WO2018220057A1

WO2018220057A1 - Sound reproduction system

Info

Publication number: WO2018220057A1
Application number: PCT/EP2018/064264
Authority: WO
Inventors: Antoine PETROFF
Original assignee: Devialet
Priority date: 2017-05-30
Filing date: 2018-05-30
Publication date: 2018-12-06
Also published as: DE112018002756T5; FR3067205B1; FR3067205A1

Abstract

The invention relates to an assembly consisting of a motor vehicle and at least one sound reproduction system, comprising: at least one enclosure (22A) comprising at least one sound diffusion loudspeaker (28) that can emit sound waves; and at least one tubular sound diffusion line (23) comprising a wall (30) defining an internal conduit (31) for propagation of the sound waves emitted, the conduit (31) leading to a first end (32) of the sound diffusion line (23) to which the sound diffusion loudspeaker (28) is connected. The sound diffusion line (23) comprises at least three diffusion points (36) arranged throughout the wall (30), which are substantially aligned along the sound diffusion line (23), each diffusion point (36) being suitable for redirecting a portion of the sound waves propagated in the conduit (31) in order to respectively form a diffused sound wave.

Description

Sound restitution system

The present invention relates to a sound reproduction system. The invention also relates to an assembly comprising a motor vehicle and at least one such sound reproduction system. The invention further relates to a sound diffusion method.

Such a sound reproduction system allows for example the driver and passengers of a motor vehicle to listen to music or a radio program during a trip.

For the sound system of motor vehicles, it is known to use speakers comprising so-called directive speakers, that is to say whose transmission axis is oriented towards the interior of the passenger compartment.

The interior of a motor vehicle is usually a small space, where sound waves travel short distances before reflecting on the walls. In addition, to reduce the ambient noise level due to the vehicle engine and the traffic, it is usual to cover the interior walls of the cabin with a coating at least partially absorbing the sound waves, which reduces the amplitude reflected sound waves.

However, it is known that an acoustic environment in which the sound waves travel distances of several meters and are reflected several times while remaining audible, as in a large room delimited by walls, is more pleasing to the ear, especially for the music listeners.

An object of the invention is therefore to provide a restitution system intended to reproduce at least partially the desirable acoustic conditions described above, in a confined and low-reflective environment such as the passenger compartment of a motor vehicle.

For this purpose, the subject of the invention is a sound reproduction system of the aforementioned type, comprising:

at least one enclosure comprising at least one diffusive loudspeaker, capable of emitting sound waves, and

at least one tubular sound diffusion line comprising a wall defining an internal duct for propagation of sound waves emitted, the duct opening at a first end of the sound diffusion line,

the diffusive loudspeaker being connected to the first end of the sound diffusion line, the sound diffusion line comprising at least three diffusion points disposed across the wall, substantially aligned along the sound diffusion line, each diffusion point being adapted to redirect a portion of the sound waves propagated in the conduit to respectively form a broadcast sound wave.

According to particular embodiments, the sound reproduction system comprises one or more of the following characteristics, taken separately or in any technically possible combination:

the wall has an acoustic impedance, and in which each diffusion point has an acoustic impedance lower than the acoustic impedance of the wall, in particular at least ten times lower, advantageously at least a hundred times lower;

the diffusion points comprise orifices defined by the wall;

the enclosure also comprises a directional loudspeaker capable of emitting sound waves in phase with the sound waves emitted by the diffusive loudspeaker, the directional loudspeaker and the diffusive loudspeaker having emission axes forming between them an angle greater than or equal to 90 °;

the chamber also comprises a box defining a charge volume of the diffusive loudspeaker, the box being disposed away from the diffusive loudspeaker, the chamber further comprising a charge line connecting the charge volume to a loudspeaker; rear output of the diffusive speaker;

- Any two successive scattering points of the diffusion points are separated from each other by a distance greater than a longitudinal dimension of one of the diffusion points, measured tangentially to the sound diffusion line;

the diffusion points are arranged to form diffused sound waves having mean acoustic intensities of near field substantially equal to each other;

the scattering points are arranged to form diffused sound waves having, for each frequency of a transmission range, a difference between a near-field acoustic intensity at the frequency in question and an average near-field acoustic intensity between -12 dB and 12 dB; and

the sound reproduction system also comprises a rear module, the rear module comprising at least five enclosures and at least two diffusion lines,

the sound diffusion line extends along a horizontal axis.

The invention also relates to an assembly comprising a motor vehicle and at least one sound reproduction system as described above, the enclosure and the sound diffusion line of the sound reproduction system being integrated into a structure of the vehicle.

