FR3014236A1 - MODULAR ACOUSTIC CORRECTION SYSTEM - Google Patents

Abstract

The present invention relates to a modular system for correcting room acoustics. The device comprises several boxes (1) containing absorbers (2), diverters (3) and diffusers (4) acoustic, complementary to each other and permutable. Depending on the application, some boxes house a speaker (5). The boxes slide on rails (6) adjacent to the walls (7), allowing a horizontal translational movement to adapt to the dimensions of the room. The space separating the boxes receives open-cell foam or foam screens (8) or a reflective panel (9) depending on the acoustic characteristics sought. The invention is intended for listening rooms or sound production.

Description

The present invention relates to a modular device for acoustic correction of listening rooms or sound production.

Any architectural volume has its own acoustic characteristics and responds differently when exposed to a sound emission. Sound waves propagate in space and inevitably encounter rigid surfaces on which they reflect.

The listener receives the sound coming directly from the source, immediately followed by a series of reflections more or less offset in time. The collisions between the direct signal and the reflections generate a quantity of interferences, some desirable and others not, which must be mastered in order to obtain a neutral and balanced answer, faithful to the intention of the author of the recorded work. The acoustic response of a room or a living room is governed by its volume, its geometric shape and the impedance of the walls that constitute it. This last parameter is often forgotten. Thus two pieces of the same volume and the same shape will have a different answer if the materials that make up the walls are of different nature.

Small volumes, ie rooms with a volume of less than about 300 cubic meters, have particular acoustic characteristics, namely: When the dimensions are small and the shapes rectilinear, the average free path of the reflections 30 does not allow the creation of the homogeneous field of diffuse reflections, necessary for the establishment of the reverberation. The interferences born from the first so-called "early" reflections which carry a considerable energy, generate pronounced colorations. The tonal balance is affected. Some details are exaggerated while others disappear. The sensation of breadth, depth and width of the sound image are affected. The location of the sources 5 is fluctuating and uncertain. For the same reasons, the interferences produced by the repeated collision of waves whose length corresponds to the multiple or submultiple of a dimension of the part causes the formation of stationary pressure zones. This natural phenomenon produces resonances all the more audible as the dimensions of the piece are reduced. Parallel surfaces facilitate the formation of floating echoes, characterized by low frequency repetition of transient or high frequency signals. Distortion is felt like a metallic resonance, when you clap your hands, for example. Note that these phenomena vary in amplitude and frequency in considerable proportions depending on the position of the sources and that of the listeners in the room. The spectrum audible by the human ear extends over a wide frequency range whose wavelengths vary from 17 mm to 20 kHz up to 17 meters at 20 Hz. These waves have a fluctuating behavior depending on the frequency of the signal and the nature of the source. Such a gap and such great diversity make it impossible to process the entire spectrum by a single device. The present invention groups together a number of different devices capable of absorbing, deflecting or dispersing the incident sound waves, each having a particular acoustic function. These devices, hereinafter referred to as "acoustic correction elements", are organized in kind, in number and in arrangement according to the original acoustic parameters of the part to be corrected and the acoustic objectives to be achieved.

The operating principle of each "correction element" belongs to the prior art and does not form part of the claims of the present invention. The main devices are briefly described in paragraphs 1 to 8 below to facilitate the understanding of the principle of the invention. However, the detailed operation, calculation methods and result curves are deliberately omitted to not load the file with a part that is not directly claimed. The acoustic correction elements currently proposed by the industry are of disparate nature and form, each manufacturer having his specialty. Their assembly forms a heterogeneous whole unsuitable for integration in a place of life for domestic use or even professional. Although the drawings of FIGS. 2 to 10 represent these correction elements in identical boxes, they are normally proposed and supplied in the raw state, that is to say in their original shape and dimensions, without any particular covering. , sometimes without a fixation system. In addition, it is difficult to find correction systems with complementary acoustic characteristics other than in special manufacture.

