Electroacoustic plasma transducer system

Abstract

An electroacoustic plasma transducer system 50 comprises an electroacoustic plasma transducer device 100. The plasma electrode arrangement 110 includes a corona electrode 120 and a collector electrode 130 positioned spaced apart from the corona electrode via an air gap. A peripheral support 150 supporting the plasma electrode arrangement is electrically insulating. A housing 170 defines a chamber 172 that receives back radiation from the plasma electrode arrangement. A driving means supplies a voltage U(t) between the corona electrode and the collector electrode. The plasma electrode arrangement 110 is configured as follows: The central effective region of the corona electrode 120 is spaced apart from the collector electrode 130 by an electrode spacing distance d. The peripheral portion of the corona electrode is positioned spaced apart from the collector electrode and / or the peripheral support 150. Any path from the corona electrode through the peripheral support to the collector electrode has a path length c satisfying c≧1.085d.

Description

[Technical Field]

[0001] The present invention relates to an electroacoustic plasma transducer system. More particularly, but not limited to, an electroacoustic plasma transducer system used as part of an active noise reduction (ANR) system employing acoustic impedance control. [Background technology]

[0002] Active noise reduction (ANR) is a technology aimed at reducing unwanted noise within a specific control location or space. It utilizes acoustic sensing means for detecting unwanted noise or sound fields, a controller for deriving one or more control signals, and one or more electroacoustic drivers (e.g., speakers or earphone drivers) for reproducing the control signals as one or more control sounds. ANR can be implemented using active noise cancellation based on the principle of destructive interference of signals, or using active acoustic impedance control. The former is widely used in commercial applications such as active noise-canceling earphones, while the latter remains limited in use due to performance limitations of available transducers.

[0003] Electromagnetic loudspeakers are widely used for active noise reduction (ANR) due to their simple structure and affordable price. They typically feature a diaphragm suspended within a mounting structure and are driven by an electromagnetic force between a permanent magnet located within a support structure and a coil attached to the diaphragm. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2023 / 0020879 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The acoustic response of a dynamic loudspeaker can be represented by a single-degree-of-freedom resonator. This resonator is controlled by its compliance at frequencies below the resonant frequency and by its mass at frequencies above the resonant frequency. In other words, this transducer is not ideal, and its inertia reduces the sharpness of the acoustic response.

[0006] Therefore, while reducing the diaphragm mass of an electrodynamic loudspeaker is a desirable design goal, this can be difficult, especially in applications requiring high acoustic output strength and durability. Furthermore, mitigating performance limitations caused by the diaphragm mass of an electrodynamic loudspeaker through the application of active control methods not only increases the complexity of the connected controllers but also reduces the overall robustness of the system and increases the risk of instability.

[0007] Therefore, there is a need for alternative transducer technologies for active noise reduction (ANR) applications that operate without the limitations imposed by mass and compliance. Loudspeakers based on atmospheric corona discharge can generate audible sound by modulating a high voltage applied between the corona electrode (the electrode where ionization of air particles occurs) and the collector electrode (the electrode to which the ionized air particles are attracted) at an audible frequency. This modulation alters the transfer of mechanical energy from charged particles to neutral air, resulting in the propagation of sound waves. While conventional corona discharge loudspeakers can generate sound over a wide surface area, they are not suitable for active noise reduction (ANR) applications. This is because they are not optimized to generate control sounds over the specific frequency ranges that are important for active noise reduction (ANR) applications.

[0008] Furthermore, conventional corona discharge transducers are prone to arc discharge, and their sound generation capability is limited because the voltage difference they can supply to generate sound is restricted. They also generate ozone, and high concentrations of ozone can be harmful.

[0009] These problems associated with conventional technologies need to be resolved in order to successfully implement corona discharge-based transducers in active noise reduction (ANR) applications. The applicant of the present invention recognized the need for a novel electroacoustic plasma transducer device to solve, or at least mitigate, the problems associated with the prior art. [Means for solving the problem]

[0010] According to a first aspect of the present invention, an electroacoustic plasma transducer system is provided which includes an electroacoustic plasma transducer device (converter apparatus). The electroacoustic plasma transducer device is A plasma electrode arrangement comprising a corona electrode and a collector electrode separated from the corona electrode via an air gap, A peripheral support (e.g., a frame) having the function of supporting the arrangement of plasma electrodes (e.g., mechanically coupling the corona electrode to the collector electrode), wherein the peripheral support (peripheral support) is electrically insulating, A housing (enclosure) that defines (specifies, defines, defines) a chamber for receiving back radiation from the aforementioned plasma electrode arrangement, A drive means (drive means, e.g., a drive circuit) that operates to supply a voltage U(t) between the corona electrode and the collector electrode of an electroacoustic plasma transducer device, It is equipped with.

[0011] In one embodiment, the plasma electrode arrangement of the plasma transducer device is configured as follows. That is, the central active region (central active area) of the corona electrode is spaced (spaced) from the collector electrode by an electrode separation distance d. The peripheral portion (periphery, for example, substantially the entire periphery) of the corona electrode is spaced from the collector electrode and / or the peripheral support. For any path (path) from the corona electrode to the collector electrode via the peripheral support, the path is set to have a path length c that satisfies c≧1.085d.

[0012] In this way, an electroacoustic plasma transducer system is provided. The electroacoustic plasma transducer system makes it possible to maximize the sound output level generated by the plasma electrode while minimizing unnecessary heating or damage to the support material having electrical insulation.

[0013] In one embodiment, 1.085d≦c≦2d. In one embodiment, the electrode separation distance d = 2 to 10 mm. In one embodiment, the driving means operates to supply a constant bias voltage component U DC and a time-varying alternating current component U AC (t). The voltage difference applied to the plasma electrode arrangement is represented by the formula: U(t)=U DC +U AC (t).

[0014] In one embodiment, the driving means operates to maintain a voltage difference range U(t) range between the corona electrode and the collector electrode in the operating state (i.e., the plasma generation mode). The voltage difference range U(t) range is represented by the formula: U(t) range =(0.35~0.85)×E breakdown × electrode separation distance d, where E breakdown =3×10 6 V / m.

[0015] In one embodiment, the driving means operates to supply a voltage difference Umax between the corona electrode and the collector electrode at the maximum acoustic output of the electroacoustic plasma transducer device. Relationship: Umax≧0.65×E breakdown × electrode separation distance d, where E breakdown =3×10 6 V / m, is satisfied.

[0016] In one embodiment, the plasma electrode arrangement defines an axial axis (longitudinal axis) along which the corona electrode and the collector electrode are spaced apart from each other (for example, a configuration in which the collector electrode forms the front or outer electrode and the corona electrode forms the rear or inner electrode).