According to a particular embodiment, the assembly according to the invention has one or more of the following characteristics, taken separately or in any technically possible combination:

the sound diffusion line extends along a middle foot of the structure; and

the sound reproduction system comprises two loudspeakers and two sound diffusion lines integrated into the structure respectively in two middle feet, as well as a rear module comprising at least five loudspeakers and at least two sound diffusion lines integrated into the structure in a rear block.

The invention further relates to a method of broadcasting sounds in an internal space by a sound reproduction system as described above, comprising the steps of:

- emission of sound waves by the diffusive loudspeaker;

- propagation along the line of diffusion, in the duct, sound waves emitted; and

formation by each diffusion point of a diffused sound wave, from a part of each propagated sound wave, the sound wave being directed towards the internal space;

each broadcast sound wave having an average near-field acoustic intensity substantially equal to the average near-field acoustic intensities of the other broadcast sound waves,

each broadcast sound wave having, for each frequency of a transmission range, a maximum difference between a near field acoustic intensity at the frequency in question and the near field average acoustic intensity between

-12 dB and 12 dB.

The invention further relates to a method of broadcasting sounds in an internal space by a set as described above, comprising the steps of:

- emission of sound waves by the diffusive loudspeaker;

formation by each diffusion point of a diffused sound wave, from a part of each propagated sound wave, the sound wave being directed towards the internal space; each broadcast sound wave having an average near-field acoustic intensity substantially equal to the average near-field acoustic intensities of the other broadcast sound waves,

each broadcast sound wave having, for each frequency of a transmission range, a maximum deviation between near-field acoustic intensity at the frequency in question and near-field average sound intensity between -12 dB and 12 dB.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, among which:

- Figure 1 is a partial schematic perspective view of an assembly according to the invention comprising a motor vehicle and a sound reproduction system;

FIG. 2 is a perspective view of an enclosure and a sound diffusion line of the sound reproduction system of the assembly represented in FIG. 1;

FIG. 3 is a sectional view of the enclosure and the sound diffusion line shown in FIG. 2;

FIG. 4 is a schematic view of a diffusion point distribution of the sound diffusion line of FIGS. 2 and 3; and

FIG. 5 is a side view of the rear module of the sound diffusion system of the assembly represented in FIG. 1.

Referring to Figure 1, there is described an assembly 10 comprising a motor vehicle 12, itself comprising a structure 14 partially shown, and a sound reproduction system 16 (shown schematically) according to the invention.

The structure 14 of the vehicle 12 defines an internal space 18 constituting a passenger compartment suitable for accommodating for example a driver and passengers of the vehicle 12.

The structure 14 comprises at least one middle pillar 20, of elongate shape, extending substantially vertically along the internal space 18. The central pillar 20 is situated for example between a front seat and a rear seat of the vehicle 12, and supports a seatbelt of the front seat.

In the example shown in FIG. 1, the structure 14 comprises two central feet 20 extending on either side of the structure 14.

The structure 14 further comprises a rear block 21 A, located for example behind the rear seats of the vehicle 12, and a front block 21 B.

The sound reproduction system 16 is adapted to emit sound waves in the internal space 18, for example music or a radio program, for the occupants. The sound reproduction system 16 is integrated in the structure 14 of the vehicle 12, that is to say that the sound reproduction system 16 is contained for the most part in a volume of the structure 14 and in a small part in the space internal 18.

For example, the sound reproduction system is more than 80% by volume in the volume of the structure 14, and less than 20% by volume in the internal space 18. The sound reproduction system 16 comprises ten speakers 22A -22J substantially identical, distributed in the structure 14 of the vehicle 12.

In the example shown in the figures, the sound reproduction system 16 comprises two identical speakers 22A, 22B and two identical sound diffusion lines 23, shown in more detail in FIGS. 2 and 3, integrated into the structure 14 and respectively fixed. at one of the two middle feet 20.

The sound reproduction system 16 also comprises a rear module 24 shown in FIG. 5, integrated in the structure 14 in the rear block 21 A, gathering five of the speakers 22C, 22D, 22E, 22F, 22G and further comprising two lines of sound diffusion 23.

The three speakers 22H, 22I, 22J, the sound reproduction system 16 are integrated in the structure 14 in the front block 21 B, and two sound diffusion lines.

The chamber 22A, shown in FIGS. 2 and 3, comprises at least one directional loudspeaker 26 and a diffusive loudspeaker 28, able to emit sound waves.

The directional loudspeaker 26 and the diffusive loudspeaker 28 are mid-high-frequency loudspeakers, that is to say, loudspeakers adapted to emit sound waves whose frequencies are within a range of emission ranging between 500 Hz and 10 kHz, for example.

