A hybrid sound radiating device for vibrating a heavy rigid plate at audio frequencies.

Abstract

A hybrid sound radiating device according to the invention is used to vibrate a heavy rigid plate at audio frequencies. The device comprises two voice coils arranged concentrically, the outer voice coil being coupled to a fluid reservoir containing a medium including three fluids with a substantially constant viscosity depending on the frequency. A third coil is arranged around the side wall of the fluid reservoir, and two electrodes with opposite polarity are provided in the fluid reservoir to provide a substantially constant electric field in the fluid reservoir. The device further comprises a vibrating element in the form of a heavy rigid plate rigidly connected to the fluid reservoir, and a control circuit connected to the first, second and third coils and to the electrodes.

Description

[Technical field]

[0001] The present invention relates to a sound emitting device that integrates an electromechanical transducer and a liquid-containing vibration transducer to vibrate a heavy rigid plate at audio frequencies. [Background technology]

[0002] According to the current state of the art, a wide variety of loudspeaker designs are known. The widely used loudspeaker and other loudspeaker devices are essentially physical systems that convert an input voltage signal into vibrations of audio frequencies. In loudspeakers, different designs of diaphragm and vibration transducers are known depending on the requirements of the use.

[0003] US Patent No. 5,399,633 discloses a modular speaker in which several integrated mechanisms vibrate a panel to produce an acoustic output. These mechanisms can be, for example, moving coil units, moving magnetic units, or piezoelectric units. The individual mechanisms are connected to each other via switching elements, which ensure the transmission of energy to the panel. By combining different mechanisms, the output of the modular speaker can be adjusted and optimized.

[0004] US Patent No. 5,399,633 discloses a loudspeaker having a switching unit with a rheological medium. The rheological medium may be a magnetorheological or electrorheological fluid. By controlling the viscosity of the rheological medium, the vibration transducer can be rigidly or elastically connected to the acoustic vibration element, so that bending waves excited by the device can result in an acoustic output on the vibration element.

[0005] The drawback of the above solutions is that vibration transducers are only suitable for vibrating lightweight vibrating elements that are elastically deformable by vibration, but are not suitable for vibrating large mass rigid sheets such as glass or stone sheets at suitable sound frequencies.

[0006] The vibration of a heavy and large rigid vibrating element such as a glass or stone plate at low frequencies can be achieved by one or more large vibration transducers capable of generating forces of sufficient magnitude. The vibration of such a heavy rigid plate at higher frequencies, typically above 1000 Hz, cannot be performed by conventional electroacoustic transducers without significant sound quality degradation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application No. 1250827 [Patent Document 2] U.S. Patent Application No. 2005226445 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to overcome the above-mentioned problems by providing a sound radiating device capable of vibrating a large, heavy, rigid plate in the low and high ranges of the audio frequency spectrum with a substantially linear transmission characteristic. [Means for solving the problem]

[0009] These objects are achieved by a hybrid sound radiating device as defined in the appended claims.

[0010] The invention will now be explained in more detail with reference to the drawings. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of the structure of a hybrid acoustic vibration system according to the present invention. [Diagram 2]FIG. 2 is a schematic diagram illustrating a device design of an electronic control unit of the hybrid sound and vibration system according to the present invention. [Diagram 3] 1A and 1B are partial longitudinal sectional and partial perspective views showing the structural design of a hybrid acoustic vibration device according to the present invention; [Figure 4] FIG. 2 is a perspective view of the structure of a hybrid acoustic vibration device according to the present invention; [Diagram 5] FIG. 1 shows a hybrid sonic vibration device according to the present invention in an assembled state ready for installation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As shown in Figures 1 and 3 to 5, the hybrid sonic vibration device 100 of the present invention includes a vibration element 160 formed as a large, heavy, rigid flat plate. The material of the vibration element 160 is preferably sandstone, stone, glass, wood, etc. The vibration element 160 is particularly preferably an indoor wall covering element. The outer surface of the vibration element 160 according to the present invention, i.e. the surface facing the acoustic space, may be flat, but it may also be a surface with a spatial (3D) pattern suitable for generating acoustic waves.

[0013] The actuation unit of the hybrid sonic vibration device 100 may be located on the front side of the vibrating element 160, i.e., on the back side generally hidden from the user. The device 100 has a fixed location support member 120 that secures the device 100 to the ground or other rigid support structure. The support member 120 may comprise one or more unloading support members that substantially retain the vibrating element 160, thereby freeing up other components of the hybrid sonic vibration device 100.