[0017] In one embodiment, at least one of the corona electrode and the collector electrode is spaced a lateral distance b from the peripheral support along a lateral axis that is a lateral axis with respect to the axial axis, and this lateral distance b satisfies the condition regarding the electrode path length c described above.

[0018] In one embodiment, at least one of the corona electrode and the collector electrode has an axially extending inclined end shape (for example, an end section of an inclined panel / wire / rod). The spacing between the corona electrode and the collector electrode in the region where the plasma electrode arrangement contacts the peripheral support is configured to satisfy the condition regarding the electrode path length c described above (for example, the spacing (for example, the axial spacing) between the corona electrode and the collector electrode in the region where the plasma electrode arrangement contacts the peripheral support is greater than the electrode separation distance d and is configured to be within the range of the parameter c).

[0019] In one embodiment, the axially extending inclined end shape defines a surface that curves (for example, curves convexly) facing the air gap. In one embodiment, the collector electrode is a panel-shaped (panel form, for example, grid or lattice) collector electrode (for example, a porous (for example, perforated) plate or grid) and is coupled to the peripheral support.

[0020] In another embodiment, the corona electrode comprises a plurality of elongated corona electrode members (e.g., wires or rods) (e.g., arranged laterally spaced apart), which are coupled to the peripheral support.

[0021] In one embodiment, each of the plurality of elongated corona electrode members substantially extends along a first transverse axis of the plasma electrode arrangement (for example, an axis substantially perpendicular to the axial axis).

[0022] In one embodiment, the elongated corona electrode member is spaced axially from the collector electrode by an electrode spacing distance d. In one embodiment, the multiple elongated corona electrode members extend substantially parallel to one another.

[0023] In one embodiment, the elongated corona electrode members are spaced apart from each other by a lateral distance a in the lateral direction. In one embodiment, the corona electrode (e.g., a panel-shaped corona electrode or each of a plurality of elongated corona electrode members) supports at least one projection projecting toward the collector electrode along the axial axis (i.e., the tip or leading edge of at least one projection forms the central active region of the corona electrode).

[0024] In one embodiment, at least one of the protrusions is spaced apart from the surrounding support (for example, along a first transverse axis). In one embodiment, at least one of the projections comprises a plurality of projections (e.g., pins) extending in the axial direction, which are spaced apart along a first transverse axis.

[0025] In one embodiment, at least one of the protrusions comprises an axially extending elongated blade (for example, an elongated blade along a first transverse axis). In one embodiment, at least one of the protrusions is spaced at a minimum lateral distance b from the surrounding support with respect to the first lateral axis.

[0026] In one embodiment, at least one of the projections has a tapered shape (tapered profile) that defines a leading surface (e.g., tip). The leading surface is spaced a minimum lateral distance b from the peripheral support with respect to a first lateral axis.

[0027] In one embodiment, the lateral distance b = 0.45d. In one embodiment, the elongated corona electrode member has an axially extending inclined end shape (inclined end profile, e.g., an inclined end section of a wire or rod). The distance between the elongated corona electrode member and the collector electrode in the region where the elongated corona electrode member is in contact with the surrounding support satisfies the condition with respect to c described above.

[0028] In one embodiment, the axially extending inclined end shape is curved (for example, convexly curved) to define a surface facing the air gap. In one embodiment, the long corona electrode member located closest to the peripheral support (for example, the first and last long corona electrodes, which are spaced apart along the second transverse axis) is positioned laterally from the peripheral support by a lateral distance b.

[0029] In one embodiment, the collector electrode is substantially planar. In one embodiment, the collector electrode is a panel-shaped (e.g., grid or lattice-shaped) collector electrode (e.g., a porous (e.g., perforated) plate or grid).

[0030] In one embodiment, the collector electrode comprises a plurality of elongated collector electrode members (e.g., rods) coupled to a peripheral support. In one embodiment, a plurality of elongated collector electrode members substantially extend along a first transverse axis of the plasma electrode arrangement or along a second transverse axis of the plasma electrode arrangement (for example, in a direction substantially perpendicular to the first transverse axis).

[0031] In one embodiment, a plurality of elongated collector electrode members extend substantially parallel to one another. In one embodiment, the long collector electrode members are arranged so that they are spaced apart from each other by a'.

[0032] In one embodiment, the lateral distance a' = a. In one embodiment, each elongated collector electrode member has an inclined end shape extending in the axial direction (for example, the end section of an inclined rod), so that the distance between the elongated collector electrode member and the corona electrode in the region where the elongated collector electrode member is in contact with the surrounding support satisfies condition c.

[0033] In one embodiment, the axially extending inclined end shape is curved (for example, convexly curved) to form a surface facing the air gap. In one embodiment, 0.8d ≤ a ≤ 3d.

[0034] In one embodiment, 0.8d ≤ a' ≤ 3d. In one embodiment, b = a / 2 (for example, a / 4 ≤ b ≤ 3a / 4). In one embodiment, the elongated corona electrode member has an effective diameter in the range of 100 to 1000 μm.

[0035] In one embodiment, the plasma electrode arrangement is substantially transparent to sound wave propagation (for example, to effectively perform active noise reduction (ANR)). In one embodiment, the plasma electrode arrangement has an acoustic power transfer coefficient of 80% or more in the frequency range of 0 to 5000 Hz.

[0036] In one embodiment, the plasma electrode arrangement has an acoustic output reflection coefficient of 10% or less in the frequency range of 0 to 5000 Hz. If the transmission coefficient is low, the plasma transducer's ability to interact with the external acoustic field will decrease. If the reflection coefficient is high, the acoustic response of the plasma transducer may cause unstable operation of the control system.

[0037] In one embodiment, the housing is a substantially sealed housing. In one embodiment, the housing is a ventilated housing. In one embodiment, the chamber has an axial length l (lowercase L).

[0038] In one embodiment, the axial length l is less than 20 mm. In one embodiment, the electroacoustic plasma transducer device further includes acoustic response tuning means (e.g., an acoustic response tuning structure) provided within or as part of the housing.

[0039] In one embodiment, the acoustic response tuning means includes an acoustic absorption structure (e.g., formed from a porous or granular material) provided within the chamber. The acoustic absorption structure may operate to absorb sounds at a low frequency threshold (e.g., above about 300 Hz).

[0040] In one embodiment, the acoustic response adjustment means includes passive resonator means (passive resonator means, e.g., a Helmholtz resonator, a diaphragm resonator, or a passive radiator (e.g., formed on the rear wall of the housing)). The passive resonator means may operate to absorb low-frequency sounds (e.g., less than about 300 Hz).

[0041] In one embodiment, the acoustic response adjustment means comprises a combination of an acoustic absorption structure and a passive resonator. In one embodiment, the acoustic response adjustment means may be located within one or more walls of the chamber.

