EP3824652A1

EP3824652A1 - Device for playing audio having a set non-constant curvature

Info

Publication number: EP3824652A1
Application number: EP19753182.5A
Authority: EP
Inventors: Yoachim HORYN; Christophe Combet; Christian Heil
Original assignee: L Acoustics SAS
Current assignee: L Acoustics SAS
Priority date: 2018-07-19
Filing date: 2019-07-19
Publication date: 2021-05-26
Also published as: US20210297772A1; FR3084230B1; US11463807B2; FR3084230A1; CN112655222A; WO2020016538A1

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

NON-CURVED SOUND BROADCASTING DEVICE

CONSTANT FROZEN

DESCRIPTION

Technical area

[01] 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.

State of the art

[02] The objectives of modern PA systems are to provide sound coverage for the most homogeneous audience possible, and this across the entire audio spectrum (20Hz - 20kHz).

[03] It is a question of giving spectators a sound volume (dB SPL - decibel "Sound Pressure Level") of preferably equivalent intensity, while being able to be adapted as desired by the installer. In addition, optimal sound quality, that is to say interference-free, must be guaranteed.

[04] For 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, an acoustic source having a significant volume.

[05] In addition, the use of "source point type" speakers makes it impossible to achieve the objective of homogeneous sound intensity because the natural decay of this type of product is 6 dB by doubling the distance.

[06] In order to obtain a higher SPL level, it is also possible to combine several speakers of this type. This arrangement generates on the audience an interference sound field for frequencies whose half-wavelength is smaller than the distance separating the elements. [07] The use of so-called “source line” speakers makes it possible to achieve the objectives mentioned above by considerably improving the ability to send sound intensity far away while ensuring a loss of 3dB only by doubling the distance at high frequencies. , and ensuring an interference-free sound field.

[08] “Source line” type enclosures consist of

• stack the bass and mid-range speakers on top of each other until they form a curved line, respecting a pitch between speakers less than the smallest half-wavelength that each speaker speaker must reproduce;

• use tweeters (compression motors) coupled to rectangular output waveguides, the assembly generating an isophase linear wavefront free of interference even if the pitch between two motors is good larger than the smallest wavelength to reproduce.

[09] A waveguide is a physical device used to obtain a possibly flat isophase wavefront. As such, it plays the same role as a roof that would be loaded on 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 pavilion of infinite length, contrary to the compactness objectives of a sound diffusion device.

[10] In addition, in order to be able to adapt to all types of audiences and to be able to model the decrease in SPL over the audience as desired, these speakers are generally designed in a modular fashion as relatively small elements, the overall height is that of the largest speaker.

[1 1] Each enclosure can then be tilted with respect to its neighbor in a variable manner in order to ensure the objectives of coverage, intensity and homogeneity. [12] This angular flexibility makes it possible to focus the energy in one direction (generally the distant audience) by stacking a lot of speakers with little or no inter-element angle or, on the contrary, covering a large angular sector with little energy by assembling the speakers with large inter-element angles.

[13] This flexibility linked to the modularity in small orientable elements has however a certain number of drawbacks:

the proliferation of variable angle fixing devices between the speakers, which implies a longer installation time, an additional cost and an overweight;

many wooden panels to close the acoustic volume of each element, which also generates additional cost and overweight;

a discontinuity of the wave front due to the presence of these separation panels and assembly clearances, leading to the appearance of parasitic lobes off axis. These uncontrolled lobes can, for example, be the source of unwanted feedback (i.e. feedback) for the musician who is on the stage; and

a loss of acoustic volume due to the generally trapezoidal shape of the section of an enclosure (in order to be able to tilt it with an adjacent element without amplifying the discontinuity of the wave front).

[14] Thus, there is a real need for a simple and rapid installation sound system, making it possible to adapt to any audience and offering a high quality of sound distribution (no parasitic lobe).

Description of the invention

[15] To resolve one or more of the drawbacks mentioned above, the invention relates to a sound diffusion device comprising a single box and, in this single box, at least two superimposed high frequency acoustic sources, and several medium frequency acoustic sources and / or low frequency superimposed and arranged to the left and / or right of the high frequency acoustic sources, the acoustic sources high frequency being individually coupled to a waveguide so as to generate a vertical wavefront with fixed non-constant curvature.

