Anti-wind system for an assembly comprising at least one microphone
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- THALES SA
- Filing Date
- 2024-06-06
- Publication Date
- 2026-04-22
AI Technical Summary
Existing anti-wind systems for microphones are not suitable for non-standardized antenna geometries, such as miniature microphones, and lack effective wind protection and mechanical adaptation, leading to high adaptation costs and complexity, especially for complex acoustic direction-finding applications.
A mechanical anti-wind system comprising a rigid structure with a layer of material featuring through channels with multiple changes of direction, allowing sound transmission while converting kinetic energy into heat, and adaptable via additive manufacturing for complex geometries.
The system provides effective wind protection and mechanical adaptation for non-standard microphone geometries, optimizing resistance-to-mass ratio and acoustic performance, while being cost-effective and suitable for additive manufacturing.
Smart Images
Figure EP2024065662_19122024_PF_FP_ABST
Abstract
Description
DESCRIPTION Title of the invention: Windproof system for an assembly comprising at least one microphone
[0001] The invention relates to a wind protection system for an assembly comprising at least one microphone.
[0002] The acoustic pressure changes generated by the wind on a microphone constitute the main limitation to the collection of weak useful signals, both by the level of noise generated and by its very low frequency content, often confused with that of distant noise sources in airborne acoustics.
[0003] The desired anti-wind effect consists of trapping the entire microphone in a barrier that is acoustically transparent to the desired frequencies, and therefore in communication with the outside air, while guaranteeing a volume of air at rest around the sensitive surface of the sensor. To do this, an anti-wind device must move the turbulent air away from the sensor, either by separating the turbulent transition zone (for a sensor in rapid rectilinear motion), or, in the more general case concerned by the invention, by braking the moving air masses that constitute the wind, while allowing the transmission of sound, that is to say the microscopic oscillations of the air around its equilibrium position.
[0004] The principle of a wind deflector is then to convert the kinetic energy of the moving air mass into tiny amounts of heat via multiple imposed changes in the direction of the air flow, the interposition of a fixed porous material (potentially generating unwanted vibrations) or flexible / mobile material on which the energy is deposited.
[0005] It is also highly desirable that the windproof device also integrates the mechanical structure which supports it and: - has sufficient strength to ensure mechanical protection of the microphone assembly; - can adapt to different microphone geometries; and - be simple and inexpensive to produce.
[0006] Many solutions are available, ranging from the classic open foam windscreen slipped over the microphone, to stacks of barriers concentric, the most exposed of which can be made of polar fleece (widely used in outdoor reporting).
[0007] All these devices rely on braking moving air: - either by chicanes (tortuous device comprising obstacles), such as open-cell foams; - either by absorption of the kinetic energy of the wind by mobile materials such as furs; - either by interposing fixed porous materials: this type of protection can generally only be used behind one of the first two protections or, of course, a mechanical structure decoupled from the microphone, otherwise the kinetic energy of a sustained wind would be transformed into vibrations, potentially transmitted to the microphone.
[0008] Many manufacturers offer standard or COTS products, which stand for "commercial off-the-shelf" in English, using these principles, alone or in combination.
[0009] Another category of anti-wind system is also known, usable on carriers in rapid linear motion, by moving the turbulent air zone away from the sensitive surface via a separation of the flow boundary layer.
[0010] All these products are generally standardized to microphone diameters, usually in fractions of an inch, and are not, for example, suitable for antennas made up of miniature microphones. A specific interface must then be designed. In addition, the new generations of highly integrated microphones (MEMS), widespread in consumer electronics such as smartphones, are called "bottom port" or lower port. As such, the microphones are directly mounted on the surface of a printed circuit board, which prohibits the use of conventional windshields, suitable for studio microphones. As a result, the state of the art is not suitable for use on non-standardized antenna geometries: this results in significant costs and constraints on the study and implementation of mechanical adaptations specific to the use for acoustic direction finding.
[0011] Furthermore, whether they are foams or furs, as illustrated in [Fig.1], these windscreens must be fixed to supporting mechanical structures designed to keep them away from the microphone. In addition, foams have an intrinsic fragility which requires them to be provided with an external mechanical structure designed to protect them against abrasion, tears, and more generally against any external contact (for example, a grille) during outdoor use.