The search is usually done by a specialist, users are not able to find sources and choose models. Finally, the bulky volume and the unsightly appearance of the elements discourage many consumers who prefer to leave their premises in the state to the detriment of the listening quality of the installation. Figure 1, for the abstract, shows in perspective the device of the invention. The accompanying drawings on sheets 1 to 7 show in perspective the prior art, in a configuration adapted to the invention.

Figure 2a shows in section the principle of a Helmholtz resonator. Figures 2b and 2c show Helmholtz resonators with circular and oblong openings.

Figure 3 shows a slatted resonator. Figure 4 shows an acoustic deflector. Figures 5a and 5b show broadband absorbers. Figure 6a shows a tympanic membrane resonator. Figure 6b shows a piston diaphragm resonator. Figures 7a and 7b show convex diaphragm sound resonators. Figures 8a and 8b show quadratic residue acoustic diffusers. FIG. 9 represents a bidirectional acoustic diffuser with a primitive root. FIG. 10 represents an electroacoustic attenuator 20 with a controlled circuit. The accompanying drawings 8 to 14 illustrate the invention. Figure 11 shows in perspective the entire device of the invention. Figure 12 shows a side view of mounting a module on a wall. Figure 13 shows in perspective the inclusion of an acoustic enclosure in a module. Figure 14 shows in perspective the implementation of the lighting system.

