WO2007052866A1

WO2007052866A1 - Electret condenser microphone including wind screen filter and external frame for building the elctret condenser microphone

Info

Publication number: WO2007052866A1
Application number: PCT/KR2006/000461
Authority: WO
Inventors: Jungmin Kim; Dooyoung Park
Original assignee: BSE Co Ltd
Current assignee: BSE Co Ltd
Priority date: 2005-10-31
Filing date: 2006-02-08
Publication date: 2007-05-10
Anticipated expiration: 2008-04-30
Also published as: KR100673843B1

Abstract

The present invention relates to an electret condenser microphone including a wind screen filter and an external frame for housing the same which reduces a wind noise while maintaining a small thickness. The electret condenser microphone in accordance with the present invention comprises a signal processor for converting an acoustic signal to an electrical signal, and a casing for covering the signal processor, the microphone comprising: a wind screen filter disposed at a first side of the casing, wherein the wind screen filter includes a metal mesh. In accordance with the electret condenser microphone in accordance with the present invention, the wind screen filter is manufactured using a metal mesh to replace the nylon or the urethane foam to maintain a high density and obtain a uniform density compared to the conventional product.

Description

ELECTRET CONDENSER MICROPHONE INCLUDING WIND

SCREEN FILTER AND EXTERNAL FRAME FOR BUILDING

THE ELECTRET CONDENSER MICROPHONE

Technical Field

[1] The present invention relates to an electret condenser microphone including a wind screen filter and an external frame for housing the same which reduces a wind noise while maintaining a small thickness. Background Art

[2] Recently, a high integration and a high precision have been achieved for high- technology electronic products. Accordingly, components constituting the high- technology electronic products also require the high integration and the high precision. Particularly, a size of a microphone inserted in a mobile phone or a radio communication device is drastically reduced to achieve a light weight and a miniaturization of the product. In addition, a distance between condensers are varied according to a variation in an acoustic signal for a miniaturization of the microphone, resulting in intensive development of an electret condenser microphone wherein the acoustic signal is converted to an electrical signal.

[3] Fig. 1 is a cross-sectional view illustrating a conventional electret condenser microphone, and Fig. 2 is a perspective view illustrating the conventional electret condenser microphone.

[4] Referring to Fig. 1 and 2, the conventional electret condenser microphone 100 comprises a cylinder type casing 111 having an acoustic hole 11 Ia, a conductive polar ring 112, a diaphragm 113, a spacer 114 and a insulation ring 115 sequentially stacked at a bottom surface of the casing 111, a back electret 116 often referred to as a back electrode disposed in the insulation ring 115 to be in contact with the spacer 114; the back electret 116 is insulated from the vertical line 11 by the insulation ring 115. The electret condenser microphone 100 also comprises a metal ring 117 inserted on an upper portion of the back electret 116 to be electrically connected to a printed circuit board 119. The printed circuit board 119 having a field effect transistor 118 mounted thereon is disposed on the metal ring 117. The polar ring 112 and the diaphragm 113 may be bonded as a single body to constitute a diaphragm. The casing 111 has a structure wherein the components are inserted therein and a curled surface of the casing 111 is in contact with an upper surface of the printed circuit board 119 to prevent a movement of the components. The conventional electret condenser microphone 100 comprises a wind screen filter 120 bonded to the casing 111 for removing a wind noise generated by a wind coming in through the acoustic hole I l ia of the casing 111.

[5] The wind noise refers to a noise generated by a wind when the microphone is placed in an air flow, i.e. in a space where the wind blows, and a noise generated when a man pronounces a plosive consonant is also a type of the wind noise. The wind noise degrades a quality of a voice recording or a voice call.

[6] In order to remove the wind noise, the conventional electret condenser microphone

100 includes the wind screen filter 120 disposed on a front surface. The wind screen filter 120 has a round shape similar to a surface of the casing 111 using a thin fabric of a nylon or a urethane foam, and disposed on one side of the casing 111.

[7] Since the conventional wind screen filter 120 is manufactured using the nylon or the urethane foam, a pore density is not uniform when a size is reduced, and the wind noise is not reduced substantially. Therefore, a product for replacing the conventional wind screen filter 120 consisting of a nylon or a urethane foam is needed. Disclosure of Invention Technical Problem

[8] It is an object of the present invention to provide an electret condenser microphone including a wind screen filter and an external frame for housing the same wherein the wind screen filter is manufactured using a metal mesh to replace the nylon or the urethane foam to maintain a high density and obtain a uniform density compared to the conventional product.

