Device for playing audio having a set non-constant curvature

Abstract

The present invention relates to a device (300) for playing audio comprising a single enclosure (310) and, in this single enclosure (310), at least two superposed high-frequency acoustic sources (320) and a plurality of superposed medium-frequency and / or low-frequency sources (330) placed to the left and / or to the right of the high-frequency acoustic sources (320), the high-frequency acoustic sources (320) being individually coupled to a waveguide (340) so as to generate a vertical wavefront having a set non-constant curvature. Such a device (300) makes it possible to minimise the discontinuities between the acoustic sources, allowing high-quality audio to be played (no parasitic lobes), to considerably decrease weight and cost of manufacture, and also a rapid installation requiring no angular adjustment of each of the acoustic sources with respect to one another, contrary to current devices.

Description

Domaine technique

[0001] The present invention relates to a sound diffusion device for a performance stage such as the stage of a concert hall or an open-air festival. Etat de la technique

[0002] The objectives of modern sound reinforcement are to ensure the most homogeneous sound coverage possible for the audience, across the entire audio spectrum (20Hz - 20kHz).

[0003] The aim is to provide the audience with a sound volume (dB SPL - decibel "Sound Pressure Level") of preferably equivalent intensity, while being able to be adapted as desired by the installer. It is also important to ensure optimal sound quality, i.e. free from interference.

[0004] To achieve this, it is common to multiply the acoustic sources within a sound diffusion device or system. The contributions of each of the acoustic sources would add up correctly if all the acoustic sources were arranged at the same point. In practice, this is impossible, as an acoustic source has a significant volume.

[0005] Furthermore, the use of "point source" speakers makes it impossible to achieve the objective of homogeneous sound intensity because the natural decrease of this type of product is 6 dB per doubling of the distance.

[0006] To achieve a higher SPL, it is also possible to combine several speakers of this type. This arrangement generates an interference sound field on the audience for frequencies whose half-wavelength is smaller than the distance between the elements.

[0007] EP 1 686 830 A1 shows a loudspeaker enclosure for forming linear arrays with adjustable horizontal and vertical directivity.

[0008] The use of so-called "line source" speakers makes it possible to achieve the aforementioned objectives by considerably improving the ability to send sound intensity far away while ensuring a loss of only 3dB per doubling of distance at high frequencies, and ensuring a sound field free from any interference.

[0009] Line source speakers consist of stacking the bass and midrange speakers on top of each other to form a curved line, respecting a pitch between speakers less than the smallest half-wavelength that each speaker must reproduce; using tweeters (compression drivers) coupled to rectangular output waveguides, the assembly generating a linear isophase wavefront free of interference even though the pitch between two drivers is much greater than the smallest wavelength to be reproduced.

[0010] A waveguide is a physical device that allows a possibly flat isophase wavefront to be obtained at the output. As such, it plays the same role as a horn that would be loaded onto a compression engine, with the major difference that it requires a reduced physical size. Indeed, obtaining a flat isophase wavefront at the output would require a horn of infinite length, contrary to the compactness objectives of a sound diffusion device.

[0011] Furthermore, in order to be able to adapt to all types of audiences and to be able to shape the SPL decay as desired on the audience, these speakers are generally designed in a modular way as relatively small elements, whose height is generally that of the largest loudspeaker.

[0012] Each speaker can then be tilted relative to its neighbor in a variable manner to ensure coverage, intensity and homogeneity objectives.

[0013] This angular flexibility makes it possible to focus energy in one direction (usually the distant audience) by stacking many speakers with little or no inter-element angle or, conversely, to cover a large angular sector with little energy by assembling the speakers with large inter-element angles.

[0014] This flexibility linked to modularity in small adjustable elements, however, presents a certain number of disadvantages: the multiplication of variable angle fixing devices between the speakers which involves a longer installation time, additional cost and excess weight; numerous wooden panels in order to close the acoustic volume of each element, which also generates additional cost and excess weight; a discontinuity of the wavefront due to the presence of these separation panels and assembly clearances, leading to the appearance of off-axis parasitic lobes. These uncontrolled lobes can, for example, be the cause of the establishment of feedback (i.e. larsen) which is not desired for the musician on stage; and a loss of acoustic volume due to the generally trapezoidal shape of the section of a speaker (in order to be able to tilt it with an adjacent element without amplifying the discontinuity of the wavefront).

[0015] Thus, there is a real need for a sound diffusion device that is simple and quick to install, can be adapted to any audience and offers high quality sound diffusion (no parasitic lobe). Description de l'invention

[0016] To solve one or more of the drawbacks cited above, the invention relates to a sound diffusion device according to claim 1.

[0017] More specifically, the at least two superimposed high-frequency acoustic sources form a curved vertical stack. This curved vertical stack has a fixed, non-constant physical curvature. Each high-frequency acoustic source has a main emission direction. The physical curvature of a curved vertical stack is clearly equal to the curvature of the arc representing the profile curve of this curved vertical stack.

[0018] Another definition of the physical curvature of the curved vertical stack of high-frequency acoustic sources can also be the succession of angles formed by the main emission directions of two consecutive acoustic sources.