[16] More particularly, 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 direction of emission. 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.

[17] 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 directions of emission of two consecutive acoustic sources.

[18] 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 alphaj, formed by the main directions emission 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.

[19] A physical curvature of the curved vertical stack of frozen high frequency acoustic sources is, more precisely, a curvature that is not capable of being modified by a user.

[20] Particular characteristics or embodiments, which can be used alone or in combination, are:

• each waveguide includes an outlet, the outlets of the waveguides being arranged in a perfectly contiguous manner, so as to form a continuous ribbon;

• the curvature of the vertical wavefront is not constant and fixed, and its evolution is monotonous; • the high frequency sources are individually electronically controlled in amplitude and in phase so as to adapt the resulting wavefront to the broadcasting objectives for an audience;

• 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 from at least one of the high frequency acoustic sources to produce a directivity of sound emission from the high frequency acoustic source according to a chosen angular sector, the high frequency acoustic source and the acoustic source emitting on a medium frequency range being configured to transmit 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 over a medium frequency range so as to apply in the frequency range common at least one magnitude parameter on the high frequency acoustic source and / or on the acoustic source emitting over 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 couple consisting of the high frequency acoustic source and the acoustic source emitting over a medium frequency range according to the same angular sector chosen as the directivity produced by the orientable flaps. [21] Another characteristic that can be used alone or in combination with the previous ones is that the curvature of the curved vertical stack has a monotonous evolution.

[22] Another characteristic which can be used alone or in combination with the previous ones is that the sound diffusion device comprises at least three high frequency acoustic sources.

[23] Another characteristic which can be used alone or in combination with the preceding 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 acoustic sources. medium frequency and / or low frequency.

[24] To cover an audience far from the scene, the invention relates in particular to a sound broadcasting device with a wide range, in which all of the high frequency acoustic sources produce a directivity of overall sound emission having an angle d total vertical opening less than or equal to 20 °.

[25] To cover an audience close to the scene, the invention also relates to a sound diffusion device with extended vertical opening, in which the set of high frequency acoustic sources produces a directivity of overall sound emission having an angle d total vertical opening greater than 20 °.

[26] To cover a larger audience, the invention also relates to a sound diffusion assembly which may include at least a first sound diffusion device with extended range and a sound diffusion device as defined above, superimposed on such so that the resulting sound diffusion assembly generates a vertical wave front with fixed non-constant curvature.

[27] In other words, advantageously, the sound diffusion device with extended range is couplable and is assembled with another sound diffusion device as previously defined. [28] In particular, the extended range sound broadcasting device can be coupled to a wide range sound broadcasting device identical to itself. The term "identical" should be understood to mean a device being a strict copy of the 300_F "extended range" sound diffusion device, having exactly the same technical, geometric and physical characteristics. In other words, the extended range sound diffusion device can be homo-couplable.

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

[30] Particular characteristics or embodiments, which can be used alone or in combination with this set, are:

• the high frequency sources are individually electronically controlled in amplitude and in phase so as to adapt the resulting wavefront to the broadcasting objectives for an audience and to compensate for any non-monotony generated by an assembly of the devices between them; and or

• the sound diffusion assembly further comprises 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 .

[31] Another characteristic of this assembly, which can be used alone or in combination with the preceding ones, is that the high frequency sources of the various sound diffusion devices of the sound diffusion assembly are individually electronically controlled in amplitude and in phase so as to adapt a resulting wavefront to the objectives of diffusion on an audience and to compensate for a possible non-monotony of the physical curvature of the curved vertical stack formed by the diffusion assembly, generated by an assembly of the devices between them. [32] Another characteristic which can be used alone or in combination with the previous ones is that the individual electronic amplitude and phase control of high frequency sources, combined with electronic amplitude and phase control of several medium frequency and / or low frequency acoustic sources may be dependent on the frequency considered.

[33] Another characteristic which can be used alone or in combination with the previous ones is that each of a plurality of electronic control and amplification channels can supply one or more of 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 among the plurality of medium frequency and / or low frequency acoustic sources of the various sound diffusion devices of the sound diffusion assembly.