[0042] In one embodiment, the sound-absorbing structure may include any one or more sound-absorbing materials such as activated carbon, wool or fibers, and / or foam. In one embodiment, the acoustic response adjustment means includes a hole having a specific diameter, which is covered with porous paper or foam exhibiting a predetermined acoustic resistivity.

[0043] In one embodiment, the peripheral support is formed from an electrically insulating ceramic or plastic polymer. According to a second aspect of the present invention, an electroacoustic plasma transducer system is provided which includes an electroacoustic plasma transducer device. That is, the electroacoustic plasma transducer device is A plasma electrode arrangement comprising an inner electrode (e.g., corona electrode) and an outer electrode (e.g., collector electrode) separated from the inner electrode by an air gap, A peripheral support (e.g., a frame) that acts to support the plasma electrode arrangement (e.g., mechanically coupling the collector electrode to the corona electrode), A housing that defines a chamber that receives rearward radiation from the plasma electrode arrangement, A driving means (e.g., a driving circuit) that operates to supply a voltage U(t) between the corona electrode and the collector electrode of an electroacoustic plasma transducer device, It is equipped with, The electroacoustic plasma transducer apparatus further comprises an ozone-reducing material (ozone-reducing material, such as an ozone-reducing catalyst).

[0044] In this way, an electroacoustic plasma transducer system is realized that provides an improved acoustic generation means for active noise reduction (ANR) while removing unwanted ozone. In one embodiment, the ozone reduction material comprises manganese (for example, a manganese oxide-based catalyst).

[0045] In one embodiment, the electroacoustic plasma transducer device is provided with a porous structure, and the ozone reduction material is provided on the porous structure (for example, applied inside the porous structure or as a coating).

[0046] In one embodiment, the plasma electrode arrangement defines an axial direction (longitudinal, vertical axis) in which the inner electrode and the outer electrode are arranged with a gap between them. In one embodiment, the collector electrode forms an outer electrode, and the corona electrode forms an inner electrode.

[0047] In one embodiment, the porous structure comprises a perforated plate (e.g., a perforated plate) or a mesh structure. In one embodiment, the porous structure includes an outward ozone filter provided in front of the plasma electrode arrangement (for example, the forward airflow from the plasma electrode arrangement passes through the outward ozone filter before leaving the electroacoustic plasma transducer device).

[0048] In one embodiment, the thickness of the outer ozone filter is less than 15 mm. In one embodiment, the outer ozone filter is positioned at a distance of up to 10 mm in the axial direction from the collector electrode.

[0049] In one embodiment, the outer ozone filter is in contact with the outer electrode (e.g., the outer electrode) of the plasma electrode arrangement. In one embodiment, the outer ozone filter is incorporated into at least one electrode (e.g., the outer electrode) of the plasma electrode arrangement.

[0050] In one embodiment, the ozone-reducing material is incorporated into the outer electrode (e.g., the collector electrode). In one embodiment, the outer electrode (e.g., collector electrode) defines an inner surface of the outer electrode facing the inner electrode (e.g., corona electrode), an outer surface of the outer electrode substantially opposite to the inner surface of the outer electrode, and an internal surface of the outer electrode defined by an opening within the outer electrode.

[0051] In one embodiment, the ozone-reducing material is applied to the inner surface of the outer electrode and / or the outer surface of the outer electrode. In one embodiment, the ozone-reducing material is not substantially applied to the inner surface of the outer electrode.

[0052] In one embodiment, the outer electrode (e.g., the collector electrode) is detachably coupled to the peripheral support (e.g., a suitable electrical connection is provided that allows the outer electrode to be electrically disconnected).

[0053] In one embodiment, the outer ozone filter has an average effective aperture diameter in the range of 0.1 to 2 mm. In one embodiment, the outer ozone filter has an aperture density of 30 or more per square centimeter.

[0054] In one embodiment, the outer ozone filter is acoustically sealed around the peripheral edge of the plasma electrode arrangement. In one embodiment, the outer ozone filter is configured to achieve a predetermined acoustic response.

[0055] In one embodiment, the external ozone filter is configured to have an acoustic power transfer coefficient of more than 50% in the frequency range of 0 to 5000 Hz (for example, its acoustic response is tuned).

[0056] In one embodiment, the outer ozone filter is configured to have an acoustic output reflection coefficient of 10% or less in the frequency range of 0 to 5000 Hz (for example, its acoustic response is tuned).

[0057] In one embodiment, the acoustic response of the external ozone filter is configured such that the external ozone filter does not reduce the control sound level generated at 5000 Hz by more than 3 dB.

[0058] In one embodiment, the porous structure (e.g., an external ozone filter) comprises a honeycomb structure, or a mesh, grid, or perforated structure formed from clay ceramic.

[0059] In one embodiment, the outer ozone filter is tightly fixed to the front of the plasma electrode arrangement using an adaptable adhesive or suspension. In one embodiment, the housing is a substantially sealed housing.

[0060] In one embodiment, the ozone-reducing material is provided inside the enclosure (for example, inside or on the walls of the enclosure, or inside or on a porous structure provided inside the chamber).

[0061] In one embodiment, the electroacoustic plasma transducer apparatus further includes an airflow blocking screen (e.g., an airflow suppression screen) provided in front of the plasma electrode arrangement (e.g., in front of the outer electrodes), which operates to substantially prevent the transmission of airflow while substantially allowing the transmission of acoustic pressure waves.

[0062] In one embodiment, the airflow blocking screen is formed from a porous sheet material (e.g., wire mesh or fibrous material). In one embodiment, the airflow blocking screen has an axial thickness of less than 5 mm.

[0063] In one embodiment, the porous structure is provided inside the chamber. In one embodiment, the porous structure is an acoustic absorption structure. In one embodiment, the acoustic absorption structure is a honeycomb structure in which the openings are directed toward the plasma electrode arrangement (e.g., the inner electrodes).

[0064] In one embodiment, the ozone-reducing material is provided inside the honeycomb structure or applied as a coating to the surface of the honeycomb structure. In one embodiment, the peripheral support is formed from an electrically insulating ceramic or plastic polymer.

[0065] In one embodiment, the ozone filter has a rectangular porous structure. In one embodiment, at least 10% of the upper surface area of ​​the ozone filter is open, and this opening is covered with an ozone catalyst such as manganese, thereby capturing ozone in the air passing over it.

[0066] In a series of other embodiments of the present invention, the ozone filter comprises a honeycomb structure, or a mesh, grid, or perforated structure formed from clay ceramic. In one embodiment, the ozone filter is sealed in close contact with the front surface of the plasma electrode arrangement using an adaptable adhesive or suspension.

[0067] In one embodiment, the plasma electrode arrangement, peripheral support, and housing constitute part of an integrated mechanical structure. In another embodiment, the housing and / or ozone filter are separate components and are detachably attached to the plasma electrode arrangement, or to a frame or structure surrounding the plasma electrode arrangement, using coupling means (e.g., at least one coupling device).

