Patent Application
20220279261
The present invention relates to a microphone.
Microphones used under conditions where they are exposed to water are known. Such conditions include, for example, an outdoor use, a placement on a desk where beverages and the like may be spilled, or using by embedding in a desk.
In the past, for example, there has been disclosed a microphone having a windscreen which covers a first opening of a case with a sheet member imparted with air permeability and water repellency and has a drainage property on an outside of the case (for example, see a published unexamined patent application JP2017-55228A).
The microphone disclosed in JP2017-55228A is difficult to miniaturize because a windscreen is required. In addition, since the windscreen has a high water retentivity and easily absorbs water, it has been difficult to restore the windscreen to its original performance once it has been wet.
An object of the present invention is to provide a microphone having high waterproofness and water repellency.
A microphone according to the present invention includes an outer wall member having a sound hole, a first mesh arranged inside the outer wall member and made of Dutch weave, a spacer having a diameter corresponding to an inner diameter of the outer wall member and pressing the first mesh to an inside the outer wall member while a first surface of which is in contact with the first mesh, a second mesh is in contact with a second surface of the spacer and having water repellency, and a microphone unit stored under the second mesh.
According to the present invention, a microphone having high waterproofness and water repellency can be provided.
A microphone according to embodiments of the present invention will be described below with reference to the drawings. In the following description, an axial direction of a microphone 1 is referred to as a z direction, and a direction orthogonal to the z direction is referred to as a x direction and a y direction. A surface facing in a +z direction is also called a top surface, and a surface facing in a −z direction is called a bottom surface. Note that a direction arrangement of the microphone is not limited to this direction.
As illustrated in
As illustrated in
The microphone unit 11 includes a diaphragm, which is a member that converts sound waves from an outside of the microphone 1 into an electric signal. The microphone unit 11 is a substantially cylindrical member. In this embodiment, a bottom surface of the microphone unit 11 does not communicate with the outside. In other words, the microphone 1 is omnidirectional. The technical scope of the present invention is not limited thereto.
The outer wall member 12 is a member that constitutes an upper surface outer wall of the microphone 1, and is a bottomed cylindrical member provided with a plurality of sound holes. The outer wall member 12 is composed of, for example, an etching plate or a punching plate having holes of a small diameter. Alternatively, the outer wall member 12 may have an etching plate provided in a wire mesh. Further, the outer wall member 12 may have one large hole on a top surface instead of the plurality of sound holes. The first mesh 13 is pressed against an inner wall of the outer wall member 12.
The first mesh 13 is a mesh made of metal or resin. The first mesh 13 is woven by a Dutch weave. The Dutch weave is, for example, a plain Dutch weave or a twilled Dutch weave. A plain Dutch-woven wire gauge is a wire gauge woven by enlarging a mesh by vertical lines and sequentially adhering horizontal lines. A twilled Dutch-woven wire gauge is that a structure of a Dutch woven wire gauge is further made into twill weave. Since horizontal lines of the twilled Dutch-woven wire gauge are in close contact with each other on both front and back sides of wire metals, a density of the twilled Dutch-woven wire gauge is higher than that of the plain Dutch-woven wire gauge.
The Dutch weave is a weave in which horizontal lines travel diagonally from a front surface to a back surface of adjacent vertical lines with respect to a plane of a wire gauge. Therefore, ventilation holes do not go straight. Thus, according to the first mesh 13 made of the Dutch weave, there are no planar openings of the weave as in case of a plain weave or the like, and a liquid passes through gaps at intersections of the vertical lines and the horizontal lines. In other words, the liquid traveling from an outside toward the first mesh 13 meanders into an inside. Therefore, according to the first mesh 13, the water pressure of the liquid from the outside can be reduced.
Further, by using the first mesh 13 made of the Dutch-woven wire gauge, the microphone 1 can be made smaller than a microphone having a urethane windscreen. In addition, according to the first mesh 13 made of the Dutch-woven wire gauge, a performance of the microphone 1 can be ensured because dust, sand, and dirt, are less likely to stick on the mesh and the mesh is less likely to be clogged as compared with the urethane windscreen. Therefore, the microphone 1 can be used outdoors.