The directional loudspeaker 26 and the diffusive loudspeaker 28 are arranged in the enclosure 22A to emit sound waves in substantially opposite directions. Thus, the directional speaker 26 and the diffusive speaker 28 have transmission axes 29, visible in Figure 3 forming between them an angle greater than or equal to 90 °, preferably equal to 180 °.

The transmission axis 29 is for example an axis of symmetry of the directional loudspeaker 26 or of the diffusive loudspeaker 28.

The directional loudspeaker 26 and the diffusive loudspeaker 28 are adapted to emit identical sounds, the sound waves emitted by the directional speaker 26 being in phase with the sound waves emitted by the diffusive loudspeaker 28.

The directional speaker 26 is oriented towards the interior space 18, so as to emit sounds directly towards the driver and the passengers. The diffusive loudspeaker 28 is oriented towards the outside of the vehicle 12.

The diffusion line 23 comprises a wall 30 having a tubular structure, defining an internal conduit 31.

The wall 30 is made of rigid material, for example plastic. The sound diffusion line 23 extends along the central pillar 20, between a first end 32 and a second end 34. The sound diffusion line 23 has a length, taken between the first end 32 and the second end 34, and a width taken transversely to the length, the length being greater than the width, advantageously at least ten times greater.

The duct 31 opens at the first end 32 and is closed at the second end 34.

The first end 32 is connected to the diffusive loudspeaker 28, so that the duct 31 is arranged to guide the sound waves emitted by the diffusive loudspeaker 28 from the first end 32 to the second end 34.

Advantageously, the sound diffusion line 23 extends substantially parallel to the emission axis 29 of the diffusive loudspeaker 28 at the first end 32, in order to allow optimal transmission of the sound waves from the diffusive speaker. 28 to the conduit 31.

The sound diffusion line 23 comprises a plurality of diffusion points 36 arranged along the diffusion line 23, through the wall 30, between the duct 31 and the interior space 18. The sound diffusion line 23 comprises, in particular, the minus three points of diffusion 36.

Advantageously, the diffusion points 36 extend over the sound diffusion line 23 over a length greater than 40 cm.

In one embodiment, the sound diffusion line 23 extends, for example, along a horizontal axis.

The acoustic impedance of the diffusion points 36 is less than the acoustic impedance of the wall 30, in particular at least ten times lower, advantageously at least a hundred times lower.

The diffusion points 36 are, for example, orifices defined by the wall 30, opening into the duct 31 and into the internal space 18.

According to a variant not shown, the diffusion points 36 are inserts through the wall 30, made of material having a low acoustic impedance.

According to another variant not shown, the diffusion points 36 are regions of the wall 30 having a smaller thickness than the rest of the wall 30. The diffusion points 36 are adapted to redirect part of the guided sound waves in the conduit 31 from the conduit 31 to the interior space 18. Each diffusion point 36 thus acts as an independent sound source emitting sounds towards the internal space 18.

The diffusion points 36 have substantially equal transverse stretches, tangentially to the diffusion line 23. For example, the diffusion points 36 are orifices of substantially circular cross section, and all have the same diameter.

Advantageously, the diffusion points 36 have cross sections of equal areas. In this case, the diffusion points 36 have transverse dimensions, measured tangentially to the wall 30, all greater than 2 mm.

In the example shown diagrammatically in FIG. 4, the diffusion points 36 are oblong orifices oriented parallel to the direction of extension of the diffusion line 23. The oblong orifices have cross sections of equal areas. The oblong orifices have for example all a length equal to 1 1, 10 mm and a width equal to 2.50 mm.

Diffusion points 36 are separated from each other by distances greater than their transverse extent.

In the example shown, the diffusion points 36 are divided into two groups. The diffusion points 36 of the first group, located on the side of the first end 32, are separated by a distance equal to 34.35 mm. The diffusion points 36 of the second group, located on the side of the second end 34, are separated by a distance equal to 15.80 mm.

More generally, the diffusion points 36 are arranged to verify two emission constraints, that is to say that the shapes, the dimensions and the distribution of the diffusion points 36 are determined, for example by numerical simulation, in order to check both emission constraints.

The first transmission constraint is that during the diffusion of a sound emitted by the diffusive loudspeaker 28 through the diffusion line 23, for each diffusion point 36, an average near-field acoustic intensity is that is measured at less than 1 cm from the diffusion point 36, averaged over all the frequencies of the emission range of the diffusive loudspeaker 28, is substantially equal to the average field acoustic intensities close to the other points of the broadcasting 36.