[9] It is another object of the present invention to provide an electret condenser microphone including a wind screen filter and an external frame for housing the same wherein the wind screen filter for removing the wind noise to provide an improved acoustic characteristic of the electret condenser microphone.

[10] It is yet another object of the present invention to provide an electret condenser microphone including a wind screen filter and an external frame for housing the same wherein a wind screen filter consisting of a metal mesh plated by a wet-plating to reduce a pore and to provide a high density wind screen filter.

[11] It is yet another object of the present invention to provide an electret condenser microphone including a wind screen filter and an external frame for housing the same wherein a metal mesh and a plated windscreen filter are disposed on a second frame to face the electret condenser microphone disposed on a first frame to maintain a predetermined distance between the electret condenser microphone and the wind screen filter. Technical Solution

[12] In order to achieve the above-described object, there is provided an electret condenser microphone comprising a signal processor for converting an acoustic signal to an electrical signal, and a casing for covering the signal processor, the microphone comprising: a wind screen filter disposed at a first side of the casing, wherein the wind screen filter includes a metal mesh.

[13] The casing comprises an acoustic hole for inflow of the acoustic signal, and the wind screen filter is disposed at a region where the acoustic hole of the casing is formed.

[14] The electret condenser microphone further comprises an adhesive for fixing the wind screen filter to the first side of the casing.

[15] The wind screen filter is one of a plain weave type, a dutch weave type, a plain dutch weave type, a twilled dutch weave type, a crimped weave and a twist weave type.

[16] The wind screen filter comprises one of a gold, a silver, a copper, a nickel and a stainless steel.

[17] The wind screen filter is plated.

[18] The wind screen filter is plated via a wet-plating.

[19] The wind screen filter is plated with one of a gold, a silver, a copper and a nickel.

[20] There is also provided an electret condenser microphone comprising a signal processor including a printed circuit board for converting an acoustic signal to an electrical signal, the printed circuit board including an acoustic hole for inflow of the acoustic signal, and a casing for covering the signal processor, the microphone comprising: a wind screen filter disposed on the printed circuit board including the acoustic hole, wherein the wind screen filter includes a metal mesh.

[21] The wind screen filter is fixed on the printed circuit board, and further comprising an adhesive for insulating the wind screen filter from the printed circuit board.

[22] There is also provided an external frame for mounting an electret condenser microphone, the external frame comprising: an electret condenser microphone comprising a signal processor for converting an acoustic signal to an electrical signal, and a casing for covering the signal processor; a first frame for mounting the electret condenser microphone; a second frame coupled to the first frame, wherein second frame comprises a wind screen filter consisting of a metal mesh disposed at a region opposite to that of the electret condenser microphone.

[23] The second frame comprises a groove for disposing the wind screen filter.

[24] The electret condenser microphone further comprises an adhesive for fixing the wind screen filter to the second frame.

[25]

Advantageous Effects [26] In accordance with electret condenser microphone including wind screen filter and external frame of the present invention, the wind screen filter is manufactured using a metal mesh to replace the nylon or the urethane foam to maintain a high density and obtain a uniform density compared to the conventional product. [27] In accordance with electret condenser microphone including wind screen filter and external frame of the present invention, the wind screen filter for removing the wind noise to provide an improved acoustic characteristic of the electret condenser microphone. [28] In accordance with electret condenser microphone including wind screen filter and external frame of the present invention, a wind screen filter consisting of a metal mesh plated by a wet-plating to reduce a pore and to provide a high density wind screen filter. [29] In accordance with electret condenser microphone including wind screen filter and external frame of the present invention, a metal mesh and a plated windscreen filter are disposed on a second frame to face the electret condenser microphone disposed on a first frame to maintain a predetermined distance between the electret condenser microphone and the wind screen filter.

