SOUND DIFFUSION DEVICE WITH CONTROLLED BROADBAND DIRECTIVITY

Abstract

A loudspeaker enclosure comprising a plurality of acoustic sources and having controlled broad-band directivity.

Claims

1. Acoustic enclosure (E) having a volume shape with a front face (F.sub.Eav), a rear face (F.sub.Ear), two first and second side faces (F.sub.Elat1) and (F.sub.Elat2), and said enclosure (E) having a main emission direction (D.sub.av) perpendicular to the front face (F.sub.Eav) of the acoustic enclosure (E) as well as a rear emission direction (D.sub.ar) perpendicular to the rear face (F.sub.Ear) of the acoustic enclosure (E), said acoustic enclosure (E) comprising: at least one front acoustic source (S.sub.av) configured to emit a sound flux through the front face (F.sub.Eav) and having a main front source emission direction (D.sub.Sav), said main front source emission direction being substantially equal to the main emission direction (D.sub.av) of the acoustic enclosure (E), at least one lateral acoustic source (S.sub.lat) oriented towards at least one lateral face with source (F.sub.Elat), at least one lateral acoustic source (S) oriented towards at least one lateral face with a source (F), the said lateral face with a source (F.sub.Elat) being one and/or the other of the two first and second lateral faces (F.sub.Elat1) and (F.sub.Elat2), the said lateral acoustic source (S.sub.lat) having a main lateral source emission direction (D.sub.Slat) substantially perpendicular to one and/or the other of the lateral faces (F.sub.Elat1) and (F.sub.Elat2) said waveguide (G) being positioned in front of the at least one side acoustic source (S) so as to occlude the sound flux (F) emitted from said side acoustic source (Slat) in the main side source emission direction (D.sub.Slat), and to direct the sound flux (F.sub.lat) emitted from said side acoustic source to two first and second pluralities of side directions (D.sub.Slat1) and (D.sub.Slat2) on either side of the main side source emission direction (D.sub.Slat), and said waveguide (G) being joined to said side face with source (F.sub.Elat) by joining means, at least one front hole (O.sub.SLat av) formed by a gap between said side face with source (F.sub.Elat) and said sound waveguide (G) at least one front orifice (O.sub.SLat_av) formed by a space between the said lateral face with source (F) and the said sound waveguide (G), so as to allow the sound flow (F.sub.lat) emitted by the acoustic source (S.sub.lat) to pass in directions pointing towards a hemisphere defined by the main direction of emission (D.sub.av), at least one rear orifice (O.sub.SLat_ar) formed by a space between the said lateral face with source (F.sub.Elat) and the said sound waveguide (G), so as to allow the sound flow (F.sub.lat) emitted by the lateral acoustic source (S.sub.lat) to pass in directions pointing towards a hemisphere defined by the direction of emission (D.sub.ar) at the rear end of the enclosure.

2. Acoustic enclosure (E) according to claim 1, wherein the at least one front sound source (S.sub.av) is located in a front volume (V.sub.Sav) and the at least one side sound source (S.sub.lat) located in a side volume (V.sub.SLat) separated from the volume (V.sub.Sav) by at least one partition (C).

3. Acoustic enclosure (E) according to claim 1, wherein said front acoustic source (S.sub.av) and said side acoustic source (S.sub.lat) are high frequency, and/or medium frequency, and/or low frequency, and/or very low frequency acoustic sources.

4. Acoustic enclosure (E) according to claim 1, wherein said front acoustic source (S.sub.av) and said side acoustic source (S.sub.lat) are configured to be individually fed by DSP and amplification channels and electronically controlled in amplitude and phase so as to control the directivity of the sound radiation of the loudspeaker (E).

5. Acoustic enclosure (E) according to claim 1, wherein said loudspeaker (E) is adapted to be stacked with a second loudspeaker (E′) according to claim 1, wherein said loudspeakers (E) and (E′) each further comprise a first upper face (F.sub.Esup) and a first lower face (F.sub.Einf) on the one hand, and a second upper face (F) and a second lower face (F) on the other hand wherein the acoustic enclosures (E) and (E′) each further comprise a first upper face (F) and a first lower face (F) on the one hand, and a second upper face (F.sub.E′sup) and a second lower face (F.sub.E′inf) on the other hand, wherein said acoustic enclosure (E) is adapted to be stacked with the second acoustic enclosure (E′) from below, from above, or from the side.

