 3058762 B1 EP3058762 B1 EP 3058762B1 EP 14806713 A EP14806713 A EP 14806713A EP 3058762 B1 EP3058762 B1 EP 3058762B1
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- 230000015572 biosynthetic process Effects 0.000 title claims description 16
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Classifications
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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
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
- H04R3/14—Cross-over networks
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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
- H04R27/00—Public address systems
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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
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
- H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
- H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
- H04R1/403—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers loud-speakers
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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
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
- H04R2201/401—2D or 3D arrays of transducers
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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
- H04R2227/00—Details of public address [PA] systems covered by H04R27/00 but not provided for in any of its subgroups
- H04R2227/007—Electronic adaptation of audio signals to reverberation of the listening space for PA
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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
- H04R2430/00—Signal processing covered by H04R, not provided for in its groups
- H04R2430/01—Aspects of volume control, not necessarily automatic, in sound 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 a method for operating an arrangement of sound transducers according to the principle of wave field synthesis for supplying an audience area with an audio signal and a device for supplying the audience area.
- loudspeaker systems which are tailored to the special requirements of supplying large public areas with sufficiently high acoustic energy, so-called public address systems or PA systems for short. These are implemented as loudspeaker units, typically designed as multi-path systems with high-efficiency sound converters that are adapted to the transmission range. Individual loudspeaker units or loudspeaker units combined to form a large loudspeaker, so-called line arrays, are used as designs. With them it is possible, with appropriate dimensioning, to generate the sound pressure levels required by the organizer even in the public areas far away from the loudspeaker units.
- the "acoustic curtain" is created. From a single mono signal, by means of convolution into an impulse response, or from the corresponding calculations of sound propagation time and level from the distance between a virtual sound source and the respective sound transducer, the signals can be obtained in a model-based approach that a loudspeaker from a position immediately behind microphone arranged in a partition would be obtained from a real sound source at the position of the virtual sound source. The wave front of a real sound source is reconstructed as if through a "curtain".
- the device of sound transducers works like a piston radiator in the bass range. Even large wavelengths of the signal can, depending on the overall size of the device consisting of sound transducers, still be aimed at the public area.
- the alignment of the wave fronts which can be controlled in the azimuth and elevation planes, can significantly reduce the amount of interfering noise that extends beyond the event site at open air events.
- this electronically controllable sound emission has further advantages compared to fixed systems. Due to the more targeted alignment of the wave fronts, the proportion of direct sound in the listener is significantly increased in relation to the diffusely reflected sound from the reflection surfaces. This increases the degree of clarity of the transmission and improves speech intelligibility. This is essential for a high-quality transmission, especially under unfavorable acoustic conditions at the performance location. In addition, radiation with a small opening angle also solves the problem of conventional PA systems, which often generate high sound pressure levels close to the stage area that are hazardous to health when public areas further away are to be supplied with a sufficiently high sound pressure level.
- each individual radiator works more efficiently than an individual radiator of the same type in a conventional arrangement.
- the advantage should be retained that in the audience areas that are far away from the arrangement of sound transducers based on the principle of wave field synthesis, approximately the same sound pressure can be generated as in the areas immediately in front of the stage.
- the associated device of sound transducers typically comprises an arrangement of loudspeakers, typically dynamic loudspeakers, which are arranged in a flat surface.
- loudspeakers typically dynamic loudspeakers
- MEMS microelectromechanical systems
- a curvature of the surface or an angled arrangement of flat partial surfaces is also conceivable; even an irregular arrangement of the sound transducers at defined spatial points could generate a defined wave front according to the principle of wave field synthesis.
- a special case is the design of the surface as a single row of loudspeakers. The procedure described is only effective to a limited extent.
- Different public areas can also be supplied with different signal content or with adapted level and equalization values with the same signal content from a common device comprising sound transducers. This makes it possible to generate almost the same sound pressure levels in distant audience areas as directly in front of the stage area of a major event.
- the device for supplying an extensive public area does not emit a single wavefront that spreads over a wide emission angle extends over the entire audience area, but the area to be supplied is supplied from a large number of individual virtual sound sources, which are generated by the arrangement of sound transducers according to the principle of wave field synthesis, in a narrow radiation angle. All of these virtual sound sources have the signal content of the one virtual sound source that would otherwise have to supply the entire audience area. On the one hand, this has the advantage that the sound pressure of the individual wave fronts hardly decreases with distance given the small opening angle.
- the level of each of these virtual sound sources can be far higher than their share in the one virtual sound source otherwise required for the wide radiation angle.
- the signals are subtracted and added according to their phase position. Comb filter effects arise in the resulting frequency response.
- the signals from virtual sources with the same signal content are delayed from one another in such a way that their signals arrive simultaneously at the point in the middle of the overlap area. This also minimizes the comb filter effects in this area, but the coverage area can, if necessary, be better adapted to the shape of the public area due to the greater freedom in positioning the virtual sound sources.
- n virtual sound sources which has to supply a large audience area with a wide beam angle, as the addition of n virtual sound sources in a common point.
- these n virtual sound sources could then be spatially distributed in such a way that they could supply the original area again with individual wave fronts emitted at a narrower angle. If the level of each individual virtual sound source would then be the nth part of the level of the original one virtual source, the conditions would not have changed in principle.
- this area at the upper end of the transmission area only includes a few sound transducers near the center point; the area only increases with the wavelength of the signal.
- the better adaptation of the arrangement of sound transducers ensures increasing efficiency.
- the entire public area may also be necessary to supply the entire public area from several spatially separated virtual sound sources so that a spatial impression is created in the entire public area.
- virtual sound sources can also be generated that emit the signal that is otherwise fed to the stereo speakers.
- the respective signal content of the described method can also be emitted by two or more virtual sound sources at different positions.
- Fig. 1 shows the emission of an arrangement of sound transducers based on the principle of wave field synthesis (1) in which the virtual sound source (2) would supply the entire public area (3). This would mean that the sound pressure would decrease rapidly with the distance from the arrangement of sound transducers (1), because the energy of the wave front is distributed over a surface that grows rapidly with increasing distance.
- the problem is solved in that the signal is generated by several virtual sound sources (5), (6), (7), (8) with the same signal content instead of the individual virtual sound source (2).
- This distribution of the same signal to several starting points is made possible according to the invention in that all virtual sound sources generate their wave fronts from such positions from which they start from the center of the respective, inevitable overlap area in the audience (9), (10) and (11) are equidistant.
- the overlapping virtual sound sources are positioned on a common radius around the center of the overlapping area.
- the surface of the wave fronts emanating from the virtual sound sources (5), (6), (7) and (8) increases significantly more slowly with the distance from (1) because of the small opening angle of the radiation in front of the arrangement of sound transducers (1) ), as the surface of a wave front that would emanate from the individual virtual sound source (2). Their level drops correspondingly less with distance.
- level and equalization can now be regulated separately for each sub-range.
- the public area (3) is again supplied by the arrangement of sound transducers (3) from the four virtual sound sources (5), (6), (7) and (8).
- the sub-areas for the supply are now selected to be of different sizes.
- the different opening angles of the wave fronts emanating from the virtual sound sources (5) and (6) mean that these starting points can no longer be arranged on a common radius around the center of their overlap area (9).
- the radiation can be adapted to the given conditions.
- the available sound power can also be better used. Public areas that are far away are supplied at a very narrow angle, while the sound power is sufficient for nearby areas if it is distributed over a wide angle of radiation.
- the signal of the virtual sound source (6) is to be delayed by the time it takes for the sound to travel (dt).
- the speed of sound must be used in the calculation of the transit time according to the current outside temperature so that transit times in the virtual and real part of the radiation match.
- the current temperature must therefore be measured in the audience area and the sound velocity calculated from this must be updated regularly for all calculations.
- a measurement of the wind direction and wind speed in the spectator area can increase the accuracy of the individual wave fronts in the audience area.