[0068] In one embodiment, the coupling means may be mechanical, electrical, and / or magnetic. In one embodiment, the electroacoustic plasma transducer system is an electroacoustic plasma transducer system according to a first aspect of the present invention (for example, any embodiment thereof).

[0069] According to a third aspect of the present invention, an active noise reduction (ANR) system is provided, which comprises the following: An electroacoustic plasma transducer system according to the first aspect of the present invention (for example, any embodiment thereof) or the second aspect (for example, any embodiment thereof), Acoustic detection means (e.g., at least one acoustic sensor), and An active noise reduction (ANR) circuit that receives signals from acoustic detection means and operates to reduce noise by controlling the output of the electroacoustic plasma transducer system, It is equipped with.

[0070] In one embodiment, the acoustic detection means includes at least one detection microphone. In one embodiment, the active noise reduction (ANR) circuit operates to perform active acoustic impedance control.

[0071] In the case of an electroacoustic plasma transducer device equipped with an external structure (external ozone filter or airflow blocking screen), the acoustic sensing means includes an external sensing microphone (e.g., one positioned directly in front of the external structure) for monitoring the forward pressure p1 of the external structure.

[0072] In one embodiment, the acoustic sensing means includes an internal sensing microphone (for example, one positioned between the outer structure and the forward collector electrode, i.e., immediately before the plasma electrode arrangement) for monitoring the pressure p2 between the outer structure and the plasma electrode arrangement.

[0073] In one embodiment, the outer structure (outer ozone filter or forward airflow blocking screen, or additional acoustic screen) has an acoustic resistance (e.g., frequency-dependent acoustic resistance) Res, and part of the active noise reduction ANR circuit has an estimated acoustic velocity V est It is working to calculate V est =(P1-P2) / Res

[0074] Embodiments of the present invention will be described illustratively with reference to the accompanying drawings. [Brief explanation of the drawing]

[0075] [Figure 1A] This is a schematic diagram of an active noise reduction (ANR) system equipped with an electroacoustic plasma transducer device according to the first embodiment of the present invention. [Figure 1B] Figure 1A is an exploded schematic diagram of the active noise reduction (ANR) system, showing details of the electroacoustic plasma transducer device. [Figure 1C] Figure 1A is a block diagram showing the operation of the active noise reduction (ANR) system. [Figure 2A] Figure 1B is a schematic diagram of the electroacoustic plasma transducer device. [Figure 2B] Figure 1B is a schematic diagram of the electroacoustic plasma transducer device. [Figure 2C] Figure 2B is a schematic cross-sectional view showing the cross-section BB. [Figure 2D] This is a schematic cross-sectional view showing section AA in Figure 2B. [Figure 3A] This illustrates the design principle of minimum path separation in the peripheral area of ​​a plasma transducer device. [Figure 3B] This illustrates the design principle of minimum path separation in the peripheral area of ​​a plasma transducer device. [Figure 3C] This illustrates the design principle of minimum path separation in the peripheral area of ​​a plasma transducer device. [Figure 4A] Figure 1A is a schematic diagram of an electroacoustic plasma transducer device according to a second embodiment of the present invention, used in the active noise reduction ANR system. [Figure 4B] Figure 4A is a schematic diagram of an electroacoustic plasma transducer device after disassembly. [Figure 4C] Figure 4A is a schematic plan view of the electroacoustic plasma transducer device. [Figure 4D] Figure 4C is a schematic cross-sectional view showing the cross-section BB. [Figure 4E] This is a schematic cross-sectional view showing section AA in Figure 4C. [Figure 5A] Figure 1A is a schematic diagram of an electroacoustic plasma transducer device according to a third embodiment of the present invention, used in the active noise reduction ANR system. [Figure 5B] Figure 5A is a schematic diagram of an electroacoustic plasma transducer device after disassembly. [Figure 5C] Figure 5A is a schematic plan view of the electroacoustic plasma transducer device. [Figure 5D] Figure 5C is a schematic cross-sectional view showing the cross-section BB. [Figure 5E] This is a schematic cross-sectional view showing section AA in Figure 5C. [Figure 6A] Figure 1A is a schematic diagram of an electroacoustic plasma transducer device according to a fourth embodiment of the present invention, used in the active noise reduction ANR system. [Figure 6B] Figure 6A is a schematic diagram of an exploded view of an electroacoustic plasma transducer device. [Figure 6C] Figure 6A is a schematic plan view of the electroacoustic plasma transducer device. [Figure 6D] Figure 6C is a schematic cross-sectional view showing the cross-section BB. [Figure 6E] This is a schematic cross-sectional view showing section AA in Figure 6C. [Figure 7A] Figure 1A is a schematic diagram of an electroacoustic plasma transducer device according to a fifth embodiment of the present invention, used in the active noise reduction ANR system. [Figure 7B] Figure 7A is a schematic diagram of the electroacoustic plasma transducer device after disassembly. [Figure 7C] Figure 7A is a schematic plan view of the electroacoustic plasma transducer device. [Figure 7D] Figure 7C is a schematic cross-sectional view showing the cross-section BB. [Figure 7E] This is a schematic cross-sectional view showing section AA in Figure 7C. [Figure 8A]This is a schematic diagram of an active noise reduction (ANR) system comprising an electroacoustic plasma transducer device according to yet another embodiment of the present invention. [Figure 8B] Figure 8A is an exploded schematic diagram of the active noise reduction (ANR) system, showing details of the electroacoustic plasma transducer device. [Figure 8C] Figure 8B is a schematic plan view of the electroacoustic plasma transducer device. [Figure 8D] Figure 8C is a schematic cross-sectional view showing the cross-section BB. [Figure 8E] This is a schematic cross-sectional view showing section AA in Figure 8C. [Figure 9A] This is a schematic partial cross-sectional view of an active noise reduction (ANR) system comprising an electroacoustic plasma transducer device according to yet another embodiment of the present invention. [Figure 9B] Figure 9A is a schematic partial cross-sectional view of the active noise reduction ANR system with the forward airflow blocking screen removed. [Figure 9C] Figure 9A is an exploded schematic diagram of the active noise reduction (ANR) system, showing details of the electroacoustic plasma transducer device. [Figure 9D] Figure 9C is a schematic plan view of the electroacoustic plasma transducer device. [Figure 9E] Figure 9D is a schematic cross-sectional view showing the cross-section BB. [Figure 9F] Figure 9D is a schematic cross-sectional view showing section AA. [Figure 10] Figure 1A is an exploded schematic diagram of a modified version of the active noise reduction (ANR) system, which is equipped with internal and external sensing microphones. [Figure 11A] Figure 1A is a schematic cross-sectional view of the first alternative enclosure related to the electroacoustic plasma transducer device. [Figure 11B] Figure 1A is a schematic cross-sectional view of the second alternative enclosure for the electroacoustic plasma transducer device. [Modes for carrying out the invention]

[0076] Figures 1A to 1C show the active noise reduction ANR system 10. The active noise reduction ANR system 10 comprises an electroacoustic plasma transducer system 50 having an electroacoustic plasma transducer device 100 and a drive means 160, at least one sensing microphone 200, and an active noise reduction ANR circuit 300 that receives signals from the at least one sensing microphone 200 and controls the output of the electroacoustic plasma transducer system 50 to reduce noise.