The first mesh 13 can repel a small amount of liquid or a liquid having a small water pressure due to surface tension. Therefore, the microphone 1 can be easily restored to its original condition by wiping off water droplets on the surface when the water is spilled from a cup or a light rain. Further, according to a structure in which the first mesh 13 located on the outside is made of metal, the microphone 1 has lower water retentivity than the urethane windscreen, so that it can be easily dried even when liquid adheres. For example, in a case where the microphone 1 is embedded in a desk and only an upper part is exposed to the upper surface of the desk, the microphone 1 can be easily dried even when the liquid is spilled on the desk, and a sound collecting performance can be maintained.
The first mesh 13 made of metal has higher durability than that of urethane. Therefore, since a frequency of maintenance of the microphone 1 can be reduced, the microphone 1 can be easily used even in a place where operators cannot easily reach, such as outdoors or a ceiling.
The spacer 14 is a substantially annular member. The spacer 14 has an annulus 14a, a small annulus 14b, and plurality of spokes 14c. The annulus 14a constitutes an outer periphery of the spacer 14, and the small annulus 14b is substantially concentric with the annulus 14a and is arranged inside the annulus 14a. Further, the spokes 14c connect the annulus 14a and the small annulus 14b. In other words, the spacer 14 has a plurality of through holes 14d surrounded by the annulus 14a, the small annulus 14b, and the plurality of spokes 14c. Further, a rib 14e protruding in a thickness direction over an entire circumference of an outer edge is arranged on the annulus 14a.
The spacer 14 has a diameter that fits inside the outer wall member 12. Further, the spacer 14 is an elastic member made of, for example, a resin or the like. An outer diameter of the annulus 14a in a natural state is slightly larger than an inner diameter of the outer wall member 12. According to this configuration, when the first mesh 13 and the spacer 14 are press-fitted into the outer wall member 12 together with the spacer 14, the spacer 14 expands inside the outer wall member 12. In other words, a first surface of the spacer 14 is in contact with the first mesh 13 and presses the first mesh 13 into the outer wall member 12. Then, the first mesh and the spacer 14 are fixed to inside the outer wall member 12.
The annulus 14a of the spacer 14 has a pair of recess parts 14f facing each other. The recess parts 14f are fitted into protrusion parts 16e of the cover 16 in an assembled state.
The cover 16 is a bottomed cylindrical member having an opening 16a on a bottom surface side (−z side) of the microphone 1. The cover 16 is made of, for example, resin. The cover 16 has the second mesh 15 fixed to a bottom part 16b and an outer peripheral surface 16c. In other words, a second surface of the spacer 14 is in contact with the second mesh 15 fixed to the bottom part 16b.
The second mesh 15 is a mesh having water repellency, for example, made of plain weave. The second mesh 15 may be made of metal or resin. The second mesh 15 repels liquid entering from the outside and prevents the liquid from entering the inside of the cover 16. Further, the cover 16 has a plurality of holes in the bottom part 16b and the outer peripheral surface 16c. External sound reaches the microphone unit 11 through the holes and the second mesh 15.
As described above, the microphone 1 according to the present invention realizes high waterproofness and water repellency by the first mesh 13 and the second mesh 15, which are having different weaves. Specifically, as a result of the liquid spilled on the microphone 1 being dispersed by the first mesh 13, a weight of the liquid is reduced and a water pressure per unit is reduced. By repelling the liquid with the second mesh 15, the microphone 1 can surely prevent the liquid from entering the inside. The outer wall member 12 arranges an inflow direction of the liquid in a direction orthogonal to the first mesh 13 by the sound holes. In other words, an effect of reducing water pressure by the first mesh 13 is more increased by the outer wall member 12. Further, a first gap K1 between the first mesh 13 and the second mesh 15 further reduces the water pressure and reliably prevents the liquid from entering by the second mesh 15.
The first mesh 13 has a high acoustic resistance because not only the liquid but also gas cannot pass straight through the first mesh 13. Therefore, a configuration for controlling an acoustic resistance value generated by the first mesh 13 and ensuring the characteristics of the microphone 1 will be described below.
As described above with reference to
According to the configuration in which the spacer 14 presses the first mesh 13 against an inner wall of the outer wall member 12, volumes of the first gap K1 and the second gap K2 formed between the first mesh 13 and the second mesh 15 can be made constant. In other words, the acoustic resistance value generated by the first mesh 13 becomes substantially constant for each individual in mass production and is maintained over a long period of time. As a result, the microphone 1 can be designed in consideration of the acoustic resistance by the first mesh 13, so that characteristics of the microphone 1 can be ensured while the first mesh 13 having the high acoustic resistance is arranged outside the microphone unit 11.