Figure 15 shows in perspective the cover by a grid. Figure 16 shows in perspective the rear of a module with the access door to an enclosure, the fixing rail and the flexible stops. Figure 17 shows in perspective a synthetic foam screen column and its attachment. Figure 18 shows in perspective a flat reflector panel and its attachment. Figure 19 shows in perspective an absorbent wool mattress and its attachment, covered by a decorative grid. The acoustic correction elements applicable to the invention can be classified into three major families according to their respective functions: they are the absorbers, the deflectors and the diffusers. As their name indicates, the absorbers have the function of absorbing all or part of the incident sound waves. They use the porosity of the materials, the vibration of soft or rigid membranes and the resonance of cavities. 1- The Helmholtz type selective resonator (FIG. 2a) is a selective absorber. It houses a cavity (11) open to the air through an orifice. This device uses the vibration of the air column (12) contained in the neck (13) of the orifice and the elasticity of the air trapped in the cavity to absorb the middle frequencies. Its generally high selectivity makes it possible to target a narrow frequency band. The volume of the cavity, the section of the orifice and the length of the neck determine the frequency. The resonance can be amortized by filling, at least partially, the cavity with a porous or fibrous absorbent material (14). Several methods make it possible to simplify the construction by means of a box forming a single cavity shared by a network of circular (15) or oblong openings (16) made in an inert panel. An alternative to this type of resonator (FIG. 3) uses parallel slats (17) whose width, thickness, spacing, associated with the depth of the cavity determine the band of the frequencies absorbed. 2- The so-called "broadband" absorbers (Figure 5a) cover an extended spectrum. An open-celled mineral wool (20) and open-cell foam mat (21) of the selected resistivities absorb the higher frequencies by converting vibratory energy into heat while the low frequencies are trapped by the vibration of a weighted membrane (22). ). The range of frequencies absorbed can be further extended, especially towards the bottom of the spectrum, by increasing the thickness of the device (1b). 3- Traditionally, the very low frequencies, more concerned by the modal resonances, are controlled by specific absorbers called "basstraps". Some models rely on the velocity of air particles. They are very bulky and rarely accepted by users. For the purposes of the invention, membrane resonators which work in pressure and have the advantage of requiring less thickness are preferred. Several types of membrane coexist. Tympanic resonators (Figure 6a) use the vibration of a deformable membrane (23) resting on the edges of a cavity containing a damping material (24). The so-called piston piston resonators (FIG. 6b) use a rigid diaphragm (25) forming a piston supported by an elastic suspension (26). A bellows (28) covering the entire perimeter seals the casing while preserving the free movement of the membrane. These resonators absorb a limited frequency band and must be broken down into several models, each addressing a specific band. 4- Resonances of modal origin can be controlled by a controlled electroacoustic system (Figure 10). This device includes a sensor (microphone) that detects and measures the resonances to drive a servo circuit that emits a phase signal opposite to the incident wave. The unit includes a plurality of speakers (55) for controlling multiple frequencies simultaneously. The function of the deviators is to deflect the trajectory of a wave and / or to disperse it. They break the echoes and / or deflect some reflections outside the listening area. The range of deviated frequencies is a function of the dimensions of the deflector surfaces. The asymmetrical models have a grazing incident surface (18) and a reflecting face (3) which deviates the wave trajectory for the other angles of incidence. Diffusivity suppresses interference by de-correlating sound waves. It broadens the sound stage, removes echoes and colorations. Diffusers are solid objects whose geometric shapes have the ability to break the specular component of a wave to make it diffuse. Pyramidal or semi-cylindrical planar diffusers and cell diffusers composed of juxtaposed cavities are mainly distinguished. Other less popular models exist, such as lens diffusers. The "polycylinders" are planar diffusers whose convex surface has the main function of redistributing the incident energy onto a wider beam of reflections. The radius of curvature and the horizontal (27) or vertical (29) position of the cylinder axis determine the angle of radiation and the orientation of the plane of reflection. Unlike cellular models, this type of diffuser does not control the temporal distribution of the reflections or the spatial uniformity. Some hollow models operate on the principle of resonators. They have the particularity of absorbing the low frequencies not radiated by the membrane effect of the cylinder body, associated with a sensor housed inside (30). The principle of cellular scatterers is based on the number theory proposed by Manfred Schroeder (1984), to break the reflection of incident waves in a given frequency band and distribute it in space and time in a relatively uniform and homogeneous manner. Several mathematical models have been developed. 7- The quadratic residue diffuser (Figures 8a and 8b) has a series of cavities (31) whose depth follows a proportionality factor equal to the product of the modulo of a prime number by the square of the position of the cell. The illustrated models diffuse the reflection of incident waves on a single axis, horizontal or vertical. 8- Based on the same principle, the primitive root diffuser (32) has a different sequence that is obtained by multiplying the modulo of a prime number by the prime root of the high number to the power of the cell position. Figure 9 shows such a diffuser operating on two axes, that is to say offering a hemispherical diffusion. The present invention is characterized by the incorporation of these "acoustic correction elements" in physically interchangeable modules (FIG. 11) in order to make possible the integration of such devices in most architectures and to respond in a simple manner to acoustic requirements. multiple applications. To avoid confusion on reading the following, it is established that the invention is composed of "modules". The term designates boxes (1) containing the "acoustic correction elements" described in paragraphs 1 to 8 above. The box is a component of a module (33).

The modules (33) cover the walls of a room or a living room intended for listening to recorded sound programs or sound production. The envelope of each module consists of a box (1) formed by a wooden frame, metal or synthetic material. The frame can remain open or receive a bottom to form a waterproof case when the device it contains requires. The framework of the frame must be strong enough to support the weight of the device it contains. The boxes (1) are suspended from the walls of the room by a sliding rail. The details of the binding are visible in FIG. 12. A rail (6) made of wood or metal is fixed to the wall (7) by means of dowels adapted to the nature of the material that constitutes this wall. A second rail (36) complementary to the first is fixed to the housing. Each housing (1) comprises in the lower part, flexible wedges (37) forming a support so as to maintain the verticality of the module. The resilience of the wedge material limits the transmission of vibration from the free end of the module to the wall. The geometry of the rails (6, 36) allows the horizontal translation of the modules so as to facilitate the lateral positioning. A gap forming a hollow joint (34) is arranged under each housing. This arrangement which reveals the underside of the module and the top of the next lower module, aims to widen the surface exposed to sound waves and therefore the amount of acoustic energy absorbed. The back of the case is extended at the bottom to form a stop (38) which delimits the vertical positioning. This stop obscures the surface of the wall that would be visible through the hollow joint. Advantageously, the hollow joint thus formed makes it possible to receive lighting (FIG. 14) which visually emphasizes the separation of the modules and embellishes the aesthetics of the assembly. The underside of the module is illuminated by a ribbon of light-emitting diodes (41). The adhesive tape is glued to an aluminum light reflector (42) which also forms a heat sink. The ribbons are connected in series from one module to another by means of electrical wires (43) provided with connectors (39). The section of the conductors must be sufficient to support the intensity of the current consumed by a series of several modules. The supply leads are protected by an anti-pulling flange (40). The power transformers (44) are screwed to the sides of the modules. The transformers are dimensioned so that a single unit can feed 6 to 12 modules.