[0077] As shown in Figures 1B and 1C, the electroacoustic plasma transducer apparatus 100 comprises a plasma electrode arrangement 110 having a panel-shaped collector electrode 130 separated from the corona electrode 120 via an air gap 140, a peripheral frame 150 that operates to support the plasma electrode arrangement 110 and is electrically insulating, a housing 170, and an (optional) outward ozone filter 180 provided on the front of the plasma electrode arrangement 110. The electroacoustic plasma transducer system 50 is also shown to include a drive means 160 that operates to supply a voltage U(t) between the corona electrode 120 and the collector electrode 130.

[0078] The plasma electrode arrangement 110 defines an axial axis "L" in which the corona electrode 120 and the collector electrode 130 are spaced apart from each other (for example, the collector electrode 130 forms the front or outward electrode, and the higher voltage and more fragile corona electrode 120 forms the rear or inward electrode). Referring to Figure 2B, the plasma electrode arrangement 110 further defines a first transverse axis AA extending perpendicular to the axial axis "L", and a second transverse axis BB coplanar with the first transverse axis AA and extending perpendicular to the first transverse axis AA.

[0079] The corona electrode 120 comprises a plurality of parallel, elongated corona electrode wires 122, each connected to a peripheral frame 150 at its respective end. The collector electrode 130 has a panel shape and is composed of a substantially porous collector electrode plate 132. The corona electrode wires 122 are spaced axially from the collector electrode 130 by an electrode separation distance d and are spaced laterally apart by an equal lateral distance a. Each corona electrode wire has an effective diameter in the range of 100 to 1000 μm.

[0080] Referring to Figures 3A to 3C, the shape of the plasma electrode arrangement 110 is designed to satisfy optimized conditions. Specifically, the effective area in the center of the corona electrode is spaced axially from the collector electrode by an electrode spacing distance d. The peripheral area of ​​the corona electrode (shown by the dashed rectangle) is spaced from the collector electrode and / or peripheral support to satisfy the following condition: In any path from the corona electrode through the peripheral support to the collector electrode, the inter-electrode path length c is in the range of 1.085d ≤ c ≤ 2d.

[0081] In this example, this condition is satisfied by moving the outermost corona electrode wire 122 along the second lateral axis BB away from the inner surface 152 of the peripheral frame 150 by a lateral distance b. Here, the lateral distance b = 0.45d.

[0082] Along the first lateral axis AA, this condition is satisfied by providing a curved end shape 134' on the collector electrode plate 132. This curved shape is configured such that the axial distance between the corona electrode wire 122 and the collector electrode 130 in the central effective region of the corona electrode is equal to the electrode separation distance d, and in the region where the corona electrode wire 122 is in contact with the peripheral frame 150, the path length from any point on the corona electrode wire 122 to any point on the collector electrode 130 via the peripheral frame is equal to the inter-electrode path length c. As shown in the figure, the curvature of the curved end shape 134 starts at a position approximately lateral distance b (b=0.45d) from the inner surface 152 of the peripheral frame 150.

[0083] During use, this shape of the plasma electrode arrangement 110 makes it possible to maximize the applied voltage U(t) for a predetermined electrode separation distance d, thereby achieving high-efficiency operation without the risk of discharge (arc) generation. This enables high-performance active noise reduction (ANR).

[0084] The outer ozone filter 180 has a fine aperture structure 184 (for example, an average effective aperture diameter in the range of 0.2 to 1 mm and an aperture density of 1 cm²). 2 The device is configured with a porous filter plate 182 having more than 30 ozone-reducing elements per plate. The ozone-reducing catalyst (e.g., a manganese oxide-based catalyst) is provided on the porous structure (e.g., inside the porous structure or as a coating). In one embodiment, the filter plate 182 is a porous metal plate (e.g., a steel plate or an aluminum plate), and the ozone-reducing catalyst is applied as a coating to the outer surface of the porous metal plate (e.g., the inner and outer opposing surfaces and the inner surface of the openings).

[0085] The outer ozone filter 180 is generally less than 15 mm thick and is positioned at a distance of at least 10 mm from the center of the collector electrode 130. It is desirable that the outer ozone filter 180 be low-flammability or non-flammable.

[0086] The outer ozone filter 180 is acoustically sealed around the periphery of the plasma electrode arrangement 110. To avoid interference with the control sound (which may have frequency components in the 0-5 kHz range) emitted from the plasma transducer device, the shape of the outer ozone filter 180 (including its depth and perforation structure) is configured to adjust its acoustic response. Specifically, this adjustment includes, but is not limited to, the following conditions: By adjusting the shape of the outer ozone filter 180, the acoustic output transfer coefficient of the outer ozone filter 180 is calibrated to be 50% or more, while the reflection output coefficient is 10% or less. More generally, the purpose of this adjustment is to prevent the sound pressure level of the control sound generated by the outer ozone filter 180 from dropping by more than 3 dB at 5 kHz. The outer ozone filter 180 described herein can capture ozone from the air while minimizing its impact on the acoustic output of the plasma transducer device. The rectangular shape and perforated structure of the outer ozone filter 180, along with the use of an ozone catalyst and acoustic tuning, make the outer ozone filter 180 an extremely efficient and high-precision component within the plasma transducer device.

[0087] The housing 170 is a sealed housing that defines a chamber 172 that receives back radiation from the plasma electrode arrangement 110. The chamber 172 has an axial length l (lowercase L), which is typically less than 20 mm. An acoustic response adjustment means 190 is housed inside the chamber 172.

[0088] The sound generated by the electroacoustic plasma transducer device 100 can be described as a combination of two sound sources arising from different physical phenomena. First, the sound is generated by heat transfer from the ionized region around the corona electrode 120 to neutral air particles. This sound source behaves as a unipolar (monopole) sound source. The generated heat output H at each frequency is approximated by the following equation.

[0089]

number

[0090] Here, U0 is the critical voltage at which corona discharge begins, and C is the dimensional constant. U0 and C measure the voltage-current characteristics of the transducer and can be determined by approximating them with the equation: I=CU(U-U0), where I and U represent the total current and total voltage, respectively. Secondly, the dipole sound source is associated with an electromechanical force F, which is transmitted from accelerated ions to neutral air particles and acts from the corona electrode 120 to the collector electrode 130.

