microphone

Abstract

This improves the characteristics of microphones equipped with MEMS microphones or similar electroacoustic conversion elements. [Solution] The shape of the microphone holder 211 that fixes the MEMS microphone unit 22 to the front end surface is a truncated cone shape that narrows from back to front with the front-to-back direction as the axis, and the side surface is tapered, approaching the axis from back to front. By making the structure around the MEMS microphone unit 22 smaller, the peak value of the resonant frequency can be reduced, and the reflection of acoustic signals (sound waves) arriving from the front towards the MEMS microphone unit 22 can be suppressed.

Description

Technical Field

[0001] The present invention relates to a technology for improving the characteristics of a microphone.

Background Art

[0002] As a microphone, a microphone using a MEMS (Micro Electro Mechanical Systems) microphone as an electroacoustic conversion element that converts an acoustic signal (sound wave) in space into an electrical signal is known. Further, as such a microphone, a microphone having a cylindrical shape and having a MEMS microphone disposed at the tip of the cylindrical shape is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] } When the structure around the MEMS microphone becomes large, the components of the acoustic signal due to reflection, diffraction, interference acting on the MEMS microphone, and wave phenomena in which these are combined become large, which may cause deterioration of the characteristics of the microphone. For example, an increase in the peak value of the resonance frequency and a change in the peak frequency can be cited. On the other hand, if the shape of the microphone is made such that the size of the structure around the MEMS microphone becomes small, it becomes difficult to physically hold the MEMS microphone. Therefore, an object of the present invention is to improve the characteristics of a microphone provided with an electroacoustic conversion element such as a MEMS microphone.

Means for Solving the Problems

[0005] To achieve the above objectives, the present invention provides a microphone for sound collection, which is equipped with a holding portion at its front end to which an electroacoustic conversion element that converts an acoustic signal into an electrical signal is fixed, with the sound collection direction of the microphone being the forward direction and the opposite direction being the rear direction. However, the size of the holding portion in the direction perpendicular to the front-rear direction is larger at the rear end than at the front end, and at any position in the front-rear direction between the front and rear ends, the size of the position in the direction perpendicular to the front-rear direction is greater than or equal to the size of the position in the direction perpendicular to the front-rear direction at a position further forward.

[0006] Alternatively, the present invention provides a configuration in which the holding portion has a shape in which the rear end is larger in the direction perpendicular to the front-rear direction than the front end, and the area between the front end and the rear end is a smooth surface. In the microphone described above, the holding portion may have a shape in which the size gradually increases from the front end to the rear end in the direction perpendicular to the front-rear direction. Alternatively, in the microphone described above, the holding portion may have the shape of a frustoconical pyramid with the front-to-back direction as its axial direction, and the diameter increasing from front to rear. Alternatively, in the microphone described above, the holding portion may consist of a rear portion having a shape in which the size gradually increases in the front-to-rear direction and in the direction perpendicular to the front-to-rear direction from the front end to the rear end, and a front portion having a cylindrical shape that extends in the front-to-rear direction and is connected to the rear portion without any steps.

[0007] Herein, the microphone may be provided with a main body having a holding portion and a cap connecting portion connected to the rear end of the holding portion, and a cap portion. The cap portion is connected to the front of the cap connecting portion of the main body, and the space between the cap portion and the holding portion on which the electroacoustic conversion element is fixed houses the holding portion, shielding the holding portion on which the electroacoustic conversion element is fixed from the forward direction and from directions perpendicular to the front-rear direction. Furthermore, the cap portion has high acoustic transparency in the forward direction and from directions perpendicular to the front-rear direction.

[0008] In this case, the cap portion may have a cylindrical shape and form a cylindrical framework, with gaps on the front end surface and sides of the cylindrical shape, and a mesh that closes the gaps on the front end surface and sides of the frame. Here, the electroacoustic conversion element described above may be a MEMS (Micro Electro Mechanical Systems) microphone. These microphones allow for minimizing the structure surrounding the electroacoustic converter, thereby suppressing the magnitude of the peak value of the resonant frequency and reducing the reflection of the acoustic signal (sound wave) towards the electroacoustic converter, thus suppressing the degradation of the microphone's characteristics. [Effects of the Invention]

[0009] As described above, the present invention makes it possible to improve the characteristics of a microphone equipped with an electroacoustic conversion element such as a MEMS microphone. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a microphone according to an embodiment of the present invention. [Figure 2] This figure shows the head portion according to an embodiment of the present invention. [Figure 3] This figure shows the cap portion of an embodiment of the present invention. [Figure 4] This is a comparative diagram illustrating the effects of embodiments of the present invention. [Figure 5] This figure shows another example of a head portion according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below. Figure 1 shows the microphone according to this embodiment. As shown in the diagram, the direction in which the microphone picks up sound is defined as the forward direction and the opposite direction as the rear direction within the axial direction of the microphone. Figure 1a shows the front of the microphone, Figure 1b shows the side of the microphone, and Figure 1c shows the rear of the microphone. Figure 1d shows the microphone viewed at an angle. As shown in the figure, the microphone has an overall cylindrical shape and is configured by connecting a cap portion 1, a head portion 2, and a body portion 3 in that order from front to back. The head unit 2 is equipped with a MEMS (Micro Electro Mechanical Systems) microphone, which is an electroacoustic conversion element that converts acoustic signals (sound waves) in space into electrical signals. The body unit 3 also contains a preamplifier that amplifies the electrical signal output by the MEMS microphone in the head unit 2, and the output of the preamplifier is output externally from the terminal at the rear end of the body unit 3 as either an analog or digital output. The cap unit 1 is connected to the front of the head unit 2 to protect the MEMS microphone in the head unit 2.