Brief Description of the Drawings [30] Fig. 1 is a cross-sectional view illustrating a conventional electret condenser microphone. [31] Fig. 2 is a perspective view illustrating the conventional electret condenser microphone. [32] Fig. 3 is a perspective view illustrating a wind screen filter in accordance with a first embodiment of the present invention. [33] Figs. 4 through 7 are diagrams illustrating various structures the wind screen filter of Fig. 3. [34] Fig. 8 is a cross-sectional view illustrating a wind screen filter in accordance with a second embodiment of the present invention. [35] Fig. 9 is a cross-sectional view illustrating an electret condenser microphone in accordance with a first embodiment of the present invention. [36] Fig. 10 is a perspective view illustrating a disassembled electret condenser microphone of Fig. 9. [37] Fig. 11 is a cross-sectional view illustrating an electret condenser microphone in accordance with a second embodiment of the present invention. [38] Figs. 12 and 13 are graphs illustrating an acoustic characteristic of the conventional electret condenser microphone and the electret condenser microphone in accordance with the second embodiment of the present invention. [39] Fig. 14 is a diagram illustrating an external frame including the electret condenser microphone in accordance with the present invention. Best Mode for Carrying Out the Invention

[40] Fig. 3 is a perspective view illustrating a wind screen filter in accordance with a first embodiment of the present invention.

[41] Referring to Fig. 3, a wind screen filter 30 in accordance with an embodiment of the present invention is weaved into a mesh using a metal thread having a diameter of a few D. Various metals such as gold, silver, copper may be used for the mesh. A metal alloy of various metals and a stainless steel are generally used in order to reinforce a strength and a tension. Since the stainless steel is not easily oxidized, is robust to a corrosion, and is not easily magnetized, the stainless steel is less affected by an environment or a manufacturing process of the electret condenser microphone. Therefore, a normal use or a reuse is possible since the stainless steel is not oxidized even if a high temperature heat is applied during a reflow wherein a SMD (Surface Mount Device) method is applied to mount the condenser microphone on a main board or remove the condenser microphone from the main board.

[42] On the other hand, as shown in Figs. 4 through 7, the wind screen filter 30 may be manufactured using various metal weaving products such as a plain weave mesh, a twilled weave mesh, a dutch weave mesh and a twilled dutch weave mesh, and a twist weave mesh and a crimped weave mesh may also be used.

[43] Referring to Fig. 4, the plain weave metal mesh is manufactured such that a vertical line 11 and a horizontal line 13 cross each other orthogonally. The plain weave metal mesh may be a square type or a rectangular type according to a distance between the vertical lines 11 and the horizontal lines 13. A pore 15 is larger than other metal meshes as shown.

[44] Referring to Fig. 5, since the twilled weave metal mesh has a pore 18 smaller than that of the plain weave metal mesh shown in Fig. 4a, the twilled weave metal mesh is manufactured to be denser than the plain weave metal mesh. The twilled weave metal mesh is manufactured by crossing two of vertical lines 16 and two of the horizontal line 17.

[45] Referring to Fig. 6, the dutch weave metal mesh (or a plain dutch weave metal mesh) is manufactured by increasing a distance between the vertical lines 19 and crossing two the horizontal line 20 for a single vertical line 19. The dutch weave metal mesh is much more dense and has small pore rate compared to the plain weave metal mesh.

[46] Referring to Fig. 7, the twilled dutch weave metal mesh is manufactured such that the vertical line 22 is attached at both sides of the horizontal line 21 wherein both the twilled weave and the dutch weave are applied. The twilled dutch weave metal mesh has a density two times higher than that of the twilled weave metal mesh. Mode for the Invention

[47] Fig. 8 is a cross-sectional view illustrating a wind screen filter in accordance with a second embodiment of the present invention.

[48] Referring to Fig. 8, a wind screen filter 50 in accordance with the second embodiment of the present invention is manufactured by plating the wind screen filter 30 in accordance with the first embodiment of the present invention. The wind screen filter 50 comprises horizontal line 5a and 5b weaved horizontally, a horizontal line 13 weaved to cross the horizontal line 5a and 5b, a plating material 7 plated on a metal mesh weaved by the horizontal line 5a and 5b and the horizontal line 13, and a pore 9 formed between the plated wind screen filter 50. The wind screen filter 50 has a more dense weaving by plating the pore formed in the wind screen filter 30 in accordance with the first embodiment of the present invention which includes the plain weave mesh, the twilled weave mesh, the dutch weave mesh and the twilled dutch weave mesh to reduce a size of the pore. Therefore, the plated wind screen filter 50 in accordance with the second embodiment of the present invention may achieve a high density weaving to reduce the wind noise. When the plated wind screen filter 50 in accordance with the second embodiment of the present invention is manufactured using the stainless steel, it is preferable that the plating material 7 is plated via a wet- plating using the nickel which has a good plating characteristic for the stain less and relatively inexpensive. While the metal is plated mainly on a surface of the metal mesh 2, i.e. an exposed portion of the metal mesh 2 when the dry-plating such as a sputtering is used, the metal is plated uniformly including a gap between the mesh when the wet- plating is used. A porous rate of the plated wind screen filter 50 may be adjusted using the wet-plating to increase a reduction efficiency of the wind noise of the plated wind screen filter 50. That is, a density of the plated wind screen filter 50 may be adjusted by adjusting an amount of the plating material to achieve the high density of the metal mesh. Metal mesh consisting of other metals such as gold, silver, copper and aluminum may also be plated by nickel.