[0014] A primary resonator 200 is directly connected to the fixed support member 120. The primary resonator 200 is designed as a moving coil unit that is free to move in a given axial direction within a magnetic field in response to an applied voltage, thereby generating acoustic vibrations, as known in conventional electrodynamic loudspeakers.

[0015] The primary resonator 200 includes at least one permanent magnet 210 in a fixed position, with the magnetic axis of the permanent magnet 210 perpendicular to the plane of the vibration element 160. Hereinafter, the direction of the magnetic axis of the permanent magnet 210 is referred to as the primary axis direction 110. The permanent magnet 210, which is attached to the support member 120, provides a very strong homogeneous magnetic field to the primary resonator 200. The material of the permanent magnet 210 is preferably neodymium or a neodymium-containing material or alloy.

[0016] Preferably, the first coil 220 is fixedly disposed around the permanent magnet 210. The central axis of the first coil 220 is parallel to the primary axial direction 110. The magnetic field homogeneity and magnetic field strength of the first coil 220 disposed around the permanent magnet 210 are enhanced by the permanent magnet 210, and therefore the linearity of the transmission characteristic of the primary resonator 200 can be improved by using the permanent magnet 210 and the first coil 220 together.

[0017] A moving coil unit is disposed around the first coil 220, the moving coil unit comprising a support member 230 and a second coil 240 disposed on the support member 230. The support member 230 is substantially cylindrical and annular, and the second coil 240 is preferably wound on the outer surface of the cylindrical shell. An air gap is formed between the inner surface of the moving coil unit and the first coil 220, thereby allowing the support member 230 with the second coil 240 to move along the primary axis direction 110 relative to the first coil 220.

[0018] Preferably, the primary resonator 200 may have a first magnetic shield 250 on the side of the support member 120 facing the intermediate member 140, and a second magnetic shield 260 on the side of the intermediate member 140 facing the support member 120.

[0019] The shielding elements 250, 260 magnetically isolate the permanent magnetic field within the primary resonator 200 from other parts of the hybrid sonic vibration device 100. The magnetic shielding elements 250, 260 are preferably made from a material having a high magnetic permeability.

[0020] To operate the primary resonator 200, the hybrid sound radiating device 100 includes a control circuit 270 as shown in Fig. 2, which provides a corresponding applied voltage to the first coil 220 and a voltage signal at audio frequency to the second coil 240, so that the primary resonator 200 (or more precisely its moving coil) generates mechanical vibrations in the frequency range of 20Hz to 20,000Hz. The control circuit 270 includes conventional electronic circuit units well known to those skilled in the art for the above mentioned purposes.

[0021] An end of the support member 230 remote from the support member 120 is fixed to a first side of the movable intermediate member 140. The support member 120 further comprises at least one, preferably four, guiding support members 130, which hold the reciprocating intermediate member 140 on the one hand and guide it along the primary axial direction 110, following the vibrations of the moving coil on the other hand. Thus, the vibrations of the second coil 240 are transmitted to the intermediate element 140 substantially without distortion.

[0022] The intermediate member 140 is preferably formed from a composite material, thereby minimizing the weight and undesirable inherent vibrations of the intermediate member 140 while maintaining mechanical efficiency. In a preferred embodiment of the device 100, the guiding support member 130 is connected to the intermediate member 140 by a damping member 134 made from rubber. The purpose of the directional damping is to absorb and damp any vibrations and resonances in structural elements other than the vibrating element 160, so as to prevent as much (or preferably none) of such vibrations from being transferred to the rear support element 120, which in many cases is directly connected to the stationary structure of the building.

[0023] The guiding and supporting element 130 neutralizes the shear forces acting on the unit 240 formed from the coil 240 and the permanent magnet 210. In order to minimize possible negative effects on the sound, the guiding and supporting element 130 should preferably be connected to the intermediate element 140 via said damping element.

[0024] A secondary resonator 300 is connected to a second side of the intermediate element 140, located opposite the first side. The function of the secondary resonator 300 is to transmit the mechanical vibrations generated by the primary resonator 200 to the heavy vibrating element 160.

[0025] The secondary resonator 300 includes a fluid reservoir 320 having a sidewall 320 of variable length along the primary axial direction 110. The variable length sidewall 320 is preferably comprised of wall sections sealed together, although optionally the sidewall can be a flexible elastic sheet wall by bending the length of the fluid reservoir along the primary axial direction 110.