[0019] For a number of high-frequency acoustic sources N greater than or equal to three, a physical curvature of the curved vertical stack of non-constant high-frequency acoustic sources is a curvature for which at least one angle alpha_i, formed by the main emission directions of two consecutive high-frequency acoustic sources, i being an integer between 1 and N-1, is different from the other angles alpha_n, for n different from i.

[0020] A physical curvature of the curved vertical stack of fixed high-frequency acoustic sources is, more precisely, a curvature that is not able to be modified by a user.

[0021] Particular features or embodiments, usable alone or in combination, are: each waveguide comprises an output, the outputs of the waveguides being arranged in a perfectly contiguous manner, so as to form a continuous ribbon; the curvature of the vertical wavefront is non-constant and fixed, and its evolution is monotonous; among the plurality of medium and / or low frequency acoustic sources there is at least one acoustic source emitting over a medium frequency range, the sound diffusion device also comprising: o orientable flaps acting on a sound emission of at least one of the high frequency acoustic sources to produce a sound emission directivity of the high frequency acoustic source according to a chosen angular sector, the high frequency acoustic source and the acoustic source emitting over a medium frequency range being configured to emit over a common frequency range;and o at least one control module of the digital signal processor type acting on a signal intended for the high-frequency acoustic source and on a signal intended for the acoustic source emitting on a medium-frequency range so as to apply in the common frequency range at least one magnitude parameter on the high-frequency acoustic source and / or on the acoustic source emitting on a medium-frequency range as well as at least one phase parameter on the high-frequency acoustic source and / or on the acoustic source emitting on a medium-frequency range so as to produce a sound emission directivity of the pair consisting of the high-frequency acoustic source and the acoustic source emitting on a medium-frequency range according to the same angular sector chosen as the directivity produced by the adjustable flaps. ;

[0022] Another feature that can be used alone or in combination with the previous ones is that the curvature of the curved vertical stack has a monotonic evolution.

[0023] Another feature that can be used alone or in combination with the previous ones is that the sound diffusion device includes at least three high-frequency acoustic sources.

[0024] Another feature that can be used alone or in combination with the previous ones is that electronic control and amplification channels are capable of supplying each or more of the high frequency sources, as well as each or more acoustic sources among the plurality of medium frequency and / or low frequency acoustic sources.

[0025] To cover an audience far from the stage, the invention relates in particular to an extended range sound diffusion device, in which all of the high-frequency acoustic sources produce an overall sound emission directivity having a total vertical opening angle of less than or equal to 20°.

[0026] To cover an audience close to the stage, the invention also relates to a sound diffusion device with extended vertical opening, in which all of the high-frequency acoustic sources produce an overall sound emission directivity having a total vertical opening angle greater than 20°.

[0027] To cover a larger audience, the invention also relates to a sound diffusion assembly which may comprise at least a first extended-range sound diffusion device and a sound diffusion device as previously defined, superimposed such that the resulting sound diffusion assembly generates a vertical wavefront with fixed non-constant curvature.

[0028] In other words, advantageously, the extended range sound diffusion device is coupleable and is assembled with another sound diffusion device as previously defined.

[0029] In particular, the extended-range sound diffusion device may be coupled to an identical extended-range sound diffusion device. The term "identical" should be understood to mean a device that is a strict copy of the "extended-range" sound diffusion device 300_F, having exactly the same technical, geometric and physical characteristics. In other words, the extended-range sound diffusion device may be homo-coupleable.

[0030] The diffusion assembly comprising at least a first extended range sound diffusion device and a sound diffusion device as previously defined, superimposed, forms a curved vertical stack having a fixed non-constant physical curvature.

[0031] Particular features or embodiments, usable alone or in combination with this set, are: the high-frequency sources are individually electronically controlled in amplitude and phase so as to adapt the resulting wavefront to the broadcasting objectives on an audience and to compensate for any non-monotony generated by an assembly of the devices together; and / or the sound broadcasting assembly further comprises fixing means configured so that each sound broadcasting device is connected to the sound broadcasting device located above, respectively below, by fixing points without angular adjustment.

[0032] Another feature of this assembly, usable alone or in combination with the previous ones, is that the high frequency sources of the different sound diffusion devices of the sound diffusion assembly are individually electronically controlled in amplitude and phase so as to adapt a resulting wavefront to the diffusion objectives on an audience and to compensate for any non-monotony of the physical curvature of the curved vertical stack formed by the diffusion assembly, generated by an assembly of the devices together.

[0033] Another feature that can be used alone or in combination with the previous ones is that the individual electronic control in amplitude and phase of the high frequency sources, combined with the electronic control in amplitude and phase of the several medium frequency and / or low frequency acoustic sources can be dependent on the frequency considered.

