Method for direction-dependent correction of frequency response of acoustic wavefront

Abstract

The invention relates to a method for operating and / or arranging a two-dimensional acoustic transducer assembly (1) comprising a plurality of separately controllable acoustic transducers (9), in which the acoustic transducers (9) of the acoustic transducer assembly (1) each generate element waves according to the wave field synthesis principle and / or according to a beamforming method, which element waves are superimposed wavefronts, the local propagation direction for the at least one acoustic wave array is known or can be determined at each transducer (9) of the transducer assembly (1). At least one acoustic interference factor which causes a frequency-dependent and / or direction-dependent change in the acoustic pressure of at least one first acoustic transducer (9) of the acoustic transducer arrangement (1) is detected, and an input signal of the at least one first acoustic transducer (9) of the acoustic transducer arrangement (1) is coupled to at least one correction device, in particular a filter device, the at least one correction device adjusts the acoustic interference factor as a function of a local propagation direction of the at least one acoustic wave array surface on the at least one first acoustic transducer (9), in particular by minimizing the acoustic interference factor by means of a forward correction.

Description

Technical Field

[0001] The proposed solution describes a method for direction - dependent correction of the frequency response of an acoustic wavefront generated in a two - dimensional transducer assembly according to the wave field synthesis principle or according to a beamforming method. Background Art

[0002] Using a plurality of separately controlled acoustic transducers, it is possible to radiate several acoustic wavefronts simultaneously in different directions. The vector - based method known from German patent application DE 10 2021 207 302 A1 adapts the shape and sound level of each wavefront among the wavefronts generated from a plurality of elementary waves to the audience area, so that almost no unwanted reflections in the reproduction space are excited even under adverse acoustic conditions. This results in an extremely high speech intelligibility in the entire audience area. Additionally, the signal levels are adjusted by the described method so that a very balanced sound pressure level is achieved in the audience area even if the shape of the entire audience area is irregular and the distances of the listeners from the transducer surface vary greatly.

[0003] For this purpose, the delay times and sound levels are calculated separately for each individual transducer of the transducer assembly and for each individual wavefront. For example, a mathematical method for calculating the delay time is described in patent application DE 10 2021 207 302 A1. In one embodiment, each transducer of the transducer assembly is associated with coordinates in the audience area. For each individual input signal in the input signal, the vector calculation of the distance between the transducer and the associated point in the audience area, with the corresponding correction of the sound level, results in a very uniform sound pressure distribution in the audience area.

[0004] According to the wave field synthesis principle (A.J. Berkhout, A Holographic Approach to Acoustic Control, J.Audio Eng.Soc, Vol. 36, No. 12, 1988), a plurality of acoustic transducers generate a wavefront that supplies a very uniform high - audio - quality level to a given listener area without causing excessive radiation from adjacent reflecting surfaces undesirably.

[0005] As the size of the audience area for large events continues to grow, the demand for sound systems also increases. Generally, in the case of low - direction radiation of sound waves, the sound pressure differences between individual audience measurement points are intolerable, and the reproduction, frequency response, and speech intelligibility suffer from sound level drops, air - borne sound insulation, and unwanted reflections.

[0006] For this reason, speaker assemblies from several independent sound sources direct sound more strongly to a more distant listener area. A typical application is the so-called line arrays, which are arranged, for example, on the left and right above the front of the stage. The curvature of these line arrays is adapted to the listener area so that the radiation wavefront in the elevation plane is directed to a more distant listener area. Almost cylindrical waves are generated around this part of the speaker assembly.

[0007] The surface of the cylinder grows linearly with its radius, which is why the sound pressure drops by 3 decibels for every doubling of the distance.

[0008] In the lower region of the sound transducer assembly, the larger curvature of the transducer surface produces a larger vertical opening angle. In this region, the wavefront is almost a spherical segment. Here, the surface of the sphere, which grows quadratically with the radius, causes a 6 dB drop in sound pressure for every doubling of the distance. Since the sound pressure drops rapidly in the vicinity and is wide with respect to the axis of the distant cylinder, the sound pressure difference between the front listener area and the rear listener area is significantly reduced.

[0009] In recent years, sound lines with electronic control of individual sound transducers have also been used. Each sound transducer has its own amplifier, which is controlled by a signal processor. Compared to what can be achieved with the mechanical alignment of individual sound transducers, mathematical methods allow the radiation to adapt significantly better to the listener area. The curvature of the sound transducer assembly can be simulated and electronically adjusted according to Huygen's principle, with a small delay in the control of each transducer. However, for available sound lines, these possibilities are limited to the elevation plane.

[0010] Since the directivity characteristics can also be adjusted using this improved radiation only in the elevation plane, the sound field still only roughly adapts to the given listener area. In the azimuth plane, the radiation is given only by the mechanical alignment of the speaker group. Here, at most, the listener area can be adapted by choosing speaker elements with a wider or narrower horizontal directivity characteristic.

[0011] Speaker fields (such as those available for audio reproduction according to the wave field synthesis principle (e.g., in WO2015036845A1)) are significantly more flexible. Here, each sound transducer operates on a separate final amplifier. According to Huygen's principle, the wavefront is composed of the superposition of elementary waves of each individual sound transducer, which reconstructs a spherical segment of the wavefront of a real sound source. The center of this spherical segment is the virtual sound source of the wave field synthesis. The boundaries of the spherical segment are determined by the size of the sound transducer field in combination with the positioning of the virtual sound source. Summary of the Invention

[0012] Each sound transducer of at least one sound transducer assembly radiates elementary waves during operation, and these elementary waves are superimposed to form a common wavefront. Whenever the radiation of elementary waves from a sound transducer is mentioned hereinafter, it means the acoustic center of the sound transducer.

[0013] At least one sound transducer assembly and the listener area are associated with a common coordinate system, in particular with a Cartesian coordinate system.

[0014] As will become clear hereinafter, the coordinate system on the side of at least one sound transducer assembly is particularly used to provide a starting point for a positioning vector which, together with a direction vector determines the radiation of sound from at least one sound transducer assembly. Thus, the coordinate system links at least one sound transducer assembly with at least one listener area.

[0015] There is a spatial association between the positioning vector and the physical positioning of the transducer. In the simplest case, the acoustic center of the sound transducer is located at the origin of the positioning vector . However, the sound transducer may not be exactly located at the origin of the positioning vector . If the positioning of the acoustic center of the sound transducer deviates from the intersection point of the auxiliary grid, the changes in the delay time and sound level associated with this deviation can be corrected by spatial interpolation or other methods. For example, the positioning vector can be stored in the form of a list.

[0016] By introducing a coordinate system, the points in the listener area and the points on at least one sound transducer assembly - and thus indirectly including the sound transducers themselves - can be simply geometrically related to each other, such as when calculating the distance from a sound transducer to a point in the listener area.

[0017] The method starts with the point association of the coordinate system to the points in at least one listener area and accordingly associates the positioning vector . Thus, the positioning vector points to a specific position in the listener area 3.

[0018] According to the positioning vectors (the positioning of each sound transducer can be determined indirectly or directly based on these positioning vectors), the direction vectors, in particular the normalized direction vectors , can be determined, and these direction vectors determine the radiation direction of the wavefront in the area of the corresponding sound transducer.

[0019] Now, based on the spatial association between the positioning vector and the sound transducer, the delay time for the transducer is determined , and then radiate elementary acoustic waves at these delay times. In each case, the delay times of the acoustic transducers are selected such that the local direction of the common wavefront corresponds to the direction of the direction vector, in particular to the direction of the normalized direction vector .

[0020] Thus, the acoustic transducers of at least one acoustic transducer assembly each operate with a specific delay time . The delay time of the acoustic transducer determines the time at which the elementary wave is generated at the corresponding acoustic transducer. Specifically, the delay times of the individual acoustic transducers can be determined relative to the input signal . In other words, each acoustic transducer is assigned an individual delay time . The delay times of the individual acoustic transducers may differ substantially, but some acoustic transducers may also operate with the same delay time .

[0021] The overall delay time at which the individual acoustic transducers of the acoustic transducer assembly operate affects the shape of the common wavefront, which is composed of the elementary waves generated by the individual acoustic transducers. Specifically, the shape of the common wavefront can be determined by the overall delay time .

[0022] Specifically, complex wavefronts can be generated by certain selections of the delay time . Thus, for example, correspondingly shaped wavefronts with different curvatures are due to different delay times in the acoustic transducer assembly . The wavefront formed by the elementary waves is no longer a spherical segment, since the wavefront is generated by virtual sound sources of a two-dimensional wave field synthesis acoustic transducer assembly. Depending on the shape and size of the supply area (i.e., the supply area of at least one listener area), there are areas of stronger curvature and flatter curvature. In the direction away from the audience position, the convex curvature of the wavefront is generally smaller, and the stronger curvature in the direction of the front audience position allows the sound pressure level to decrease more rapidly with distance and distributes the energy over a larger audience area.

[0023] The delay times of the individual acoustic transducers can be determined such that the common wavefront is adapted to the geometry of the listener area. Specifically, the local direction of the wavefront is determined by the delay time Control. The irregularly shaped wavefronts thus formed are in principle associated with the same number of grid points of the acoustic transducer assembly (i.e., the grid points of the coordinate system in the area of the acoustic transducer assembly), and thus also with the same number of acoustic transducers with the same listener area size. In this regard, such wavefronts are fundamentally different from the spherical segments of the point-like virtual sound sources of wave field synthesis, in which the audience surface supplied by the same number of acoustic transducers continuously increases with distance.

[0024] In each case, the local direction of the common wavefront at a location on the wavefront describes the direction in which the common wavefront propagates at the corresponding location. In each case, the local direction of the common wavefront can be described by a direction vector perpendicular to the corresponding point on the common wavefront. When the wavefront moves perpendicular to the direction vector, the direction vector describes the local propagation direction of the common wavefront.

[0025] It is possible to adapt the common wavefront to the geometry of at least one listener area by a determinable association, which in each case associates a positioning vector (which can be associated with the respective wave transducers, for example) with the positioning in the listener area corresponding to the positioning vector . A standardized direction vector results from the respective association. Subsequently, a delay time is selected in each case such that the local direction of the common wavefront at the positioning described by the positioning vector in the listener area corresponds to the direction of the direction vector . Specifically, the local propagation direction of the common wavefront is given by the standardized direction vector .

[0026] The acoustic transducers of at least one acoustic transducer assembly can be arranged on a plane or in a plane. Alternatively, the acoustic transducers of the acoustic transducer assembly can be arranged on at least a partially curved surface or in at least a partially curved surface. For example, the assembly can be grid-shaped. Specifically, the distance between the acoustic transducers can be uniform. For example, in each case, the distance in a first direction (specifically, in the vertical direction) and / or the distance in a second direction (specifically, in the horizontal direction) can correspond or result in a regular sequence of distance variables. The geometry in which the acoustic transducers are arranged or on which they are located can be complex. For example, the acoustic transducers can be located on the planar surface of an area, while other acoustic transducers of the same acoustic transducer assembly are located on a curved surface. Different parts of the surface can also have different radii of curvature.

[0027] Alternatively, the acoustic transducers of at least one acoustic transducer assembly are arranged in a three-dimensional region, in particular in space. The assembly of the individual acoustic transducers can be determined starting from a reference surface, such as a planar surface or a curved surface, where at least a partial amount of the acoustic transducers of at least one acoustic transducer assembly are arranged on the reference surface, and the positioning of the remaining acoustic transducers of at least one acoustic transducer assembly can be determined by a spatial offset into the three-dimensional region.