6. Acoustic enclosure (E) according to claim 1, of the bass reflex type, further comprising at least one vent associated with the at least one lateral acoustic source (S.sub.Lat), characterized in that the at least one vent is positioned on the rear face (F.sub.Ear) of the loudspeaker (E).

7. A sound enclosure (E) according to claim 6, of the low reflex type, further comprising at least one vent associated with the at least one lateral sound source (Slat), characterised in that the at least one vent is positioned on the rear face (F.sub.Ear) of the sound enclosure (E).

8. A sound enclosure (E) according to claim 7, wherein said means (Gsup, Ginf) occluding the sound flow connect the lateral face with source (F.sub.Eiat) and said sound waveguide (G) in a solid and continuous manner on an upper face (F.sub.Esup) and a lower face (F.sub.Einf) of the sound enclosure (E)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further advantages and features of the present invention will result from the following description, given as a non-limiting example and made with reference to the attached figures:

[0033] FIG. 1, already described, illustrates the radiation diagram in polar coordinates corresponding to different types of sound directivities.

[0034] FIG. 2, already described, shows a front-rear alignment of two subwoofer stacks.

[0035] FIG. 3, already described, shows a stacked-returned source array.

[0036] FIGS. 4A to 4D, already described, show the acoustic performance of a state-of-the-art sound diffusion system comprising two stacks of sound sources aligned one behind the other, controlled by an electronic “End Fire” type control.

[0037] FIGS. 5A to 5D, already described, show the acoustic performance of a state-of-the-art sound diffusion system comprising two stacks of sound sources aligned one behind the other, controlled by a “Gradient” type electronic control.

[0038] FIGS. 6A to 6D, already described, show the acoustic performance of a state-of-the-art sound diffusion system comprising two stacks of sound sources aligned one behind the other, controlled by an electronic “All Pass Filter” type control.

[0039] FIG. 7, already described, shows a top view of the geometry of an acoustic enclosure comprising sound sources at the front and rear of the acoustic enclosure.

[0040] FIG. 8, already described, shows the geometry of an acoustic enclosure with sound sources at the front and additional sound sources positioned more or less to the sides of the acoustic enclosure in top view.

[0041] FIGS. 9A and 9B, already described, show a comparison of the performance of a loudspeaker with front sources only, with that of an acoustic enclosure with sources positioned more or less to the sides of acoustic enclosures in addition to the front sources.

[0042] FIG. 10, already described, illustrates schematically the stacking from the side of acoustic enclosures with additional sources on the sides of the acoustic enclosures.

[0043] FIGS. 11A and 11B show a three-dimensional view and a two-dimensional top view, respectively, of a digital model of an acoustic enclosures according to an embodiment of the invention.

[0044] FIG. 12 shows a top view of a schematic diagram of another type of acoustic enclosure according to an embodiment of the invention.

[0045] FIGS. 13A and 13B show two maps of the SPL value of an acoustic enclosure without and with a sound waveguide.

[0046] FIGS. 14A and 14B show a comparison of the performance in terms of phase difference and magnitude, as a function of sound frequency, of an enclosure E without and with a sound waveguide

[0047] FIG. 15A to 15D show the performance of a sound enclosure E with a waveguide electronically controlled in amplitude and phase according to a first type of electronic control.

[0048] FIG. 16A to 16D show the performance of an electronically amplitude and phase controlled acoustic enclosure E according to a second type of electronic control.

[0049] FIG. 11A-B to 16A-D are discussed in more detail in the following detailed description and examples, which illustrate embodiments of the invention without limiting its scope.

DETAILED DESCRIPTION OF THE DRAWINGS

[0050] FIGS. 11A and 11B show a three-dimensional view and a top view of an acoustic enclosure E according to an embodiment of the invention. By acoustic enclosure, is meant an enclosure comprising one or more acoustic sources, allowing the reproduction of sound from an electrical signal supplied by an audio amplifier. The acoustic enclosure E has a volumetric shape defining an area inside and an area outside the enclosure, hereinafter referred to as the inside and outside of the enclosure, with a front face F.sub.Eav, a rear face F.sub.Ear, and two first and second side faces F.sub.Elat1 and E.sub.Elat2. In the case of figures A11 and B, this is a parallelepiped. The enclosure could take any other volumetric shape such as an extruded trapezoid, where the first and second side faces F.sub.Elat1 and F.sub.Elat2 are not perpendicular to the front face F.sub.Eav of the acoustic enclosure E, as shown in FIG. 12.