[0034] Another feature usable alone or in combination with the preceding ones is that each of a plurality of electronic control and amplification channels can supply one or more of the high frequency sources of the different sound diffusion devices of the sound diffusion assembly as well as one or more of the plurality of medium frequency and / or low frequency acoustic sources of the different sound diffusion devices of the sound diffusion assembly. Brief description of the figures

[0035] The invention will be better understood by reading the following description, given solely by way of example, and with reference to the appended figures in which: THE figures 1a et 1b represent a scene equipped with sound diffusion devices arranged in a classic stereo arrangement ( figure 1a ) or an arrangement adapted to broadcast a spatialized sound signal ( figure 1b ) ; there figure 2 represents a scene, the physical distribution of an audience seen from the side, as well as the positioning of four characteristic points of the audience: the mixing booth (“FOH”), the vertical (“Below”), the rear (“Behind”) and the ceiling (“Above”) of the sound diffusion device; the figures 3a et 3b respectively represent the acoustic pressure field around a sound diffusion device composed of a curved vertical stack of speakers generating a non-continuous wavefront and the sound level generated by such a sound diffusion device at the four characteristic points of the figure 2 , referenced to the sound level at the mixing booth; the figure 4 represents a sound diffusion device according to a first embodiment of the invention; the figures 5a et 5b respectively represent the acoustic pressure field around a sound diffusion device according to the embodiment of the figure 4 and the sound level generated by such a sound diffusion device at the four characteristic points of the figure 2 referenced to the sound level at the mixing booth; the figure 6 represents the evolution of a maximum angle θ 0 beyond which parasitic lobes appear as a function of the height of an acoustic source whose inclination of the sound emission directivity is electronically controlled; figures 7a à 7e represent the results of a numerical simulation carried out for a vertical rectilinear stack of speakers; in particular: o the figure 7a represents the physical deployment of this stack in the vertical plane and the positioning of two characteristic points of the audience: the mixing booth (“FOH”) and the start of the audience (“Proximity”); ∘ the figure 7b represents the set of frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, without application of electronic control; ∘ the figure 7c represents the phase frequency response curves of this deployment at the two characteristic points of the Figure 7a , without application of electronic control, and after subtraction of the minimum propagation delay; ∘ the figure 7d represents the set of frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, after application of electronic control for homogenization purposes; and ∘ the figure 7e represents the phase frequency response curves of this deployment at the two characteristic points of the Figure 7a , after application of electronic control for homogenization purposes, and after subtraction of the minimum propagation delay; figures 8a à 8e represent the results of a numerical simulation carried out for a curved vertical stack of speakers; in particular: o the figure 8a represents the physical deployment of this stack in the vertical plane and the positioning of two characteristic points of the audience: the mixing booth (“FOH”) and the start of the audience (“Proximity”); ∘ the figure 8b represents the set of frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, without application of electronic control; ∘ the figure 8c represents the phase frequency response curves of this deployment at the two characteristic points of the Figure 8a , without application of electronic control, and after subtraction of the minimum propagation delay; ∘ the figure 8d represents the set of frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, after application of electronic control for homogenization purposes; and ∘ the figure 8e represents the phase frequency response curves of this deployment at the two characteristic points of the Figure 8a , after application of electronic control for homogenization purposes, and after subtraction of the minimum propagation delay; figures 9a à 9c represent the results of a digital simulation carried out for a sound diffusion device according to a second embodiment of the invention; in particular ∘ the figure 9a represents the physical deployment of this device in the vertical plane and the positioning of two characteristic points of the audience: the mixing booth (“FOH”) and the start of the audience (“Proximity”); o the figure 9b represents the set of frequency response curves in magnitude of this device on the audience, on the stage and on the ceiling, without application of electronic control; ∘ the figure 9c represents the frequency-phase response curves of this device at the two characteristic points of the Figure 9a , without application of electronic control, and after subtraction of the minimum propagation delay; ∘ the figure 9d represents the set of frequency response curves in magnitude of this device on the audience, on the stage and on the ceiling, after application of electronic control for homogenization purposes; and ∘ the figure 9e represents the frequency-phase response curves of this device at the two characteristic points of the Figure 9a , after application of electronic control for homogenization purposes, and after subtraction of the minimum propagation delay; the figure 10 represents an “extended range” sound diffusion device; the figure 11 represents an “extended vertical opening” sound diffusion device; the figure 12 represents a sound diffusion assembly according to a first embodiment; and the figure 13 represents a sound diffusion assembly according to a second embodiment. Définitions

[0036] In the remainder of the description, a “sound diffusion device” consists of one or more acoustic sources whose frequency ranges or bands may be identical or different.

[0037] An arbitrary, but frequently used division in the profession, divides the sound spectrum, covering at least partially the human audible spectrum: 20 Hz - 20 kHz, into three or four frequency bands. A high frequency band, HF, covers the highest frequencies corresponding to so-called high-pitched sounds, typically a 1 kHz - 20 kHz interval. A medium frequency band, MF, covers the intermediate frequencies, typically a 200 Hz - 1 kHz interval. A low frequency band, BF, covers the low frequencies corresponding to so-called bass sounds, typically a 60 Hz - 200 Hz interval. Finally, a very low frequency band corresponding to so-called sub-bass or infra-bass sounds, TBF, optional, covers the lowest frequencies, typically frequencies below 60 Hz. In practice, the same component can be used to reproduce the signals of the BF and MF bands.Generally speaking, an acoustic source can emit over several frequency ranges but will subsequently be defined by its main emission range.

[0038] In the following description, the term "audience" refers to the physical distribution of listeners or spectators present during a performance in relation to a stage. As illustrated in the Figures 1a-1b et 2, This physical distribution can take different configurations.

[0039] For example, in a concert hall audience 2 may be relatively close to stage 1, whereas at an outdoor festival audience 2 may be more spread out.

[0040] Audience 2 can also be divided in height, depending on whether the spectators are at ground level Z0 or are raised by bleachers or any other similar structure ZH.