The second transmission constraint is that, for each diffusion point 36, for each frequency of the emission range of the diffusive loudspeaker 28, an intensity Near-field acoustic frequency at the frequency in question is within the range of -12 dB to +12 dB around the near-field average sound intensity.

According to parameters of the structure 14 and the dimensions of the duct 31, the diffusion points 36 can be distributed according to an infinity of arrangements, without there being any simple rule making it possible to describe all the possible arrangements. The arrangements of the diffusion points 36 making it possible to verify the two emission constraints are advantageously obtained by numerical simulation, starting from the structure 14 and the duct 31, in a manner known to those skilled in the art.

Thus, the sounds emitted through the scattering points 36 exhibit phase shifts and spatial distributions of sound sources around the internal space 18 partially reproducing the acoustic conditions of a sound that is reflected several times over the walls of a larger space. bigger than the cockpit.

Advantageously, the chamber 22A also comprises two bass drivers 38, able to emit sound waves whose frequencies are below 500 Hz. The bass speakers 38 are for example oriented upwards and downwards, respectively. the enclosure 22, that is to say that each bass speaker 38 has an emission axis oriented substantially along the center pillar 20.

The enclosure 22A further comprises a box 40 defining a load volume 42 of the loudspeakers. The charge volume 42 is intended to receive the return waves emitted by the rear outputs of the loudspeakers when the loudspeakers emit sounds.

The casing 40 is disposed away from the loudspeakers of the enclosure 22A, the enclosure 22A comprising a charging duct 44 connecting the charge volume to the rear outlets of the loudspeaker or speakers. The charging duct 44 is adapted to guide the waves back to the load volume 42, and the load volume 42 of the loudspeakers is then said remote.

The rear module 24 shown in FIG. 5 comprises five clustered speakers 22C-22G, with four speakers 22D-22G aligned substantially vertically behind a wall of the rear block 21A, and a fifth chamber 22C protruding from the wall in the space. 18. The rear module 24 also comprises two sound diffusion lines 23 integrated into the structure 14, extending substantially horizontally on each side of the speakers 22C-22G along the internal space 18.

The sound diffusion lines 23 are connected to two diffusive loudspeakers 28 of one of the speakers 22D of the rear module 24. In this case, the enclosure 22D connected to the Diffusion lines 23 comprises two diffusive loudspeakers 28 and does not have a directional loudspeaker 26.

According to a variant not shown, the two diffusion lines 23 are connected to a single diffusive speaker 28 by a T-connector.

Each of the speakers 22C-22G of the rear module 24 comprises two bass drivers 38, oriented parallel to each other, with their transmission axes oriented substantially horizontally, tangentially to the internal space 18.

The rear module 24 further comprises a box 40 defining a charge volume 42 common to the five speakers 22C-22G.

Each of the speakers 22H, 22J located in the sides of the front block 21B comprises only a diffusive loudspeaker, connected to a sound diffusion line extending along the internal space 28.

The speaker 22I located in the center of the front block 21 B comprises a directional speaker, two woofers and a diffusive loudspeaker adapted to broadcast sound waves through the ventilation ducts of the vehicle 12. The operation of the sound reproduction system 16 will now be described.

An operator, for example the driver or one of the passengers of the vehicle 12, actuates the sound reproduction system 16, for example by actuating a manual control. The operator selects a sound to be transmitted by the sound reproduction system 16, for example music or a radio program.

The directional speaker 26, the diffusive loudspeaker 28 and the bass speakers 38 emit sound waves reproducing the sound to be emitted.

The sound waves emitted by the directional loudspeaker 26 and the diffusive loudspeaker 28 are in phase and amplitudes substantially equal, so that the sounds emitted by the directional speaker 26 and the diffusive loudspeaker 28 are the same

The directional speaker 26 emits the sound waves directly towards the internal space 18. The bass speakers 38 emit sound waves whose low frequencies pass through the structure 14, which allows the sounds emitted by the loudspeakers. bass speakers 38 to reach the internal space 18.

The diffusive loudspeaker 28 emits sound waves in the duct 31, through the first end 32 of the diffusion line 23. The sound waves emitted propagate along the diffusion line 23, in the duct 31, until at the second end 34.

When one of the propagated sound waves passes at one of the scattering points 36, a portion of the sound wave is redirected through the diffusion point 36 to the internal space 18, forming a broadcast sound wave. Each sound wave diffused by a diffusion point 36 has an average near-field acoustic intensity, that is to say an average of the acoustic intensities of the broadcast sound wave, over all the frequencies of the emission range. , measured at a distance less than 1 cm from the diffusion point 36, substantially equal to the average acoustic field intensities close to the sound waves diffused by the other diffusion points 36.