[0051] The acoustic enclosure E has a main direction of emission D.sub.av perpendicular to the front side F.sub.Eav directed towards the outside of the acoustic enclosure E, as well as a rear direction of emission D.sub.ar perpendicular to the rear side F.sub.Ear directed towards the outside of the acoustic enclosure E. In the following, the main direction of emission of the acoustic enclosure E will be referred to as D.sub.av or the 0° axis of emission.

[0052] The acoustic enclosure E comprises at least one front acoustic source S.sub.av configured to emit a sound stream through the front face F.sub.Eav. The at least one front acoustic source S.sub.av has a main front source emission direction D.sub.Sav that is substantially equal to the main emission direction D.sub.av of the acoustic enclosure E.

[0053] The acoustic enclosure E also comprises at least one lateral acoustic source S.sub.av oriented towards at least one lateral face with source F.sub.Elat which corresponds to one and/or the other of the two first and second lateral faces F.sub.Elat1 and F.sub.Elat2 of the enclosure. The at least one lateral acoustic source S.sub.lat has a main lateral source emission direction D.sub.Slat substantially perpendicular to one and/or the other of the side faces F.sub.Elat1 and F.sub.Elat2 and directed towards the outside of the acoustic enclosure E.

[0054] In one or more embodiments, said front acoustic sources and side acoustic sources can be separated in different volumes, respectively front volume V.sub.Sav and side volume V.sub.SLat, materialized by partitions C inside the acoustic enclosure E. An example of these embodiments is visible in FIG. 12. Such volumes make it possible to obtain a better quality of diffusion because they separate sound diffusion spaces in which the sound signals sent, respectively to the said front acoustic sources and side acoustic sources, are different. These volumes can thus attenuate possible undesired effects that degrade the diffusion quality of the complete acoustic enclosure, such as interference. Several configurations are possible: for example, in the case of the existence of several front acoustic sources, each of them may be located in a separate volume, or several may be grouped together in the same volume; similarly, in the case of the existence of several side acoustic sources, each of them may be located in a separate volume, or several may be grouped together in the same volume.

[0055] The acoustic enclosure E also comprises at least one sound waveguide G. By sound waveguide is meant a physical device capable of directing the flow of an incident sound wave onto this device. The sound waveguide G may, for example, take the form of a simple wall, or any other three-dimensional shape designed to guide the flow of sound meeting the waveguide G in determined directions. The waveguide may, for example, be designed to converge, or diverge, the sound flow incident on it.

[0056] The waveguide G according to the invention is positioned in front of the at least one lateral acoustic source S.sub.lat so as to occlude the sound flux F.sub.lat emitted by the at least one lateral acoustic source S.sub.lat in the main lateral source emission direction D.sub.Slat, and to direct the sound flux F.sub.lat towards two first and second pluralities of lateral directions D.sub.Slat1 and D.sub.Slat2 on either side of the main lateral source emission direction D.sub.Slat. By the terms first and second pluralities of lateral directions are meant directions oriented respectively towards each of the half-spaces separated by the main lateral source emission direction D.sub.Slat. The waveguide G is assembled to said lateral face with source F.sub.Elat by assembly means. The waveguide G has an outer face and an inner face.

[0057] The acoustic enclosure E also has at least one front opening O.sub.SLat_av formed by a gap between the inner face of the sound waveguide G and a first inner partition of the acoustic enclosure E, so as to allow the sound flow F.sub.lat emitted by the acoustic source S.sub.lat to pass in directions towards a hemisphere defined by the main emission direction D.sub.av. FIGS. 11A-B and 12 show such a front opening O.sub.SLat_av.

[0058] Preferably, the front orifice O.sub.SLat_av allows the sound flow F.sub.lat from the at least one acoustic source S.sub.lat to pass in directions included in a hemisphere defined by a direction D.sub.OSLatav of the enclosure E determined by the front orifice O.sub.SLat_av. Advantageously, the front orifice O.sub.Slat_av allows the sound flow F.sub.lat of the at least one acoustic source Slat to pass in directions included in a cone with an axis parallel to the direction D.sub.OSLatav of the enclosure and with an opening half angle of 30°. Other arrangements are possible, in particular involving different opening angles.