[0028] In each case, the acoustic transducers associated with the positioning vectors operate with a delay time and can be controlled by means of a computer system. Specifically, this control can be adjusted digitally using the delay time or can be implemented by digital control. The delay time can be in the millisecond range. For adjacent acoustic transducers, the time difference is typically only a few microseconds, such that the entire system requires a very stable system clock.

[0029] Additionally or alternatively, the delay time of the acoustic transducer operation can be subject to mechanical or geometric influences. For example, the delay time of an acoustic transducer can be controlled by means of a spatial offset (in particular in the radiation direction of the acoustic transducer assembly) relative to the other acoustic transducers of the acoustic transducer assembly.

[0030] The listener area can have at least partially a planar or concave shape and / or at least partially a convex shape. The listener area can be described as a continuous area or as a discontinuous area comprising at least two continuous parts. Examples of listener areas consisting of several areas are the large hall of the Philharmonie, Berlin or an opera house with several tiers. However, the listener area can also be represented by a plurality of coordinate points.

[0031] In a coordinate system, the positioning vectors associated with the acoustic transducers of an acoustic transducer assembly

[0032] can generate a regular grid. Additionally or alternatively, the positioning vectors can generate a regular grid on a reference surface

[0033] associated with the listener area. The association of each positioning vector in the acoustic transducer array with the point in the listener area corresponding to the positioning vector can be determined by means of a connecting line from the acoustic transducer assembly into the listener area. Specifically, the connecting line can be a half-line starting from the positioning vector Subsequently, the positioning vector can be associated with the sound transducer, which is generated by the intersection of the half-line with the listener area or a reference surface associated with the listener area .

[0034] Additionally or alternatively, the sound level of the sound transducer operation of at least one sound transducer assembly can be determined by means of a relative amplification factor, in particular based on the defining equation to determine, where in each case, describes the positioning vector of the reference surface .

[0035] By operating the sound transducer according to the relative amplification factor , the sound pressure level at the receiver position is ensured to be independent of the angle between the direction vector and the normal . Thus, a uniform volume in the listener area to be sound-irradiated can be ensured.

[0036] Furthermore, the proposed solution includes a method for determining the delay time for a sound transducer assembly having a plurality of sound transducers , which are used to generate elementary waves according to the delay time to sound-irradiate at least one listener area.

[0037] The method includes the following steps: determining a coordinate system by means of which at least one sound transducer assembly is approximately described as a reference surface , and the listener area is approximately described as a reference surface ; determining the positioning vector on the reference surface of at least one sound transducer assembly, based on which the positioning of the sound transducers of at least one sound transducer assembly can be determined; starting from the positioning vector to determine the normalized direction vector , where the normalized direction vector points to the reference surface of the listener area; and determining the delay time for the sound transducer such that the elementary waves of the sound transducers of the sound transducer assembly overlap during operation according to the delay time to form a common wavefront, where the normalized direction vector describes the local propagation direction of the common wavefront.

[0038] In other words, the common wavefront is substantially perpendicular to the normalized direction vector Propagation. In this way, the normalized direction vector describes the propagation process of the common wavefront. Specifically, by appropriately selecting the normalized direction vector , the common wavefront can be adapted to the geometry of the listener area.

[0039] To adjust the sound level, the relative amplification factor for at least a portion of the localization vectors can be determined according to the following defining equation:

[0040]

[0041] where is the normal to the reference surface of the sound transducer assembly at the point determined by the localization vector , and is the normalized direction vector starting from the localization vector .

[0042] The localization vector can correspond in whole or in part to the localization of the sound transducers on the sound transducer assembly. In each case, there is a spatial association between the physical localization of the individual sound transducers in at least one sound transducer assembly and the localization vector used to set the coordinates in the area of at least one sound transducer assembly.

[0043] The localization vector can be the same as or different from the number of sound transducers in the sound transducer assembly. Specifically, the number of localization vectors can be higher than the number of transducers on the sound transducer assembly.

[0044] The localization vector can describe the intersection points of an auxiliary grid described on the reference surface of at least one sound transducer assembly. However, the localization vector does not have to be located at all the intersection points of the auxiliary grid. For example, the auxiliary grid can describe a rectangular plane.

[0045] In each case, the number of grid lines in the horizontal direction and / or the vertical direction can correspond to the number of rows and / or columns of the sound transducers in the sound transducer assembly. However, the number of grid lines in the horizontal direction and / or the vertical direction can also be greater than the number of rows and / or columns of the sound transducers in the sound transducer assembly.

[0046] The method can also include determining the localization vectors on the reference surface of the listener area, where in each case, the localization vector is associated with a positioning vector . This association can be effected by a connecting line from the positioning vector to the positioning vector . A corresponding normalized direction vector can be determined based on these positioning vectors. Specifically, in each case, the direction vector can be determined by means of the calculation definition formula .

[0047] In one embodiment, the connecting lines as a whole are such that they do not cross or intersect pairwise. Specifically, no connecting line intersects the corresponding other connecting line.

[0048] The association of the positioning vector with the positioning vector can be automatic, in particular by means of a 3D CAD file of the listener area. This association can be accomplished according to a suitable mapping method. Specifically, points and / or regions of the reference surface of the listener area can be omitted during the association, for example, points and / or regions corresponding to areas in the listener area that will not be hit by a common wavefront.

[0049] The positioning vector can be evenly distributed on the reference surface of the listener area. This allows these positioning vectors to correspond to evenly distributed points in the listener area. For example, the even distribution of the points is ensured by the fact that two adjacent points are at the same distance from each other.

[0050] The reference surface of the listener area can be described by an auxiliary grid. The positioning vector can at least partially correspond to the intersection points of the auxiliary grid.

[0051] Similarly, the reference surface of the acoustic transducer assembly can be described by an auxiliary grid, and the positioning vector corresponds at least partially to the intersection points on this auxiliary grid. Such an auxiliary grid is particularly important for numerical processing because, for example, numerical integration can be easily performed in this auxiliary grid by means of the trapezoidal rule.

[0052] The auxiliary grid on the reference surface of at least one acoustic transducer assembly and the auxiliary grid on the reference surface of the listener area can be converted into each other. Specifically, these auxiliary grids can have the same number of lines in the horizontal plane and / or the vertical plane. By connecting the intersection points of the auxiliary grids, a reference plane of at least one acoustic transducer assembly and a reference plane Establish a suitable connection therebetween.

[0053] The reference surface of at least one acoustic transducer assembly can be a planar or, for example, at least partially curved surface. Specifically, the reference surface of the acoustic transducer assembly can have a different curvature in the horizontal direction than in the vertical direction.

[0054] In one embodiment, the reference surface of the acoustic transducer assembly is parameterized by means of coordinates where and are real continuous variables.

[0055] To determine the respective delay times for the acoustic transducers , first, the delay times for a finite number of positioning vectors of the form can be determined, and subsequently the delay times for the acoustic transducers can be determined at least in part by interpolation of at least two values of the form .

[0056] In one embodiment, the delay times can be determined by means of numerical integration of a discrete 2D vector field . The delay difference in the direction or the delay difference in the direction is given by:

[0057] Or

[0058] ,

[0059] where and each describe the discrete increments in the direction or the direction, describes the speed of sound, and where and are given by the following scalar product:

[0060] Or

[0061] ,

[0062] where each describe the distance from the positioning vector and a normalized direction vector starting from and describes a tangent vector to the reference surface starting from the positioning vector 。 。

[0063] The tangent vector and are given by the following partial derivatives:

[0064]

[0065] 。

[0066] In other words, in the method for determining the delay time , first, based on the two-dimensional discrete vector field defined by the following formula

[0067] or

[0068] ,

[0069] the tangent vectors to the reference surface of the acoustic transducer assembly and , the normalized direction vector and the speed of sound can be used to determine. Subsequently, the vector field can be integrated by means of a numerical integration method. The function obtained by integration describes the desired delay time.

[0070] The value of the function describes the delay time at the positioning vector 。 A separate positioning is defined for each single combination of the parameter u and the parameter v. Subsequently, the delay at the actuator positioning can be determined by spatial interpolation.

[0071] Subsequently, the calculated time is executed using the time of the closest sample pre-determined by the sampling frequency of the entire system.

[0072] Specifically, the desired delay time is described by the function , the gradient of which has a two-dimensional vector field , where the components and are given as above. The wavefront can be regarded as a relief that associates the height at this position with each intersection point of the grid. The gradient at this position is a vector pointing in the direction of the maximum elevation angle. The magnitude of this vector indicates the maximum slope at this point.

[0073] Sound velocity can depend on position, for example, in the case where there is a higher temperature in a higher region of the sound propagation area, which affects the sound velocity. The sound velocity can also depend on position, and this position is subsequently included in the calculation.

[0074] The numerical integration method can include the composite trapezoidal method, the Simpson method, the Romberg method, or a more advanced inverse gradient method.

[0075] If the reference surface of the acoustic transducer assembly is parameterized by means of the function described above the reference surface of the acoustic transducer assembly that can be used to determine the sound level correction normal is given by the cross product of and at the point described by where

[0076] , where

[0077] and are given by partial derivatives, as described above. Description of the drawings

[0078] The following describes embodiments by way of example with reference to the drawings. In the drawings

[0079] Figure 1 embodiments for operating an acoustic transducer assembly are described;

[0080] Figure 2 a schematic diagram of a method for direction-dependent correction of the frequency response is described;

[0081] Figure 3 a schematic diagram of the wavefront of a virtual sound source for wave field synthesis in a two-dimensional acoustic transducer assembly is described;

[0082] Figure 4 a schematic diagram of a wavefront depicting the shape of the wavefront of a two-dimensional acoustic transducer assembly adapted to an audience area is described;

[0083] Figure 5 a determination of the normal vector on the curved reference surface of the acoustic transducer assembly is described;

[0084] Figure 6 an association of the auxiliary grid of the acoustic transducer assembly with the auxiliary grid in the listener area is described;

[0085] Figure 7Describes the formation of the local direction vector of the wavefront and shows the listener area, which local direction vector starts from the sound transducer and originates from the surrounding elementary waves;

[0086] Figure 8 Describes the formation of the normalized direction vector of unit length;

[0087] Figure 9 Describes an embodiment in which the listener area is divided into individual partial areas with different signal contents;

[0088] Figure 10 Describes a group of sound transducers adapted to a non-variable listener area;

[0089] Figure 11 Describes an embodiment with a mechanically bent surface of the sound transducer;

[0090] Figure 12 Describes the frequency response of a woofer (left) and a tweeter (right) with and without a translucent panel without signal processing;

[0091] Figure 13 Describes the spatial transfer function of the MDI strong panel; and

[0092] Figure 14 Describes the transfer function of the optimized 120° beam at angles of 0°, 30° and 60°. Detailed Description of the Invention

[0093] In Figure 1 For purposes of explanation, an embodiment of the method from [1] is briefly represented by way of example. The method is based on the fact that each sound transducer 9 in the sound transducer assembly 1 is associated with a point in the listener area 3. For each sound transducer 9, each intersection point of the grid in the listener area 3, and each input signal in the simultaneously reproduced input signals of the system, the process is performed separately. Thus, the mathematical method described in [1] supplies a delay time τ and a relative amplification factor .

[0094] The superposition of the elementary waves of adjacent sound transducers produces the corresponding desired local direction within the wavefront. The local propagation directions are synthesized to form the wavefront, the shape of which can be irregular depending on the shape and structure of the listener area. This is the only way to achieve sound level stability within a wide, irregularly shaped audience area.