[34] Brief description of the figures

[35] The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended figures in which:

- Figures 1a and 1b show a scene equipped with sound diffusion devices arranged in a conventional stereo arrangement (Figure 1a) or an arrangement adapted to broadcast a spatialized sound signal (Figure 1b);

- Figure 2 represents a scene, the physical distribution of an audience seen in profile, as well as the positioning of four characteristic points of the audience: the mixing cabin (“FOH”), the plumb (“Below”) , the back (“Behind”) and the ceiling (“Above”) of the sound system;

- Figures 3a and 3b respectively represent the sound pressure field around a sound diffusion device composed of a vertical stack bent of speakers generating a non-continuous wavefront and the sound level generated by such a diffusion device sound to the four characteristic points of FIG. 2, referenced in relation to the sound level in the mixing cabin;

- Figure 4 shows a sound diffusion device according to a first embodiment of the invention;

- Figures 5a and 5b respectively represent the sound pressure field around a sound diffusion device according to the embodiment of Figure 4 and the sound level generated by such a sound diffusion device at the four characteristic points of Figure 2 referenced in relation to the sound level at the mixing booth;

- Figure 6 shows the evolution of a maximum angle qo beyond which parasitic lobes appear as a function of the height of an acoustic source whose inclination of the directivity of emission of sound is electronically controlled;

- Figures 7a to 7e show the results of a digital simulation performed for a vertical straight stack of speakers; in particular :

o Figure 7a shows 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");

o Figure 7b shows all the frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, without application of electronic control;

o FIG. 7c represents the frequency response curves in phase of this deployment at the two characteristic points of FIG. 7a, without application of the electronic control, and after subtraction of the minimum propagation delay;

FIG. 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 the purpose of homogenization; and

o FIG. 7e represents the frequency response curves in phase of this deployment at the two characteristic points of FIG. 7a, after application of the electronic control for the purpose of homogenization, and after subtraction of the minimum propagation delay;

- Figures 8a to 8e represent the results of a digital simulation performed for a curved vertical stack of speakers; in particular :

o Figure 8a shows 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");

o Figure 8b shows all the frequency response curves in magnitude of this deployment on the audience, on the stage and on the ceiling, without application of electronic control;

o Figure 8c shows the frequency response curves in phase of this deployment at the two characteristic points of Figure 8a, without application of electronic control, and after subtracting the minimum propagation delay;

o FIG. 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 the electronic control for homogenization purposes; and

o Figure 8e shows the frequency response curves in phase of this deployment at the two characteristic points of Figure 8a, after application of electronic control for the purpose of homogenization, and after subtraction of the minimum propagation delay; - Figures 9a to 9c show the results of a digital simulation performed for a sound diffusion device according to a second embodiment of the invention; in particular

o Figure 9a shows 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 Figure 9b shows all the frequency response curves in magnitude of this device on the audience, on the stage and on the ceiling, without application of electronic control;

o FIG. 9c represents the frequency response curves in phase of this device at the two characteristic points of FIG. 9a, without application of the electronic control, and after subtraction of the minimum propagation delay; o FIG. 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 the electronic control for the purpose of homogenization; and o FIG. 9e represents the frequency response curves in phase of this device at the two characteristic points of FIG. 9a, after application of the electronic control for the purpose of homogenization, and after subtraction of the minimum propagation delay;

- Figure 10 shows a sound diffusion device "at extended range";

- Figure 11 shows a sound diffusion device "extended vertical opening";

- Figure 12 shows a set of sound diffusion according to a first embodiment; and - Figure 13 shows a set of sound diffusion according to a second embodiment.

Definitions

[36] In the following description, a "sound diffusion device" consists of one or more acoustic sources whose ranges or frequency bands can be identical or different.

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

[38] In the following description, the term "audience" designates the physical distribution of the listeners or spectators present during a performance in relation to a scene. As illustrated in Figures 1a-1b and 2, this physical distribution can take different configurations.

[39] For example, in a concert hall audience 2 can be relatively close to stage 1 while at an outdoor festival, audience 2 can be larger. [40] Audience 2 can also be divided in height, depending on whether the spectators are at ground level ZO or are raised by bleachers or any other similar structure ZH.

[41] Depending on the audience, sound diffusion objectives are set by the sound engineers. These objectives relate to the distribution of the sound level and the quality of the sound on the audience. For this, the sound engineers are based on the frequency response curves like 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 depending on the frequency that a listener, placed at a point in the hearing, hears.