- the virtual sound sources (7) then also have to be delayed accordingly so that the wave fronts arrive at the same time in their overlapping area (10) with the virtual sound source (6). Accordingly, the transit times from (7) to each individual transducer are calculated first. Then the time difference to the virtual sound source (6) plus the transit time (dt 5) is added to each of the calculated values. In this way the curvature of the wave front is retained, it is only emitted later.
- the smallest transit time calculated in the overall system can be subtracted from all calculated transit times in the system in order to fix the final values. This avoids any unnecessary latency in the overall system.
- Fig. 3 represents the phase relationships of the individual signals in the plane of the arrangement of sound transducers. The geometric relationships are the same as in Fig. 1 .
- the spherical sections of the wave fronts directed towards the public area (2) and emanating from the virtual sound sources (3), (4), (5) and (6) that are equidistant from the overlapping areas are only visible a single point in the center of the array of transducers in phase. Only there do the diaphragm deflections of the affected sound transducer add up linearly for all virtual sound sources. Due to the requirement that neighboring virtual sound sources must be equidistant from the center of the area where their wave fronts overlap in the public area, this condition is always met. Only in the center of the arrangement of sound transducers are the signals from all virtual sound sources with the same signal content in phase up to the highest frequencies of the transmission range. A corresponding reduction in this area prevents them from being overloaded. Because of the relatively small area concerned, the level loss in the upper transmission range can easily be compensated for by appropriate equalization of the overall signal.
- Fig. 4 shows the arrangement of sound transducers based on the principle of wave field synthesis (1), behind which two virtual sound sources (2r) and (2l) are supposed to generate a spatial reproduction. It would also be possible to split the arrangement of sound transducers in order to arrange the virtual sound sources (2l) and (2r) on a broader base line.
- the method described for a single source can then be used for each partial area. In the sketch this is only shown for the left channel of the stereo playback. Again (3) is the audience area.
- the virtual sound sources (5), (6), (7) and (8) then reproduce the signal from the left source from their starting points on the radii around the overlap areas (9), (10) and (11).
- the right channel is split mirror-inverted into individual virtual sound sources; this is not shown in the sketch for reasons of clarity.
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Otolaryngology (AREA)
- Circuit For Audible Band Transducer (AREA)
- Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
Description
Die vorliegende Erfindung betrifft ein Verfahren zum Betreiben einer Anordnung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese zur Versorgung eines Publikumsbereiches mit einem Audiosignal und eine Vorrichtung zur Versorgung des Publikumsbereiches.The present invention relates to a method for operating an arrangement of sound transducers according to the principle of wave field synthesis for supplying an audience area with an audio signal and a device for supplying the audience area.
Im Veranstaltungstechnikbereich sind Lautsprecheranlagen bekannt, die auf die speziellen Anforderungen der Versorgung auch von großen Publikumsbereichen mit ausreichend hoher akustischer Energie zugeschnitten sind, so genannte Public Address- oder kurz PA- Anlagen. Diese werden als Lautsprechereinheiten realisiert, typischer Weise ausgeführt als Mehrwegesysteme mit jeweils an den Übertragungsbereich angepassten Schallwandlern hohen Wirkungsgrades. Als Ausführungen kommen einzelne Lautsprechereinheiten oder zu einem Großlautsprecher kombinierte Lautsprechereinheiten, sogenannte Line-Arrays, zum Einsatz. Mit ihnen ist es bei entsprechender Dimensionierung möglich, die vom Veranstalter geforderten Schalldrücke auch in den weit von den Lautsprechereinheiten entfernten Publikumsbereichen zu erzeugen.In the event technology sector, loudspeaker systems are known which are tailored to the special requirements of supplying large public areas with sufficiently high acoustic energy, so-called public address systems or PA systems for short. These are implemented as loudspeaker units, typically designed as multi-path systems with high-efficiency sound converters that are adapted to the transmission range. Individual loudspeaker units or loudspeaker units combined to form a large loudspeaker, so-called line arrays, are used as designs. With them it is possible, with appropriate dimensioning, to generate the sound pressure levels required by the organizer even in the public areas far away from the loudspeaker units.
Weil bei einer einzelnen Lautsprechereinheit die Abstrahlung im Wesentlichen die ungerichtete Abstrahlung einer Punktschallquelle ist, nimmt der Schalldruck systembedingt mit jeder Verdoppelung der Entfernung von der Schallquelle auf die Hälfte, also um 6 dB ab. Daher geht man bei ausgedehnten Publikumsbereichen zunehmend zum Einsatz von Line Arrays über. Im Grundtonbereich erzeugen Line- Arrays Zylinderwellen. Die Oberfläche eines Zylinders wächst nur linear mit dem Radius, nicht quadratisch, wie die einer Kugel. Entsprechend langsamer, nämlich mit 3 dB pro Entfernungsverdoppelung, nimmt ihr Schalldruck mit der Entfernung ab. Erst in vierfacher Entfernung ist er jeweils auf die Hälfte abgesunken. Dazu kommt der Vorteil des Line- Arrays, dass bei den übereinander angeordneten Lautsprechereinheiten der Schall in der Elevationsebene ausgerichtet werden kann. Das vermindert den Anteil des Störschalls, der bei Open- Air- Veranstaltungen über den Publikumsbereich hinaus in das Umfeld, wie z. B. Wohngebiete, abgestrahlt wird. Der Bassbereich wird jedoch ungerichtet von getrennt aufgestellten Subwoofern abgestrahlt.Because the radiation of a single loudspeaker unit is essentially the non-directional radiation of a point sound source, the sound pressure decreases by half, i.e. by 6 dB, every time the distance from the sound source is doubled. For this reason, line arrays are increasingly being used for large public areas. In the fundamental range, line arrays generate cylindrical waves. The surface of a cylinder only grows linearly with the radius, not square like that of a sphere. Correspondingly more slowly, namely at 3 dB per doubling of distance, their sound pressure decreases with distance. Only at four times the distance does it drop by half. In addition, there is the advantage of the line array that the sound can be aligned in the elevation plane when the loudspeaker units are arranged one above the other. This reduces the proportion of interfering noise that is released into the environment at open-air events beyond the public area, e.g. B. residential areas, is radiated. However, the bass range is emitted non-directionally from separately installed subwoofers.
Am besten kann die Abstrahlung der Wellenfronten auf den Publikumsbereich begrenzt bleiben, wenn sie in der Azimut- und in der Elevationsebene ausgerichtet werden kann. Mit Hilfe des von A. J. Berkhout 1988 in [3] beschriebenen Verfahrens zur Wellenfeldsynthese wird eine noch exaktere Ausrichtung der Wellenfronten möglich.The best way to limit the radiation of the wave fronts to the audience area is to align them in the azimuth and elevation planes can. With the aid of the wave field synthesis method described by AJ Berkhout in 1988 in [3], an even more precise alignment of the wave fronts is possible.
Wenn dieses Verfahren, wie in [4] beschrieben, in einer zweidimensionalen Anordnung aus Schallwandlern angewendet wird, entsteht der "Akustische Vorhang". Aus einem einzigen Mono Signal können mittels Faltung in eine Impulsantwort, oder aus der entsprechenden Berechnungen von Schallaufzeit und Pegel aus der Distanz zwischen einer virtuellen Schallquelle und dem jeweiligen Schallwandler in einem modellbasierenden Ansatz die Signale gewonnen werden, die ein Lautsprecher von einem unmittelbar hinter einer Position in einer Trennwand angeordneten Mikrofon von einer realen Schallquelle an der Position der virtuellen Schallquelle erhalten würde. Wie durch einen "Vorhang" wird die Wellenfront einer realen Schallquelle rekonstruiert.If this method, as described in [4], is used in a two-dimensional arrangement of sound transducers, the "acoustic curtain" is created. From a single mono signal, by means of convolution into an impulse response, or from the corresponding calculations of sound propagation time and level from the distance between a virtual sound source and the respective sound transducer, the signals can be obtained in a model-based approach that a loudspeaker from a position immediately behind microphone arranged in a partition would be obtained from a real sound source at the position of the virtual sound source. The wave front of a real sound source is reconstructed as if through a "curtain".