[0041] Depending on the audience, sound engineers set sound diffusion objectives. These objectives relate to the distribution of sound level and sound quality across the audience. To do this, sound engineers use frequency response curves such as those shown in 7b to 7e, or 8b to 8e. In these graphs, each curve represents the sound level in dB or the phase in degrees as a function of the frequency that a listener, positioned at a point in the audience, hears.

[0042] Ideally, when the sound broadcast is homogeneous across the entire audience (i.e. the same sound level and the same frequency contour), all the magnitude curves should be superimposed. However, in reality, we observe a decrease in level between the front (near the stage) and the rear (far from the stage) of the audience.

[0043] One of the objectives is therefore that all the curves have the same shape (i.e. the same frequency contour) and are as close as possible to each other. Other types of objectives exist, such as: have a linear decrease in sound level between the front and the back of the audience, which would be represented by regularly spaced curves; or have a constant level in a first part of the audience then linearly decreasing in a second part, which would be represented by a first set of tight curves and a second with regularly spaced curves.

[0044] Also, one of the objectives is that all the frequency components of the sound signal emitted by the sound diffusion device arrive at the same time and in phase at any point in the audience.

[0045] Ideally, according to this objective, the frequency-phase response curves should all coincide with the horizontal zero-phase axis after subtracting the minimum propagation delay.

[0046] The minimum propagation delay is defined as the time taken for the sound pressure wave to reach a given audience point, from the nearest speaker.

[0047] After defining the desired sound diffusion objectives, it is necessary to choose the sound diffusion device(s) to use.

[0048] Each sound diffusion device can be defined by three main technical characteristics: its total vertical opening, its total horizontal opening and its range.

[0049] The term "range" refers to the distance between the sound diffusion device 3, generally located at the front of the stage 1, and the depth at which the sound diffused by this device 3 is correctly heard (intelligibly / coherently) in the audience 2.

[0050] The term "total aperture", or directivity lobe, usually refers to twice the angle for which a loss of 6 dB is observed, corresponding to a 50% reduction in sound intensity, compared to the axis of the sound device considered, namely vertical or horizontal. This axis is defined as the direction where the sound intensity is maximum in the direction considered. Modes de réalisation

[0051] There Figure 1a illustrates a conventional stereo arrangement 10 comprising two sound diffusion devices 3, both located high above stage 1, one located to the left L and the other to the right R of stage 1. The Figure 1b illustrates an arrangement 100 adapted to broadcast a spatialized sound signal and comprising four sound broadcasting devices 3.

[0052] Each sound diffusion device 3 comprises a vertical stack of speakers inclined relative to each other so as to mechanically tilt the overall vertical directivity of the sound diffusion device 3 towards the audience 2.

[0053] To illustrate this phenomenon, the profile view of scene 1 and such a sound diffusion device 3, Figure 2 ,allows to see in dotted line the normal axis to each speaker and its inclination according to the zone of the targeted audience 2. Thus, the installation of such a device 3 is very complex because it requires determining the optimum angle of inclination between each speaker to target according to the audience 2 key or median points allowing a homogeneous distribution of the sound diffused on the audience 2. In addition, such a stack of speakers generates a non-continuous wavefront.

[0054] There Figure 3a represents the sound pressure field around such a device 3 at the particular frequency of 1324 Hz, corresponding to the appearance of a peak in sound intensity at the rear of the device 3. A dark gray level represents a high sound pressure, and therefore a high sound level. Conversely, a light gray level represents a reduced sound level. The Figure 3b represents the sound level generated at four characteristic points of the audience: the mixing booth ("FOH"), the vertical line ("Below"), the rear ("Behind") and the top ("Above") of such a sound diffusion device 3, referenced in relation to the sound level at the mixing booth. The device 3 is here composed of an assembly of 12 speakers with variable curvature, each speaker being composed of an HF source and two MF sources, having separation panels 13mm thick and assembly clearances of the order of 5mm between each speaker. These graphs make it possible to observe the presence of significant and unwanted sound levels vertically, behind and above the sound diffusion device 3, compared to the sound level at the mixing booth.

[0055] To address these installation difficulties as well as the presence of parasitic lobes on stage 1, a first embodiment of the invention relates to a sound diffusion device 300 as illustrated Figure 4 .

[0056] The sound diffusion device 300 comprises a single box 310, and in this single box, at least two superimposed high-frequency acoustic sources 320, and several superimposed medium-frequency and / or low-frequency acoustic sources 330 arranged to the left and / or to the right of the high-frequency acoustic sources 320, the high-frequency acoustic sources 320 being individually coupled to a waveguide 340 so as to generate a vertical wavefront with fixed non-constant curvature.

[0057] The at least two superimposed high-frequency acoustic sources form a curved vertical stack. Advantageously, this curved vertical stack has a fixed, non-constant physical curvature. Each high-frequency acoustic source has a main emission direction. The physical curvature of a curved vertical stack is clearly equal to the curvature of the arc representing the profile curve of this curved vertical stack.

[0058] Another definition of the physical curvature of the curved vertical stack of high-frequency acoustic sources can also be the succession of angles formed by the main emission directions of two consecutive acoustic sources.

[0059] Advantageously, the sound diffusion device 300 comprises at least three high-frequency acoustic sources 320.