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

[43] One of the objectives is therefore that all the curves have the same shape (that is to say the same frequency contour) and are as tight as possible with each other. Other types of objectives exist such as, for example:

• have a decrease in the linear sound level between the front and the rear 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.

[44] Also, one of the objectives is that all of the frequency components of the sound signal emitted by the sound diffusion device arrive at the same instant and in phase at any point of the hearing. [45] Ideally, according to this objective, the frequency response curves in phase should all be confused with the horizontal axis of zero phase after subtracting the minimum propagation delay.

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

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

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

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

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

Modes of realization

[51] Figure 1a illustrates a conventional stereo arrangement 10 comprising two sound broadcasting devices 3, both situated high above the stage 1, one situated to the left G and the other to the right D of the stage 1. FIG. 1 b illustrates an arrangement 100 suitable for broadcasting a spatialized sound signal and comprising four sound broadcasting devices 3.

[52] Each sound diffusion device 3 comprises a vertical stack of speakers inclined with respect to each other so as to mechanically tilt the overall vertical directivity of the sound diffusion device 3 towards the audience 2. [53] To illustrate this phenomenon, the profile view of scene 1 and of such a sound diffusion device 3, Figure 2, allows to see in dotted line the axis normal to each enclosure and its inclination as a function of the area of target audience 2. Thus, the installation of such a device 3 is very complex because it requires determining the optimum angle of inclination between each enclosure in order to target, depending on the audience 2, key or median points allowing a homogeneous distribution of the sound broadcast over the audience 2. In addition, such a stack of speakers generates a non-continuous wavefront.

[54] 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 level of dark gray represents a significant sound pressure, and therefore a significant sound level. Conversely, a light gray level represents a reduced sound level. Figure 3b represents the sound level generated at four characteristic points of the audience: the mixing cabin (“FOH”), the plumb (“Below”), the back (“Behind”) and the top ("Above") of such a sound diffusion device 3, referenced in relation to the sound level in the mixing cabin. The device 3 is here composed of an assembly of 12 enclosures with variable curvature, each enclosure being composed of an HF source and two MF sources, having 13mm thick separation panels and assembly plays of the 'order of 5mm between each enclosure. These graphs show the presence of significant and undesired sound levels plumb, behind and above the sound system 3, compared to the sound level in the mixing cabin.

[55] To respond to these installation difficulties and to the presence of parasitic lobes on stage 1, a first embodiment of the invention relates to a sound diffusion device 300 as illustrated in FIG. 4.

[56] 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 average acoustic sources frequency and / or low frequency 330 superimposed and arranged to the left and / or 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.

[57] 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 direction of emission. 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.

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

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

[60] 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 alphaj, formed by the main directions of emission of the i-th and i + 1 th 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.

[61] A physical curvature of the curved vertical stack of frozen high frequency acoustic sources 320 is a curvature that is not capable of being modified by a user.

[62] Advantageously, each waveguide 340 comprises an output, the outputs of the waveguides being contiguous, so as to form a continuous ribbon and therefore a continuous wavefront. [63] To obtain a satisfactory sound distribution over the audience without having to resort to electronic control, it is preferable that the non-constant curvature of the vertical wavefront be monotonous.

[64] Figure 5a shows the sound pressure field around such a device 300 at this same particular frequency of 1324 Hz and with the same color codes as in Figure 3a. Figure 5b represents the sound level generated at the same three audience characteristic points, referenced with respect to the sound level at the mixing booth. The device 300 is for this digital simulation composed of a stack of 12 high frequency sources, having neither separation panels nor 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.

[65] Thus, this kind of sound diffusion device 300 makes it possible, thanks in particular to the combination of several sources in a single enclosure (i.e. a single box 310):

• minimize discontinuities between acoustic sources reducing or even eliminating parasitic lobes;

• considerably reduce the weight and the manufacturing cost of the device by eliminating the various horizontal panels which were present between the acoustic sources in the stack of speakers also facilitating the transport of the device 300 and its installation; and

• a quick installation not requiring the angular adjustment of each of the acoustic sources one between the other.