Solch ein "Akustischer Vorhang" nach dem modellbasierenden Ansatz ist bekannt. Kennzeichnend für dieses Verfahren ist es, dass jede virtuelle Schallquelle hinter dieser Anordnung nach Huygens Prinzip aus einer Vielzahl einzelner Schallwandler physikalisch rekonstruiert wird. Die Krümmung der Wellenfront entspricht der einer Wellenfront, die von einer realen Schallquelle an der Position der virtuellen Schallquelle ausgehen würde. Die virtuelle Schallquelle verändert deshalb ihren Ausgangspunkt nicht, wie die Phantomschallquellen bei den psychoakustisch basierten Verfahren, mit der Position des Zuhörers.Such an "acoustic curtain" according to the model-based approach is known. It is characteristic of this method that every virtual sound source behind this arrangement is physically reconstructed from a large number of individual sound transducers according to Huygens' principle. The curvature of the wave front corresponds to that of a wave front that would emanate from a real sound source at the position of the virtual sound source. The virtual sound source therefore does not change its starting point, like the phantom sound sources in the psychoacoustic-based methods, with the position of the listener.
Deshalb ist sie, von Beugungseffekten aufgrund der endlichen Fläche der Vorrichtung aus Schallwandlern abgesehen, auch nur in dem Bereich hörbar, in dem sich die virtuelle Schallquelle vom Zuhörer aus gesehen innerhalb der Vorrichtung aus Schallwandlern befindet.Therefore, apart from diffraction effects due to the finite area of the device made of sound transducers, it can only be heard in the area in which the virtual sound source is located within the device made of sound transducers, as seen by the listener.
Auf dem Gebiet der Veranstaltungstechnik ist es prinzipiell möglich, diesen Umstand als deutlichen Vorteil gegenüber den oben beschriebenen PA(Public Address)-Anlagen zu nutzen. Die Abstrahlrichtung des Signals und der Öffnungswinkel der Wellenfront in Bezug auf die Vorrichtung aus Schallwandlern lassen sich mit der Position der virtuellen Schallquelle sehr einfach festlegen. So kann die Abstrahlung in der Azimut- und Elevationsebene direkt auf den Publikumsbereich ausgerichtet werden. Dazu wird eine virtuelle Schallquelle weit hinter der Anordnung aus Schallwandlern positioniert. Die Krümmung der Wellenfront entspricht dann dem Kugelausschnitt im Bereich der Anordnung aus Schallwandlern. Eine unendlich weit entfernte virtuelle Schallquelle erzeugt eine parallele Wellenfront, deren Schallpegel theoretisch nicht mit der Entfernung zum Schallwandler abnimmt.In the field of event technology, it is in principle possible to use this fact as a clear advantage over the PA (Public Address) systems described above. The direction of emission of the signal and the opening angle of the wave front in relation to the device consisting of sound transducers can be determined very easily with the position of the virtual sound source. In this way, the radiation in the azimuth and elevation planes can be aimed directly at the audience area. For this purpose, a virtual sound source is positioned far behind the arrangement of sound transducers. The curvature of the wave front then corresponds to the spherical section in the area of the arrangement of sound transducers. An infinitely distant virtual sound source generates a parallel wavefront, the sound level of which does not theoretically decrease with the distance to the sound transducer.
Dabei arbeitet die Vorrichtung aus Schallwandlern im Bassbereich wie ein Kolbenstrahler. Selbst große Wellenlängen des Signals können, abhängig von der Gesamtgröße der Vorrichtung aus Schallwandlern, noch auf den Publikumsbereich ausgerichtet werden. So kann die in Azimut- und Elevationsebene steuerbare Ausrichtung der Wellenfronten den Störschallanteil deutlich reduzieren, der bei open Air- Veranstaltungen über das Veranstaltungsgelände hinausgeht.The device of sound transducers works like a piston radiator in the bass range. Even large wavelengths of the signal can, depending on the overall size of the device consisting of sound transducers, still be aimed at the public area. The alignment of the wave fronts, which can be controlled in the azimuth and elevation planes, can significantly reduce the amount of interfering noise that extends beyond the event site at open air events.
Zudem entspringen alle Wellenfronten einem gemeinsamen Ausgangspunkt. Damit treten die deutlich wahrnehmbaren Phasenprobleme, die eine räumlich getrennte Aufstellung diverser Lautsprechereinheiten unweigerlich mit sich bringt, nicht auf. Der große Kolbenstrahler, der im Bassbereich aus den Einzelstrahlern entsteht, kann so schnell arbeiten wie jeder einzelne Lautsprecher. Die auf einer großen Lautsprechermembran sonst unvermeidlichen Partialschwingungen entstehen nicht.In addition, all wave fronts originate from a common starting point. This means that the clearly perceptible phase problems that a spatially separated installation of various loudspeaker units inevitably do not arise. The large piston radiator, which is created from the individual radiators in the bass range, can work as quickly as any individual loudspeaker. The partial vibrations that are otherwise unavoidable on a large loudspeaker membrane do not arise.
In der praktischen Anwendung hat diese elektronisch steuerbare Abstrahlung des Schalls weitere Vorteile gegenüber fest ausgerichteten Systemen. Wegen der gezielteren Ausrichtung der Wellenfronten wird beim Zuhörer der Anteil des Direktschalles im Verhältnis zu den diffus von den Reflexionsflächen zurückgeworfenen Schallanteilen deutlich erhöht. Das erhöht das Deutlichkeitsmaß der Übertragung und verbessert die Sprachverständlichkeit. Vor allem unter ungünstigen akustischen Verhältnissen am Aufführungsort ist das unabdingbar für eine hochwertige Übertragung. Zudem löst eine Abstrahlung mit geringem Öffnungswinkel auch das Problem der konventionellen PA-Anlagen, das nahe am Bühnenbereich oft gesundheitsgefährdend hohe Schalldruckpegel erzeugt werden, wenn weiter entfernte Publikumsbereiche mit ausreichend hohem Schalldruckpegel versorgt werden sollen.In practical use, this electronically controllable sound emission has further advantages compared to fixed systems. Due to the more targeted alignment of the wave fronts, the proportion of direct sound in the listener is significantly increased in relation to the diffusely reflected sound from the reflection surfaces. This increases the degree of clarity of the transmission and improves speech intelligibility. This is essential for a high-quality transmission, especially under unfavorable acoustic conditions at the performance location. In addition, radiation with a small opening angle also solves the problem of conventional PA systems, which often generate high sound pressure levels close to the stage area that are hazardous to health when public areas further away are to be supplied with a sufficiently high sound pressure level.
Trotzdem wird das Prinzip des "Akustischen Vorhanges" mit einer Anordnung aus Einzelstrahlern nach dem Prinzip der Wellenfeldsynthese bisher im PA Bereich nicht kommerziell angewendet. Die Vorteile der Abstrahlung mit geringem Öffnungswinkel gehen verloren, wenn ein ausgedehnter Publikumsbereich mit Schall versorgt werden muss.Nevertheless, the principle of the "acoustic curtain" with an arrangement of individual radiators based on the principle of wave field synthesis has not yet been used commercially in the PA sector. The advantages of radiation with a small opening angle are lost if an extensive public area has to be supplied with sound.
Wird eine virtuelle Schallquelle so positioniert, dass die erzeugte Wellenfront einen ausgedehnten Publikumsbereich versorgt, so muss nahe der Vorrichtung aus Schallwandlern ein entsprechend hoher Schalldruck erzeugt werden, der dann mit der Entfernung stark abnimmt. Deshalb geht der Vorteil, den eine solche Vorrichtung aus Schallwandlern bei der Abstrahlung in einem kleinen Öffnungswinkel hat, verloren, dass weit entfernte Publikumsbereiche nahezu mit dem gleichen Schalldruckpegel versorgt werden können, wie der Bereich unmittelbar vor der Bühne einer Großveranstaltung.If a virtual sound source is positioned in such a way that the wave front generated supplies an extensive public area, a correspondingly high sound pressure must be generated near the device from sound transducers, which then decreases sharply with distance. Therefore, the advantage that such a device of sound transducers has when it is emitted at a small opening angle is lost, namely that distant public areas can be supplied with almost the same sound pressure level as the area immediately in front of the stage of a major event.