[0095] The relevant data of each input sound channel Ch 1…Ch n are processed in the same way for these input sound channels, and the sum of all signals gives the contribution of the corresponding sound transducers to the wavefronts, which radiate simultaneously in different directions with independent signal contents and reach different audience areas.

[0096] In the method according to [1], the vector d for the local propagation direction of each wavefront is also available, and this vector is used to determine the distance for each individual sound transducer. Thus, the system knows the path that the corresponding wavefront must travel from the sound transducer to the listener. The polar coordinates φ and θ (i.e., spatial / 3D polar coordinates or spherical coordinates) can also be obtained from the calculation, and these polar coordinates are used to determine the local radiation direction of each individual wavefront.

[0097] The proposed solution describes how the spectral balance of the spatial radiation of the sound transducer assembly 1 can be significantly improved.

[0098] In principle, the proposed solution can be used as long as the local radiation direction generated by the superposition of the elementary waves of the surrounding loudspeakers is known for each radiation wavefront in the radiation wavefronts. In the method according to [1], this radiation direction is known from the direction of the vector d. However, this radiation direction can also be derived from the geometric positioning of the corresponding sound transducer relative to the virtual sound source from which the corresponding wavefront originates or determined by other methods.

[0099] In addition to uniform distribution, the goal of each audio reproduction is to maintain the audio spectrum throughout the audience area. However, in practice, there are some factors that greatly hinder the achievement of this goal. First, mention should be made of the spatial radiation characteristics of the sound transducers used. Due to the diameter of the sound transducers and other factors, direction-dependent sound level variations and frequency-dependent sound level variations are caused, which result in position-dependent spectral errors in the reproduction area. In addition, grids or other structures upstream of the radiation (e.g., a sound-transparent LED wall as described in [2]) can spectrally greatly alter the reproduction depending on the radiation direction. In a very large listener area, depending on the relative humidity, air pressure, and temperature, especially in the higher audio range, as the distance from the sound transducer assembly increases, the air-borne sound insulation severely limits the reproduction. In addition, so far, it has not been possible to achieve direction-dependent frequency response variations for, for example, correcting the specific preferences of individual listener groups or the hearing loss of individual persons or expanding the artistic possibilities for sound field design.

[0100] In Figure 2Embodiments of the proposed solution are described, which is a method for correcting the direction-dependent frequency response of acoustic wavefronts generated by a two-dimensional transducer assembly according to the principle of wave field synthesis or according to beamforming. The representation is limited to exemplary signal processing for a single transducer. Figure 2 The method represented in can be applied to the method described in [1], for example by adding software, provided that the resources of the hardware are sufficient for this purpose.

[0101] The signal lines of channels 1…n carry the input signal of the system to all transducer units and all modules. These signal lines can also be associated with the respective groups of transducers provided for radiation in different frequency ranges. Subsequently, a corresponding frequency response drop in the crossover range has been achieved and the sum signal of all frequency ranges has been equal to the linear frequency response of the entire system in its main radiation direction.

[0102] For each individual transducer, after being delayed by τ and the sound level being adjusted by a relative amplification factor dn, each input channel is supplied to a summer before the signal controls the loudspeaker. The extension of the system for correcting the direction-dependent frequency response is added before the signal delay in each input channel for the corresponding transducer. The order in which the subsequent corrections are implemented is not important. Additionally, individual corrections can be omitted or additional corrections can be added.

[0103] In the exemplary representation, the correction of the direction-dependent frequency response variation of the individual transducers is arranged at the first location in the signal path. Like other frequency response corrections, these corrections will be compensated by forward correction. For this purpose, the 3D polar coordinates of the corresponding transducers installed in the module are determined individually and stored in a low-reflection space. In principle, it will also be possible to use data on half-space radiation provided by the manufacturer or data measured in an infinite acoustic wall. However, the inhomogeneities of the acoustic wall surface of the module (especially when using multipath components) will produce significant differences from the radiation on a plane acoustic wall.

[0104] The measurement data is stored in a spherical coordinate system with a radius of 1 in angular steps, such that the relevant frequency response can be read out from the memory obtained from the transducer with the aid of the polar coordinates φ and θ, and these polar coordinates are used to determine the local radiation direction of each individual wavefront. Therefore, the data for the local direction of the wavefront known from [1] according to the relationship G (f,φ,θ) supplies a frequency response curve, and this frequency response curve can compensate for the frequency response error of the corresponding transducer in the local radiation direction of the corresponding wavefront as much as possible in the subsequent inverse filter G inv (f).

[0105] At a second location in the signal path, the compensation of the acoustic obstacle in the signal path is represented by way of example. This example can be a speaker grille having a low-pass function and forming a standing wave against the sound wall, or can be a perforated projection surface serving as a projection surface in front of the acoustic transducer module. In practice, there are also more complex requirements, such as a larger projection surface having only local openings for sound outlets, or very complex and rough-structured obstacles, such as the LED structure described in [2] in front of the acoustic transducer module.

[0106] Here, the compensation is also based on the forward correction of the acoustic transducer. Only for the measurement of the polar radiation of the acoustic transducer, the difference between the measurement of a single acoustic transducer without an acoustic obstacle and the measurement of the polar radiation in the presence of the aforementioned obstacle is stored. The additional steps are similar to the correction of the acoustic transducer and are performed in the latter component with the inverse filter of the function H inv (f) for normalized compensation.

[0107] The third correction component in the signal process is used to compensate for the airborne sound insulation in the signal process. The influence of airborne sound insulation on the frequency response depends on the relative humidity (in % units), the air pressure (in kPa), and the temperature (in K), and increases with the distance from the acoustic transducer to the listener. In principle, a data set with stored values could also be created here, but each of the three factors mentioned changes the curve in a different way; for this purpose, data sets for each distance step would have to be created for each of these values. Therefore, it is more appropriate to provide the relative humidity (in %), the air pressure (in kPa), and the temperature (in K) valid for the entire system, and to directly calculate the final frequency process of the airborne sound insulation within 1 m according to known mathematical relationships for a distance of 1 m, and to multiply these values by the distance from the acoustic transducer to the observer, which is known from the length of the vector d in [1]. Using the resulting value A inv (f), the inverse filter then compensates for the airborne sound insulation in the direction of the listener area of the relevant wavefront.

[0108] In order to be able to calculate the compensation filter for each of the three filter blocks, the data must be preprocessed. First, the data is normalized to change the overall amplification in all directions to a fixed value so as to reach the desired level. Thereafter, the data is regularized, which includes frequency limiting and spatial and spectral smoothing of the data. The smoothness depends on the required compensation quality and the available filter resolution. Finally, the normalized and regularized frequency response data for a given angle φ and θ (or d in the third block) is inverted to produce the final inverse filter.

[0109] Since compensation can cause undesired high filter amplification at certain frequencies or in certain directions, the maximum amount of compensation may be limited by the adjustment factors w G 、w H and w A .

[0110] For this purpose, limit values for a maximum compensation of, for example, up to +12 dB can be entered into the overall system. In principle, it is also possible to adapt this limit value to the current level of the corresponding input signal so that the maximum available margin is always used for compensation.

[0111] A narrowband frequency response drop that is less than one third of the width is subjectively difficult to interfere with, such as a narrowband frequency response drop that may be caused by the direction-dependent zero positioning of the sound transducer. This narrowband frequency response drop is different from the drop in the entire high-frequency range that becomes clearly audible at greater distances (especially in dry ambient air). Here, it is crucial to utilize the available margin to the maximum extent. A possibility for increasing the margin for more distant areas has been described in the patent specification [1]. As the distance from the sound transducer assembly increases, an equally large listener area is associated with a larger number of sound transducers. With the described extension of the method described in [1], a very balanced sound level process can be achieved over a wide, irregularly shaped audience area without significant sound coloring.

[0112] The described method permits further improvements. As an example, the direction-dependent frequency response variation mentioned at the beginning can be inserted as an additional correction element to specifically design the specific preferences of individual listener groups or the correction of the hearing loss of individual persons or to expand artistic possibilities.

[0113] Or the system can operate autonomously as an independent module with a permanently programmed direction effect and a permanently programmed direction-dependent correction of the frequency response. Subsequently, in the case of a fixed installation, a given audience area can be sound-irradiated with very high quality using one or more corresponding programmed modules.

[0114] It is also conceivable to use such modules in the home, which have a permanently programmed direction effect and correspondingly permanently stored values for the direction-dependent correction of the frequency response of their sound transducers. For example, when using a single input channel as a stereo speaker, the spectral constancy of the reproduction can be achieved via a specifically set radiation angle, which can never be achieved for individual speakers for each frequency range.

[0115] Further improvements and / or modifications are possible.

[0116] Figures 3 to 11Aspects for operating an acoustic transducer assembly 1 are described, which can also be operated, for example, using the proposed solution (method, computer program product, acoustic transducer assembly).

[0117] In Figure 3 a given listener area 3 to be acoustically irradiated using a planar acoustic transducer assembly 1 according to the wave field synthesis (WFS) principle is represented.

[0118] During operation, the transducers of the acoustic transducer assembly 1 generate elementary waves 8, which are superimposed to form a common wavefront 4. The common wavefront 4 is designed as if the common wavefront were emitted from a virtual sound source 12. Thus, the surface of the wavefront 4 formed by the elementary waves 8 of the transducers 9 corresponds to a spherical section. For illustration, the common wavefront 4 is divided into rectangles 105, which represent the proportion of the elementary waves 8 generated in approximately the same number of transducers of the acoustic transducer assembly 1 on the common wavefront 4 in each case.

[0119] In the spherical section 4, the corresponding partial areas 105 associated with a given number of transducers of the acoustic transducer assembly 1 have approximately the same size. Correspondingly, the sound pressure is evenly distributed on the surface of the wavefront 4 at the same time.

[0120] However, the listener areas 106 associated with these partial sections have very different larger surfaces, on which the same energy of the associated spherical axis section is distributed in each case. The sound pressure levels in different parts of the audience area 3 are correspondingly different.

[0121] The virtual sound source 12 is located Figure 1 behind the acoustic transducer assembly 1. The positioning of the virtual sound source 12 determines the curvature of the common wavefront 4 and the direction in which the common wavefront propagates. If the virtual sound source 12 is arranged near the acoustic transducer assembly 1, the supply area is wider and the curvature of the common wavefront 4 is stronger. The surface of the common wavefront 4 increases correspondingly rapidly with distance, so the sound pressure level decreases rapidly.

[0122] The farther the virtual sound source 12 is arranged from the WFS acoustic transducer assembly 1, the narrower the radiation angle and the smaller the curvature of the spherical section. At a very large distance, there is almost a parallel wavefront, and the sound level of the parallel wavefront hardly decreases with distance. However, thus, the supply area 10 narrows to such an extent that only a part of the audience area 5 is supplied. Therefore, the positioning of the virtual sound source 12 is a compromise between a wide supply range and an acceptable sound pressure drop in the back row of the listener area 3 to be acoustically irradiated. As in Figure 1It also becomes clear that the same number of acoustic transducers of the acoustic transducer assembly 1 supplies a part of the listener area 3 to be acoustically irradiated, and this part becomes significantly larger with distance, where the sound pressure drops correspondingly sharply. Additionally, it becomes clear that the surface to be acoustically irradiated outside the listener area 3 is also inadvertently hit by the common wavefront 4 in the entire supply area 10.