[66] Indeed, the curvature of the curved vertical stack of high frequency acoustic sources is fixed and cannot be modified by a user. Thus, no adjustment by the user is necessary for the installation of the different sources. [67] In order to adapt the resulting wavefront to the diffusion objectives, the high frequency sources 320 can be individually electronically controlled in amplitude and phase.

[68] 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 incline them.

[69] 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 of the plane of the arrangement, defined by a distance r and an angle Q at the source, the sound level SPL relative to the projection axis is equal to:

[70] Where k is the wave number corresponding to where f is at the frequency

considered and c the speed of the sound in the environment considered (here the air).

[71] By applying different phase adjustments to each of the sources in the arrangement, the main sound lobe can be tilted at an angle qo.

[72] We can similarly show that the relative sound level is worth:

[73] A physical or electronic setting that does not generate a parasitic lobe whose sound intensity is greater than -12dB relative to the main lobe, and at the same distance from the source, can be considered acceptable.

[74] Thus, it can be shown that there is a maximum angle qo beyond which parasitic lobes of intensity appear greater than the threshold defined above. This maximum angle can be expressed as a function of the frequency and the height of the source by the following approximate formula: q O, hiac arcsi

[75] Where xo is the solution to the equation 2.47 (E4)

[76] In order to cover a close audience, it is common to have to orient the last enclosure in an arrangement greater than 45 ° to the horizontal. This is all the more true when the arrangement is suspended at significant heights, which can be the case when it is placed above the stage or when the geometry of the place does not allow low siting.

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

[78] We note that in order to reach an angle qo of 45 ° at 10 kHz, a unit source of 10mm in height is required, and that this source can only be tilted electronically by 27 ° at 16kHz. Such 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.

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

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

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

[82] Conversely, a line with sources 140mm high makes it possible to reach a maximum angle qo of 3 ° at 10kHz and 2 ° at 16kHz. Thus the association of a physical curvature adapted from the stacking of high frequency acoustic sources with the individualized electronic control of these, combined or not with an individualized electronic control of the low and / or medium frequency sources in amplitude and phase, appears to be an optimal solution.

[83] More visually and quantitatively, the following numerical simulations make it possible to highlight the advantages and disadvantages of these different configurations.

[84] Figures 7a to 7e show 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. In Figure 7a, the solid lines starting from the vertical rectilinear stack represent the total vertical opening covered. Figure 7b represents the frequency response curves in magnitude generated by such a vertical rectilinear stack before the application of electronic control on the acoustic sources. The dark gray curves correspond to the audience, and the light gray dotted curves correspond to the stage and the ceiling. FIG. 7c represents the frequency response curves in phase generated by such a vertical rectilinear stack, at the mixing booth (“FOH”) and at the start of the hearing (“Proximity”), before the application of the electronic control on acoustic sources, and after subtracting the minimum propagation delay. FIG. 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 in FIG. 7b. FIG. 7e represents the frequency response curves in phase generated by such a vertical rectilinear stack, after the 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 hearing.

[85] Figures 8a to 8e show the results obtained with a curved vertical stack of speakers including an acoustic source high frequency located between two medium and / or low frequency acoustic sources on the same horizontal plane. In FIG. 8a, the solid lines starting from the curved vertical stack represent the total vertical opening covered. Figure 8b shows 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 in Figure 7b. FIG. 8c represents the frequency response curves in phase generated by such a curved stack after optimization of the angles between each source, at the mixing booth and at the start of the hearing, before the application of the electronic control on the acoustic sources and after subtracting the minimum propagation delay. 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 in Figure 7b. FIG. 8e represents the frequency response curves in phase 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 level of the mixing cabin and at the start of the hearing.

[86] Finally, Figures 9a to 9e show the results obtained with a sound diffusion device 300 with a non-constant physical curvature fixed as described above. In FIG. 9a, the solid lines starting from the sound device 300 represent the total vertical opening covered. FIG. 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 in FIG. 7b. FIG. 9c represents the frequency response curves in phase 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 hearing. FIG. 9d represents the frequency response curves in magnitude generated by such a device 300, after the application of electronic control in magnitude and in phase, with an acoustic source per DSP channel, and with the same color codes as in FIG. 7b. FIG. 9e represents the frequency response curves in phase generated by such a device 300, after application of the electronic control in magnitude and in phase, with an acoustic source by DSP channel, and after subtraction of the minimum propagation delay, calculated in the cabin and at the start of the hearing.