[0026] A third coil 330 is disposed around the fluid reservoir, with the central axis of the third coil 330 parallel to the primary axis direction 110, and generates a magnetic field within the fluid reservoir.

[0027] A first electrode 340 is disposed on the side of the fluid reservoir connected to the intermediate member 140, preferably within the fluid reservoir, and a second electrode 350 of opposite polarity is disposed opposite the first electrode, preferably within the fluid reservoir, to generate a substantially constant electric field within the fluid reservoir.

[0028] The fluid reservoir is filled with a medium 310 consisting of a mixture of at least two non-Newtonian fluids and a magnetic fluid. One non-Newtonian fluid is a thixotropic composite elastomer such as polydimethylsiloxane (PDMS, C2H6OSi). The other non-Newtonian fluid is lithium hydroxystearate (C 18 H 35 The medium 310 preferably has rheopexy properties, such as LiO3 mixed with silicone oil. The proportion of rheopexy material in the mixture is about 20% by volume, i.e. the mixture contains about 80% by volume of silicone oil. The ratio of the two non-Newtonian fluids in the medium 310 is preferably about 30% by volume of thixotropic fluid and 70% by volume of rheopexy fluid.

[0029] The medium 310 also contains a magnetorheological fluid, so that the entire medium 310 is placed in an electric field successively by the electrodes 340, 350, causing the medium to vibrate at audio frequencies. The volume fraction of the magnetorheological fluid in the medium 310 is preferably close to 40%.

[0030] As magnetorheological materials, for example magnetite-based magnetic fluids in which coarser particles (diameter about 0.1-50 micrometers) of magnetite or iron particles are dispersed are used. The magnetorheological fluids thus obtained behave in an external magnetic field similarly to electrorheological fluids in an external electric field: the particles are organized by the magnetic field into chains and rows parallel to the field lines, as a result of which the fluid viscosity increases by several orders of magnitude. After the end of the magnetic field, within a few milliseconds, the chains also stop and the fluid viscosity returns to its original value.

[0031] For optimal operation, the temperature of the medium 310 should preferably be between 1° C. and 70° C. The volume of the liquid container is preferably about 50 cm 3 That's about it.

[0032] The magnetorheological fluid forming medium 310 preferably contains iron oxide (FeO) particles having a particle size of tens of nanometers to a few micrometers. Under the influence of a time-varying magnetic field provided by third coil 330, medium 310 continuously changes its size in the primary axial direction 110 within the liquid container. This size change can occur up to about 5,000 times per second.

[0033] The medium 310 in the fluid reservoir is maintained in a substantially constant electric field by the electrodes 340, 350. This electrical bias is required to adjust the optimal viscosity of the medium 310, which contains two non-Newtonian fluids and a magnetorheological fluid. The constant electric field strength can be fine-tuned using the control circuit 370 based on the acoustic field characteristics and physical properties of the acoustic waves generated by the hybrid sound emitting device 100 using acoustic field measurements, but this does not significantly affect the constancy of the electric field.

[0034] A suitable mixture of two non-Newtonian fluids and a magnetorheological fluid results in a medium of substantially constant viscosity versus frequency, said medium being capable of behaving as a high inertia vibration medium of sufficiently large mass within a relatively wide frequency range (approximately 200 Hz to 5 kHz), thereby enabling the mechanical vibrations generated by the primary resonator 200 to be transmitted to the heavy vibration element 160 with minimal distortion.

[0035] To operate the secondary resonator 300, i.e. to control the magnetic and electric fields of the medium 310, the device 100 according to the invention comprises a control circuit 370, shown in Figure 2, which provides suitable voltages to the electrodes 340, 350 and an audio frequency signal to the coil 330. The control circuit 370 operates the secondary resonator 300 such that the operation of the hybrid sound emitting device 100 as a whole is substantially linear.

[0036] The hybrid sound emitting device 100 of the present invention can further include a special frequency transmission and pulse response compensation digital signal processing unit (DSP) 400 as shown in FIG. 2, and various acoustic sensors 402 for compensating for possible acoustic distortions observed in the irradiated space by the control circuits 270 and 370.