The device housed inside the module is concealed behind a grid or ventilated fabric (Figure 15). This coating (45) covers all visible parts of the module. It is essential that the coating has sufficient acoustic transparency to not in any way disturb the operation of the device that it conceals. Tests have shown that the sound loss measured at 10kHz must remain below 1 decibel. As part of a multichannel listening system (Dolby 5.1 or 7.1 or other), surround channels are intended to envelop listeners / viewers in a diffuse sound field. As it is a wrap, it is desirable that the surround speakers are embedded in the decoration without allowing the possibility of distinguishing their position (unlike the main speakers placed on the front). The absence of a visual cue helps listeners to get away from the positioning of the ambient sources. For this reason, the surround speakers are directly integrated in the modules (figure 13). The module can accept all makes and models of speakers that do not exceed its internal dimensions. The chamber (5) housed inside the module is surrounded by bidirectional diffusing elements (32) which participate in the decorrelation of the surround channels and the widening of the sound field. The speaker is positioned in the axis of symmetry of the module or off-center to the right or left of the axis.

This freedom of placement facilitates the obtaining of a uniform and homogeneous sound field adapted to the position of the spectators and to the geometric and acoustic characteristics of the piece. The chamber (5) is mounted on a hatch (46) forming a cover, accessible at the rear of the housing. This arrangement avoids the disassembly of visible parts in case of technical intervention on the speaker. The connection terminals of the enclosure are accessible without any disassembly, through an orifice (47) made for this purpose, accessible from the rear of the housing. The cables supplying the loudspeakers run freely between the wall and the housing in the interval corresponding to the thickness of the fixing rail. Mounting: Figure 11 illustrates the assembly and layout of the complete correction system. After fixing the rails (6) on the walls, the modules are simply placed and positioned by simply sliding, according to the assembly plan that accompanies each system. Given the placement of the modules, specific to each installation, they can be separated by an optional longitudinal space, of variable width (dl) depending on the dimensions of the room. The separation space (d1) also serves to conceal the power supply boxes, a remote control receiver, the electrical cables of the loudspeakers, the lighting or the like, or to house a ventilation duct with an opening directed towards the bottom of the wall.

The spaces thus created are covered by new acoustic correction elements (8, 35). These elements are mainly porous absorbers, convex deflectors or flat surfaces (50).

The porous absorbers are in several variants depending on the acoustic constraints. The flexible models (8) are made of polyurethane foam or flame retardant melamine foam cut in a decorative outline chosen at the discretion of the user. The range of frequencies and the amount of energy absorbed depend on the thickness of the foam, which varies according to the acoustic characteristics of the room and the depth of the plenum which separates the anterior face of the wall element which supports it. .

The angles of the room (d2 figure 11) receive a specific screen more for the absorption of low frequencies (35). We know that a naturally omnidirectional sound source becomes hemispherical when its source point coincides with a surface. The hemisphere that should be at the back of the surface is returned forward and the two hemispherical pressure zones are merged. This doubles the sound pressure on the surface of the radiation side. At the intersection of two surfaces forming a 90 degree angle, the field of propagation is reduced by half and the pressure is again multiplied by two. Thus, the angles of the room are areas of predilection for the treatment of resonances, especially at low frequencies. Considering the considerable wavelengths at these frequencies, the dimensions of the angle absorber need to be larger than those of its surface counterparts. In addition, the plenum, that is to say the volume of air that is trapped behind the absorber, must also be more important. To meet this last constraint, the absorber is placed on the outer face of the modules so as to move away from the reflection surfaces (the walls of the room). The foam absorbers (8, 35) are arranged in columns of several elements, separated from each other by spacers of EPDM type elastomer material or equivalent, forming a hollow seal aligned with that which separates the modules (48). The low weight of the foam absorbers (500g) allows their attachment by self-gripping tape (49) distributed over several points.