Zudem wird es bei einer solch breiten Abstrahlung einer Wellenfront mit der Anordnung aus Schallwandlern sehr aufwendig, auch in den entfernten Publikumsbereichen einen ausreichenden Schalldruckpegel zu erreichen. Im Bereich großer Wellenlängen, also im Bass- und Mitteltonbereich, hat die großflächige Anordnung aus Schallwandlern den Vorteil der besseren Anpassung an den Wellenwiderstand der Luft. Herkömmliche Lautsprecher haben hier das Problem, dass in diesem Bereich die Luft einfach um die Lautsprechereinheit herum ausweicht. Der erzeugte Schalldruck verteilt sich dann in alle Richtungen, im Bereich der Zuhörer kommt nur ein Bruchteil der erzeugten Energie an. Einzelne Lautsprecherchassis müssen im Bassbereich viel kleiner bleiben als die Wellenlänge des von ihnen erzeugten Signals, weil ihre Membrane sonst instabil würde. Deshalb arbeiten sie in diesem Bereich fast ins Leere, der sich bewegenden Membran setzt sich kaum ein Lastwiderstand entgegen. Wegen dieser Fehlanpassung ist der Wirkungsgrad von einzelnen dynamischen Lautsprechern im Bassbereich sehr niedrig.In addition, with such a broad radiation of a wave front with the arrangement of sound transducers, it becomes very expensive to achieve a sufficient sound pressure level even in the distant public areas. In the long wavelength range, i.e. in the bass and mid-range, the large-area arrangement of sound transducers has the advantage of better adaptation to the wave resistance of the air. Conventional loudspeakers have the problem that in this area the air simply evades around the loudspeaker unit. The generated sound pressure is then distributed in all directions; only a fraction of the generated energy reaches the audience. Individual loudspeaker chassis must remain much smaller in the bass range than the wavelength of the signal they generate, otherwise their membrane would become unstable. That is why they work almost in the void in this area, the moving membrane is hardly opposed to a load resistance. Because of this mismatch, the efficiency of individual dynamic loudspeakers in the bass range is very low.
Mit einer ausreichend großen, zweidimensionalen Vorrichtung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese ist dieses Problem gelöst. Im Bassbereich arbeiten die einzelnen Schallwandler nahezu synchron, benachbarte Lautsprecher erzeugen zum gleichen Zeitpunkt fast identischen Schalldruck. Die Luft kann nicht mehr zur Seite ausweichen, weil der benachbarte Lautsprecher dort zum gleichen Zeitpunkt den gleichen Luftdruck erzeugt. Der Bewegung der Membran stellt sich nun die Masseträgheit einer Luftsäule, die mit wachsender Gesamtfläche immer weiter vor die Anordnung aus Schallwandlern reicht, als Arbeitswiderstand entgegen. Das verbessert den Wirkungsgrad der Abstrahlung ganz erheblich. Der Effekt ist vergleichbar mit Hornlautsprechern, bei denen die Schallführung ein Ausweichen der Luftsäule verhindert. Auch hier wird die Eigenresonanz des Schallwandlers durch die zusätzliche Luftmasse vor der Membran deutlich nach unten verschoben, der Wirkungsgrad wird deutlich gesteigert.This problem is solved with a sufficiently large, two-dimensional device consisting of sound transducers based on the principle of wave field synthesis. In the bass range, the individual transducers work almost synchronously, while neighboring loudspeakers generate almost identical sound pressure at the same time. The air can no longer escape to the side because the neighboring loudspeaker there generates the same air pressure at the same time. The movement of the membrane is now countered by the inertia of an air column, which extends further and further in front of the arrangement of sound transducers as the total area increases, as a working resistance. This significantly improves the efficiency of the radiation. The effect is comparable to horn loudspeakers, in which the sound guide prevents the air column from escaping. Here, too, the self-resonance of the sound transducer is shifted significantly downwards by the additional air mass in front of the membrane, the efficiency is significantly increased.
Leider verliert sich dieser Vorteil der Vorrichtung aus Schallwandlern mit steigender Frequenz. Im oberen Übertragungsbereich kommen auch schon die Durchmesser einzelner Schallwandler in den Bereich der Wellenlängen des abzustrahlenden Signals. Das Problem der Fehlanpassung verliert sich hier, auch Einzelstrahler können in diesem Bereich schon einen hohen Wirkungsgrad, der sich in ihrer Kennempfindlichkeit SPL ausdrückt, erzeugen.Unfortunately, this advantage of the device of sound transducers is lost with increasing frequency. In the upper transmission range, the diameters of individual sound transducers come into the range of the wavelengths of the signal to be emitted. The problem of mismatching disappears here; even single radiators can generate a high degree of efficiency in this area, which is expressed in their sensitivity SPL.
Um mit der Anordnung aus Einzelstrahlern nach dem Prinzip der Wellenfeldsynthese bei einem breiten Abstrahlwinkel der Wellenfront auch in den weit entfernten Publikumsbereichen am oberen Ende des Übertragungsbereiches vergleichbar hohen Schalldruck zu erzeugen wie mit den üblichen Line Arrays, wären dann in der Anordnung aus Schallwandlern solche Schallwandler einzusetzen, die eine vergleichbar hohe Schallleistung erzeugen können wie ihre Pendants in den konventionellen Applikationen. Wegen der Vielzahl der benötigten Einzelstrahler ist dann der Einsatz der Anordnung aus Einzelstrahlern im PA Bereich ökonomisch nicht sinnvoll.In order to use the arrangement of individual radiators according to the principle of wave field synthesis with a wide angle of radiation of the wave front to generate sound pressure that is comparable to that with the usual line arrays in the far away audience areas at the upper end of the transmission range, such sound transducers would then have to be used in the arrangement of sound transducers that can generate a sound power level comparable to that of their counterparts in conventional applications. Because of the large number of individual radiators required, the use of the arrangement of individual radiators in the PA area does not make economic sense.
Erfindungsgemäß ist deshalb eine Lösung zu beschreiben, bei der auch am oberen Ende des Übertragungsbereiches jeder Einzelstrahler effizienter arbeitet als ein einzelner Strahler gleichen Typs in einer konventionellen Anordnung.According to the invention, a solution is therefore to be described in which, even at the upper end of the transmission range, each individual radiator works more efficiently than an individual radiator of the same type in a conventional arrangement.
Zudem sollte der Vorteil erhalten bleiben, dass in den weit von der Anordnung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese entfernten Publikumsbereichen annähernd der gleiche Schalldruck erzeugt werden kann wie in den Bereichen unmittelbar vor der Bühne.In addition, the advantage should be retained that in the audience areas that are far away from the arrangement of sound transducers based on the principle of wave field synthesis, approximately the same sound pressure can be generated as in the areas immediately in front of the stage.
Die vorstehenden Aufgaben sowie weitere, der Beschreibung zu entnehmende Aufgaben werden von einem Verfahren gemäß den Merkmalen des Anspruchs 1 und einer Vorrichtung gemäß den Merkmalen des Anspruchs 7 gelöst. Weitere vorteilhafte Ausführungsformen der Erfindung sind in den abhängigen Ansprüchen angegeben. Eine bevorzugte Ausführungsform der vorliegenden Erfindung ist in nachfolgenden Zeichnungen und in einer detaillierten Beschreibung dargestellt, soll aber die vorliegende Erfindung nicht darauf begrenzen.The above objects and other objects to be found in the description are achieved by a method according to the features of claim 1 and a device according to the features of claim 7. Further advantageous embodiments of the invention are specified in the dependent claims. A preferred embodiment of the present invention is shown in the following drawings and in a detailed description, but is not intended to limit the present invention thereto.