[0060] For a number of high-frequency acoustic sources N greater than or equal to three, a physical curvature of the curved vertical stack of non-constant high-frequency acoustic sources is a curvature for which at least one angle alpha_i, formed by the main emission directions of the i-th and i+1th consecutive high-frequency acoustic sources 320, i being an integer between 1 and N-1, is different from the other angles alpha_n, for n different from i.

[0061] A physical curvature of the curved vertical stack of high-frequency acoustic sources 320 fixed is a curvature that is not suitable for modification by a user.

[0062] Advantageously, each waveguide 340 comprises an output, the outputs of the waveguides being joined, so as to form a continuous ribbon and therefore a continuous wavefront.

[0063] To achieve satisfactory sound distribution over the audience without resorting to electronic control, it is preferable that the fixed non-constant curvature of the vertical wavefront be monotonous.

[0064] There Figure 5a represents the acoustic pressure field around such a device 300 at this same particular frequency of 1324 Hz and with the same color codes as the Figure 3a . There Figure 5b represents the sound level generated at the same three characteristic points of the audience, referenced in relation to the sound level in the mixing booth. For this digital simulation, the device 300 is composed of a stack of 12 high-frequency sources, with no separation panels or assembly clearances, and therefore generating a continuous wavefront. These graphs show the disappearance or very strong attenuation of the parasitic lobes of unwanted sound levels directly above, behind and above the sound diffusion device 300.

[0065] Thus, this type of sound diffusion device 300 allows, thanks in particular to the combination of several sources in a single enclosure (i.e. a single box 310): to minimize discontinuities between the acoustic sources, reducing or even eliminating parasitic lobes; to considerably reduce the weight and manufacturing cost of the device by eliminating the various horizontal panels that were present between the acoustic sources in the stack of speakers, also facilitating the transport of the device 300 and its installation; and rapid installation not requiring angular adjustment of each of the acoustic sources between each other.

[0066] In fact, the curvature of the curved vertical stack of high-frequency acoustic sources is fixed and cannot be modified by a user. Thus, no user adjustment is necessary for the installation of the different sources.

[0067] In order to adapt the resulting wavefront to the broadcasting objectives, the high frequency sources 320 are individually electronically controlled in amplitude and phase.

[0068] Electronic control (or DSP - Digital System Processing, i.e. Digital Signal Processor) allows, among other things, to modify the inclination of the directivity lobe of the assembly without having to physically tilt them.

[0069] To understand the phenomenon, if we consider a vertical rectilinear arrangement of N point sources spaced by a distance d and having the directivity of a rectangular source of height d, we can show that, at any point in the plane of the arrangement, defined by a distance r and an angle θ to the source, the sound level SPL relative to the projection axis is: SPL r θ = 20 log 10 sin kdsinθ 2 kdsinθ 2 sin N kd 2 sinθ Nsin kd 2 sinθ

[0070] Where k is the wave number corresponding to 2 πf c where f is the frequency considered and c the speed of sound in the medium considered (here air).

[0071] By applying different phase settings to each of the sources in the arrangement, it is possible to tilt the main sound lobe by an angle θ 0 .

[0072] It can be shown in a similar way that the relative sound level is: SPL r θ θ 0 = 20 log 10 sin kdsinθ 2 kdsinθ 2 sin N kd 2 sinθ − sinθ 0 Nsin kd 2 sinθ − sinθ 0

[0073] A physical or electronic adjustment that does not generate a parasitic lobe with a sound intensity greater than -12dB compared to the main lobe, and at the same distance from the source, can be considered acceptable.

[0074] Thus, it can be shown that there is a maximum angle θ 0 beyond which parasitic lobes appear with an intensity greater than the previously defined threshold. This maximum angle can be expressed as a function of the frequency and height of the source by the following approximate formula: θ 0 , max ≈ arcsin 2 π − x 0 kd

[0075] Where x 0 is the solution to the equation sin x x = 10 − 12 20 ; x 0 ≈ 2.47

[0076] In order to cover a close audience, it is common to have to orient the last speaker in an arrangement at an angle greater than 45° from the horizontal. This is especially true when the arrangement is suspended at significant heights, which may be the case when it is placed above the stage or when the geometry of the venue does not allow for low installation.

[0077] The abacus of the Figure 6 describes the evolution of the maximum angle θ 0 for two frequencies, 10kHz and 16kHz, as a function of the height of each source.

[0078] It can be seen that in order to achieve an angle θ 0 of 45° at 10kHz, a unit source of 10mm height is required, and that this source can only be electronically tilted by 27° at 16kHz. Such a discretization of the source line implies a very large number of small components and amplification channels with DSP, a solution which does not seem advantageous.

[0079] On this same chart, we see that, for a source 30mm high, the maximum angle θ 0 is 14° at 10kHz, and 9° at 16kHz.

[0080] Such a source could be used without too much complexity, but it would not allow the 45° angle mentioned to be reached, even at 10kHz, without creating parasitic lobes outside the field.

[0081] For these reasons, the technique of electronically bending a vertical straight line source does not achieve results as good as a physically curved line source.

[0082] Conversely, a line with 140mm high sources allows a maximum angle θ 0 of 3° at 10kHz and 2° at 16kHz to be reached. Thus, the combination of an adapted physical curvature of the stack of high-frequency acoustic sources with individual electronic control of these, combined or not with individual electronic control of the low and / or medium-frequency sources in amplitude and phase, appears to be an optimal solution.