[0123] The possibility of supplying a given listener area with a number of virtual sound sources having the same signal content is known. A method for this operation is described in WO 2015 / 022579 A3. A three-dimensional further development of this method is described in the patent application DE 10 2019 208631 A1. The combination of a number of wavefronts emitted from different virtual sound sources permits a very balanced sound level process within the broad listener area 3. Reflective surfaces can be deliberately omitted, and the sound level can be adjusted individually for each individual wavefront. Even in an acoustically adverse environment, a high direct sound level with correspondingly good speech intelligibility can be achieved throughout the listener area 3. These methods come close to the goal of a complete and very uniform acoustic irradiation of a given listener area 3 using a two-dimensional acoustic transducer assembly 1 according to the wave field synthesis principle.

[0124] However, due to the different positioning of the virtual sound sources, a time offset between the individual beams arises in these methods (such as sound radiation within a specific spatial angle range). If the time difference between the beams is not compensated, this will cause a comb filter effect on the frequency response in the boundary regions of the beams. This time compensation is possible because the individual virtual sound sources can be controlled independently of each other in time. However, in the boundary regions of the individual beams, the offset can only be completely compensated for one point; at other positions, if wavefronts with coherent signal content overlap in the transition region, a perceptible comb filter effect in the higher reproduction frequency range is inevitable.

[0125] The listener area 3 at the venue is in principle pre-determined, and it is actually very difficult to adapt the shape and size of this listener area to the acoustic requirements for high-quality sound. The area to be supplied is rarely a planar rectangle. Usually, this area is asymmetric and rises more in the rear area to ensure a clear view of the stage. The positioning of the two-dimensional acoustic transducer assembly 1, which can be operated according to the wave field synthesis principle, is also in principle pre-determined because the sound sources will be located in the stage area.

[0126] An embodiment of a method for generating a closed wavefront without transitions between the individual beams, as known from wave field systems, using a substantially two-dimensional acoustic transducer assembly 1 is utilized hereinafter Figures 4 to 11To explain, the shape of the closed wavefront in its azimuth plane and elevation plane is designed such that it ensures a uniform distribution of the sound pressure level within the given listener area 3. This can be achieved if the spatial angle ω of a given number of the sound transducers on the wavefront to be generated is adapted to a given part of the listener area 3 such that the spatial angle supplies an equally large part of the listener area 3 respectively. This would not be possible for discrete virtual sound sources of wave field synthesis.

[0127] Figure 4 A sound transducer assembly 1 with a plurality of sound transducers is shown. The sound transducer assembly 1 is used for acoustic irradiation of the listener area 3. During operation, the individual sound transducers 9 of the sound transducer assembly 1 radiate elementary waves 8, and these elementary waves overlap to form a common wavefront 4.

[0128] The sound transducers 9 of the sound transducer assembly 1 operate at respective delay times i.e., the sound transducers 9 radiate the elementary waves 8 at respective delay times. The common wavefront 4 is formed by the operation of the sound transducer assembly 1 at respective delay times . Specifically, the common wavefront 4 can be shaped by the operation at respective delay times such that the common wavefront is adapted to the geometry of the listener area 3.

[0129] The sound transducer assembly 1 and the listener area 3 are associated with a common coordinate system 2, wherein the positioning of the individual sound transducers of the sound transducer assembly 1 is determined by the positioning vectors . If the sound transducers are not precisely arranged at the origin of the positioning vectors , the precise delay times of the individual sound transducers can be determined by interpolation starting from the calculation of the delay times at the surrounding intersection points of the auxiliary grid.

[0130] The sound transducers associated with these positioning vectors are driven at separate delay times for radiating the elementary waves 8. Basically, the individual delay times of the sound transducers 9 are different from each other, but these delay times can also be at least partially the same.

[0131] The delay times are determined by means of an association that associates each intersection point of the auxiliary grid 5 with an intersection point of the auxiliary grid 6 in the listener area 3. Specifically, this association associates the sound transducer 9 with the positioning vector with the point in the listener area 3 corresponding to the positioning vector

[0132] Direction vectors 7 are generated from the associations, which point in the direction from the intersection points of the auxiliary grid 5 to the associated intersection points of the auxiliary grid 6 in the listener area 3. In each case, the normalized direction vectors starting from the positioning vectors in the cuboid 60 are determined by the defining formula .

[0133] The delay times of the acoustic transducers determined by the associated positioning vectors are then each selected such that the local direction 50 of the common wavefront 4 at the positioning vector corresponds to the direction of the normalized direction vector 61 respectively. According to the proposed solution, the normalized direction vector 61 thus determines the shape of the common wavefront 4. Specifically, the local direction 50 of the common wavefront 4 can be determined by the direction vectors 7. In each case, the normalized direction vector 61 is perpendicular to the common wavefront 4.

[0134] By appropriately selecting this association (see

[0135] Figure 8 ) - and thus appropriately selecting the normalized direction vector 61 - the common wavefront 4 can be shaped such that the common wavefront adapts to the geometry of the listener area 3. This is done through the association of the grid points.

[0136] The wavefront 4 is then shaped such that the same number of acoustic transducers of the acoustic transducer assembly 1 are associated with equal partial areas 106 of the listener area 3. The corresponding partial surfaces 105 of the wavefront 4 then have different sizes at the same time. At this distance, the upper partial area of the schematic diagram is still significantly smaller than the lower partial area. Correspondingly, in this area, the sound pressure within the same wavefront is significantly higher than in the lower partial area intended for nearby viewer positions.

[0137] Figure 5 shows the reference surface 30 of the acoustic transducer assembly 1 simulated in the coordinate system 2 . On the reference surface 30 of the acoustic transducer assembly 1 , a regular curved auxiliary grid 5 is arranged, and the positioning of the individual acoustic transducers 9 of the acoustic transducer assembly 1 is aligned on this regular curved auxiliary grid. With the aid of the reference surface 30 , in particular with the aid of the auxiliary grid 5, the coordinates of the individual acoustic transducers 9 of the acoustic transducer assembly 1 in 3D space can be determined.

[0138] The reference surface 30 is parameterized by a curvilinear coordinate system with the aid of the equation , where and ​is a real-valued variable.

[0139] By definition, the normal 202 on the at of the reference surface 101 and is the normal of the tangent plane spanned by the tangent vectors 201 and is given by the partial derivatives

[0140]

[0141] The normal 31 on is given by the cross product of and

[0142]

[0143] The individual transducers 9 of the transducer assembly 1 do not necessarily have to be mounted at the intersection points of the auxiliary grid 5. The corresponding delays and sound levels of these transducers are interpolated to the intersection points in three-dimensional space. The reference surface 30 and the curvature of the auxiliary grid 5 can be different in the azimuth plane than in the elevation plane, and it is also possible to bend the auxiliary grid 5 only in one plane.

[0144] In fact, the reference surface 30 of the transducer assembly 1 will usually be a planar surface, so the auxiliary grid 5 will be a planar auxiliary grid. This corresponds to the case where the transducers 9 are mounted substantially in a two-dimensional assembly. The planar surface is considered a special case of a curved surface.

[0145] Figure 6 Shows the association of the auxiliary grid 5 of the transducer assembly 1 with the auxiliary grid 6 in the listener area 3. The solution represented here does not start with the localization of virtual sound sources (as represented in Figure 3 ), but rather starts from the given geometry of the listener area 3 to be sound-irradiated and the geometry of the transducer assembly 1.

[0146] In principle, the listener area 3 to be sound-irradiated can have any desired shape, planar, curved, or rising. Figure 6 Represents a listener area 3 with an irregular shape to be sound-irradiated, which is particularly asymmetric and rises more strongly in the rear area on the right side than on the left side.

[0147] For conventional methods, and also for the virtual sound sources of wave field synthesis, towards such as Figure 6The task of supplying the listener area represented in [text] with direct sound very evenly is only difficult to solve sufficiently because the curvature of the wavefront of the virtual sound sources of wave field synthesis is always a spherical section.

[0148] On the other hand, by means of the represented association of the auxiliary grid 5 and the auxiliary grid 6, a common wavefront 4 can be generated, the shape of which is adapted to the geometry of the listener area 3 to be sound-irradiated.

[0149] To solve this problem, the coordinate system 2 is determined.

[0150] The coordinate points distributed within the listener area 3 to be sound-irradiated are associated with the coordinate system 2. In Figure 6 [text], these coordinate points in the listener area 3 are arranged at the intersection points of the auxiliary grid 6, but these coordinate points can also be distributed in the listener area 3 by other mapping methods.

[0151] In addition, the auxiliary grid 5 is associated with the coordinate system 2, by means of which the positioning of the sound transducers 9 of the sound transducer assembly 1 can be determined. The auxiliary grid is represented in Figure 5 [text] as a planar, regular auxiliary grid. However, in principle, the auxiliary grid can also be curved, i.e., have curves. In principle, the auxiliary grid 5 can be arranged on a reference surface through which the sound transducer assembly 1 is simulated.

[0152] The number of coordinate points in the listener area 3 corresponds to the number of intersection points of the auxiliary grid 6. Therefore, the coordinate points of the auxiliary grid 6 in the listener area 3 can be associated with each intersection point of the auxiliary grid 5. The distribution of the coordinate points will occur throughout the listener area 3, with the intervals between the individual coordinate points being as even as possible.

[0153] With positioning The coordinate points are associated with each intersection point of the grid 5 in the listener area 3. The connecting lines 7 between the intersection points of the auxiliary grid 5 and their associated coordinate points in the listener area 3 then form vectors in the coordinate system 2, which are the basis for calculating the travel time and sound level of the audio signal.

[0154] The represented planar auxiliary grid 5 of the sound transducer assembly 1 has a rectangular shape, the aspect ratio of which is similar to the aspect ratio of the planned sound transducer assembly 1, for example in the form of a sound transducer array. This planar auxiliary grid should have at least as many intersection points as the sound transducers 9 provided in the sound transducer assembly 1. In principle, the aspect ratio is not defined, such that if it is suitable for the given spatial situation in the listener area 3, it will also be possible to construct a single-row sound transducer.

[0155] The distances of the grid lines of the auxiliary grid 5 may be different in the horizontal plane and the vertical plane, but should at least correspond to the number of rows and columns of the two-dimensional sound transducer assembly 1 .

[0156] The acoustic transducers 9 of the acoustic transducer assembly 1 may be mounted so that their acoustic centers are at the intersection points of the auxiliary grid 5. However, the positioning of the acoustic transducers may also be offset from the intersection points, wherein the respective operating times and sound levels of the acoustic transducers are determined by interpolating the values ​​calculated for the surrounding grid points.

[0157] A higher number of grid lines increases the accuracy of the interpolation. A lower number of grid lines results in a wavefront that is not uniformly curved but consists of flat surface sections. The resulting diffraction effects cause local irregularities in the frequency response.

[0158] In principle, not all intersection points of the auxiliary grid 5 need be associated with a physical sound transducer 9. This makes it possible to interrupt the installation in the area in which the low-medium frequency sound transducers 9 have their sound outlet openings. In addition, as described in DE 10 2009 006762 A1, all sound transducers 9 can be distributed slightly irregularly on the surface. In this way, undesired aliasing effects in the audience area 3 can be reduced, because the resulting comb filter effect is statistically compensated to a certain extent in the frequency response.

[0159] An auxiliary grid 6 placed in the audience area 3 completely surrounds the audience area. The shape of the auxiliary grid 6 is adapted to the audience area 3. In principle, this can be done manually. In practice, however, several hundred to several thousand grid points are required so that the distances between the sound transducers 9 are small enough to achieve a reproduction that is largely free of audible aliasing effects. The low number of grid lines in the schematic diagram serves to explain a clear functional principle.