Die zugehörige Vorrichtung aus Schallwandlern umfasst typischerweise eine Anordnung von Lautsprechern, typischerweise dynamischen Lautsprechern, die in einer ebenen Fläche angeordnet sind. Jedoch ist auch der Einsatz anderer Wandlerprinzipien, wie elektrostatischen oder piezoelektrischen Wandlern oder auch Microelectromechanical Systems (MEMS) [1] [2] möglich. Auch eine Krümmung der Fläche oder eine abgewinkelte Anordnung von ebenen Teilflächen ist denkbar, selbst eine unregelmäßige Anordnung der Schallwandler an definierten Raumpunkten könnte nach dem Prinzip der Wellenfeldsynthese eine definierte Wellenfront erzeugen. Ein Sonderfall ist die Ausführung der Fläche als eine einzelne Lautsprecherreihe. Bei ihr ist das beschriebene Verfahren nur bedingt wirksam.The associated device of sound transducers typically comprises an arrangement of loudspeakers, typically dynamic loudspeakers, which are arranged in a flat surface. However, it is also possible to use other converter principles, such as electrostatic or piezoelectric converters or microelectromechanical systems (MEMS) [1] [2]. A curvature of the surface or an angled arrangement of flat partial surfaces is also conceivable; even an irregular arrangement of the sound transducers at defined spatial points could generate a defined wave front according to the principle of wave field synthesis. A special case is the design of the surface as a single row of loudspeakers. The procedure described is only effective to a limited extent.
Verschiedene Publikumsbereiche können auch mit unterschiedlichem Signalinhalt oder auch mit angepassten Pegel- und Entzerrungswerten bei gleichem Signalinhalt von einer gemeinsamen Vorrichtung aus Schallwandlern versorgt werden. Dadurch wird es möglich, in entfernten Publikumsbereichen nahezu gleiche Schalldrücke zu erzeugen wie unmittelbar vor dem Bühnenbereich einer Großveranstaltung.Different public areas can also be supplied with different signal content or with adapted level and equalization values with the same signal content from a common device comprising sound transducers. This makes it possible to generate almost the same sound pressure levels in distant audience areas as directly in front of the stage area of a major event.
Erfindungsgemäß strahlt die Vorrichtung zur Versorgung eines ausgedehnten Publikumsbereiches nicht eine einzelne Wellenfront ab, die sich in breitem Abstrahlwinkel über den gesamten Publikumsbereich ausdehnt, sondern der zu versorgende Bereich wird von einer Vielzahl einzelner virtueller Schallquellen, die von der Anordnung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese erzeugt werden, in engem Abstrahlwinkel versorgt. Alle diese virtuellen Schallquellen haben den Signalinhalt der einen virtuellen Schallquelle, die sonst den gesamten Publikumsbereich versorgen müsste. Das hat einerseits den Vorteil, dass der Schalldruck der einzelnen Wellenfronten bei dem geringen Öffnungswinkel kaum mit der Entfernung abnimmt. Zweitens kann wegen der inkohärenten Addition der Einzelsignale in der Ebene der Anordnung aus Lautsprechern der Pegel jeder einzelnen dieser virtuellen Schallquellen weit höher sein, als es ihrem Anteil an der sonst für den breiten Abstrahlwinkel notwendigen einen virtuellen Schallquelle entspricht. Bei einer Vielzahl virtueller Schallquellen mit gleichem Signalinhalt ist es nicht zu vermeiden, dass sich die Versorgungsgebiete der einzelnen Bereiche überlappen. Soweit dann die Ausgangspunkte der betreffenden Wellenfronten unterschiedlichen Abstand zum Zuhörer haben, subtrahieren und addieren sich die Signale entsprechend ihrer Phasenlage zueinander. Es entstehen Kammfiltereffekte im resultierenden Frequenzgang. Dieses Problem wird erfindungsgemäß dadurch gelöst, dass die einzelnen virtuellen Schallquellen mit gleichem Signalinhalt an solchen Positionen erzeugt werden, die gleich weit von einem Punkt in der Mitte des Überlappungsbereiches entfernt sind.According to the invention, the device for supplying an extensive public area does not emit a single wavefront that spreads over a wide emission angle extends over the entire audience area, but the area to be supplied is supplied from a large number of individual virtual sound sources, which are generated by the arrangement of sound transducers according to the principle of wave field synthesis, in a narrow radiation angle. All of these virtual sound sources have the signal content of the one virtual sound source that would otherwise have to supply the entire audience area. On the one hand, this has the advantage that the sound pressure of the individual wave fronts hardly decreases with distance given the small opening angle. Second, because of the incoherent addition of the individual signals in the level of the arrangement of loudspeakers, the level of each of these virtual sound sources can be far higher than their share in the one virtual sound source otherwise required for the wide radiation angle. With a large number of virtual sound sources with the same signal content, it cannot be avoided that the coverage areas of the individual areas overlap. If the starting points of the wave fronts in question are then at different distances from the listener, the signals are subtracted and added according to their phase position. Comb filter effects arise in the resulting frequency response. This problem is solved according to the invention in that the individual virtual sound sources with the same signal content are generated at positions that are equidistant from a point in the middle of the overlap area.
Gemäß der erfindungsgemäßen Lösung werden die Signale virtueller Quellen mit gleichem Signalinhalt so gegeneinander verzögert, dass ihre Signale gleichzeitig an dem Punkt in der Mitte des Überlappungsbereiches eintreffen. Auch dadurch werden die Kammfiltereffekte in diesem Bereich minimiert, das Versorgungsgebiet kann aber durch die größere Freiheit bei der Positionierung der virtuellen Schallquellen gegebenenfalls besser an die Form des Publikumsbereiches angepasst werden.According to the solution according to the invention, the signals from virtual sources with the same signal content are delayed from one another in such a way that their signals arrive simultaneously at the point in the middle of the overlap area. This also minimizes the comb filter effects in this area, but the coverage area can, if necessary, be better adapted to the shape of the public area due to the greater freedom in positioning the virtual sound sources.
Mit den in engerem Winkel abgestrahlten Wellenfronten kann gegenüber einer Versorgung des gesamten Publikumsbereiches mit einer einzelnen virtuellen Quelle die Forderung, dass die weit von der Vorrichtung aus Schallwandlern entfernten Publikumsbereiche nahezu mit dem gleichen Schalldruckpegel versorgt werden können, wie der Bereich unmittelbar davor, dadurch erfüllt werden, dass die Pegel der einzelnen Wellenfronten getrennt regelbar sind.With the wave fronts emitted at a narrower angle, compared to supplying the entire public area with a single virtual source, the requirement that the public areas far away from the device can be supplied with almost the same sound pressure level as the area immediately in front of it that the levels of the individual wavefronts can be regulated separately.
Mit der erfindungsgemäßen Anordnung aus Schallwandlern und Betrieb derer nach dem Prinzip der Wellenfeldsynthese ist es möglich, die zu versorgenden Bereiche sowohl in der Azimut Ebene als auch in der Elevationsebene voneinander zu trennen. So können für nahe der Bühne gelegene Publikumsbereiche abwärts ausgerichtete Wellenfronten erzeugt werden, deren Pegel abgesenkt wird, während die darüber liegenden Wellenfronten für die hinteren Publikumsbereiche mit höherem Pegel abgestrahlt werden. Auch eine getrennte Entzerrung des Frequenzganges, beispielsweise um den Höhenabfall durch die Luftschalldämmung für die weiter entfernten Publikumsbereiche auszugleichen, wird mit der erfindungsgemäßen Lösung möglich.With the arrangement according to the invention of sound transducers and their operation on the principle of wave field synthesis, it is possible to separate the areas to be supplied from one another both in the azimuth plane and in the elevation plane. In this way, downwardly directed wave fronts can be generated for audience areas close to the stage, the level of which is lowered, while the wave fronts above for the rear audience areas with a higher level be emitted. Separate equalization of the frequency response, for example to compensate for the drop in height due to the airborne sound insulation for the more distant public areas, is also possible with the solution according to the invention.