[0083] In a more visual and quantitative manner, the following numerical simulations highlight the advantages and disadvantages of these different configurations.

[0084] THE Figures 7a à 7e represent the results obtained with a vertical rectilinear stack of speakers comprising a high-frequency acoustic source located between two medium and / or low-frequency acoustic sources on the same horizontal plane. On the Figure 7a ,the solid lines starting from the vertical rectilinear stack represent the total vertical opening covered. Figure 7b represents the frequency-magnitude response curves generated by such a vertical rectilinear stack before the application of electronic control to the acoustic sources. The dark gray curves correspond to the audience, and the light gray dotted curves correspond to the stage and the ceiling. The Figure 7c represents the frequency-phase response curves generated by such a vertical rectilinear stack, at the mixing booth (“FOH”) and at the beginning of the audience (“Proximity”), before the application of electronic control on the acoustic sources, and after subtraction of the minimum propagation delay. The Figure 7d represents the frequency response curves in magnitude generated by such a vertical rectilinear stack, after the application of electronic control on the acoustic sources, and with the same color codes as the Figure 7b . There Figure 7e represents the frequency-phase response curves generated by such a vertical rectilinear stack, after applying electronic control to the acoustic sources and subtracting the minimum propagation delay, calculated at the mixing booth and at the start of the audience.

[0085] THE Figures 8a à 8e represent the results obtained with a curved vertical stack of speakers comprising a high-frequency acoustic source located between two medium and / or low-frequency acoustic sources on the same horizontal plane. On the Figure 8a , the solid lines extending from the curved vertical stack represent the total covered vertical opening. Figure 8b represents the frequency response curves in magnitude generated by such a curved stack after optimization of the angles between each source and before the application of electronic control on the acoustic sources, and with the same color codes as the Figure 7b . There Figure 8c represents the frequency-phase response curves generated by such a curved stack after optimization of the angles between each source, at the mixing booth and at the beginning of the audience, before the application of electronic control on the acoustic sources and after subtraction of the minimum propagation delay. The Figure 8d represents the frequency response curves in magnitude generated by such a curved stack, after optimization of the angles between each source and application of electronic control on the acoustic sources, and with the same color codes as the Figure 7b . There Figure 8e represents the frequency-phase response curves generated by such a curved stack after optimization of the angles between each source, application of electronic control on the acoustic sources and subtraction of the minimum propagation delay, calculated at the mixing booth and at the start of the audience.

[0086] Finally, the Figures 9a à 9e represent the results obtained with a sound diffusion device 300 with fixed non-constant physical curvature as described previously. On the Figure 9a , the solid lines starting from the sound device 300 represent the total vertical opening covered. The Figure 9b represents the frequency response curves in magnitude generated by such a device 300 from only the fixed non-constant physical curvature, and with the same color codes as the Figure 7b . There Figure 9c represents the frequency-phase response curves generated by such a device 300 from only the fixed non-constant physical curvature, after subtracting the minimum propagation delay, calculated at the mixing booth and at the start of the audience. The Figure 9d represents the frequency response curves in magnitude generated by such a device 300, after the application of electronic control in magnitude and phase, with one acoustic source per DSP channel, and with the same color codes as the Figure 7b . There Figure 9e represents the frequency response curves in phase generated by such a device 300, after application of electronic control in magnitude and phase, with one acoustic source per DSP channel, and after subtraction of the minimum propagation delay, calculated at the mixing booth and at the start of the audience.

[0087] We note that the solution of the Figures 8a à 8e gives a generally satisfactory response, nevertheless perfectible in high frequencies (less tight beam of magnitude curves, and more choppy phase curves). On the other hand, the sound level on the stage and on the ceiling (visible on the light gray curves of the Figures 8b et 8d ) has a lot of high frequency peaks, at a level equivalent to that on the audience, which is problematic.

[0088] The vertical rectilinear arrangement of the Figures 7a à 7e , for which audience coverage is obtained by electronic means only (case of Figures 7d et 7e ),leads to a generally satisfactory frequency response in magnitude on the audience. However, the sound level on the stage and especially the ceiling, presents peaks from 6kHz of a level equivalent to that on the audience, linked to the appearance of off-axis parasitic lobes, following the application of excessive magnitude and phase parameters as in the case of a tilt carried out solely electronically. In addition, the phase curves are very choppy, and reflect significant time shifts in the arrival on the audience of the different frequency components of the sound signal.

[0089] On the other hand, the results obtained by the configurations of the Figures 9a à 9e are satisfactory across the entire audio spectrum, both in magnitude and phase. The sound level on the stage and ceiling is much lower than that in the audience, and the phase curves show little fluctuation, both before and after applying the electronic magnitude and phase correction parameters.

[0090] Another way to improve the directivity control and sound emission quality of the device 300, and compatible with the previously described embodiments, is to add adjustable flaps.

[0091] For this, among the plurality of medium and / or low frequency acoustic sources there must be at least one acoustic source emitting over a medium frequency range. The sound diffusion device 300 can then be equipped with adjustable flaps acting on a sound emission from at least one of the high frequency acoustic sources 320 to produce a sound emission directivity of the high frequency acoustic source according to a chosen angular sector, the high frequency acoustic source and the acoustic source emitting over a medium frequency range being configured to emit over a common frequency range.