[0160] Therefore, it is advantageous to automatically determine the coordinate points in the audience area 3 with the aid of the 3D CAD file of the audience area 3 using a suitable mapping method. Areas that are not intended to be directly hit by the common wavefront 4 can also remain free of associated grid points, because undesired reflections are emitted from these areas. Therefore, these areas are not associated with the sound transducers 9, the wavefronts of which are sent directly in their direction. The coordinate points are displaced from these areas without changing their number. The surrounding coordinate points are shifted accordingly to maintain a uniform distribution across the audience area 3. Each intersection point of the auxiliary grid 5 in the plane of the two-dimensional sound transducer assembly 1 will be associated with a reference point in the audience area 3 to be irradiated with sound.

[0161] The visualization in the 3D CAD file makes it easier to switch off the unoccupied listener areas 3. In this case, the calculations remain unchanged in principle, only the acoustic transducers associated with the unoccupied listener areas 3 are not supplied with a signal. This results in lower diffuse field sound levels at the venue, which contributes to better speech intelligibility in the occupied listener areas 3.

[0162] Figure 7 By way of example, it is explained how a local curvature 50 of a wavefront 4 arises from the superposition of elementary waves 8 of surrounding acoustic transducers 9, which, according to the method described, need not be a spherical segment. For simplicity, the acoustic centers of the acoustic transducers 9 are mounted in this example at the intersection points of the auxiliary grids.

[0163] According to the wave field synthesis principle, the single acoustic transducer 9 represented in black in the schematic diagram has non-directional half-space radiation. Therefore, the elementary wave 8 generated by the single acoustic transducer alone cannot form a direction vector. By superimposing the elementary waves 8 of the surrounding acoustic transducers, only a local direction vector of the wavefront associated with the single acoustic transducer is generated at a certain distance from the acoustic transducer assembly 1. .

[0164] The direction vector 7 can be determined for this intersection point using the following definition:

[0165]

[0166] . This direction vector is always orthogonal on the local wavefront 50.

[0167] exist Figure 7 In the exemplary representation of The points depicted are located at the intersections of the auxiliary grid 6 of the audience area 3 .

[0168] In principle, the direction vector 7 It can also be determined without the help of the auxiliary grids 5 and 6. In this case, the direction vector 7 From the reference surface 30 of the simulated acoustic transducer assembly 1 The positioning vector on Start with a positioning vector pointing to the audience area 3 , or point to the description of the simulated audience area 3 The positioning vector of the point on the reference surface 30 .

[0169] In the following, a method is described for deriving delay times and sound levels for individual sound transducers 9 from a given direction vector 7 such that the superposition of their elementary waves 8 is superimposed on a wavefront aligned consistently with a given listener area 3 .

[0170] In Figure 8 it is selected by way of example from the Figure 6 direction vector 7 is returned to the normalized direction vector 61 the length of which is defined as

[0171]

[0172] The desired wavefront generated by the acoustic transducer assembly 1 (in particular in the form of a curved or planar array) can be locally approximated by a plane wave extending (i.e., locally extending in the direction of this normalized direction vector) along the normalized direction vector 61 By operating the acoustic transducers 9 of the acoustic transducer assembly 1 according to the corresponding delay times of the signals, each local plane wave can be directed in the desired direction.

[0173] Each position on the reference surface 30 of the acoustic transducer assembly 1 the delay time at is determined by the scalar delay function determined.

[0174] In vector calculus, the gradient of a scalar function of several variables is the vector field the components of which can be determined by the partial derivatives from specifically, the following applies:

[0175]

[0176] The delay gradient can be determined as follows:

[0177] The normalized direction vector 61 and the tangent vectors and or the tangent vectors and the scalar product of which is given by

[0178]

[0179] The scalar and can be physically interpreted as the local differentials of the path lengths between the plane wave and the tangent plane of the acoustic transducer assembly 1.

[0180] In the special case of a planar acoustic transducer assembly 1, as Figure 8 represented in and equals​Figure 8 the quantities described in and , which represent the x- and z-components of a vector .

[0181] The delayed gradient from equation (5) and the components and are related by the speed of sound . Thus, the partial derivatives of the delay function can be described as

[0182]

[0183] In practice, the distance between the acoustic transducers 9 is finite. Thus, the differential equations from equations (7a) and (7b) must be rewritten as discrete difference equations. The delay differences in the or direction and are now given by

[0184]

[0185] where and are the discrete step sizes in the direction or direction. The required delay can be found by numerical integration of the discrete 2D vector field .

[0186] There are several mathematical integration methods available, such as the composite trapezoidal method, Simpson's method, or more advanced inverse gradient methods. The integration constant can be freely chosen. To satisfy the causality condition and minimize the system time delay, the minimum delay across all drivers is subtracted from the calculated delay.

[0187] The relative amplification factor for each positioning in the acoustic transducer assembly 1 is given by the scalar product of the normalized direction vector 61 and the normal

[0188]

[0189] where the normal is defined as in equation (2).

[0190] By operating the acoustic transducers 9 according to the relative amplification factor , the sound pressure level at the receiver positioning is made independent of the direction vector With respect to the normal angle.

[0191] As the inclination of the radiation with respect to the normal increases, the number of acoustic transducers 9 becomes larger in a given spatial angle Ω, such that the sound pressure level will increase here.

[0192] The compensation according to equation (9) corrects this sound pressure level according to Figure 6 the cosine function of the angle γ in. Using the uniform distribution of the coordinate points this ensures that the sound pressure is distributed very uniformly over the entire listener area 3 to be acoustically irradiated.

[0193] Figure 9 It is also possible to divide the listener area 3 to be acoustically irradiated into partial areas 701, 702, 703 with different signal contents.

[0194] In principle, these partial areas can also be distributed over the partial areas of the acoustic transducer assembly 1. However, if the high directivity of the entire assembly is used to align the signal content with the desired listener area 3, then a significantly precise acoustic irradiation will result. In each of the partial areas 701, 702, 703, the number of intersection points 6 then corresponds to the number of intersection points 5 of the auxiliary grid of the acoustic transducer assembly 1.

[0195] For the same signal content, dividing into partial areas does not make sense if the partial areas are not sufficiently spatially separated. If the signal content is coherent, then a comb filter effect will occur at the area boundaries.

[0196] The individual partial areas can also be smaller than the surface of the associated acoustic transducer 9, provided that the intersection points of the auxiliary grid are closer to each other in the listener area 3 than in the auxiliary grid of the acoustic transducer assembly 1. In this case, concave wave fronts are formed, and the sound pressure level of these concave wave fronts is higher in the listener area 3 than at the radiator surface itself.

[0197] It is also possible to reduce the size of the auxiliary grid in the listener area 3 to a point. The two-dimensional acoustic transducer assembly 1 then generates the same concave wave fronts according to the described vector-based method as if this concave wave front occurred in the two-dimensional acoustic transducer assembly 1 here according to the wave field synthesis principle in virtual sound sources.

[0198] Using the coordinates of the grid points 5 on the reference surface of the acoustic transducer assembly 1 and the associated coordinates 6 of these grid points in the listener area 3, it is also possible to compensate for the sound pressure drop at higher frequencies by air-borne sound insulation. At a given humidity, the frequency-dependent attenuation value per meter of air is precisely known. Because (by Figure 7 the direction vector in The distance to the relevant listener position (given by the length) is known, so the corresponding inverse equalization curve can be associated with each sound transducer 9.

[0199] In the larger listener area 3, the sound pressure drop at the upper limit of the audio range can rise to well above ten dB in dry air. In any case, this frequency range must be controlled significantly higher in the flat sound transducer assembly 1, because the sound level gain resulting from the improved adaptability of the synchronously operating speaker groups only acts at relatively long wavelengths. Therefore, the additional compensation for airborne sound insulation in the distant listener area 3 may bring the system to the limit of controllability at high signal levels in the higher audio frequency range.

[0200] The solution to this problem is to arrange the coordinate points at a distance closer to the sound transducer assembly 1. In the distant listener area 3, the same number of sound transducers 9 are then associated with a smaller partial area 106. Each half of the surface produces a 3 dB sound level increase, whereby the control of the associated sound transducers 9 must be reduced so that the sound pressure level remains almost the same throughout the listener area 3. The correspondingly reduced control signal is associated with a larger margin in the associated amplifier. This can then be used to equalize the drive signal to a greater extent.

[0201] In the method described, the localization of the sound source is fundamentally different from the localization of the virtual point sound sources for wave field synthesis. In wave field synthesis, in contrast to the real sound source, the virtual sound sources are in principle located at the virtual starting points of these virtual sound sources independently of the localization of the listener in the supply area.

[0202] However, the wavefront adapted to the listener area 3 does not start from the defined localization of the virtual sound sources. So to speak, this wavefront is formed from an extended source at many different starting points in the area behind the sound transducer surface. An observer in the Figure 4 left - front position will associate the starting point with the wavefront at the lower left corner of the sound transducer assembly 1, and for an observer in the right - rear, the sound comes from the upper right corner of the sound transducer assembly 1. For the reproduction without an optical reference for the sound source, this is not a drawback, but according to Figure 4 , spatial reproduction is only possible to a limited extent.

[0203] However, the method can be associated with the field of wave field synthesis, as it is possible to generate any desired form of wavefront from the theoretical derivation of wave field synthesis based on the Kirchhoff-Helmholtz integral (Jens Ahrens: The Single-layer Potential Approach Applied to Sound Field Synthesis Including Cases of Non-enclosing Distributions of Secondary Sources, doctoral thesis, Technische Universität Berlin, 2010).

[0204] Further improvements

[0205] So far, it has been assumed that the transducers 9 of the transducer assembly 1 are arranged in a regular grid. However, in practice, the distribution of the transducers 9 can also be irregular. First, the running time is calculated on a sufficiently dense regular grid , and thereafter the running time is interpolated to the irregularly placed transducers.

[0206] Figure 10 A listener area 3 with a complex design of partial areas 802 is shown, and the provision of the transducer assembly 1 with transducers 9 is illustrated, wherein the provision is adapted to the complex design of the listener area 3.

[0207] In the represented embodiment, the association between the points on the transducer assembly 1 and the points in the listener area 3 is achieved by means of the association of the intersection points of the auxiliary grid 5 of the transducer assembly 1 with the intersection points of the auxiliary grid 6 of the listener area 3.

[0208] However, not all intersection points of the auxiliary grid 5 are associated with the transducers 9 of the transducer assembly 1. In other words, the intersection points of the auxiliary grid 5 remain unprovisioned. Specifically, there are unprovisioned intersection points between the provisioned intersection points.

[0209] Therefore, the shape of the transducer assembly 1 can be adapted to the complex design and / or the geometry of the listener area 3 in a fixed installation. This allows for a more efficient use of the transducers.

[0210] The auxiliary grid 6 in the listener area 3 can be, for example, rectangular, and the auxiliary grid can in particular extend beyond the listener area.

[0211] The irregular shape of the auxiliary grid 6 may lead to incorrect results when calculating according to the described method.

[0212] The intersection points of the auxiliary grid 6 in the listener area 3 that do not have associated listeners (i.e., in the current case, the intersection points located outside the partial areas 5a, 5b, 5c of the listener area 3 to be sound-irradiated) are associated with the auxiliary grid points of the sound transducer surface of the auxiliary grid 5 that are not equipped with sound transducers or are turned off.

[0213] The auxiliary grid 5 of the sound transducer assembly 1 is optionally also aligned with the low- and mid-frequency sound transducers employed. The calculation of the operating time and sound level of these low- and mid-frequency sound transducers depends on the nearby grid points. The time offset for possible depth offsets will be compensated. The phase positioning of the subwoofers can also be effectively adjusted in this way. According to this method, the shortest of all the calculated operating times for each sound transducer is subtracted from all the calculated operating times, so that the front part of the wavefront adapted to the listener area 3 is always generated directly.