In addition, each broadcast sound wave has, for each frequency in the transmission range, a maximum difference between near-field sound intensity at that frequency and near-field average sound intensity between -12 dB and 12 dB.

The scattered sound waves partially reproduce the acoustic effect of multiple reflections of sound waves in a room.

The directional loudspeaker 26, the diffusive loudspeaker 28 and the bass speakers 38 also emit return waves, which are guided through the charging duct 44 to the charge volume 42, in which it is located. reflect and are attenuated.

The sound reproduction system 16 thus solves the problem of at least partial reproduction of the acoustic conditions of multiple reflections in a spacious environment, in the confined and low-reflective environment constituted by the internal space 18 of the vehicle 12.

Claims

1. Assembly (10) comprising a motor vehicle (12) and at least one sound reproduction system (16), the sound reproduction system (16) comprising:

at least one enclosure (22A) comprising at least one diffusive loudspeaker (28), capable of emitting sound waves, and

at least one tubular sound diffusion line (23) comprising a wall (30) defining an internal channel (31) for propagating sound waves emitted, the duct (31) opening at a first end (32) of the diffusion line; sound (23),

the diffusive loudspeaker (28) being connected to the first end (32) of the sound diffusion line (23),

the sound diffusion line (23) comprising at least three diffusion points (36) disposed through the wall (30), substantially aligned along the sound diffusion line (23), each diffusion point (36) being adapted to redirect part of the sound waves propagated in the conduit (31) to respectively form a broadcast sound wave,

the enclosure (22A) and the sound diffusion line (23) of the sound reproduction system (16) being integrated in a structure (14) of the vehicle (12). An assembly (10) according to claim 1, wherein the wall (30) has an acoustic impedance, and wherein each diffusion point (36) has an acoustic impedance lower than the acoustic impedance of the wall (30), in particular at least ten times lower, advantageously at least a hundred times lower. 3. Assembly (10) according to any one of claims 1 and 2, wherein the diffusion points (36) comprise orifices defined by the wall (31).

4. The assembly (10) according to any one of claims 1 to 3, wherein the enclosure (22A) also comprises a directional speaker (26), able to emit sound waves in phase with the sound waves emitted by the diffusive loudspeaker (28), the directional loudspeaker (26) and the diffusive loudspeaker (28) having emission axes (29) forming an angle greater than or equal to 90 ° between them.

5. The assembly (10) according to any one of claims 1 to 4, wherein the enclosure (22A) also comprises a box (40) defining a load volume

(42) of the diffusive loudspeaker (28), the box (40) being disposed away from the loudspeaker diffusive (28), the enclosure (22A) further comprising a charge conduit (44) connecting the charge volume (42) to a rear output of the diffusive speaker (28).

An assembly (10) according to any one of claims 1 to 5, wherein any two successive scattering points (36) of the diffusion points (36) are separated from each other by a distance greater than one longitudinal dimension of one of the diffusion points (36), measured tangentially to the sound diffusion line (23).

An assembly (10) according to any one of claims 1 to 6, wherein the diffusion points (36) are arranged to form diffused sound waves having average near-field acoustic intensities substantially equal to each other.

The assembly (10) according to any one of claims 1 to 7, wherein the diffusion points (36) are arranged to form diffused sound waves having, for each frequency of a transmission range, a difference between Near-field acoustic intensity at the frequency in question and an average near-field sound intensity between -12 dB and 12 dB. 9. An assembly (10) according to any one of claims 1 to 8, further comprising a rear module (24), the rear module comprising at least five enclosures (22C-22G) and at least two diffusion lines (23) .

10. Assembly (10) according to any one of claims 1 to 9, wherein the sound diffusion line (23) extends along a horizontal axis.

1 1. An assembly (10) according to any one of claims 1 to 9, wherein the sound diffusion line (23) extends along a center pillar (20) of the structure (14). 12. Assembly (10) according to any one of claims 1 to 1 1, wherein the sound reproduction system (16) comprises two enclosures (22) and two sound diffusion lines (23) integrated in the structure (14). respectively in two bottom legs (20), and a rear module (24) comprising at least five enclosures (22) and at least two sound diffusion lines (23) integrated in the structure (14) in a rear block (21). AT).

13. A method of broadcasting sounds in an internal space (18) by an assembly (10) according to any one of claims 1 to 12, comprising the steps of:

- emission of sound waves by the diffusive speaker (28);

- propagation along the diffusion line (23), in the conduit (31), sound waves emitted; and

- formation by each diffusion point (36) of a broadcast sound wave, from a portion of each propagated sound wave, the sound wave is directed towards the inner space (18);