[0092] The sound diffusion device also comprises at least one control module of the digital signal processor type acting on a signal intended for the high-frequency acoustic source and on a signal intended for the acoustic source emitting on a medium-frequency range so as to apply in the common frequency range at least one magnitude parameter on the high-frequency acoustic source and / or on the acoustic source emitting on a medium-frequency range as well as at least one phase parameter on the high-frequency acoustic source and / or on the acoustic source emitting on a medium-frequency range so as to produce a sound emission directivity of the pair consisting of the high-frequency acoustic source and the acoustic source emitting on a medium-frequency range according to the same angular sector chosen as the directivity produced by the adjustable flaps.

[0093] The different variants of this embodiment are described in document EP 3 063 950 B1.

[0094] Depending on the physical distribution of the audience 2, it may be advantageous to produce two specific types of sound diffusion device 300 as described previously.

[0095] For the case where the sound diffusion device emits towards an audience far from the scene or at grazing incidence, an “extended range” sound diffusion device 300_F is defined in which all of the high-frequency acoustic sources 310 produce an overall sound emission directivity having a total vertical opening angle less than or equal to 20°, as illustrated Figure 10 . This corresponds to a relatively small fixed non-constant curvature, represented by lines perpendicular to the short wavefront on the right-hand device.

[0096] The graph on the right of the Figure 10 illustrates another representation of the evolution of the physical curvature of the curved vertical stack of high-frequency acoustic sources 310 formed by the “extended range” sound diffusion device 300_F, with respect to the sub-figure of the figure 10 where the curvature values ​​of the "extended range" sound diffusion device 300_F are represented by lines perpendicular to the wavefront. This graph shows the evolution of the value of the angle alpha_i between the i-th and i+1-th acoustic source, for i integer ranging from 1 to N-1, N being the number of high-frequency acoustic sources 310. It can be seen that the difference between the angle between the two highest high-frequency acoustic sources 310 and that between the two lowest high-frequency acoustic sources 310 (in the vertical direction) is small, which corresponds to a relatively small fixed non-constant curvature. In this particular case, the physical curvature of the curved vertical stack is monotonous.

[0097] For the case where the sound diffusion device would emit towards an audience close to the stage or where the latter would be distributed over a large vertical angular sector, a sound diffusion device “with extended vertical opening” 300_W is defined in which all of the high-frequency acoustic sources 310 produce an overall sound emission directivity having a total vertical opening angle greater than 20°, as illustrated Figure 11 . This corresponds to a larger fixed non-constant curvature represented by lines perpendicular to the long wavefront on the right-hand device.

[0098] The graph on the right of the Figure 11 illustrates another representation of the evolution of the physical curvature of the curved vertical stack of high-frequency acoustic sources 310 formed by the “extended vertical aperture” sound diffusion device 300_W, with respect to the sub-figure of the figure 11 where the curvature values ​​of the “extended vertical aperture” sound diffusion device 300_W are represented by lines perpendicular to the wavefront. This graph shows the evolution of the physical curvature of the curved vertical stack of high-frequency acoustic sources 310 formed by the “extended vertical aperture” sound diffusion device 300_W, i.e. the evolution of the value of the angle alpha_i between the i-th and i+1-th acoustic source, for i being an integer ranging from 1 to N-1, N being the number of high-frequency acoustic sources 310. It can be seen that the difference between the angle between the two highest high-frequency acoustic sources 310 and that between the two lowest high-frequency acoustic sources 310 (in the vertical direction) is wider than on the Figure 10 , which corresponds to a fixed non-constant curvature greater than in the case of the Figure 10 and a 300_F "extended range" sound diffusion device. In this particular case too, the physical curvature of the curved vertical stack is monotonous.

[0099] For physical audience distribution configurations 2 requiring greater sound power or for more complex and / or more extensive distributions, a sound diffusion assembly comprises at least a first “extended range” sound diffusion device 300_F and a sound diffusion device 300, 300_F or 300_W as defined previously and superimposed such that the resulting sound diffusion assembly generates a vertical wavefront with fixed non-constant curvature as illustrated in the Figure 12 .

[0100] In other words, the “extended range” sound diffusion device 300_F can be coupled with another sound diffusion device 300, 300_F or 300_W as defined previously and assembled by fixing means.

[0101] In particular, the “extended range” sound diffusion device 300_F can be coupled with an “extended range” sound diffusion device 300_F identical to itself.

[0102] A sound diffusion assembly, resulting from the superposition of two sound diffusion devices as previously described, forms a curved vertical stack presenting a fixed non-constant physical curvature.

[0103] To compensate for any possible non-monotony generated by the assembly of the devices together as in the case of Figures 12 et 13 , The high-frequency sources are individually electronically controlled in amplitude and phase.

[0104] This may in particular involve the non-monotony of the physical curvature of the curved vertical stack formed by the sound diffusion assembly. The electronic amplitude and phase control of the high-frequency acoustic sources 320 and / or the low and / or medium-frequency acoustic sources 330 may thus make it possible to adjust a sound wavefront emitted by the sound diffusion assembly to the diffusion objectives on an audience.

[0105] Indeed, the superposition of two “extended range” 300_F devices can generate a discontinuity in the curvature and therefore a non-monotony that can be seen thanks to the hatching on the Figure 13 .