The outer peripheral surface 16c of the cover 16 has the protrusion parts 16e protruding in a radial direction. The protrusion parts 16e are formed in pairs at positions facing each other and are aligned with the recess parts 14f of the spacer 14. In this embodiment, a number of the recess parts 14f and a number of the protrusion parts 16e are two each, but the numbers are examples. Further, the cover 16 has a rib 16d protruding in a radial direction over an entire circumference at an end of the opening 16a. The rib 16d is in contact with an inner wall of a stepped part 20c (see
A unit holding member 17 is a cylindrical member that holds the microphone unit 11 inside. The unit holding member 17 is made of a member having an elastic force such as an elastomer or rubber. As illustrated in
The fixing section 20 is an annular member that holds the cover 16. The fixing section 20 has a shape in which a first annulus 20a and a second annulus 20b having different diameters are connected by a stepped portion 20c over an entire circumference. The inner diameter of the first annulus 20a is larger than that of the second annulus 20b. The outer wall member 12 is fitted inside the first annulus 20a. The first annulus 20a and the outer wall member 12 integrally hold the first mesh 13, the spacer 14, and the second mesh 15. The upper end part of the case 30 is inserted through the second annulus 20b, and the second annulus 20b and the case 30 are connected to each other. A mode of connection can be appropriately selected, but the second annulus 20b and the case 30, for example, may be connected by screws inserted into small holes 20d of the second annulus 20b and holes of the case 30.
As described above, according to the microphone 1 of the present invention, high waterproofness and water repellency can be realized.
A second embodiment of the microphone according to the present invention will be described with reference to parts different from those of the first embodiment. The microphone according to the second embodiment is different from the microphone according to the first embodiment in that a side of the front surface and the rear side of the microphone unit are opened to constitute a directional microphone. In the following figures, the same components as those in the first embodiment are denoted by the same reference numerals.
As illustrated in
The acoustic adjustment member 50 is a member that holds the microphone unit 11 and connected to the case 30. The acoustic adjustment member 50 may be made of an elastic material. For example, the acoustic adjustment member 50 is made of an elastomer or a rubber molded product. According to this configuration, the acoustic adjustment member 50 is press-fitted and expanded inside the case 30, whereby the acoustic adjustment member 50 is connected to the case without any gap.
The acoustic adjustment member 50 mainly has a base 51 and the acoustic adjustment unit 52. The base 51 is a substantially columnar member having an outer diameter corresponding to an inner peripheral surface of the case. The base 51 is a member that holds the microphone unit 11 and is connected to the case in a lower part of the acoustic adjustment member 50.
The base 51 has a substantially cylindrical housing member 51a on an upper surface. The housing member 51a has a shape corresponding to the outer circumference of the microphone unit 11. The housing member 51a is formed in the x direction. The housing member 51a stores the microphone unit 11 in an assembled state.
The acoustic adjustment unit 52 is a member arranged on an upper part of the base 51. The base 51 and the acoustic adjustment unit 52 may be integrally formed. The acoustic adjustment unit 52 is a crescent-shaped member. In other words, an outer peripheral surface of the acoustic adjustment unit 52 has a shape in which a first curved surface 52a, curved in a convex shape, and a second curved surface 52b, curved in a concave shape, are connected. The first curved surface 52a and the second curved surface 52b are cylindrical surfaces, and a curvature of the second curved surface 52b is larger than a curvature of the first curved surface 52a. The first curved surface 52a may be formed along an outer periphery of the base 51. An upper surface of the acoustic adjustment unit 52 is in contact with an inner wall of the cover 16.
According to the configuration in which the acoustic adjustment unit 52 and the case 30 are integrated, even a small-sized microphone 101 can have a long distance between acoustic terminals. Therefore, according to this configuration, a microphone with high directivity can be realized. The acoustic terminal refers to a position of an air that effectively applies a sound pressure to the microphone unit, and is a center position of the air that moves at the same time as a diaphragm provided in the microphone unit.