[0012] Mosses are also susceptible to waterlogging as soon as they are exposed to rain, which clogs their cells and drastically reduces their acoustic transparency. Furs, even when treated with a water-repellent substance, retain some of the rainwater, which weighs down their hairs and reduces their effectiveness. In both cases, the freezing of the water they contain has a detrimental effect on their acoustic transparency and wind protection capabilities.
[0013] Also, there is no single solution that combines both effective wind protection and mechanical adaptation to complex antenna geometries such as those used in acoustic direction finding. Furthermore, recognized manufacturers are geared towards high-volume markets and only offer custom-made products at prohibitive prices.
[0014] In fact, while it is simple and economical to acquire third-party windshield solutions, their adaptation to a non-standard geometry is long, complex and very expensive, when it is not impossible (MEMS). It often involves modeling operations to verify their effectiveness (no simulation possible) and, when this is not conclusive, the entire adaptation process must be reviewed.
[0015] Also, in order to address the problems mentioned above, there is proposed, according to one aspect of the invention, an anti-wind system for an assembly comprising at least one microphone provided with a housing, the anti-wind system comprising: - -a rigid structure comprising an axis of revolution, and at least one layer of material provided with at least one through channel comprising at least two changes of direction, the external surface portion of the rigid structure surrounding a first cavity, and in any plane including the axis of revolution, the external surface includes at least one point whose tangent makes an angle with the axis of revolution included in the interval ]0°;360°[; and - a second cavity, intended to connect the first cavity to the microphone by a channel in the housing, the cross-sectional area of which gradually decreases between the output section of the first cavity and the input section of the channel in the housing.
[0016] In one embodiment, the second cavity is a truncated right circular cone.
[0017] According to one embodiment, the external surface portion of the rigid structure surrounding the first cavity is concave.
[0018] In one embodiment, the outer surface portion of the rigid structure surrounding the first cavity is convex.
[0019] According to one embodiment, the external surface portion of the rigid structure surrounding the first cavity is a truncated right circular cone.
[0020] In one embodiment, said layer of material comprises at least one triply periodic surface portion.
[0021] A triply periodic surface is a surface consisting of an elementary building block that is repeated in all three spatial directions, or in other words, the surface is invariant in all directions.
[0022] According to one embodiment, said layer of material comprises at least one portion of Schwartz surface.
[0023] A Schwartz surface is a special case of a triply periodic surface with zero mean curvature. Minimal Schwarz surfaces are triply periodic minimal surfaces mathematically described by Hermann Schwarz.
[0024] In one embodiment, said layer of material comprises at least one through channel comprising at least two changes of direction, each channel portion connecting two successive changes of direction being rectilinear.
[0025] According to one embodiment, the material comprises a polymer, and / or a metal, and / or a ceramic.
[0026] According to another aspect of the invention, there is also provided a method of manufacturing an anti-wind system as previously described, using an additive manufacturing step.
[0027] The invention will be better understood by studying some embodiments described as non-limiting examples and illustrated by the appended drawings in which - [Fig.1] schematically illustrates a windscreen foam and a windscreen fur for a microphone, according to the state of the art; - [Fig.2] schematically illustrates an assembly comprising at least one microphone, and an anti-wind system, formed of a rigid structure comprising at least one layer of material provided with at least one through channel comprising at least two changes of direction, according to one aspect of the invention; - [Fig.3] schematically illustrates elementary patterns of periodic Schwartz surfaces, according to one aspect of the invention; - [Fig.4] schematically illustrates an assembly comprising at least one microphone, and an anti-wind system comprising several layers of material each provided with at least one through channel comprising at least two changes of direction, according to one aspect of the invention; - [Fig.5] schematically illustrates an assembly comprising at least one microphone, and an anti-wind system opening into the hermetic housing pierced to allow the sound to pass through, according to one aspect of the invention; - [Fig.6] schematically illustrates an assembly comprising at least one microphone, and an anti-wind system in which a layer of material comprising at least two changes of direction, each portion of channel connecting two successive changes of direction being rectilinear, according to one aspect of the invention; - [Fig.7A], [Fig.7B] and [Fig.7C] schematically illustrate a windshield system for an assembly comprising at least one microphone provided with a housing, in which the external surface portion of the rigid structure surrounding the first cavity is concave, according to one aspect of the invention; - [Fig.8A] and [Fig.8B] schematically illustrate variants of figure [Fig.7B], in which the second cavity is respectively of concave and convex shape; [Fig.9A] and [Fig.9B] schematically illustrate a variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure surrounding the first cavity is convex, according to one aspect of the invention; [Fig.10A] and [Fig.10B] schematically illustrate another variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure surrounding the first cavity is convex, according to one aspect of the invention; [Fig.11A], and [Fig.11B] schematically illustrate a variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure surrounding the first cavity is a truncated right circular cone; and [Fig.12A], and [Fig.12B] schematically illustrate another variant of the figures [Fig.7A] and [Fig.7B], wherein the outer surface portion of the rigid structure surrounding the first cavity is a truncated right circular cone.