[0059] The acoustic enclosure E also has at least one rear opening O.sub.SLat_ar formed by a gap between the inner face of the sound waveguide G and a second inner partition of the acoustic enclosure E, so as to allow the sound flow (F.sub.lat) emitted by the acoustic source S.sub.lat to pass in directions towards a hemisphere defined by the rear emission direction D.sub.ar. FIGS. 11A-B and 12 show such a rear opening O.sub.SLat_ar.

[0060] Preferably, the rear orifice O.sub.SLat_ar allows the sound flow F.sub.lat emitted by the at least one acoustic source Slat to pass in directions included in a hemisphere defined by a direction D.sub.Slat_ar of the acoustic enclosure E determined by the rear orifice O.sub.Slat ar. Other arrangements are possible, in particular involving different opening angles.

[0061] Thus, the enclosure E according to the invention with at least one sound waveguide G and at least one front opening O.sub.Slat_av and at least one rear opening O.sub.SLat_ar represents a new modified emissive part, compared to a sound enclosure without waveguide.

[0062] In particular, the acoustic enclosure E may have symmetry with respect to a plane corresponding to the median plane of the front face F.sub.Eav of the enclosure E. In this case, the enclosure E has a first plurality of acoustic sources Slat1 oriented towards the lateral face F.sub.Elat1 of the enclosure, and a second plurality of acoustic sources S.sub.lat2 identical to the plurality of acoustic sources S.sub.lat1 and positioned symmetrically with respect to the plane corresponding to the median plane of the front face F.sub.Eav of the enclosure E, thus oriented towards the lateral face F.sub.Elat2 of the enclosure E.

[0063] FIGS. 13A and 13B show the comparison of a top view mapping of the SPL value (dB response) of an acoustic enclosure E without a waveguide, with a mapping of the same enclosure E with a waveguide. These maps are derived from numerical simulations obtained with the COMSOL Multiphysics software commercialized by the COMSOL company. The simulations are based on the finite element method. The brightest areas correspond to areas with high SPL values, while the darkest areas correspond to areas with low SPL values. The waveguide is formed by a flat wall joined to the source side (F.sub.Elat) of the enclosure. The enclosure has several sources at the front (drivers and vents) and acoustic sources at the sides (drivers). It can be observed that with the waveguide, the sound flow on the right side of the enclosure is decreased, compared to the mapping of the enclosure without waveguide G. Furthermore, the sound level is increased at the rear port.

[0064] FIGS. 14A and 14B show a comparison of the performance in terms of modulus and phase difference between the front sources and the sources on the sides of the loudspeaker E previously shown in FIGS. 11A and 11B, as a function of frequency. The curves correspond to a listening direction in the 0° axis, i.e. towards the front, and therefore towards the audience. A better minimization of the phase difference can be observed in the frequency range between 180 Hz and 310 Hz, which corresponds to a better summation of the waves emitted by the set formed by the front sources and the sources on the sides.

[0065] In one or more embodiments of the acoustic enclosure E, the at least one front acoustic source S.sub.av and the at least one side acoustic source S.sub.lat are high frequency, and/or medium frequency, and/or low frequency, and/or very low frequency acoustic sources.

[0066] In one or more embodiments of the loudspeaker E, the at least one front acoustic source S.sub.av and the at least one side acoustic source Slat are configured to be individually fed by DSP and amplifier channels and electronically controlled in amplitude and phase. The DSP channel feeding, and electronic amplitude and phase control are intended to control the directivity of the sound radiation from the acoustic enclosure E.

[0067] The sound flow distribution created by the use of the at least one waveguide G in the loudspeaker E thus allows for a wider range of directivities of the loudspeaker E through the feeding of the DSP channels and the electronic control in amplitude and phase of the at least one front acoustic source S.sub.av and of the at least one side acoustic source Slat. The waveguide G allows for better control and a wider range of directivities of loudspeakers having lateral sources in addition to their main forward emitting sources.

[0068] Two examples will be described, which show the control of directivity that can be achieved by the use of a waveguide in an acoustic enclosure E with front and side sources.