[0214] A further improvement relates to a device shaped according to the rules of the described method. With this device, a single wavefront whose shape is adapted to a given listener area can be generated from a mono signal without electronic time-shifting of the signal. This mechanical solution is advantageous for fixed installations in acoustically problematic environments. For example, it is possible to install an audio system with reasonable effort that ensures a high proportion of direct sound and correspondingly good speech intelligibility even under adverse acoustic conditions.

[0215] Figure 11 The mechanically bent sound transducer assembly 1 is illustrated by way of example.

[0216] With the mechanically bent sound transducer assembly 90, reference Figure 6 The listener area 3 to be sound-irradiated described can be supplied with a cut-to-size common wavefront 4.

[0217] In this case, the operation of the sound transducers 9 of the sound transducer assembly 1 is mechanically implemented according to the delay times obtained by the described method. All the sound transducers are supplied with a coherent signal, i.e., a signal from a mono signal source.

[0218] The mechanical implementation is achieved by the proper positioning of the sound transducers 9 on the mechanically bent sound transducer assembly 90, in particular by a suitable spatial offset of the sound transducers 9 relative to each other (especially an offset in the propagation direction of the common wavefront).

[0219] To determine the corresponding positioning of the sound transducers 9 in the sound transducer surface adapted to the listener area 3 to be sound-irradiated, starting from the associated grid points of the planar auxiliary grid 5, the removal is along the intended unit vector 61 Distance of the extended diagonal of the cuboid 40 。

[0220] With the known alternating angles thus obtained and it is possible to determine the new coordinates of the acoustic center of the relevant sound transducer 9 and its orientation in the right-angled triangles of the cuboid 40.

[0221] The delay times calculated according to the method described for each sound transducer 9 are formed by the mechanical offset of the acoustic center of the respective sound transducer 9 along the diagonal S of the respective cuboid d .

[0222] The different signal levels of the individual sound transducers 9 of this two-dimensional sound transducer assembly 1 can then be approximately realized at a common final amplifier by suitable parallel and series connections of the sound transducers 9 or by connection to different amplifiers, these common final amplifiers being respectively associated with sound transducers 9 having approximately the same sound level values.

[0223] As long as the spatial radiation characteristics of the sound transducers 9 do not decrease significantly, these sound transducers do not have to be oriented in the direction of the diagonal of the cuboid. As described in WO 2015 / 004526 / A2, the method can also be implemented by means for the lateral displacement of the sound transducers. The displacement of the acoustic center of the original sound transducer grid from the grid points is then obtained by the quotient .

[0224] A single mechanical device cannot produce spatial sound irradiation of the listener area 3. This single mechanical device is suitable for ensuring sound irradiation with a manageable effort, in which the distribution of the sound pressure level is very uniform throughout the listener area 3 and which ensures a high level of speech intelligibility even in acoustically unfavorable spaces.

[0225] In the following, some embodiments of a method and a device for sound irradiation of a given listener area 3 by means of a sound transducer assembly 1 are described, which are controlled according to the wave field synthesis principle using the individual delay times and sound levels.

[0226] Thus, for example, in variant 1 of the method, the shape of the acoustic common wavefront 4, which is composed of the superposition of the elementary waves 8 of the acoustic transducer 9, can be determined according to the given geometry of the listener area 3 and the acoustic transducer assembly 1, such that in the common coordinate system 2, the coordinate points in the listener area 3 are associated with each intersection point of the regular, at least partially planar and / or curved grid associated with the acoustic transducer, where vectors are generated from the connecting lines of these acoustic transducers, and the delay times of the corresponding associated acoustic transducers 9 can be calculated from these vectors through mathematical linkage. Thus, the local curvature of the wavefront formed by the superposition of the elementary waves 8 of the surrounding acoustic transducers 9 advances in the direction of this vector, such that a closed wavefront is formed, which can reach the entire listener area 3, and in this closed wavefront, for each acoustic transducer 9 from its associated vector, sound level correction is also possible, which improves the uniformity of the sound pressure within the entire listener area 3.

[0227] In an improvement of variant 1, for example, the coordinate points in the plane of the two-dimensional acoustic transducer assembly 1 are the intersection points of a planar or curved grid, and the coordinate points in the listener area 3 are associated with these intersection points in the common coordinate system 2, where the connecting lines between the respectively associated grid points and the points in the listener area 3 do not cross or intersect.

[0228] In a further improvement, in each case, the number of grid lines in the plane of the two-dimensional acoustic transducer assembly 1 in the horizontal and vertical directions corresponds to the number of acoustic transducers installed in the rows and columns of the two-dimensional acoustic transducer assembly 1. Alternatively, the number of grid lines can be greater than the number of acoustic transducers 9 in the rows and columns of the two-dimensional acoustic transducer assembly 1, where the acoustic centers of the individual acoustic transducers 9 may be arranged at the intersection points of the grid lines. The values for the delay time and / or the sound level can be determined, for example, by interpolating the values of the surrounding grid points, since the reference points in the listener area 3 can be adapted to the requirements of the geometry of the listener area 3 in all three spatial dimensions, where it must be noted that the areas between the individual grid points remain approximately the same size within the entire listener area 3, thus resulting in a relatively uniform distribution of the sound pressure level within the entire listener area 3.

[0229] In a further improvement of variant 1 or one of the above variants, the vector generated from the difference in the corresponding positioning of the coordinates of the grid points associated with the respective acoustic transducer 9 in the plane of the two-dimensional acoustic transducer assembly 1 and the associated coordinate points in the listener area 3 is applied to the components of the unit vector to form a mathematical basis for determining the time difference between adjacent acoustic transducers.

[0230] In principle, the physical acoustic transducer 9 radiating the same frequency range does not have to be associated with all intersection points of the auxiliary grid. For example, this makes it possible to interrupt the equipment in the area where the low- and mid-frequency acoustic transducer 9 has its sound outlet opening, or to place the high-frequency loudspeaker in front of the low- and mid-frequency acoustic transducer, where the running time difference is compensated by mechanical offset by interpolation at the intersection points of the auxiliary grid.

[0231] In a further refinement of the variant described above, the influence of the angle presented by the synthetic wavefront at a given grid point relative to the plane of the transducer assembly 1 on the signal level perceived at the associated point in the listener area 3 is compensated, since the sound level of the transducer associated with the respective point is compensated using the cosine function of the relevant angle, where the value of this cosine function corresponds to the component of the unit vector of the value.

[0232] In principle, several auxiliary grids in the listener area (each having the same number of points as the grid in the plane of the two-dimensional transducer assembly 1) can also be associated with the intersection points of the planar or curved grid in the plane of the two-dimensional transducer assembly 1, so that partial areas within the listener area can be supplied with different signal contents simultaneously, for example.

[0233] The reference points in the listener area 3 can be distributed more narrowly as the distance from the two-dimensional transducer assembly 1 increases. For example, it is intended that the area between the reference points becomes smaller as the distance from the two-dimensional transducer assembly 1 increases, so that the associated transducers 9 of the two-dimensional transducer assembly 1 can be controlled at a lower sound level while the sound pressure in the corresponding area remains unchanged, and thus more margin is available to compensate for the height drop caused by airborne sound insulation in these areas.

[0234] The influence of airborne sound insulation on the signals of the individual transducers 9 at the audience positions can be compensated, since the respective input signals of these transducers are compensated by inverse equalization of the influence of airborne sound insulation at a given atmospheric humidity according to the distance of the associated vector

[0235]

[0235] In principle, the individual listener areas 3 can be excluded from the supply temporarily, for example. If these listener areas are not occupied during an event, this increases the proportion of direct sound in the remaining part of the listener area 3.

[0236] In a device for acoustic irradiation of a given listener area 3, the run times at which the individual acoustic transducers 9 of the two-dimensional acoustic transducer assembly 1 radiate according to one of the method variants described above are not achieved by electronic delay of the signal content, but rather by mechanical positioning of the acoustic transducers controlled by coherent signals, where the signal level of the respective acoustic transducer 9 corresponds to the value determined for the original intersection points of the grid.

[0237] In the following, some embodiments of a method for direction-dependent correction of the frequency response of an acoustic wavefront are described.

[0238] Thus, for example, in variant 1a, the direction-dependent correction of the frequency response of the acoustic wavefront generated by the two-dimensional acoustic transducer assembly according to the wave field synthesis principle or according to the beamforming method, for example as an extension of the method for acoustic irradiation of a given audience area described in German patent application No. 10 2021 207302.6 [1], where several input signals can be associated with different audience areas simultaneously and independently of one another, where the signal levels are adjusted such that a very balanced sound pressure level is ensured throughout the audience area, the non-linearity of the frequency response of the individual wavefronts within the entire listener area can be largely compensated by additionally inserting a corresponding correction element into the signal path of each input channel for each respective acoustic transducer, and the implementation is based on the local radiation direction of the wavefront to be corrected relative to the front surface of the two-dimensional acoustic transducer assembly in each case, and is compensated for each input channel in the input channels of the system by inverse forward correction of the factors physically affecting the radiation linearization of each acoustic transducer.

[0239] In an improvement of variant 1a, the radiation direction-dependent non-linearity of the frequency response is largely compensated by the data of the respective acoustic transducers installed in the module by forward correction of the individual acoustic transducers of the acoustic transducer assembly, the data being stored in 3D spherical coordinates determined and stored separately in a low-reflection space such that the frequency response of these acoustic transducers in the radiation direction of the respective wavefront can be retrieved from the memory by means of the spherical coordinates φ and θ, and as a function Ginv(f), the frequency response error of the respective acoustic transducer in the local radiation direction of the respective wavefront is largely compensated by an inverse filter additionally inserted into the respective signal path.

[0240] Additionally or alternatively, in one embodiment, the frequency response error caused by an acoustic obstacle in the propagation direction of the wavefront can be largely compensated by forward correction, because the differences between the 3D spherical coordinates of each acoustic transducer between unobstructed radiation and radiation behind a structure that obstructs the propagation of the corresponding wavefront are spatially detected and stored as 3D spherical coordinates, such that the difference between two frequency responses in the radiation direction of the corresponding wavefront is called by means of the polar coordinates φ and θ, and the difference is normalized and inverted into a function Hinv(f), and the frequency response error caused by an acoustic obstacle in the local radiation direction of the corresponding wavefront is compensated to the greatest extent by an inverse filter additionally inserted into the corresponding signal path.

[0241] Additionally or alternatively, the influence of airborne sound insulation on the frequency response of the corresponding wavefront can be largely compensated, because the attenuation process for a 1 m distance is directly calculated according to known mathematical relationships using the actual values of relative humidity (in %), atmospheric pressure (in kPa), and temperature (in K) in the listener area, and the inverted and normalized values are multiplied by the distance from the acoustic transducer to the listener area towards which the local part of the relevant wavefront is directed, in order to compensate for the distance-dependent sound level loss of the relevant wavefront in the direction of the listener area by means of a filter in the signal path using the resulting function Ainv(f).

[0242] Additionally or alternatively, the inversion of the frequency response generated from the stored or calculated data can be connected upstream of the filter in the signal path to compensate for the frequency response drop by means of a correspondingly higher amplification and to reduce the resonance increase by attenuating the signal in the corresponding frequency range, where the correction can be implemented in octave, third-octave, or smaller frequency steps, and where the shift of the total level of the relevant sound channel upstream of the filter is compensated by a corresponding correction of the total level of the correction curve, and where the maximum value for compensation subsequently prevents over-control of subsequent stages in the individual frequency ranges.