Die weitere Aufgabenstellung, dass mit einer gegebenen Vorrichtung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese jeder einzelne Schallwandler auch im oberen Frequenzbereich des Wiedergabespektrums effizienter arbeitet als bei der Reproduktion einer einzigen, breit abgestrahlten Wellenfront, wird mit der erfindungsgemäßen Lösung realisiert. Dazu wird der nachfolgend beschriebene Effekt angewendet.The further task that with a given device made of sound transducers according to the principle of wave field synthesis each individual sound transducer works more efficiently in the upper frequency range of the playback spectrum than when reproducing a single, broadly emitted wave front, is realized with the solution according to the invention. The effect described below is used for this purpose.
Man kann sich die eine virtuelle Schallquelle, die einen großen Publikumsbereich in weitem Abstrahlwinkel versorgen muss, auch als Addition von n virtuellen Schallquellen in einem gemeinsamen Punkt vorstellen. Prinzipiell ließen sich diese n virtuellen Schallquellen dann räumlich auch so verteilen, dass sie mit einzelnen, in einem engeren Winkel abgestrahlten Wellenfronten wieder den ursprünglichen Bereich versorgen könnten. Soweit der Pegel jeder einzelnen virtuellen Schallquelle dann der n-te Teil des Pegels der ursprünglichen einen virtuellen Quelle wäre, hätte sich an den Verhältnissen prinzipiell nichts geändert.One can imagine the one virtual sound source, which has to supply a large audience area with a wide beam angle, as the addition of n virtual sound sources in a common point. In principle, these n virtual sound sources could then be spatially distributed in such a way that they could supply the original area again with individual wave fronts emitted at a narrower angle. If the level of each individual virtual sound source would then be the nth part of the level of the original one virtual source, the conditions would not have changed in principle.
Diese erfindungsgemäße Lösung kann aber nun von dem physikalischen Effekt profitieren, das sich die Pegel von mehreren virtuellen Schallquellen mit gleichem Signalinhalt in den einzelnen Schallwandlern nur dann linear addieren, wenn sie gleiche Phasenlage haben. Solange alle n Ausgangspunkte der virtuellen Schallquellen an der gleichen geometrischen Position sind, addieren sich all ihre Signalanteile in jedem Punkt der Anordnung aus Schallwandlern linear als kohärente Signalanteile.However, this solution according to the invention can now benefit from the physical effect that the levels of several virtual sound sources with the same signal content in the individual sound transducers only add up linearly if they have the same phase position. As long as all n starting points of the virtual sound sources are at the same geometric position, all of their signal components add up linearly as coherent signal components at each point in the arrangement of sound transducers.
Wenn die gleichen Einzelsignale aber von unterschiedlichen Raumpositionen ausgehen, so liegen sie mit unterschiedlichen Laufzeiten an jedem Schallwandler an. Deshalb addieren und subtrahieren sich ihre Anteile. Im Unterschied zur Addition phasengleicher Signale ergibt sich für die Addition zweier nicht phasenkorrelierter Signalanteile nicht mehr eine Verdoppelung des Signalpegels, sondern nur eine Vektoraddition auf den Wert von Wurzel aus 2 = 1,414, das entspricht nur +3 dB Pegelanhebung. Noch deutlicher wird dieser Unterschied zur linearen Addition bei einer großen Zahl virtueller Quellen mit gleichem Signalinhalt an unterschiedlichen Positionen. So ergibt zum Beispiel der Addition von 256 kohärenten Signalquellen einen Pegelanstieg um +48 dB, die Addition von 256 inkohärenten Quellen aber nur einen Pegelanstieg von +24 dB. Um die Differenz zwischen beiden Werten, in diesem Fall also um +24 dB, kann nun erfindungsgemäß der anteilige Pegel der räumlich verteilten virtuellen Schallquellen mit dem Signalinhalt der einen ursprünglichen virtuellen Schallquelle angehoben werden, ohne dass die einzelnen Schallwandler überlastet werden.If the same individual signals come from different spatial positions, however, they are applied to each sound transducer with different transit times. Therefore, their parts add and subtract. In contrast to the addition of signals in phase, the addition of two non-phase-correlated signal components no longer results in a doubling of the signal level, but only a vector addition to the value of the square root of 2 = 1.414, which corresponds to only +3 dB level increase. This difference to linear addition becomes even clearer with a large number of virtual sources with the same signal content at different positions. For example, the addition of 256 coherent signal sources results in a level increase of +48 dB, while the addition of 256 incoherent sources only results in a level increase of +24 dB. According to the invention, the proportional level of the spatially distributed virtual sound sources can now be compared with the difference between the two values, in this case by +24 dB Signal content of an original virtual sound source can be increased without overloading the individual sound transducers.
Somit wird es möglich, auch mit Schallwandlern geringer Leistung und Kennempfindlichkeit in einer Anordnung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese ausreichend hohe Schallpegel in einem ausgedehnten Zuschauerbereich zu realisieren. Nur im Zentrum der Anordnung aus Schallwandlern bleiben bei dem Verfahren die Signale der verteilten virtuellen Schallquellen in Phase, weil nur dann die Forderung erfüllt werden kann, dass die Wellenfronten im Überlappungsbereich mit gleicher Phasenlage eintreffen.It is thus possible to achieve sufficiently high sound levels in an extensive audience area even with sound transducers of low power and sensitivity in an arrangement of sound transducers based on the principle of wave field synthesis. In the process, the signals of the distributed virtual sound sources only remain in phase in the center of the arrangement of sound transducers, because only then can the requirement be met that the wave fronts arrive in the overlapping area with the same phase position.
Jedoch umfasst dieser Bereich am oberen Ende des Überragungsbereiches nur wenige Schallwandler nahe des Mittelpunktes, die Fläche wird erst mit der Wellenlänge des Signals größer. Hier sorgt aber die bessere Anpassung der Anordnung aus Schallwandlern für steigenden Wirkungsgrad.However, this area at the upper end of the transmission area only includes a few sound transducers near the center point; the area only increases with the wavelength of the signal. Here, however, the better adaptation of the arrangement of sound transducers ensures increasing efficiency.
Es kann auch notwendig sein, den gesamten Publikumsbereich aus mehreren räumlich getrennten virtuellen Schallquellen zu versorgen, damit im gesamten Publikumsbereich ein räumlicher Eindruck entsteht. So können zum Beispiel hinter der als akustischer Vorhang wirkenden Vorrichtung aus Schallwandlern nach dem Prinzip der Wellenfeldsynthese auch virtuelle Schallquellen erzeugt werden, die das Signal abstrahlen, das sonst den Stereolautsprechern zugeführt wird. Um die Vorzüge des beschriebenen Verfahrens zu nutzen, kann auch deren jeweiliger Signalinhalt nach dem beschriebenen Verfahren von jeweils zwei oder mehr virtuellen Schallquellen an unterschiedliche Positionen abgestrahlt werden.It may also be necessary to supply the entire public area from several spatially separated virtual sound sources so that a spatial impression is created in the entire public area. For example, behind the device consisting of sound transducers, which act as an acoustic curtain, based on the principle of wave field synthesis, virtual sound sources can also be generated that emit the signal that is otherwise fed to the stereo speakers. In order to use the advantages of the described method, the respective signal content of the described method can also be emitted by two or more virtual sound sources at different positions.
Das Verfahren ist in
Das Problem wird dadurch gelöst, dass das Signal statt von der einzelnen virtuellen Schallquelle (2) von mehreren virtuellen Schallquellen (5), (6), (7), (8) mit gleichem Signalinhalt erzeugt wird.The problem is solved in that the signal is generated by several virtual sound sources (5), (6), (7), (8) with the same signal content instead of the individual virtual sound source (2).