Other models of porous absorbers incorporate a foam or mineral wool mattress in a metal or wood frame (53) covered with a fabric with acoustic transparency. The set is capped by a decorative grid (54) forged or cut metal, wood, resin or staff, depending on the choice of the user. The absorbent mattress attenuates the incident reflections and participates in the control of the reverberation while the role of the grid remains essentially decorative. The rigid column is suspended from the modules which border it by means of angles (52) pierced with holes which cap two pins (51) inserted near the ends at the top of the upper modules. The middle and the bottom of the column are held at the modules by self-gripping tape (49).

Depending on the acoustic characteristics of the room, the horizontal space between the modules may require, instead of an absorbent material, the presence of a flat reflective surface (50) or convex. This surface is materialized by a column of wood or synthetic material rather than metal to limit the intrinsic resonances. It is suspended from the upper modules as described in the previous paragraph. Alternatively, the body of the column may consist of a translucent backlit panel, possibly protected by a decorative grid.

The present invention is intended for the field of architectural acoustics and finds its utility in domestic applications such as residential rooms for use of musical listening (hifi) or cinematographic (home-5 cinemas), in the production sites such as music recording studios, cinematographic post-production, broadcasting, concert halls, discotheques, lecture and reading rooms.

The present invention aims to: 1- Gather a series of acoustic correction devices belonging to the prior art and adapt their physical characteristics so as to facilitate their integration into the room. 2- Provide a versatile correction system, compatible with most requirements and applications. The elements are complementary and physically permutable so as to adapt the correction to the acoustic characteristics of the room. The error of position or choice of the model is correctable. 3- To answer the architectural constraints by proposing a modular system, compatible with most geometries and types of construction. 4- Access listening quality in accordance with the standards 25 and professional recommendations of the film and sound recording industry, including in the context of family leisure use. 5- Offer the non-specialist installer a pre-designed acoustic correction system that is easy to install.

Claims (7)

CLAIMS1- Modular acoustic correction system characterized in that it comprises several boxes (1) containing various devices individually acting on the behavior of sound waves, such as absorbers (15, 16, 17, 21, 23, 25) acoustic deviators (3) or diffusers (27, 29, 31, 32), forming modules (33) complementary to each other, protected by a grid or a textile coating with acoustic transparency (45), all adjacent to the walls (FIG. 7) a room for listening or sound production. 2- System according to claim 1 characterized in that the attachment mode, the geometric shape and the dimensions of the modules allow their permutation. 3- System according to claim 1 characterized in that 15 the housings (1) are placed on a rail (6) of wood or metal provided with a groove and fixed on the wall, allowing sliding by a horizontal translational movement . 4- System according to claim 1 characterized in that the housings (1) have a hollow joint (34) for housing a backlight comprising a strip of light emitting diodes (41) fixed on a light reflector (42). 5- System according to claim 1 characterized in that the housings (1) are arranged to receive inside 25 an acoustic chamber (5), which can be arranged indifferently to the right, left or center of the axis of symmetry vertical case. 6. System according to claim 5 characterized in that the connection terminals of the acoustic chamber (5) are accessible without disassembly through a hole (47) provided for this purpose. 7- System according to claim 1, characterized in that the spaces which separate the modules are covered by removable screens (8, 35) of synthetic foam or by a rigid panel (50) or by a porous mattress (53) mineral wool, vegetable or synthetic protected or not by a grid (54).