[0243] Additionally or alternatively, additional polar frequency response data and inverse or non-inverse filters, which affect the direction-dependent frequency response variation for a selected wavefront, and the specific preferences of each listener group or the correction of hearing loss for an individual person or the extended artistic design possibilities for a spatial sound field or other acoustic targets can be inserted into the signal path as additional correction elements using these polar frequency response data and inverse or non-inverse filters.

[0244] In principle, the order of the correction elements in the signal path can be freely selected, and individual correction possibilities can be bridged or omitted.

[0245] Additionally or alternatively, if the direction of the wavefront is fixed in the system, the fixed correction values can be stored in the system.

[0246] In principle, in a system with permanently programmed direction effects and permanently programmed direction-related corrections of the frequency response, it is possible to operate autonomously as a separate module or to engage with another correspondingly programmed module to form a permanently programmed acoustic transducer array.

[0247] Additionally or alternatively, data for the direction characteristics can be stored in a separate module, can be read from a central memory, and can be rewritten via a data bus during the setup process.

[0248] Additional embodiments are described below.

[0249] Example 1. A method for acoustic irradiation of at least one listener area (3) by means of at least one acoustic transducer assembly (1) having a plurality of acoustic transducers (9), wherein in each case, the individual acoustic transducers (9) of the at least one acoustic transducer assembly (1) radiate elementary waves (8), which are superimposed to form a common wavefront (4),

[0250] characterized in that

[0251] a) the at least one acoustic transducer assembly (1) and the at least one listener area (3) are geometrically linked to each other by means of a coordinate system (2), and

[0252] b) there is a spatial association between the physical positioning of the individual acoustic transducers (9) in the at least one acoustic transducer assembly (1) and the positioning vectors for determining the coordinates in the area of the at least one acoustic transducer assembly (1), and furthermore

[0253] c) there is an association between the points of the coordinate system (2) and the points corresponding to the positioning vectors in at least one listener area (5), where

[0254] d) a direction vector, in particular a normalized direction vector (61), generates the coordinate system (2), and

[0255] e) depending on the spatial association of the positioning vectors with the acoustic transducers (9), a delay time is determined for the acoustic transducers (1), by means of which the elementary waves (8) are radiated by the acoustic transducers (9), where

[0256] e) in each case, the delay time of the acoustic transducers (9) is selected such that the local direction (50) of the common wavefront (4) corresponds to the direction of the direction vector, in particular to the direction of the normalized direction vector (61) .

[0257] Example 2. The method according to embodiment 1, characterized in that the transducer (9) of the at least one transducer assembly (1) is arranged in a plane or on the plane or arranged in or on at least a partially curved or planar surface (30), in particular arranged in a grid-like manner, wherein the positioning of the acoustic center of the transducer may deviate from the intersection point of the auxiliary grid (5), provided that the associated changes in the delay time and the sound level are corrected by spatial interpolation or other methods.

[0258] Example 3. The method according to example 1, characterized in that the transducer (9) of the at least one transducer assembly (1) is arranged in a three-dimensional region, in particular arranged in space, in particular such that at least a partial amount of the transducers (9) of the at least one transducer assembly (1) are arranged on a reference surface (30), and the positioning of the remaining transducers (9) of the at least one transducer assembly (1) can be determined by an offset (91) into the three-dimensional region.

[0259] Example 4. The method according to at least one of the foregoing examples, characterized in that by means of a computer system and / or mechanically , in particular by spatially offsetting (91) the transducers (9) of the at least one transducer assembly (1) relative to each other, the operation of the transducers (9) with a delay time is controlled by a controller.

[0260] Example 5. The method according to at least one of the foregoing examples, characterized in that the at least one listener region (3) has at least a partially concave and / or at least a partially convex shape.

[0261] Example 6. The method according to at least one of the foregoing examples, characterized in that the at least one listener region (3) can be described as a continuous surface.

[0262] Example 7. The method according to at least one of the foregoing examples, characterized in that the at least one listener region (3) can be described as a discontinuous surface composed of at least two continuous surfaces.

[0263] Example 8. The method according to at least one of the foregoing examples, characterized in that the positioning vector generates a regular grid.

[0264] Example 9. The method according to at least one of the foregoing examples, characterized in that the positioning vector generates a regular grid (6) on a surface associated with the at least one listener area (3).

[0265] Example 10. The method according to at least one of the foregoing examples, characterized in that the points in the at least one listener area (3) are associated with each positioning vector corresponding to the positioning vector The association can be determined by means of a connection line from the at least one acoustic transducer assembly (1) to the listener area (3).

[0266] Example 11. The method according to at least one of the foregoing examples, characterized in that the sound level at which the acoustic transducer (9) of the at least one acoustic transducer assembly (1) operates is adjusted such that the sound pressure in the at least one listener area (3) is uniform.

[0267] Example 12. The method according to Example 11, characterized in that the sound level at which the acoustic transducer (9) of the at least one acoustic transducer assembly (1) operates can be based on a rule determined by means of a relative amplification factor, where in each case, describes the positioning vector associated with the acoustic transducer (9) on the reference surface (30) normal.

[0268] Example 13. The method according to at least one of the foregoing examples, characterized in that the at least one listener area (3) has at least two partial areas irradiated acoustically with different signal contents.

[0269] Example 14. The method according to at least one of the foregoing examples, characterized in that the common wavefront (4) is shaped such that the common wavefront adapts to the geometry of the at least one listener area (3), grid points are associated, and the common wavefront (4) is then shaped such that partial areas (106) of equal size of the at least one listener area (3) are associated with substantially the same number of acoustic transducers (9) of the acoustic transducer assembly (1).

[0270] Example 15. The method according to at least one of the foregoing examples, characterized in that a partial area of the at least one listener area (3) is assigned to a partial area of the sound transducer assembly (1), and different audio contents can be associated with the partial area simultaneously, wherein the directivity of the sound transducer device (1) is used to align the signal content with a predetermined part of the at least one listener area (3), and wherein in each of the partial areas (701, 702, 703), the number of intersection points (6) subsequently corresponds to the number of intersection points (5) of the auxiliary grid of the sound transducer assembly (1).

[0271] Example 16. A method for determining a delay time of a sound transducer (9) for operating at least one sound transducer assembly (1), the sound transducer assembly having a plurality of sound transducers (9) for generating elementary waves (8) according to a delay time for acoustic irradiation of at least one listener area (3), the method comprising the steps of:

[0272] - Determining a coordinate system (2) by means of which

[0273] ○ The at least one sound transducer assembly (1) is approximately described as a two-dimensional reference surface (30) of the at least one sound transducer assembly (1), and

[0274] ○ The at least one listener area (3) is approximately described,

[0275] - Determining a positioning vector on the reference surface (30) of the at least one sound transducer assembly (1), according to which the positioning of the sound transducers (9) of the at least one sound transducer assembly (1) can be determined,

[0276] - Determining the association of each positioning vector on the reference surface (30) of the at least one sound transducer assembly (1) with a positioning vector corresponding to a point in the at least one listener area (3),

[0277] - Determining a direction vector, in particular a normalized direction vector (61) starting from the positioning vector , wherein the normalized direction vector (61) starting from the positioning vector respectively points to the positioning vector starting from which the normalized direction vector (61) points respectively to the positioning vector the associated positioning vector ; and

[0278] - determining a delay time for the acoustic transducer j such that the elementary wave (8) generated by the acoustic transducer (9) is changed during operation according to the delay time to form a common wavefront (4), wherein the normalized direction vector (61) respectively describes the local propagation direction (50) of the common wavefront (4).

[0279] Example 17. The method according to Example 16, comprising determining a relative amplification factor for the positioning vector s for at least a portion according to the following defining equation :

[0280]

[0281] where is the normal of the reference surface (30) of the acoustic transducer assembly (1) at the point determined by the positioning vector and is the normalized direction vector (61) starting from the positioning vector .

[0282] Example 18. The method according to Example 16 or 17, characterized in that the positioning vector describes the positioning of the transducer (9).

[0283] Example 19. The method according to at least one of Examples 16 to 18, characterized in that each positioning vector on the reference surface (30) of the at least one acoustic transducer assembly (1) is associated with a positioning vector on the reference surface of the at least one listener region (3), and the determination of the direction vector, in particular the determination of the normalized direction vector (61) for at least one positioning vector is by means of the connecting line (7) between the positioning vector and the positioning vector , in particular according to the calculation defining equation .

[0284] Example 20. The method according to Example 19, characterized in that for determining the normalized direction vector (61) ​The connecting lines (7) do not cross or intersect each other in pairs.

[0285] Example 21. The method according to at least one of Examples 16 to 20, characterized in that the positioning vector and the positioning vector The association between them is automatic, in particular based on the 3D CAD file of the at least one listener area (3).

[0286] Example 22. The method according to at least one of Examples 19 to 21, characterized in that the positioning vector is evenly distributed on the reference surface of the at least one listener area (3), and thus corresponds to evenly distributed points in the at least one listener area (3).

[0287] Example 23. The method according to at least one of Examples 16 to 22, characterized in that the reference surface of the at least one listener area (3) is described by an auxiliary grid (6), on which the positioning vector is at least partially an intersection point.

[0288] Example 24. The method according to at least one of Examples 16 to 23, characterized in that the reference surface (30) of the at least one acoustic transducer assembly (1) is described by an auxiliary grid (5), on which the positioning vector is at least partially an intersection point.

[0289] Example 25. The method according to at least one of Examples 16 to 24, characterized in that the reference surface (30) of the at least one acoustic transducer assembly (1) is parameterized by means of coordinates where and are real continuous variables or discrete variables, and thus in particular, the positioning vector can be described in the form

[0290] Example 26. The method according to Examples 16 and 25, characterized in that the normal of the reference surface (30) of the acoustic transducer assembly (1) at the point described by is given by the cross product of and as

[0291] ​​, where

[0292] and are given by the following partial derivatives:

[0293]

[0294] .

[0295] 27. The method according to Example 26, characterized in that, in order to determine the corresponding delay time , first, a scalar function of the delay time of the localization vector for a finite amount of the form is determined, and the delay time for the transducer (9) having the localization vector is determined at least in part by interpolating at least two corresponding values of the form . .

[0296] Example 28. The method according to Example 27, characterized in that the scalar function of the delay time is determined by numerical integration of the discrete 2D vector field ,

[0297] - where the delay difference in the direction or the delay difference in the direction is given by

[0298]

[0299] - where and each describe the discrete increment in the direction or the direction,

[0300] - where describes the speed of sound, and

[0301] - where and are given by the following scalar product:

[0302] or

[0303] ,

[0304] where respectively describe the normalized direction vectors (61) starting from the localization vector , and and describe the tangent vector starting from the said positioning vector to the said reference surface (30) , in particular, where and are given by the following partial derivatives

[0305]

[0306] .

[0307] Example 29. The method according to Example 27 or 28, characterized in that the numerical integration method includes the composite trapezoidal method, the Simpson method, the Romberg method or a more advanced inverse gradient method.

[0308] Example 30. A computer program product for determining the delay time of a transducer (2) for operating at least one transducer assembly (1) of the transducer assembly having a plurality of transducers (2) for generating elementary waves (3) according to a delay time for acoustically irradiating at least one listener area (5) , characterized in that the computer program product comprises or uses means for executing at least one instruction for determining the delay time for the transducer according to at least one of Examples 1 to 15 or 16 to 29 . of the delay time .

[0309] Example 31. A device for acoustically irradiating at least one common area (3), comprising at least one transducer assembly (1) having a plurality of transducers (9), wherein the at least one transducer assembly (1) can be operated according to the method according to at least one of Examples 1 to 15.