[0091]

number

[0092] Here, μ is the effective mobility of the ion. Based on these sound sources, the corresponding sound pressure can be determined at a distance x from the center of the plasma electrode arrangement 110, that is, directly in front of the electroacoustic plasma transducer device 100.

[0093]

number

[0094] In these equations, S is the total cross-sectional area of ​​the plasma electrode arrangement 110 having an electrode separation distance d as an axial distance. p θ represents the specific heat capacity per unit mass, T0 is the ambient temperature, R is the complex reflection coefficient from the enclosure, c is the speed of sound in air, and k is the wavenumber.

[0095] In most active noise reduction (ANR) applications where electroacoustic plasma transducer devices are envisioned, a compact structure is desirable, so the chamber length (axial length l) must be small (preferably 20 mm or less). In this case, when the housing has a rigid end (i.e., the reflection coefficient R is close to "1"), in the low-frequency range, mainly unipolar sound pressure pH This dominates the acoustic field. This is bipolar sound pressure p F This is because, by its very nature, it is attenuated.

[0096] In a preferred embodiment of the electroacoustic plasma transducer device 100, the magnitude of the sound pressure generated by the sound source (electromechanical force F) is 3 to 4 times the pressure generated by the sound source (generated heat output H). The acoustic response of the electroacoustic plasma transducer device 100 can be optimized within a target frequency band to improve the performance of the active noise reduction ANR system 10. More specifically, it is optimized by using impedance control technology according to the method described in Patent Document 1. The acoustic response of the electroacoustic plasma transducer device can be changed by adjusting a combination of the rear wall distance (l), which is the distance to the rear wall of the housing, and the characteristics of the rear wall, which are generally defined by the reflection coefficient R. For example, in a specific frequency range, the generated composite sound pressure p H +p F This makes it possible to maximize the reflection coefficient. By fixing the rear wall distance (l), the frequency-dependent behavior of the reflection coefficient R is determined. This method for specifying desired enclosure characteristics can be used as an approximate design guideline in the enclosure design of electroacoustic plasma transducer devices and can be applied in combination with experimental methods. This acoustic response tuning means may be provided in the form of an acoustic absorption structure 192 formed from a porous material. The acoustic absorption structure 192 may operate to absorb sounds at a low frequency threshold (e.g., above about 300 Hz).

[0097] Referring to Figures 11A and 11B, the acoustic response adjustment means 190 may be configured to absorb low-frequency sounds (e.g., less than about 300 Hz). In one embodiment, the acoustic response adjustment means may include a combination of an acoustic absorption structure and a passive resonator 196. Figure 11A shows an example of an electroacoustic plasma transducer device with a housing. This electroacoustic plasma transducer device includes a passive (radiator or) resonator 196 attenuated by a porous material 194 and further has two vents 198.

[0098] Figure 11B shows an example of an electroacoustic plasma transducer device having a housing to which a passive radiator (196) is mounted instead of a rear wall. Figures 4A to 4E show alternative plasma electrode arrangements 110′ used in the electroacoustic plasma transducer apparatus 100 of Figure 1.

[0099] Plasma electrode configuration 110' is based on plasma electrode configuration 110 (common elements are denoted by the same reference numerals), with the corona electrode wire 122 replaced by a long corona electrode rod 122'. As shown in the figure, each corona electrode rod 122' is supported by a row of pins 124 extending in the axial direction. These pins 124 have tapered tips 124A and are spaced apart from the collector electrode 130' by an electrode spacing distance d.

[0100] In this example, the condition 1.085d ≤ c ≤ 2d is satisfied by moving the outermost corona electrode rod 122′ along the second lateral axis BB, away from the inner surface 152′ of the peripheral frame 150′ by a lateral distance b. Here, b = 0.45d.

[0101] Along the first transverse axis AA, this condition is satisfied by spacing the tapered tips 124A of the axially extending pins 124 that are closest to the inner surface 152' of the peripheral frame 150' (i.e., the outermost opposing pins in each row) by the same transverse distance b. As a result, the collector electrode 130' is able to maintain a uniformly planar surface in both directions of the first transverse axis AA and the second transverse axis BB, all the way to the peripheral frame 150'.

[0102] Figures 5A to 5E show another alternative plasma electrode arrangement 110′′ used in the electroacoustic plasma transducer apparatus 100 of Figure 1A. The plasma electrode configuration 110'' is based on the plasma electrode configuration 110 (common features are denoted by the same reference numerals), with the corona electrode wire 122 replaced by an elongated corona electrode rod 122''. Each corona electrode rod 122'' supports one elongated blade 124'' extending axially (for example, extending in the direction of the first transverse axis AA). This elongated blade 124'' has an extended blade tip 124A'', which is an extended blade tip, and is spaced from the collector electrode 130'' by an electrode spacing distance d as an axial distance. As shown in the figure, each axially extending elongated blade 124'' has a tapered end shape 124B. With this configuration, the extended blade tip 124A'' is spaced inward from the base of the axially extending elongated blade 124''.

[0103] In this example, the condition 1.085d ≤ c ≤ 2d is again satisfied by moving the outermost corona electrode rod 122'' along the second lateral axis BB away from the inner surface 152'' of the peripheral frame 150'' by a lateral distance b. Here, b = 0.45d.

[0104] Along the first lateral axis AA, this condition is satisfied by spacing the opposing ends of the axially extending elongated blade 124' away from the peripheral frame 150''. Specifically, the opposing ends of the axially extending elongated blade 124' are positioned such that the ends of the extension blade tips 124A' are spaced by the same lateral distance b from the inner surface 152'' of the peripheral frame 150''. In this way, the spacing of the axially extending elongated blades 124' along the first lateral axis AA allows the collector electrode 130'' to have a uniform planar surface extending to the peripheral frame 150'' in both directions of the first lateral axis AA and the second lateral axis BB.

[0105] Figures 6A to 6E show another alternative plasma electrode arrangement 110′′′ used in the electroacoustic plasma transducer apparatus 100 of Figure 1A. Plasma electrode arrangement 110′′′ is based on plasma electrode arrangement 110 (common elements are denoted by the same reference numerals), and while retaining the corona electrode wire 122′′′, the collector electrode plate 132 is replaced with multiple parallel long collector electrode rods 136. The long collector electrode rods 136 are arranged at equal intervals (a) in the lateral direction (i.e., the same as the lateral spacing of the corona electrode wire 122′′′). Furthermore, the long collector electrode rods 136 are arranged offset by a / 2 in the lateral direction relative to the corona electrode wire 122′′′, thereby ensuring that the electrode separation distance d, which is the distance between the corona electrode 120′′′ and the collector electrode 130′′′, is maintained such that the axial distance is smaller than the electrode separation distance d.