[0028] Throughout the figures, elements with identical references are similar.
[0029] The present invention relates to a system for an assembly comprising at least one microphone, formed of a rigid structure comprising at least one layer of material provided with at least one through channel comprising at least two changes of direction.
[0030] [Fig.2] schematically represents an assembly comprising at least one microphone 1, arranged on a support 2 and an anti-wind system, in this case of a half-spherical shape, formed of a rigid structure 3 comprising at least one layer of material provided with at least one through channel 4 comprising at least two changes of direction.
[0031] The technical solution is based on mechanical structures comprising at least one layer of material provided with at least one through channel comprising at least two changes of direction. Baffles or changes of direction allow the kinetic energy of the moving air mass to be converted into heat, via multiple imposed changes in the direction of the airflow. The fact that the channels are open allows the transmission of sound (i.e., the microscopic oscillations of the air around its equilibrium position). For example, additive manufacturing favors the production of complex geometries in small series without generating additional costs.
[0032] The present invention thus makes it possible to obtain an effective wind barrier capable of responding to mechanical stresses by itself, while guaranteeing an optimized resistance / mass ratio (at equal acoustic performance).
[0033] The layer of material may comprise at least one portion of a triply periodic surface, for example at least one portion of a Schwartz surface.
[0034] [Fig.3] schematically represents examples of elementary patterns of such Schwartz surfaces.
[0035] For example, the layer of material comprises at least one through channel comprising at least two changes of direction, each portion of channel connecting two successive changes of direction being rectilinear.
[0036] The material may comprise a polymer, and / or a metal, and / or a ceramic.
[0037] The present invention also relates to an assembly comprising at least one microphone, provided with a housing and an anti-wind system as previously described.
[0038] Alternatively, the assembly comprises at least one microphone, provided with a windshield system forming a housing, as previously described, as illustrated in [Fig.4],
[0039] [Fig.5] schematically illustrates an assembly comprising at least one microphone, and an anti-wind system opening into the housing 5 of the assembly.
[0040] [Fig.6] schematically illustrates an assembly comprising at least one microphone, and a wind-proof system in which a layer of material comprising at least two changes of direction, each portion of channel connecting two successive changes of direction being rectilinear.
[0041] The invention consists of producing mechanical structures of geometry adaptable to the shape of the microphone to be protected, and having an intrinsic anti-wind capacity by the use of non-linear, i.e. tortuous, through channels between the outer and inner walls, to slow down moving masses of external air, and emerging, i.e. each channel effects free contact between the external and internal air, via an arbitrarily complex path in the material.
[0042] The shape and density of these through channels in the material results from a compromise between acoustic attenuation at the frequencies of interest and the quality of the desired anti-wind effect.
[0043] The combination of these desirable characteristics can lead to internal geometries in the material that are potentially complex to produce using conventional industrial processes, but perfectly suited to additive manufacturing.
[0044] An excellent embodiment therefore consists of producing the present invention by additive manufacturing, and in a material chosen for its mechanical strength, a dense network of non-linear opening channels, the exact geometry of which is defined by triply periodic surfaces such as Schwartz surfaces.
[0045] The dense network of nonlinear discharging channels may or may not be of periodic structure.
[0046] Of course, another manufacturing process for the realization of the previous structures can be used.
[0047] The invention is not limited to the production of a single wind barrier. It may be desirable to combine the invention with more conventional wind solutions (multiplying acoustically transparent wind barriers generally has a beneficial overall effect on protection performance).
[0048] For example, it is possible to use reserves in the material to insert foams or porous fabrics (insect barrier). The outer barrier of the invention then also serves as mechanical protection for this foam.