[0037] On the side of the secondary resonator 300 opposite the intermediate element 140, a vibration transmission element 150 is preferably arranged rigidly, preferably by gluing, on the one hand to the corresponding wall of the liquid container and on the other hand to the heavy vibration element 160. As shown in Fig. 5, not only one but several, for example four, secondary resonators 300 can be connected to the vibration transmission element 150, so that a significant amount of vibration energy can be transferred to the heavier vibration element 160 as well.

[0038] In a preferred embodiment of the hybrid sound radiating device 100 of the present invention, the surface of the vibrating element 160 is approximately 1 m 2 ~20m 2and the vibration transmission element 150 is fixed to the vibration element 160 by gluing. The glue used forms a high-strength layer with minimal flexibility in order to transmit the vibrations of the vibration transmission element 150 to the vibration element 160 with as little distortion and damping as possible. As shown in Figures 3 and 4, on the other side of the vibration transmission element 150, the vibration transmission element 150 can be connected to the outer end of a piston 132 movably arranged in the guiding support member 130, so that the vibration transmission element 150 holds the vibrator 160 and thereby helps to release the fluid reservoir.

[0039] Although not shown in the drawings, the hybrid sound emitting device 100 may further comprise, if necessary, additional conventional electronic units, such as power supplies, wiring, circuit breakers, etc. The design and operation of these units are well known to those skilled in the art and will not be described in detail herein.

[0040] Under practical conditions, the hybrid sound radiating device 100 may be equipped with additional speakers, preferably tweeters and subwoofers, to meet higher user requirements. These auxiliary speakers are preferably hidden in the vicinity of the hybrid sound radiating device 100 of the present invention.

[0041] An advantage of the hybrid sound radiating device according to the invention is that heavy rigid panels such as wall cladding panels can also be used as the vibrating element of the speaker, thus eliminating the need for traditional speakers which would adversely affect the decorative appearance of the room, or the unit can be installed completely concealed behind the wall cladding elements or furniture panels used as the vibrating elements.

[0042] A further advantage of the device according to the invention over conventional wall-mounted loudspeakers is that, for example, minor damage or defects do not interfere with its operation. Due to its large vibrating element and special design, the hybrid sound radiating device has a wide directivity, resulting in a spatially extensive sound distribution and good speech characteristics.

Claims

Claim 1 A hybrid sound radiation device (100) for vibrating a heavy rigid plate with an audio frequency, comprising: - A fixed support member (120); - A permanent magnet (210) having one end fixed to the support member (120); - A fixed first coil (220) disposed around the permanent magnet (210) and having a central axis defining a primary axis direction (110); - A second coil (240) disposed around the first coil (220) and movable along the primary axis direction (110); - An intermediate member (140) having an end of the second coil (240) away from the support member (120) attached to a first side, guided along a guide support member (130) attached to the support member (120), and extending in the primary axis direction (110); - A fluid reservoir attached to a second side of the intermediate member (140) opposite to the first side, having a side wall of variable length along the first axis direction (110), wherein the fluid reservoir contains a medium (310) including at least one thixotropic fluid, a rheopectic fluid, and a predetermined mixture of a magnetorheological fluid, and the medium (310) containing the three fluids has a substantially constant viscosity with respect to frequency; A third coil (330) is disposed around the side wall (320) of the fluid reservoir, and a central axis of the third coil (330) is parallel to the primary axis direction (110); A fluid reservoir provided with a first electrode (340) and a second electrode (350) having opposite polarities on a side connected to the intermediate member (140) in the fluid reservoir, the electrodes (340, 350) providing a substantially constant electric field in the fluid reservoir; - A vibration element (160) in the form of a heavy rigid flat plate firmly connected to a side of the fluid reservoir opposite to the intermediate member (140); - A device comprising the first coil (220), the second coil (240), and the third coil (330), and control circuits (270, 370) connected to the electrodes (340, 350). Claim 2 The device according to claim 1, wherein the second coil (240) has a cylindrical annular support member (230). Claim 3 The device according to claim 1, wherein the side of the support member (120) facing the intermediate member (140) and the side of the intermediate member (140) facing the support member (120) have magnetic shielding elements (250, 260).

4. The device according to claim 1, wherein the material of the vibration element (160) is sandstone, stone, glass, or wood.

5. The device according to claim 1, wherein a vibration transmission element (150) is arranged between the fluid reservoir and the vibration element (160).

6. The device according to claim 1, wherein the thixotropic fluid is a composite elastomer.

7. The device according to claim 1, wherein the rheopectic fluid is a mixture of lithium hydroxystearate and silicone oil.

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