[0106] In this example, the condition 1.085d ≤ c ≤ 2d is satisfied by positioning the outermost corona electrode wire 122'''' along the second lateral axis BB, away from the inner surface 152'''' of the peripheral frame 150'''' by a lateral distance b. The outermost long collector electrode rod 136 is also positioned away from the inner surface 152'''' of the peripheral frame 150'''', which makes it possible to set a smaller value for the lateral distance b than in the previously described embodiment.

[0107] Along the first lateral axis AA, this condition is satisfied by providing a curved end shape 138 on the long collector electrode rod 136 on the collector side. This curved end shape 138 is configured such that, in the central effective region of the corona electrode, the distance between the corona electrode wire 122'''' and the long collector electrode rod 136 becomes the electrode separation distance d, and furthermore, in the region where the corona electrode wire 122'''' contacts the peripheral frame 150'''', the path length from any point on the corona electrode wire 122'''' to any point on the collector electrode 130'''' via the peripheral frame is equal to c. As shown in the figure, the curvature of the curved end shape 138 starts at a position approximately lateral distance b from the inner surface 152'''' of the peripheral frame 150''''.

[0108] Figures 7A to 7E show another alternative plasma electrode arrangement 110′′′′ used in the electroacoustic plasma transducer apparatus 100 of Figure 1A. The plasma electrode arrangement 110′′′′ is based on the plasma electrode arrangement 110 (common elements are given the same reference numerals), and a modified form of corona electrode wire 122′′′′ is held, and the collector electrode plate 132′′′′ is also held in a uniformly planar form.

[0109] In this example, the condition 1.085d ≤ c ≤ 2d for the inter-electrode path length c is satisfied by moving the outermost corona electrode wire 122′′′′ along the second transverse axis BB, away from the inner surface 152′′′′ of the peripheral frame 150′′′′ by a transverse distance b.

[0110] This condition is met by providing a curved end shape 126 to the corona electrode wire 122′′′′ along the first lateral axis AA, and supporting it with an opposing outer rod 128.

[0111] The curved end shape 126 is configured such that, in the central effective region of the corona electrode, the distance between the corona electrode wire 122′′′′ and the collector electrode plate 132′′′′ is equal to the electrode separation distance d, and in the region where the corona electrode wire 122′′′′ contacts the peripheral frame 150′′′′, the path length from any point on the corona electrode wire 122′′′′ through the peripheral frame to any point on the collector electrode 130′′′′ is equal to the inter-electrode path length c. As shown in the figure, the curvature of the curved end shape 126 starts at a position approximately lateral distance b from the inner surface 152′′′′ of the peripheral frame 150′′′′.

[0112] Figures 8A to 8E show an alternative active noise reduction ANR system 10′ based on the active noise reduction ANR system 10 (common elements are denoted by the same reference numerals). In this configuration, the collector electrode 130 and the outer ozone filter 180 are replaced with a collector electrode 130′′′′′ equipped with ozone reduction material.

[0113] The collector electrode 130′′′′′ comprises a honeycomb-structured porous filter / electrode plate 132′′′′′ which has an opening facing the plasma electrode arrangement. The porous filter / electrode plate 132′′′′′ has a similar internal shape to the collector electrode 130 (with a curved end shape 134′), but has a larger axial thickness (e.g., 5 to 15 mm), a smaller opening diameter / higher opening density (e.g., the average effective opening diameter is in the range of 0.1 to 2 mm, and 1 cm 2 It has a configuration that has an aperture density of more than 30 per unit.

[0114] The ozone reduction catalyst (e.g., a manganese oxide-based catalyst) is provided on a porous structure (e.g., internally or as a coating). In one embodiment, the filter / electrode plate 132′′′′′ is a porous metal plate (e.g., a steel or aluminum plate), and the ozone reduction catalyst is applied as a coating to the outer surface of the plate, excluding the inner (electrode) surface (e.g., the outer surface of the plate and the inner surface of the opening). The inner surface is generally not coated. This is to avoid reducing the electrical conductivity of the collector electrode. The collector electrode 130′′′′′ is detachably coupled to the peripheral frame 150′′′′′, allowing for the replacement of the collector electrode (e.g., appropriate electrical connections are provided to allow for the electrical disconnection of the outer electrode).

[0115] Figures 9A to 9E show another alternative configuration of the active noise reduction ANR system 10′′ based on the active noise reduction ANR system 10 (common elements are denoted by the same reference numerals). In this configuration, the acoustic response adjustment means 190 is replaced by an internal porous structure 190′′, and the external ozone filter 180 is replaced by an airflow blocking screen 250, which is positioned in front of the plasma electrode arrangement 110′′′′′.

[0116] The internal porous structure 190′′ has a honeycomb-like opening structure similar to the porous filter / electrode plate 132′′′′ shown in Figures 8A to 8E, and is configured to absorb sounds at a low frequency threshold (e.g., above approximately 300 Hz).

[0117] Furthermore, an ozone reduction catalyst (e.g., a manganese oxide-based catalyst) is provided on the internal porous structure 190'' (e.g., either inside or as a coating). In one embodiment, the internal porous structure 190'' is a porous metal plate (e.g., a steel plate or an aluminum plate), and the ozone reduction catalyst is applied as a coating to the outer surface of the plate and the inner surface of the openings. The internal porous structure 190'' is detachably coupled to the peripheral frame 150'''''''', allowing for the replacement of the structure.

[0118] The airflow barrier screen 250 operates to substantially prevent the transmission of airflow while substantially allowing the transmission of acoustic pressure waves. The airflow barrier screen 250 is formed from a porous sheet material 252 (e.g., wire mesh or fibrous material) and has an axial thickness of less than 5 mm.

[0119] In one embodiment, the airflow blocking screen 250 has an acoustic power transfer coefficient of 50% or more in the frequency range of 0 to 5000 Hz. In one embodiment, the airflow blocking screen 250 has an acoustic output reflection coefficient of 10% or less in the frequency range of 0 to 5000 Hz.

[0120] Figure 10 shows another embodiment of the Active Noise Reduction ANR system 10′′′, based on the Active Noise Reduction ANR system 10 (common elements are denoted by the same reference numerals). In this configuration, the detection microphone 200 is replaced by a pair of detection microphones (200A and 200B). The first detection microphone 200A functions as an outward detection microphone and monitors the forward pressure p1 in front of the outward ozone filter 180. The second detection microphone 200B functions as an inward detection microphone and monitors the pressure p2 between the outward ozone filter 180 and the plasma electrode arrangement 110.