[0049] It is also possible to adapt the external geometry to standard windproof fixings such as furring strips; the invention then replaces mechanical interface parts, while significantly improving the overall windproof action.
[0050] [Fig.7A], [Fig.7B], and [Fig.7C] schematically illustrate a windshield system for an assembly comprising at least one microphone 1 provided with a housing 5.
[0051] The anti-wind system comprises a rigid structure 3 comprising an axis of revolution 10, at least one layer of material provided with at least one through channel 4 comprising at least two changes of direction, the external surface portion of the rigid structure 3 surrounding a first cavity 6. In any plane comprising the axis of revolution 10, the external surface comprises at least one point whose tangent makes an angle with the axis of revolution 10 included in the interval ]0°;360°[.
[0052] The windshield system also comprises a second cavity 7, intended to connect the first cavity 6 to the microphone 1 by a channel 8 of the housing 5, the cross-sectional area of which gradually decreases between the output section of the first cavity 6 and the input section of the channel 8 of the housing 5.
[0053] The anti-wind system also comprises a connecting element 9, in this case a portion 9a provided with a male screw thread intended to be screwed into a portion 9b intended to receive it from the housing 5.
[0054] Alternatively, the connecting element 9 may be glue, solder, brazing, or any other suitable fixing means.
[0055] For example, the second cavity 7 may be a truncated right circular cone, the cross-sectional area of which decreases regularly between the outlet section of the first cavity 6 and the inlet section of the channel 8 of the housing 5.
[0056] [Fig.8A] schematically illustrates a variant of figure [Fig.7B], in which the second cavity 7 is concave in shape.
[0057] [Fig.8B] schematically illustrates a variant of figure [Fig.7B], in which the second cavity 7 is convex in shape.
[0058] [Fig.9A], and [Fig.9B] schematically illustrate a variant of the figures [Fig.7A] and, [Fig.7B], in which the external surface portion of the rigid structure 3 surrounding the first cavity 6 is convex.
[0059] [Fig.9A] and [Fig.9B] schematically illustrate another variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure 3 surrounding the first cavity 6 is convex.
[0060] [Fig.10A], and [Fig.10B] schematically illustrate a variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure 3 surrounding the first cavity 6 is a truncated right circular cone.
[0061] [Fig.11 A], and [Fig.11 B] schematically illustrate another variant of figures [Fig.7A] and [Fig.7B], in which the external surface portion of the rigid structure 3 surrounding the first 6 cavity is a truncated right circular cone.
Claims
CLAIMS 1. Windproof system for an assembly comprising at least one microphone (1) provided with a housing (5), the windproof system comprising: a rigid structure (3) comprising an axis of revolution (10), at least one layer of material provided with at least one channel (4) passing through it comprising at least two changes of direction, the external surface portion of the rigid structure (3) surrounding a first cavity (6), and in any plane comprising the axis of revolution (10), the external surface comprises at least one point whose tangent makes an angle with the axis of revolution (10) included in the interval ]0°;360°[; and - a second cavity (7), intended to connect the first cavity (6) to the microphone (1) by a channel (8) of the housing (5), the cross-sectional area of which gradually decreases between the output section of the first cavity (6) and the input section of the channel (8) of the housing (5).
2. Windproof system according to claim 1, in which the second cavity (7) is a truncated right circular cone.
3. Windproof system according to claim 1 or 2, wherein the external surface portion of the rigid structure (3) surrounding the first cavity (6) is concave.
4. Windproof system according to claim 1 or 2, wherein the external surface portion of the rigid structure (3) surrounding the first cavity (6) is convex.
5. Windproof system according to claim 1 or 2, wherein the external surface portion of the rigid structure (3) surrounding the first cavity (6) is a truncated right circular cone.
6. Windproof system according to one of the preceding claims, wherein said layer of material comprises at least one portion of triply periodic surface.
7. The windproof system of claim 6, wherein said layer of material comprises at least a portion of Schwartz surface.
8. Anti-wind system according to one of claims 1 to 6, in which said layer of material comprises at least one through channel (4) comprising at least two changes of direction, each portion of channel connecting two successive changes of direction being rectilinear.
9. Windproof system according to one of the preceding claims, in which the material comprises a polymer, and / or a metal, and / or a ceramic.
10. Method of manufacturing an anti-wind system according to one of the preceding claims, using an additive manufacturing step.