[87] It can be seen that the solution of Figures 8a to 8e gives a generally satisfactory response, nevertheless perfectible at high frequencies (bundle of curves in magnitude less tight, and phase curves more heckled). On the other hand, the sound level on the stage and on the ceiling (visible on the light gray curves of Figures 8b and 8d) has very high peaks at high frequencies, at a level equivalent to that on the audience, which is problematic .

[88] The vertical rectilinear arrangement of Figures 7a to 7e, for which the coverage of the audience is obtained by electronic means only (case of Figures 7d and 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 hearing, related to the appearance of parasitic lobes off axis, following the application of parameters excessive magnitude and phase as in the case of an inclination performed only electronically. In addition, the phase curves are very rowdy, and reflect significant time lags in the arrival on the hearing of the various frequency components of the sound signal.

[89] On the other hand, the results obtained by the configurations of Figures 9a to 9e are satisfactory over the entire audio spectrum, both in magnitude only in phase. The sound level on the stage and the ceiling is much lower than that on the audience, and the phase curves show few fluctuations, before and after application of the electronic correction parameters in magnitude and phase.

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

[91] 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 orientable flaps acting on a sound emission from at least one of the high frequency acoustic sources 320 to produce a directivity of sound emission from the high frequency acoustic source according to a chosen angular sector, the a high frequency acoustic source and the acoustic source emitting over a medium frequency range being configured to emit over a common frequency range.

[92] 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 over 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 over 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 over a medium frequency range so as to produce a sound emission directivity of the couple consisting of the high frequency acoustic source and the acoustic source emitting over a medium frequency range according to the same angular sector chosen as the directivity produced by the adjustable shutters. [93] The different variants of this embodiment are described in document EP 3,063,950 B1.

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

[95] For the case where the sound diffusion device emits towards an audience far from the scene or in grazing incidence, we define a sound diffusion device "at extended range" 300_F in which the set of high frequency acoustic sources 310 produces a global sound emission directivity having a total vertical opening angle less than or equal to 20 °, as illustrated in Figure 10. This corresponds to a relatively small fixed non-constant curvature, represented by lines perpendicular to the weak wave front length on the right device.

[96] The graph on the right of FIG. 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, compared to the sub-figure of the figure

10 where the curvature values of the 300_F "wide range" sound diffusion device are represented by lines perpendicular to the wave front. On this graph is represented the evolution of the value of the angle alphaj between the i-th and i + 1-th acoustic source, for i integer going 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.

[97] In the event that the sound diffusion device transmits to an audience close to the stage or that the latter is distributed over a sector significant vertical angular, we define a sound diffusion device "with extended vertical opening" 300_W in which the set of high frequency acoustic sources 310 produces a directivity of overall sound emission having a total vertical opening angle greater than 20 °, as shown in Figure 11. This corresponds to a larger non-constant fixed curvature represented by lines perpendicular to the long wave front on the right device.

[98] The graph on the right of Figure 1 1 illustrates another representation of the evolution of the physical curvature of the curved vertical stack of high frequency acoustic sources 310 formed by the “wide vertical opening” sound diffusion device 300_W, with respect to the sub-figure of Figure 1 1 where are represented the values of curvature of the sound diffusion device "with extended vertical opening" 300_W by lines perpendicular to the wave front. This graph shows the evolution of the physical curvature of the curved vertical stack of high frequency acoustic sources 310 formed by the sound diffusion device "with extended vertical opening" 300_W, that is to say the evolution of the value of the angle alphaj 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 wider than in Figure 10, which corresponds to a larger non-constant fixed curvature than in the case of FIG. 10 and of a “wide range” sound diffusion device 300_F. In this particular case also, the physical curvature of the curved vertical stack is monotonous.

[99] For configurations of physical distribution of the audience 2 requiring greater sound power or for more complex and / or more extensive distributions, a sound diffusion assembly comprises at least one first sound diffusion device "with extended range " 300_F and a sound diffusion device 300, 300_F or 300_W as defined above and superimposed so that the resulting sound diffusion assembly generates a vertical wave front with non-constant curvature fixed as illustrated in Figure 12.