[0121] In one embodiment, the outer ozone filter 180 has a resistance value Res, and the active noise reduction ANR circuit has an estimated airflow velocity V est It works to calculate V. est The expression is as follows:

[0122]

number

Claims

1. An electroacoustic plasma transducer system comprising an electroacoustic plasma transducer device, wherein the electroacoustic plasma transducer device is A plasma electrode arrangement comprising a corona electrode and a collector electrode positioned apart from the corona electrode via an air gap, A peripheral support that operates to support the plasma electrode arrangement, the peripheral support having electrical insulation, A housing that defines a chamber that receives back radiation from the aforementioned plasma electrode arrangement, and A driving means that operates to supply a voltage U(t) between the corona electrode and the collector electrode, It is equipped with, The aforementioned plasma electrode arrangement is The central effective region of the corona electrode is spaced apart from the collector electrode by an electrode spacing distance d, and the peripheral portion of the corona electrode is spaced apart from the collector electrode and / or the peripheral support. Any path from the corona electrode through the peripheral support to the collector electrode has a path length c that satisfies the condition c ≥ 1.085d. It is structured in such a way. Electroacoustic plasma transducer system.

2. The aforementioned path length c satisfies the condition 1.085d ≤ c ≤ 2d. The electroacoustic plasma transducer system according to claim 1.

3. The electrode spacing distance d is 2 to 10 mm. The electroacoustic plasma transducer system according to claim 1 or 2.

4. The driving means operates to maintain a voltage difference range U(t)range between the corona electrode and the collector electrode in the operating mode. The aforementioned voltage difference range U(t) ｒａｎｇｅ The formula is: U(t) ｒａｎｇｅ = (0.35 - 0.85) × E ｂｒｅａｋｄｏｗｎ ×Electrode separation distance d It is defined as, where E ｂｒｅａｋｄｏｗｎ = 3 × 10 ６ It is V / m. The electroacoustic plasma transducer system according to any one of claims 1 to 3.

5. The plasma electrode arrangement defines the axial axis along which the corona electrode and the collector electrode are spaced apart from each other. At least one of the corona electrode and the collector electrode is positioned on a lateral axis with respect to the axial axis, at a distance of lateral distance b from the peripheral support. The lateral distance b satisfies the conditions of the path length c. The electroacoustic plasma transducer system according to any one of claims 1 to 4.

6. At least one of the corona electrode and the collector electrode has an inclined end shape that extends in the axial direction. The distance between the corona electrode and the collector electrode in the region where the plasma electrode arrangement is in contact with the peripheral support satisfies the condition of the path length c. The electroacoustic plasma transducer system according to any one of claims 1 to 4.

7. The corona electrode is a panel-shaped collector electrode coupled to the peripheral support. The electroacoustic plasma transducer system according to any one of claims 1 to 6.

8. The corona electrode comprises a plurality of elongated corona electrode members coupled to the peripheral support, Each of the aforementioned elongated corona electrode members extends substantially along the first transverse axis of the plasma electrode arrangement. The electroacoustic plasma transducer system according to any one of claims 1 to 6.

9. The corona electrode supports at least one projection that protrudes in the direction of the collector electrode along the axial axis. The electroacoustic plasma transducer system according to any one of claims 1 to 8.

10. At least one of the protrusions is positioned at a minimum lateral distance b from the peripheral support with respect to the first lateral axis. The electroacoustic plasma transducer system according to claim 9.

11. At least one of the aforementioned protrusions has a tapered shape, The tapered tip surface is positioned at a minimum lateral distance b from the surrounding support with respect to the first lateral axis. The electroacoustic plasma transducer system according to claim 9 or 10.

12. The aforementioned lateral distance b satisfies the relationship b = 0.45d. The electroacoustic plasma transducer system according to claim 10 or 11.

13. The collector electrode is a panel-shaped collector electrode. The electroacoustic plasma transducer system according to any one of claims 1 to 12.

14. The collector electrode comprises a plurality of elongated collector electrode members coupled to the peripheral support. The electroacoustic plasma transducer system according to any one of claims 1 to 12.

15. The electroacoustic plasma transducer device further includes acoustic response adjustment means provided within or as part of the housing. The electroacoustic plasma transducer system according to any one of claims 1 to 14.

16. The acoustic response adjustment means includes an acoustic absorption structure provided within the chamber. The electroacoustic plasma transducer system according to claim 15.

17. The acoustic response adjustment means includes a passive resonator means. The electroacoustic plasma transducer system according to claim 15 or claim 16.

18. An electroacoustic plasma transducer system comprising an electroacoustic plasma transducer device, wherein the electroacoustic plasma transducer device is A plasma electrode arrangement comprising an inner electrode and an outer electrode positioned spaced apart from the inner electrode via an air gap, A peripheral support that operates to support the aforementioned plasma electrode arrangement, A housing that defines a chamber that receives back radiation from the plasma electrode arrangement, and A driving means that operates to supply a voltage U(t) between the inner electrode and the outer electrode, It is equipped with, The electroacoustic plasma transducer device further includes an ozone-reducing material. Electroacoustic plasma transducer system.

19. The electroacoustic plasma transducer device has a porous structure, The ozone-reducing material is provided on the porous structure, The electroacoustic plasma transducer system according to claim 18.

20. The porous structure includes an outward ozone filter provided in front of the plasma electrode arrangement. The electroacoustic plasma transducer system according to claim 19.

21. The aforementioned outer electrode is, The inner surface of the outer electrode facing the inner electrode, The outer surface of the outer electrode substantially facing the inner surface of the outer electrode, and The inner surface of the outer electrode defined by the opening within the outer electrode, It defines, The ozone-reducing material is applied to the inner surface and / or outer surface of the outer electrode. The electroacoustic plasma transducer system according to claim 18.

22. The ozone-reducing material is not substantially coated on the inner surface of the outer electrode. The electroacoustic plasma transducer system according to claim 21.

23. The outer electrode is detachably coupled to the peripheral support. The electroacoustic plasma transducer system according to claim 21 or 22.

24. The ozone reducing material is provided inside the housing, The electroacoustic plasma transducer system according to claim 18 or 19.

25. The electroacoustic plasma transducer device further includes an airflow blocking screen provided in front of the plasma electrode arrangement, The airflow blocking screen operates to substantially prevent the transmission of airflow while substantially allowing the transmission of acoustic pressure waves. The electroacoustic plasma transducer system according to claim 24.

26. The porous structure is provided inside the chamber. The electroacoustic plasma transducer system according to claim 24 (if dependent on claim 19) or claim 25 (if dependent on claim 19).

27. An active noise reduction ANR system, wherein the active noise reduction ANR system is An electroacoustic plasma transducer system according to any one of claims 1 to 26, Acoustic detection means, and An active noise reduction ANR circuit operates to reduce noise by receiving a signal from the acoustic detection means and controlling the output of the electroacoustic plasma transducer system, An active noise reduction (ANR) system equipped with [this feature].

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