[0106] As on the figures 10 et 11 , the graph on the right of the Figure 13 illustrates another representation of the evolution of the physical curvature of the curved vertical stack of high-frequency acoustic sources 310 formed by a sound diffusion assembly resulting from the assembly of two “extended range” sound diffusion devices 300_F, with respect to the sub-figure of the figure 13 where the curvature values ​​of this sound diffusion assembly are represented by lines perpendicular to the wavefront. On this graph, we observe a non-monotony of the evolution of the angles between sources 7 and 9, corresponding to a break in the monotony of the evolution of the physical curvature of the curved vertical stack formed by the sound diffusion assembly. In this case, a DSP control makes it possible to readjust the sound wavefront emitted by the sound diffusion assembly to adapt it to the diffusion objectives.

[0107] Finally, to facilitate installation, the diffusion assembly may advantageously comprise fixing means configured so that each sound diffusion device is connected to the sound diffusion device located above, respectively below, by fixing points without angular adjustment. LISTE DES REFERENCES

[0108] 1 scene 2 audience 3 sound diffusion device 10 classic stereo arrangement 100 arrangement adapted to diffuse a spatialized sound signal 300 sound diffusion device 300_F “extended range” sound diffusion device 300_W “extended vertical opening” sound diffusion device 310 subwoofer 320 high-frequency acoustic source 330 low or medium-frequency acoustic source 340 waveguide D Right FOH Mixing Booth (Front Of House) G Left L Stage width

Claims

1. Sound diffusion device (300) comprising a single box (310) and, in this single box (310), at least two superimposed high-frequency acoustic sources (320), and a plurality of superimposed medium-frequency and / or low-frequency acoustic sources (330) and arranged to the left and / or to the right of the high-frequency acoustic sources (320), the high-frequency acoustic sources (320) being coupled individually to a wave guide (340) and arranged according to a curved vertical stack having a fixed non-constant physical curvature and being controlled individually electronically in amplitude and phase in such a way as to adjust the resulting wave front to diffusion objectives for an audience.

2. Sound diffusion device (300) according to claim 1, wherein each wave guide (340) comprises an output, the outputs of the wave guides being arranged in a perfectly joined manner, so as to form a continuous band.

3. Sound diffusion device (300) according to one of claims 1 or 2, wherein the progression of the physical curvature of the curved vertical stack is monotonic.

4. Sound diffusion device (300) according to any of claims 1 to 3, such that among the plurality of medium and / or low-frequency acoustic sources (330), there is at least one acoustic source emitting in a medium-frequency range, the sound diffusion device also comprising: orientable flaps acting on a sound emission of at least one of the high-frequency acoustic sources to produce a sound emission directivity of the high-frequency acoustic source according to a selected angular sector, the high-frequency acoustic source and the acoustic source emitting over a medium-frequency range being configured to emit over a common range of frequencies; and at least one control module of the digital signal processor type acting on a destination signal of the high-frequency acoustic source and on a destination signal of the acoustic source emitting over a medium-frequency range so as to apply in the common range of frequencies at least one parameter of magnitude to the high-frequency acoustic source and / or the acoustic source emitting in a medium-frequency range as well as at least one phase parameter on the high-frequency acoustic source and / or on the acoustic source emitting in a medium-frequency range to produce a sound emission directivity of the couple formed by the high-frequency acoustic source and the acoustic source emitting in a medium-frequency range according to the same angular sector selected as the directivity produced by the orientable flaps.

5. Sound diffusion device with an extended range (300_F) according to any of claims 1 to 4, wherein the assembly of high-frequency acoustic sources (320) produces a global sound emission directivity with a total vertical opening angle less than or equal to 20°.

6. Sound diffusion device with an extended vertical opening (300_W) according to any of claims 1 to 4, wherein the assembly of high-frequency acoustic sources (320) produces a global sound emission directivity with a total vertical opening angle greater than 20°.

7. Sound diffusion device with an extended range (300_F) according to claim 5, characterised in that it can be coupled and superimposed from above or below with a second sound diffusion device (300, 300_F or 300_W) according to any of claims 1 to 6 by fixing means.

8. Sound diffusion device with an extended range (300_F) according to claim 7, wherein the second sound diffusion device is identical to the sound diffusion device with an extended range (300_F).

9. Sound diffusion device according to any of the preceding claims, wherein the electronic control and amplification channels are suitable for supplying each or a plurality of high-frequency sources, as well as each or a plurality of acoustic sources among the plurality of medium-frequency and / or low-frequency acoustic sources.

10. Sound diffusion assembly comprising at least one first sound diffusion device with an extended range (300_F) according to claim 8 and a sound diffusion device (300, 300_F or 300_W) according to any of the preceding claims 1 to 9, superimposed, and forming a curved vertical stack and having a fixed non-constant physical curvature.

11. Sound diffusion assembly according to claim 10, wherein the high-frequency sources (320) are individually controlled electronically in amplitude and in phase so as to adjust the resulting wave front to diffusion objectives for an audience and to compensate for possible non-monotonicity generated by an assembly of devices with one another.

12. Sound diffusion assembly according to claim 11, wherein the non-monotonicity is that of the physical curvature of the curved vertical stack formed by the sound diffusion assembly.

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