As illustrated in
A front side air chamber K111 is formed on a side of the front surface 11a of the microphone unit 11. The front side air chamber K111 is a region surrounded by the front surface 11a of the microphone 11, an inner wall of the through hole 53, the cover 16, and the second mesh 15 connected to an outer periphery of the cover 16. A rear side air chamber K112 is formed on a side of a rear surface 11b of the microphone unit 11. The rear side air chamber K112 is a region surrounded by the rear surface 11b of the microphone unit 11, the second curved surface 52b of the acoustic adjustment unit 52, the cover 16, and the second mesh 15 connected to the outer periphery of the cover 16.
In other words, the acoustic adjustment unit 52 partitions the front side air chamber K111 and the rear side air chamber K112 inside the microphone 101.
A volume of the rear side air chamber K112 is sufficiently larger than a volume of the front side air chamber K111. When the first mesh 13 having a large acoustic resistance is arranged between a sound source and the microphone unit 11, a distance between terminals of a front acoustic terminal and a rear acoustic terminal becomes small, and a vibration of the diaphragm becomes small. Therefore, by making the rear side air chamber K112 larger than the front side air chamber K111, an impedance on a back side becomes smaller and a driving force of the diaphragm can be maintained. In other words, according to this configuration, a microphone having waterproofness, water repellency, and high directivity can be realized.
For example, a volume ratio of the front side air chamber K111 and the rear side air chamber K112 is 1:7. In this waterproof structure, the volume ratio of the front side air chamber K111 and the rear side air chamber K112 is preferably around 1:7 to 1:10. The microphone 101 having the volume ratio of the front side air chamber K111 and the rear side air chamber K112 around 1:7 to 1:10 can sufficiently maintain the driving force of the diaphragm. When the volume ratio is smaller than 1:7 in this embodiment, a sound collection performance in a sound collection band is insufficient. A configuration in which the volume ratio is larger than 1:10 is not preferable due to restrictions on an outer shape of the microphone 101.
As illustrated in
Further, in the present embodiment, instead of the fixing section 20, a fixing section 120 in which a part of an outer peripheral surface is linearly cut out is connected to the outer wall member 12 and the case 30. Cutout surfaces of this cutting out are substantially parallel to each other. In addition, instead of the fixing section 120, the fixing section 20 having a substantially cylindrical outer periphery may be connected to the outer wall member 12 and the case 30 in this embodiment as well. Further, a number of the cutout surfaces is two in the present embodiment, but it may be one or three or more.
Here, a configuration of the microphone 101 will be described using an acoustic equivalent circuit. As illustrated in
The audio signal source P2 located on the rear side and the microphone unit 11 are equivalently connected via an acoustic resistance rr1 by the first mesh 13 and an acoustic resistance rr2 by the second mesh 15 connected in serial. Further, between the audio signal source P2 and the microphone unit 11, an acoustic stiffness Sr1 generated by the first gap K1 is connected in parallel between the acoustic resistance rr1 and the acoustic resistance rr2. Here, the acoustic resistance rr1 and the acoustic resistance rf1, the acoustic resistance rr2 and the acoustic resistance rf2, and the acoustic stiffness Sr1 and the acoustic stiffness Sf1 are substantially equivalent to each other.
An acoustic stiffness Sr2 generated by the rear side air chamber K112 is connected in parallel between the acoustic resistance rr2 and the microphone unit 11. When a difference between the acoustic stiffness Sf2 and the acoustic stiffness Sr2 is small, in a predetermined frequency range in which a distance between a front side sound wave introduction hole and a rear side sound wave introduction hole and a half wavelength of the sound wave, resonance occurs on the front side and the rear side of the microphone unit 11 and a load is generated on the diaphragm inside the microphone unit 11. In other words, a level of the sound collected in the frequency range becomes small.
When a difference between the acoustic stiffness Sf2 and the acoustic stiffness Sr2 is sufficiently large, a phase difference and a pressure difference are generated between a front surface side and a rear surface side, and the diaphragm operates sufficiently. Therefore, the microphone of the second embodiment operates as a sound pressure gradient type microphone because the diaphragm has a sufficient driving force and high directivity. Further, by shifting the resonance frequency of the front side and the rear side, the resonance at the above-mentioned predetermined frequency is suppressed.
As described above, according to the microphone in which the volume of the rear air chamber is sufficiently larger than the volume of the front air chamber, sound can be collected well over the sound collection band.
According to the embodiments described above, the microphone having high waterproofness and water repellency can be realized.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-004698 | Jan 2021 | JP | national |