[100] In other words, the 300_F "wide-range" sound diffusion device can be coupled with another 300, 300_F or 300_W sound diffusion device as defined above and can be assembled by fixing means.

[101] In particular, the “wide-range” sound diffusion device 300_F can be coupled with a “wide-range” sound diffusion device 300_F identical to itself.

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

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

[104] This may in particular be 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 can thus make it possible to adjust a sound wavefront emitted by the sound diffusion assembly to the objectives of broadcast to an audience.

[105] Indeed, the superimposition 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 in Figure 13.

[106] As in Figures 10 and 1 1, the graph on the right of 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 set of sound diffusion resulting from the assembly of two sound diffusion devices "at extended range" 300_F, compared to the sub-figure of figure 13 where are represented the values of curvature of this set of sound diffusion by lines perpendicular to the wave front. On this graph, we observe a non-monotony of the evolution of the angles between sources 7 and 9, corresponding to a break in 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 broadcasting assembly to adapt it to the broadcasting objectives.

[107] Finally, to facilitate installation, the diffusion assembly can advantageously include 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.

LIST OF REFERENCES

1 scene

2 audience

3 sound diffusion device

10 classic stereo arrangement

100 arrangement adapted to broadcast a spatialized sound signal 300 sound diffusion device

300_F "extended range" sound system

300_W "wide vertical opening" sound system

310 box

320 high frequency sound source

330 low or medium frequency sound source

340 waveguide

Right

FOH Mixing Cabin (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 several medium frequency and / or low frequency acoustic sources ( 330) superimposed and arranged to the left and / or right of the high frequency acoustic sources (320), the high frequency acoustic sources (320) being individually coupled to a waveguide (340) and arranged in a curved vertical stack having a fixed non-constant physical curvature.

2. A sound broadcasting device (300) according to claim 1, in which the high frequency sources (320) are individually electronically controlled in amplitude and phase so as to adapt the resulting wavefront to the broadcasting objectives for an audience.

3. A sound diffusion device (300) according to claim 1 or 2, in which each waveguide (340) comprises an outlet, the outlets of the waveguides being arranged in perfectly contiguous manner, so as to form a ribbon. continued.

4. Sound diffusion device (300) according to any one of claims 1 to 3 wherein the evolution of the physical curvature of the curved vertical stack is monotonous.

5. Sound diffusion device (300) according to any one of claims 1 to 4 such that among the plurality of medium and / or low frequency acoustic sources (330) there is at least one acoustic source emitting over a medium frequency range , the sound diffusion device also comprising: orientable flaps acting on a sound emission from 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 on a medium frequency range being configured to transmit over a common frequency range; and 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 over a medium frequency range so as to apply in the frequency range common at least one magnitude parameter on the high frequency acoustic source and / or on the acoustic source emitting over 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 couple consisting of the high frequency acoustic source and the acoustic source emitting a medium frequency range according to the same angular sector chosen as the directivity produced by the orientable flaps.

6. Sound diffusion device with extended range (300_F) according to one of claims 1 to 5 wherein all of the high frequency acoustic sources (320) produces a directivity of overall sound emission having a total vertical opening angle less than or equal to 20 °.

7. Sound diffusion device with extended vertical opening (300_W) according to one of claims 1 to 5 in which the set of high frequency acoustic sources (320) produces a directivity of overall sound emission having a vertical opening angle total greater than 20 °.

8. Sound diffusion device with extended range (300_F) according to claim 6, characterized in that it can be coupled and superimposed above or below with a second sound diffusion device (300, 300_F or 300_W) according to l 'one of claims 1 to 7 by fixing means.

9. An extended range sound diffusion device (300_F) according to claim 8, wherein the second sound diffusion device is identical to the extended range sound diffusion device (300_F).

10. Sound diffusion device according to any one of claims 2 to 9, in which 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 medium frequency and / or low frequency acoustic sources.

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

12. A sound diffusion assembly according to claim 11 in which the high frequency sources (320) are individually electronically controlled in amplitude and in phase so as to adapt the resulting wavefront to the objectives of diffusion on an audience and to compensate for a possible non monotony generated by an assembly of the devices between them.

13. Sound diffusion assembly according to claim 12, in which the non-monotony is that of the physical curvature of the curved vertical stack formed by the sound diffusion assembly.