Diese Aufteilung des selben Signals auf mehrere Ausgangspunkte wird erfindungsgemäß dadurch möglich, dass alle virtuellen Schallquellen von solchen Positionen aus ihre Wellenfronten erzeugen, von denen aus sie von der Mitte des jeweiligen, unvermeidlichen Überlappungsbereiches im Publikum (9), (10) und (11) gleich weit entfernt sind. Die sich überlappenden virtuellen Schallquellen sind dazu auf einem gemeinsamen Radius um das Zentrum des Überlappungsbereiches positioniert. Bei einer anderen Anordnung mehrerer virtueller Schallquellen mit gleichem Signalinhalt wären deutlich hörbare Kammfiltereffekte im Überlappungsbereich durch die Überlagerung gleicher Signale mit unterschiedlichen Laufzeiten die unvermeidliche Folge.This distribution of the same signal to several starting points is made possible according to the invention in that all virtual sound sources generate their wave fronts from such positions from which they start from the center of the respective, inevitable overlap area in the audience (9), (10) and (11) are equidistant. For this purpose, the overlapping virtual sound sources are positioned on a common radius around the center of the overlapping area. With a different arrangement of several virtual sound sources with the same signal content, clearly audible comb filter effects in the overlap area would be the inevitable consequence of the superimposition of the same signals with different transit times.
Die Oberfläche der Wellenfronten, die von den virtuellen Schallquellen (5), (6), (7) und (8) ausgehen, steigt wegen des geringen Öffnungswinkels der Abstrahlung vor der Anordnung aus Schallwandlern (1) deutlich langsamer mit der Entfernung von (1), als die Oberfläche einer Wellenfront, die von der einzelnen virtuellen Schallquelle (2) ausgehen würde. Entsprechend geringer sinkt ihr Pegel mit der Entfernung. Zudem kann nun Pegel und Entzerrung für jeden Teilbereich getrennt geregelt werden.The surface of the wave fronts emanating from the virtual sound sources (5), (6), (7) and (8) increases significantly more slowly with the distance from (1) because of the small opening angle of the radiation in front of the arrangement of sound transducers (1) ), as the surface of a wave front that would emanate from the individual virtual sound source (2). Their level drops correspondingly less with distance. In addition, level and equalization can now be regulated separately for each sub-range.
In
In der Praxis wird die Anforderung nach unterschiedlichen Öffnungswinkeln aber bestehen. Einerseits kann die Abstrahlung damit den gegebenen Verhältnissen angepasst werden. Zum anderen lässt sich dadurch aber auch die zur Verfügung stehende Schallleistung besser nutzen. Weit entfernte Publikumsbereiche werden in sehr engem Winkel versorgt, während für die nahe gelegenen Bereiche die Schallleistung auch ausreicht, wenn sie in einem breiten Abstrahlwinkel verteilt wird.In practice, however, there will be a requirement for different opening angles. On the one hand, the radiation can be adapted to the given conditions. On the other hand, the available sound power can also be better used. Public areas that are far away are supplied at a very narrow angle, while the sound power is sufficient for nearby areas if it is distributed over a wide angle of radiation.
Damit auch dann die Wellenfronten benachbarter virtueller Schallquellen in ihrem Überlappungsbereich gleichzeitig eintreffen, müssen die Signale zeitlich gegeneinander verschoben werden.So that the wavefronts of neighboring virtual sound sources also arrive at the same time in their overlapping area, the signals must be shifted relative to one another in time.
In dem Beispiel ist das Signal der virtuellen Schallquelle (6) um die Zeit zu verzögern, die der Schall für den Weg (dt) benötigt. Dabei muss die Schallgeschwindigkeit entsprechend der aktuellen Außentemperatur in der Berechnung der Laufzeit verwendet werden, damit Laufzeiten im virtuellen und realen Teil der Abstrahlung übereinstimmen. Die aktuelle Temperatur ist deshalb im Zuschauerbereich zu messen und die daraus berechnete Schallgeschwindigkeit ist für alle Berechnungen regelmäßig zu aktualisieren. Eine Messung der Windrichtung und Windgeschwindigkeit im Zuschauerbereich kann die Treffsicherheit der einzelnen Wellenfronten in den Zuschauerbereichen erhöhen.In the example, the signal of the virtual sound source (6) is to be delayed by the time it takes for the sound to travel (dt). The speed of sound must be used in the calculation of the transit time according to the current outside temperature so that transit times in the virtual and real part of the radiation match. The The current temperature must therefore be measured in the audience area and the sound velocity calculated from this must be updated regularly for all calculations. A measurement of the wind direction and wind speed in the spectator area can increase the accuracy of the individual wave fronts in the audience area.
Entsprechend müssen dann auch die virtuellen Schallquellen (7) verzögert werden, damit die Wellenfronten in ihrem Überlappungsbereich (10) zur virtuellen Schallquelle (6) zur gleichen Zeit eintreffen. Entsprechend werden zuerst die Laufzeiten von (7) zu jedem einzelnen Schallwandler berechnet. Dann wird zu jedem der berechneten Werte die Zeitdifferenz zur virtuellen Schallquelle (6) plus Laufzeit (dt 5) addiert. So bleibt die Krümmung der Wellenfront erhalten, sie wird nur entsprechend später abgestrahlt.The virtual sound sources (7) then also have to be delayed accordingly so that the wave fronts arrive at the same time in their overlapping area (10) with the virtual sound source (6). Accordingly, the transit times from (7) to each individual transducer are calculated first. Then the time difference to the virtual sound source (6) plus the transit time (dt 5) is added to each of the calculated values. In this way the curvature of the wave front is retained, it is only emitted later.
Nachdem alle Laufzeiten von allen virtuellen Lautsprechern zu allen virtuellen Schallquellen entsprechend dieser Prozedur berechnet sind, kann die kleinste im Gesamtsystem berechnete Laufzeit von allen berechneten Laufzeiten im System subtrahiert werden, um so die endgültigen Werte festzuschreiben. Damit wird jede unnötige Latenz des Gesamtsystems vermieden.After all transit times from all virtual loudspeakers to all virtual sound sources have been calculated according to this procedure, the smallest transit time calculated in the overall system can be subtracted from all calculated transit times in the system in order to fix the final values. This avoids any unnecessary latency in the overall system.
In der Ebene der Anordnung aus Schallwandlern (1) sind die auf den Publikumsbereich (2) ausgerichteten, von den zum Überlappungsbereichen gleich weit entfernten virtuellen Schallquellen (3),(4),(5) und (6) ausgehenden Kugelausschnitte der Wellenfronten nur an einem einzigen Punkt im Zentrum der Anordnung aus Schallwandlern in Phase. Nur dort addieren sich die Membranauslenkungen des betroffenen Schallwandlers für alle virtuellen Schallquellen linear. Durch die Anforderung, dass benachbarte virtuelle Schallquellen gleich weit von der Mitte des Bereiches der Überlappung ihrer Wellenfronten im Publikumsbereich entfernt sein müssen, wird diese Bedingung immer erfüllt. Nur im Zentrum der Anordnung aus Schallwandlern sind die Signale aller virtuellen Schallquellen mit gleichem Signalinhalt deshalb bis zu den höchsten Frequenzen des Übertragungsbereiches in Phase. Eine entsprechende Absenkung in diesem Bereich verhindert ihre Überlastung. Wegen der relativ kleinen betroffenen Fläche lässt sich der Pegelverlust im oberen Übertragungsbereich durch entsprechende Entzerrung des Gesamtsignals leicht ausgleichen.In the plane of the arrangement of sound transducers (1), the spherical sections of the wave fronts directed towards the public area (2) and emanating from the virtual sound sources (3), (4), (5) and (6) that are equidistant from the overlapping areas are only visible a single point in the center of the array of transducers in phase. Only there do the diaphragm deflections of the affected sound transducer add up linearly for all virtual sound sources. Due to the requirement that neighboring virtual sound sources must be equidistant from the center of the area where their wave fronts overlap in the public area, this condition is always met. Only in the center of the arrangement of sound transducers are the signals from all virtual sound sources with the same signal content in phase up to the highest frequencies of the transmission range. A corresponding reduction in this area prevents them from being overloaded. Because of the relatively small area concerned, the level loss in the upper transmission range can easily be compensated for by appropriate equalization of the overall signal.
Es wäre auch denkbar, in diesem Bereich spezielle Schallwandler für den Bassbereich anzuordnen oder die Anordnung aus Schallwandlern als Rahmen um eine mittig angeordnete Bildwiedergabe aufzubauen.It would also be conceivable to arrange special sound transducers for the bass range in this area or to build up the arrangement of sound transducers as a frame around a centrally arranged image reproduction.