[0310] Example 32. The device according to Example 31, wherein the at least one transducer assembly (1) and at least one listener area (3) are geometrically linked to each other by a coordinate system (2), and there is a spatial association between the physical positioning of each transducer (9) in the at least one transducer assembly (1) and a positioning vector for determining the coordinates in the area of the at least one transducer assembly (1), and there is further an association between the points of the coordinate system (2) and the points in at least one listener area (5) according to the positioning vector , and where the direction vector, in particular the normalized direction vector (61) generates the coordinate system (2), ​

[0311] Characterized in that:

[0312] a component for controlling the acoustic radiation of the acoustic transducer (9), the component determining a delay time for the acoustic transducer (1) based on the spatial association of the acoustic transducer (9) with a positioning vector wherein the transducer (9) radiates an elementary wave (8) at the delay time, and the delay time of the acoustic transducer (9) is respectively selected such that the local direction (50) of the common wavefront (4) corresponds to the direction of the direction vector, in particular to the direction of the normalized direction vector (61) and a component for associating each acoustic transducer (9) with a point in the at least one listener region (3) corresponding to the positioning vector such that a normalized direction vector (61) is generated

[0313] is generated, and a component for determining the delay time of the acoustic transducer (9) such that the local direction (50) of the common wavefront (4) corresponds to the direction of the normalized direction vector (61), wherein specifically, each acoustic transducer (9) of the at least one acoustic transducer assembly (1) radiates an elementary wave (8), the elementary waves are superimposed to form a common wavefront (4), and the at least one acoustic transducer assembly (1) and the at least one listener region (3) are associated with a common coordinate system (2), and the positioning of each acoustic transducer (9) of the at least one acoustic transducer assembly (1) and the acoustic transducer can each be operated at a delay time to radiate the elementary wave (8).

[0314]

[0315]

[0316]

[0317] Example 33. The apparatus according to Example 31 or 32, characterized in that the different operating times of the acoustic transducers (9) of the acoustic transducer assembly (1) are achieved using mechanical or geometric positioning of the acoustic transducers (9) controlled by coherent signals, wherein specifically, the signal level for the respective acoustic transducers (9) can correspond to the value determined for the original intersection points of the grid.

[0316] Additional exemplary embodiments are described below:

[0317] Hiding the sound system behind an acoustically translucent panel causes sound energy to be absorbed or reflected, resulting in amplified variations in the audio spectrum. The transfer function (TF) is the frequency-dependent reduction or amplification of the sound level of the sound source as it passes through the panel used to hide the sound system.

[0318] Traditionally, compensation for the TF of hidden speakers has been achieved by equalizing the average TF within a number of angles or simply taking the TF on the axis and applying an inverse curve as the characteristic curve of the equalization level. A preliminary assessment of the TF in an anechoic chamber concluded that the panels evaluated introduced very different amplification variations at different angles for the same frequency.

[0319] Therefore, the spectral balance in the audience area will deviate significantly at different angles and distances from the hidden audio module, which reduces spectral uniformity. The TF compensation described above will be insufficient, but an angle-dependent spatial transfer function will be required.

[0320] Wave field synthesis and 3D audio beamforming techniques are based on the high-resolution sensitivity and 3D directivity balloon of the transducers built into the audio module. With 3D audio beamforming algorithms, sound level and phase manipulation can be used to define individually shaped wavefronts that are fully adapted to the audience area. In addition, the resulting wavefronts are optimized for spatial and spectral uniformity based on a reference target curve.

[0321] If compensating for the spatial transfer function becomes challenging, a solution can be adopted to improve the spectral balance in the 3D space of the hidden audio module, as described herein.

[0322] If the algorithm knows the spatial transfer function introduced by the acoustic panel located in front of the sound transducer, the optimization and equalization machine will compensate for the influence of the panel in each direction and not just on the axis, thus providing similar power as if the panel were not present. Changes in the radiation balloon of the sound transducer caused by panel resonance, reflection, or acoustic absorption at a specific angle will be known in advance and will be partially compensated to achieve the desired spectral characteristic curve over the entire audible range.

[0323] The goal is to detect the direction balloon of the transducer when the transducer is attached behind, for example, a carbon fiber plate.

[0324] One possibility is to use holographic measurement methods to determine the directivity of the speaker. This method uses special solutions of the wave equation (spherical harmonics, Hankel functions) to determine the 3D sound pressure of the audio device. Compared with conventional measurement methods, this provides more comprehensive and accurate measurement data while minimizing costs and measurement time (e.g., for an expensive measurement space).

[0325] The instrument to be inspected is held in a fixed position at the center of the scanner. This simplifies the handling of heavy equipment and ensures constant spatial excitation during the scanning process and thus constant spatial reflection. The robotic arm moves the microphone around the instrument to be tested and detects the sound pressure in the near field.

[0326] By performing a double-layer scan, direct sound separation can be employed. For example, this direct sound separation uses additional phase information to detect the direction of sound waves and can remove all spatial reflections from the direct sound of the speaker. Thus, the measurement system can deliver accurate free-field data in any environment (such as a workshop or an office).

[0327] Therefore, the influence of the acoustic panel covering the audio module can be evaluated based on an exemplary pair of woofers and tweeters. Since the measurements in the near field do not include signal processing, the spectral power outside the operating range of the acoustic transducer is also shown. The frequency responses of the individual acoustic transducers with and without the acoustic panel are Figure 12 presented.

[0328] The comparison of the acoustic results of the two measurements shows the transmission loss of the frequency response close to the axis. In a conventional method, these frequency responses would be used as the basis for calculating the transmission gain and DSP would be used to compensate for this energy loss. However, if the off-axis frequency responses are also considered, the acoustically translucent panel causes further interference. At certain frequencies, especially in the range between 2 kHz and 5 Hz, there are additional resonances that affect the radiation pattern. Above f > 7 kHz, the measurements show that the transmission loss on the axis is higher than the transmission loss off the axis, which results in a lower directivity index and a slightly larger beam angle when the panel is attached.

[0329] Figure 13 The spatial transfer function of the acoustic panel in shows the amplification variation that is angle-dependent across the full spectrum. The spatial transfer function is the absolute spectral amplification difference between the bare transducer and the same transducer behind the acoustic panel after applying a frequency smoothing of 1 octave and a spatial smoothing of 15 degrees. The spatial smoothing has been applied to prevent isolated artifacts formed by the panel used for the measurement from being included in the general compensation for other panels with different characteristics: support, stiffness of the panel, and differences in manufacturing or small differences in the positioning of the panel.

[0330] To illustrate the advantages of the 3D audio beamforming method described herein compared to conventional audio solutions, the 3 kHz frequency is used as an example in Figure 13 The sound level difference between 0º (on the axis) and 45º is approximately 2 dB; thus, any global spectral correction at 2 kHz works effectively for one angle but overcompensates or undercompensates at other angles.

[0331] The spatial transfer function differences are difficult to solve with a single global equalizer. On the other hand, using 3D spectral compensation as part of an optimization engine, the sound transducers used to reproduce the beams can be spatially balanced individually, thus producing an optimal spectral balance as the listener moves across the audience area.

[0332] Once the transducer balloon data has been corrected with the panel's spatial transfer function and incorporated into the algorithm as an audio module variant, the hidden audio module can be optimized, simulated, and benchmarked.

[0333] Figure 14 Exemplary transfer functions of an optimized beam with an aperture angle of 120° are shown at 1 / 3 octave resolution for different scenarios at different angles (0º, 30º, and 60º): a simple audio module (black), the same module and beam configuration with an MDI panel in front (red), and finally an audio module with an MDI panel and spatial compensation using an algorithm.

[0334] Figure 14 Illustrates different spectral fluctuations at different angles, which can only be solved by individual equalization. The spatial compensation for the acoustic panel is achieved to restore the overall spectral balance of the desired frequency response. Isolated local artifacts or spectral colorations caused by panel resonances or reflections are not part of the correction because their compensation has been shown to be ineffective.

[0335] The audio system can be hidden in several ways. Acoustically transparent materials such as fabrics or perforated screens allow sound to pass through with minimal sound power loss and may be effective in certain environments.

[0336] If there are visible distortions when projecting video content, there may be problems. To solve this problem, a high-resolution video projection solution with a micro-perforated carbon fiber panel can be used. This has proven to be very effective because the micro-perforated carbon fiber panel provides a seamless projection surface, but has some drawbacks for the sound system behind the micro-perforated carbon fiber panel, namely, angle-dependent fluctuations in the transfer function.

[0337] Near-field scanner systems have proven to be an effective and robust method for detecting the directional characteristics of loudspeakers, including those hidden behind panels. The detection of the three-dimensional behavior of drivers mounted in an audio module and inserted behind a panel is used to obtain the data required for spatial spectral balance correction.

[0338] Spectrum balance correction compensates for the sound level differences between different angles in 3D space for the same frequencies across the entire audio spectrum. This feature greatly increases the spectral uniformity of the audio beam employed and has a distinct advantage compared to the conventional compensation methods used additionally.

[0339] Reference numeral

Claims

1. A method for operating and / or setting a two-dimensional transducer assembly (1), the two-dimensional transducer assembly comprising a plurality of discrete controllable transducers (9), wherein - the transducers (9) of the transducer assembly (1) each generate elementary waves according to the principle of wave field synthesis and / or according to a beamforming method, the elementary waves being superimposed to form at least one acoustic wavefront, wherein - the local propagation direction of the at least one acoustic wavefront on at least one first transducer (9) of the transducer assembly (1) is known or can be determined, characterized in that - at least one acoustic interference factor causing a frequency-dependent change and / or a direction-dependent change in the sound pressure of at least one first transducer (9) of the transducer assembly (1) is detected, and - the input signal of the at least one first transducer (9) of the transducer assembly (1) is coupled to at least one correction device, in particular a filter device, which adjusts the acoustic interference factor according to the local propagation direction of the at least one acoustic wavefront, in particular by minimizing the acoustic interference factor on the at least one first transducer (9) by means of forward correction.

2. The method according to claim 1, characterized in that - in a low-reflection space, the frequency response of at least one first transducer (9) of the transducer assembly (1) is determined for a plurality of radiation directions, which can in particular be described by means of spherical coordinates, - and wherein the correction device comprises an inverse filter which largely compensates for the non-linearity of the frequency response of the at least one first transducer (9) based on the frequency response error of the at least one first transducer (9) in the local propagation direction of the at least one wavefront at the at least one first transducer (9).

3. The method according to claim 1 or 2, characterized in that - the acoustic interference factor comprises an acoustic obstacle in the propagation direction of the at least one acoustic wavefront, and - the correction device comprises a filter which is based on the difference between the frequency response of the at least one first transducer (9) in the case where the radiation is disturbed by the acoustic obstacle, and the frequency response of the at least one first transducer (9) in the case where the radiation along the local propagation direction of the at least one wavefront on the at least one first transducer (9) is unobstructed, so as to minimize the influence of the acoustic obstacle.

4. The method according to at least one of claims 1 to 3, characterized in that - the acoustic interference factor comprises airborne sound insulation in the listener area in which the at least one acoustic wavefront is radiated, and / or - the correction device minimizes the influence of airborne sound insulation based on the current values of relative humidity (in %), air pressure (in kPa) and temperature (in K) in the listener area.

5. A two-dimensional transducer assembly (1) which is arranged and configured to be used for performing at least one of the methods according to claims 1 to 4.

6. A computer program product which is configured to be executed on a processor for performing at least one of the methods according to any one of claims 1 to 4.

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