Example 1: DSP Solution with Perfect Alignment in the Axis

[0069] Here we consider a symmetrical enclosure E with a front low-frequency source and a low-frequency source on two sides of the loudspeaker. The sources are fed by DSP channels and electronically controlled in amplitude and phase. The control performed aims at a perfect alignment in the 0° direction axis D.sub.av of the enclosure (E). FIGS. 15A to 15D show the curves for the evolution of the sound level (SPL) (also called modulus or magnitude) and the phase difference between the front sources and the sources on each side of the loudspeaker E, as a function of the sound frequency. Several listening directions, between 0° and 90°, i.e. distributed in the front hemisphere of the enclosure E are shown. The two configurations without and with waveguide are shown. It can be observed that the waveguide G allows a better control of the directivity lobe due to the new definition of the emissive part constituted by the front and rear ports O.sub.SILt_av and O.sub.Slat_ar.

[0070] Indeed, on the magnitude curves, it can be observed that the waveguide allows the sound level to be raised on the sides of the directivity lobe centered on the D.sub.av axis. The waveguide allows a more homogeneous distribution of sound in the front hemisphere of the enclosure E.

[0071] Furthermore, on the phase difference curves, it can be observed that the G-waveguide allows to tighten the different curves corresponding to the different directions of observation between 0° and 90°, in particular for the frequencies between 180 Hz and 380 Hz. The scattering is thus more homogeneous over a wider frequency band thanks to the use of waveguide G.

Example 2: DSP Solution for Rear Rejection Optimization

[0072] Here we consider a symmetrical enclosure E with a front low-frequency source and a low-frequency source on two sides of the enclosure. The sources are fed by DSP channels and electronically controlled in amplitude and phase. The control is aimed at optimizing the rejection at the rear of the cabinet. FIGS. 16A to 16D show the curves for the evolution of the sound level (SPL) (also called modulus or magnitude) and the phase difference between the front sources and the sources on each side of the enclosure E, as a function of frequency. Several directions of emission, between 0° and 180°, i.e. distributed in a half-space, indifferently left or right of the enclosure E because of its symmetry, are represented. The two configurations without and with waveguide are presented.

[0073] On the amplitude curves, it can be observed that with the G waveguide, the sound level, SPL, decreases less quickly in the front hemisphere of the loudspeaker, i.e. for listening directions between 0° and 90°. On the other hand, the narrowing of the curves for the directions between 90° and 180° shows that the waveguide provides better rejection homogeneity in the rear space.

[0074] On the phase difference curves between the front low frequency sources and one of the lateral low frequency sources on one of the side faces, it can be observed that the curves relative to the enclosure coverage cone, i.e. between 0° and 50°, are tightened near the axis defining a zero phase difference. This reflects a better temporal alignment in the front hemisphere of the enclosure E, i.e. in the 0° axis and off this axis.

[0075] In addition to better control of the directivity of an enclosure E comprising at least one waveguide as described above, the use of such waveguides, for products comprising acoustic sources on the sides, provides certain advantages in terms of mechanical and assembly properties.

[0076] In the case of an acoustic enclosure E comprising at least one front acoustic source S.sub.av, at least one side acoustic source S.sub.lat, and at least one sound waveguide G positioned in front of the at least one side acoustic source S.sub.lat, and where the outer face of the sound waveguide G is flat, the acoustic enclosure E may be stacked with a second acoustic enclosure E′ comprising or not a waveguide G′ as described in the present application.

[0077] The stacking can be done on the side; in this case, the stacking surfaces are the outer face of the waveguide of the enclosure E and one of the side faces of the enclosure E′.

[0078] In the case where the enclosures E and E′ each furthermore comprise a first upper face F.sub.Esup and a first lower face F.sub.Einf on the one hand, and a second upper face F.sub.E′sup and a second lower face F.sub.E′enf on the other hand, stacking can be carried out from below or from above. The stacking surfaces are then either the first upper side F.sub.Esup and the second lower side F.sub.E′inf, or the first lower side F.sub.Einf and the second upper side F.sub.E′sup.

[0079] It is possible with enclosures E as described in the present application to create loudspeaker arrays by stacking loudspeakers comprising waveguides G with a flat outer face from the side and from above or below, some of the enclosures being able to be rotated by 180° relative to the other enclosures.

[0080] Alternatively, carrying handles may be assembled on the outer face of a flat outer face G waveguide as described in the present application. In this case, the carrying handles may be designed to be integrated flush with the flat outer face of the G waveguide.

[0081] Finally, it is possible to assemble a waveguide G to an enclosure E having sources at the front and sources at the sides directed towards one or other of the side faces of the enclosure E, in a manner similar to an external accessory. In this case, the waveguide is joined to either of the side faces F.sub.Elat1 and F.sub.Elat2 of the enclosure E by joining means.