Unabhängig davon, ob eine solche geteilte Aufstellung gewählt wird, kann das für eine einzelne Quelle beschriebene Verfahren dann für jede Teilfläche angewandt werden. In der Skizze ist das nur für den linken Kanal der Stereowiedergabe eingezeichnet. Wieder ist (3) der Publikumsbereich. Die virtuellen Schallquellen (5), (6), (7) und (8) geben dann von ihren Ausgangspunkten auf den Radien um die Überlappungsbereiche (9), (10) und (11) das Signal der linken Quelle wieder. Der rechte Kanal wird spiegelbildlich in einzelne virtuelle Schallquellen aufgeteilt, aus Gründen der Übersichtlichkeit ist das in der Skizze nicht dargestellt.Regardless of whether such a split list is chosen, the method described for a single source can then be used for each partial area. In the sketch this is only shown for the left channel of the stereo playback. Again (3) is the audience area. The virtual sound sources (5), (6), (7) and (8) then reproduce the signal from the left source from their starting points on the radii around the overlap areas (9), (10) and (11). The right channel is split mirror-inverted into individual virtual sound sources; this is not shown in the sketch for reasons of clarity.
Die Merkmale der hierin beschriebenen verschiedenen Ausführungsformen können auch miteinander kombiniert werden.The features of the various embodiments described herein can also be combined with one another.
-
[1]
John J. Neumann, Jr. and Kaigham J. Gabriel, CMOS-MEMS Membrane for Audio-Frequency Acoustic Acuation, Electrical and Computer Engineering Dept., Carnegie Mellon University, 2001 , pp. 236-239 John J. Neumann, Jr. and Kaigham J. Gabriel, CMOS-MEMS Membrane for Audio-Frequency Acoustic Acuation, Electrical and Computer Engineering Dept., Carnegie Mellon University, 2001, pp. 236-239 -
[2]
US Pat. 6936524 US Pat. 6936524 -
[3]
Berkhout, A.J. (1988): A holographic approach to acoustic control'. Journal of the Audio Engineering Society, Vol.36, No.12, December 1988, pp.977-995 Berkhout, AJ (1988): A holographic approach to acoustic control '. Journal of the Audio Engineering Society, Vol.36, No.12, December 1988, pp.977-995 -
[4]
DE 10 2005 001 395 A1 DE 10 2005 001 395 A1
Claims (8)
- Method for operating an arrangement of sound transducers (1) according to the wave-field synthesis principle for the supply of an audience area (3) with a same audio signal content, wherein the arrangement of sound transducers (1) is operated such that it radiates wavefronts to the audience area (3) that correspond to those generated in a model by at least two virtual sound sources (5, 6, 7, 8) that, seen from the audience area (3), are arranged behind the arrangement of sound transducers (1), and the respective wavefronts corresponding to the same audio signal content, are each oriented to just part of the audience area (3), wherein the corresponding wavefronts of the audio signal content and beam angles of the wavefronts are obtained from positions of the at least two virtual sound sources (5, 6, 7, 8) with reference to the arrangement of the sound transducers (3),
characterized in that a signal level at the upper end of the frequency range to be transmitted is lowered in the centre of the arrangement of sound transducers (1) in order to bring about a higher efficiency for the sound generation with the remaining frequency range because of the incoherent addition of the corresponding wavefronts,
wherein in order for the supply of an audience area (3) with a same audio signal content- the virtual sound sources (5, 6, 7, 8) with the same signal content are arranged at different positions, and- the virtual sound sources (5, 6, 7, 8) with the same signal content are equidistant from a point in the middle of the part in the audience area (3) in which an overlap in their wavefronts cannot be avoided in the model, or the signal content of the virtual sound sources (5, 6, 7, 8) is delayed with respect to one another until their wavefronts arrive at this point at the same time, and- wherein the higher efficiency of the sound generation is brought about by a level increase by the spatially distributed virtual sound sources (5, 6, 7, 8). - Method according to Claim 1, characterized in that actuation of the sound transducers (1) results in a shortest propagation time, obtained from the calculation of propagation times between all virtual sound sources (5, 6, 7, 8) and all individual sound transducers (1), being subtracted from all calculated propagation times.
- Method according to Claim 1 or 2, characterized in that the levels of the virtual sound sources (5, 6, 7, 8) that supply individual audience areas (3) with the same signal content are separately regulated.
- Method according to one of Claims 1 to 3, characterized in that the levels of the virtual sound sources (5, 6, 7, 8) that supply individual audience areas (3) with the same signal content are separately equalized.
- Method according to one of Claims 1 to 4, characterized in that to the wavefronts of individual virtual sound sources (5, 6, 7, 8) that reproduce the signal content of a primary virtual sound source from discrete positions further individual signal content is mixed that remains restricted to the audience area (3) supplied by this primary virtual sound source.
- Method according to one of Claims 1 to 5, characterized in that temperature and/or wind direction and wind speed in the audience area (3) is measured in order to counteract dispersal or deflection of the wavefronts for the generation of the wavefronts by appropriately adapting parameters in the model.
- Apparatus having an arrangement of sound transducers (1) for supplying an audience area (3) with a same audio signal content according to the wave-field synthesis principle, wherein the apparatus is configured such that wavefronts to the audience area (3) that are radiated by the arrangement of sound transducers (1) correspond to those generated in a model by at least two virtual sound sources (5, 6, 7, 8) that, seen from the audience area (3), are arranged behind the arrangement of sound transducers (1), and the respective wavefronts of which, which correspond to the same audio signal content, are each oriented to just part of the audience area (3), wherein the corresponding wavefronts of the audio signal content and beam angles of the wavefronts are obtained from positions of the at least two virtual sound sources (5, 6, 7, 8) with reference to the arrangement of the sound transducers (3),
characterized in that the apparatus is furthermore configured such that a signal level at the upper end of the frequency range to be transmitted is lowered in the centre of the arrangement of sound transducers (1) in order to bring about a higher efficiency for the sound generation with the remaining frequency range on account of the incoherent addition of the corresponding wavefronts,
wherein in order for the supply of an audience area (3) with a same audio signal content- the virtual sound sources (5, 6, 7, 8) with the same signal content are arranged at different positions, and- the virtual sound sources (5, 6, 7, 8) with the same signal content are equidistant from a point in the middle of the part in the audience area (3) in which an overlap in their wavefronts cannot be avoided in the model, or the signal content of the virtual sound sources (5, 6, 7, 8) is delayed with respect to one another until their wavefronts arrive at this point at the same time, and- wherein the higher efficiency of the sound generation is brought about by a level increase by the spatially distributed virtual sound sources (5, 6, 7, 8). - Apparatus according to Claim 7, wherein the centre of the arrangement of sound transducers (5, 6, 7, 8) is equipped with sound transducers (5, 6, 7, 8) designed specifically for reproducing the bass range or is left vacant, and/or wherein the arrangement of sound transducers (5, 6, 7, 8) is arranged as a frame around an associated image reproduction and/or surrounds the image reproduction.
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DE102019106427B4 (en) * | 2019-03-13 | 2022-04-28 | Bundesrepublik Deutschland, vertreten durch den Bundesminister für Wirtschaft und Energie, dieser vertreten durch den Präsidenten der Bundesanstalt für Materialforschung und –prüfung (BAM) | Transducer and transducer arrangement for ultrasonic probe systems, ultrasonic probe system and test methods |
DE102019208631A1 (en) | 2019-06-13 | 2020-12-17 | Holoplot Gmbh | Device and method for sounding a spatial area |
CN111929365B (en) * | 2020-08-07 | 2023-08-22 | 广东汕头超声电子股份有限公司 | Ultrasonic imaging detection display method |
DE102021207302A1 (en) | 2021-07-09 | 2023-01-12 | Holoplot Gmbh | Method and device for sound reinforcement of at least one audience area |
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JP4127156B2 (en) * | 2003-08-08 | 2008-07-30 | ヤマハ株式会社 | Audio playback device, line array speaker unit, and audio playback method |
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