[49] Fig. 9 is a cross-sectional view illustrating an electret condenser microphone in accordance with the first embodiment of the present invention, and Fig. 10 is a perspective view illustrating an internal structure of the electret condenser microphone of Fig. 9. The wind screen filter in accordance with the first and the second embodiments are attached to the electret condenser microphone shown in Figs. 9 and 10.

[50] Referring to Figs. 9 and 10, the electret condenser microphone in accordance with the embodiment of the present invention comprises a signal processor 200 for converting an acoustic signal to an electrical signal, a casing 210 for covering the signal processor 200, a wind screen filter 230 consisting of a metal mesh attached to a front surface of the casing 210 having an acoustic hole 211 to reduce a wind noise.

[51] The signal processor 200 converts the acoustic signal coming through the acoustic hole 211 of the casing 210 to the electrical signal. The signal processor 200 comprises a diaphragm 203 having a film 201 and a polar ring 202 as a single body, a spacer 204 and an insulation ring 205 sequentially stacked at a bottom surface of the casing 210, a back electret 206 inserted in the insulation ring 205 and contacting the spacer 204, and a metal ring 207 disposed inside of the insulation ring 205.

[52] The diaphragm 203 is formed by depositing a metal on a high molecular film. The diaphragm 203 is assembled such that the diaphragm 203 maintains a small gap from the casing 210 by the polar ring 202, and vibrates according to the acoustic wave coming in through the acoustic hole 211 of the casing 210.

[53] The back electret 206 is manufactured by punching a panel wherein an organic film is bonded to a metal plate by a press mold. The back electret 206 comprises upper and lower copper plates electrically connected to each other, and is disposed at an outer portion of the insulation ring 205 to be insulated from the casing 210. The back electret 206 is disposed opposite to the diaphragm 203 having the metal ring 207 therebetween so that capacitance varying according to the vibration of the diaphragm 203 generated by the acoustic wave coming in may be detected.

[54] A metal ring 207 electrically connects a gate of a field effect transistor 208 and the back electret 206. The metal ring 207 is manufactured by press- punching a brass and plating the same with gold.

[55] A printed circuit board 219 functions as an output terminal by wiring a circuit with a conductive material, and also functions as a front cover of the microphone by being disposed on and supported by the metal ring 207. The field effect transistor 218 mounted on the printed circuit board 219 functions as an impedance converter by outputting the variance in the capacitance detected by the back electret 206 as a variance in an impedance and then transmitting the variance to an amplifier (not shown).

[56] The casing 210 has a hollow inside. The casing 210 comprises the acoustic hole

211 for applying the acoustic pressure from a back surface, outer portion of the casing 210 is curled toward inside to contact the printed circuit board 219, thereby supporting 219.

[57] The wind screen filter 230, as described in the first and the second embodiments, is weaved to have a form of a metal mesh or a plated metal mesh. The wind screen filter 230 is disposed at upper portion of a region where the acoustic hole 211 of the casing 210 is formed. The wind screen filter 230 may be fixed to the casing 210 using an adhesive or a double-side adhesive, and may be fixed by welding or soldering a region that is in contact with the casing 210. In another embodiment, when the acoustic hole 213 is formed on the printed circuit board 220 instead of the casing 210, the wind screen filter 230 may be fixed on the printed circuit board 220 using the adhesive. The adhesive may also insulate the printed circuit board 220 form the wind screen filter 230. The adhesive may be a double-side adhesive tape.

[58] An acoustic characteristic of the conventional electret condenser microphone and the electret condenser microphone in accordance with the second embodiment of the present invention is shown in Fig. 12. Fig. 13 is a graph illustrating an acoustic characteristic of the conventional electret condenser microphone including a conventional wind screen filter consisting of a nylon or urethane foam. Specifically, a wind noise level of the electret condenser microphone in accordance with the second embodiment of the present invention is -102dB at 100Hz as shown in Fig. 12, and a wind noise level of the conventional electret condenser microphone is -94.7dB at 100Hz as shown in Fig. 13. That is, the electret condenser microphone in accordance with the second embodiment of the present invention has the improved acoustic characteristic of 7dB over the conventional electret condenser microphone.

[59] On the other hand, when the electret condenser microphone is manufactured as a directional microphone, the electret condenser microphone may include a phase delay device inside the electret condenser microphone. Since the phase delay device overlaps with the wind screen filter to delay the phase of already delayed phase, a directional characteristic of the directional microphone is deteriorated or may destroy the directional characteristic of the directional microphone in some cases. Therefore, it is preferable that the electret condenser microphone in accordance with the present invention is manufactured as an omni-directional microphone considering an arrangement of the wind screen filter.

[60] Fig. 14 is a diagram illustrating an external frame including the electret condenser microphone in accordance with the present invention.

[61] Referring to Fig. 14, an external frame in accordance with the embodiment of the present invention comprises a first external frame 301, a second external frame 302, an electret condenser microphone 300 disposed at first side of the first external frame 301, and a wind screen filter 330 disposed on the second external frame 302 so as to face an acoustic hole 311 of a casing 310 of the electret condenser microphone 300.

[62] The first external frame 301 may be attached using the electret condenser microphone 300 and a surface mount technology, the second external frame 302 comprises a groove 302a for disposing the wind screen filter 330. Industrial Applicability [63] The external frame wherein the electret condenser microphone is attached in accordance with the embodiment of the present invention may comprise a gap between the electret condenser microphone 300 disposed on the first external frame 301 and the wind screen filter 330 disposed on the second external frame 302. The gap improves a characteristic of removing the wind noise of the wind screen filter 330.

[64]

Claims

[I] An electret condenser microphone comprising a signal processor for converting an acoustic signal to an electrical signal, and a casing for covering the signal processor, the microphone comprising: a wind screen filter disposed at a first side of the casing, wherein the wind screen filter includes a metal mesh. [2] The microphone in accordance with claim 1, wherein the casing comprises an acoustic hole for inflow of the acoustic signal, and wherein the wind screen filter is disposed at a region where the acoustic hole of the casing is formed. [3] The microphone in accordance with one of claims 1 and 2, further comprising an adhesive for fixing the wind screen filter to the first side of the casing. [4] The microphone in accordance with one of claims 1 and 2, wherein the wind screen filter is one of a plain weave type, a dutch weave type, a plain dutch weave type, a twilled dutch weave type, a crimped weave and a twist weave type. [5] The microphone in accordance with one of claims 1 through 3, wherein the wind screen filter comprises one of a gold, a silver, a copper, a nickel and a stainless steel. [6] The microphone in accordance with one of claims 1 and 2, wherein the wind screen filter is plated. [7] The microphone in accordance with claim 6, wherein the wind screen filter is plated via a wet-plating. [8] The microphone in accordance with claim 6, wherein the wind screen filter is plated with one of a gold, a silver, a copper and a nickel. [9] An electret condenser microphone comprising a signal processor including a printed circuit board for converting an acoustic signal to an electrical signal, the printed circuit board including an acoustic hole for inflow of the acoustic signal, and a casing for covering the signal processor, the microphone comprising: a wind screen filter disposed on the printed circuit board including the acoustic hole, wherein the wind screen filter includes a metal mesh. [10] The microphone in accordance with claim 9, wherein the wind screen filter is fixed on the printed circuit board, and further comprising an adhesive for insulating the wind screen filter from the printed circuit board.

[I I] An external frame for mounting an electret condenser microphone, the external frame comprising: an electret condenser microphone comprising a signal processor for converting an acoustic signal to an electrical signal, and a casing for covering the signal processor; a first frame for mounting the electret condenser microphone; a second frame coupled to the first frame, wherein second frame comprises a wind screen filter consisting of a metal mesh disposed at a region of the second frame facing a region where the electret condenser microphone is disposed. [12] The microphone in accordance with claim 11, wherein the second frame comprises a groove for disposing the wind screen filter. [13] The microphone in accordance with one of claims 12 and 13, further comprising an adhesive for fixing the wind screen filter to the second frame. [14] The microphone in accordance with one of claims 11 and 12, wherein the wind screen filter is plated. [15] The microphone in accordance with claim 14, wherein the wind screen filter is plated via a wet-plating.