[0012] Next, the configuration of the head unit 2 is shown in Figure 2a. Figure 2a1 shows the front view of the head unit 2, Figure 2a2 shows the side view of the head unit 2, and Figure 2a3 shows the rear view of the head unit 2. Figure 2a4 shows the cross-section of the head unit 2 along the cross-sectional line AA in Figure 2a1, and Figure 2a5 shows a perspective view of the head unit 2. As shown in the figure, the head unit 2 comprises a head unit body 21 and a MEMS microphone unit 22 fixed to the front end of the head unit body 21. The MEMS microphone unit 22 is a unit in which a MEMS microphone 222 is mounted on the rear surface of a substrate 221, as shown in Figure 2b1 (side view) and Figure 2b2 (cross-section along cross-sectional line AA in Figure 2a1). Note that the substrate 221 may be a flexible printed circuit board. The MEMS microphone 222 includes a MEMS sensor 2221 that converts the intensity of an acoustic signal reaching through a sound hole 2211 provided in a substrate 221 into a change in an electrically detectable physical quantity such as capacitance, and a detection circuit chip 2222 that converts the change in the physical quantity of the MEMS sensor 2221 into an electrical signal and outputs it as the output of the MEMS microphone 222.

[0013] Note that the MEMS sensor 2221 alone may be referred to as the "MEMS microphone", but the MEMS sensor 2221 does not function as an electroacoustic conversion element by itself. Returning to Fig. 2a, on the head portion main body 21, a microphone holding portion 211, a cap connecting portion 212, and a body connecting portion 213 are formed in order from the front to the back. The cap connecting portion 212 has a hollow cylindrical shape, and a male thread is provided on its outer periphery. Then, by screwing this male thread with a female thread provided on the inner periphery of the rear end of the cap portion 1, the cap portion 1 and the head portion 2 are connected. Also, the body connecting portion 213 has a hollow cylindrical shape, and a female thread is provided on its inner periphery. Then, by screwing this female thread with a male thread provided on the outer periphery of the front end of the body portion 3, the head portion 2 and the body portion 3 are connected. And the microphone holding portion 211, as a whole, has a frustum shape that narrows from the back to the front with the front-rear direction as the axial direction, and the side surface of the microphone holding portion 211 has a tapered shape that approaches the axis from the back to the front. Therefore, the reflection direction of the acoustic signal (sound wave) arriving from the front by the side surface of the microphone holding portion 211 is the outer peripheral direction. Also, since the side surface of the microphone holding portion 211 is smooth, irregular reflections due to sides, corners, etc. do not occur.

[0014] Also, the diameter of the rear end of the microphone holding portion 211 is approximately equal to the diameter of the front end portion of the cap connecting portion 212. As shown in Fig. 2c, which shows the perspective view of the head unit body 21 alone, a stepped hole 2111 for mounting the MEMS microphone unit is provided on the front end surface of the microphone holding portion 211. The MEMS microphone unit 22 is fixed to the microphone holding portion 211 with an adhesive or the like in such a manner that the outer edge portion of the substrate 221 is fitted into the step of the hole 2111 for mounting the MEMS microphone unit. However, it may also be fixed by adhering the outer edge portion of the rear surface of the substrate 221 to the front end surface of the microphone holding portion 211 without providing the step of the hole 2111 for mounting the MEMS microphone unit.

[0015] A part of the substrate 221 of the MEMS microphone unit 22 extends to the outside of the front end surface of the microphone holding portion 211 when viewed in the front-rear direction, and a cable 23 for transmitting an electrical signal between the MEMS microphone 222 and the preamplifier of the body portion 3 is connected to this portion of the substrate 221.

[0016] Next, the rear part of the front end surface of the microphone holding portion 211 is approximately hollow, and a support portion 2112 is provided in a form standing up from the inner wall in this hollow portion so as to support the rear surface of the MEMS microphone 222 of the MEMS microphone unit 22 via a support material 2113. However, the MEMS microphone 222 may not be supported by the support portion 2112 and the support material 2113.

[0017] Also, a cable hole 2114 communicating with the hollow of the microphone holding portion 211 is provided on the side surface of the microphone holding portion 211, and an electrical signal between the substrate 221 of the MEMS microphone unit 22 and the preamplifier of the body portion 3 is transmitted through the cable 23 passing through the cable hole 2114, the hollow of the microphone holding portion 211, the hollow of the cap connecting portion 212, and the hollow of the body connecting portion 213.

[0018] Next, Fig. 3 shows the positional relationship between the cap portion 1 and the head portion 2. Fig. 3a shows the perspective view of the cap portion 1 and the head portion 2 with the cap portion 1 made semi-transparent, and Fig. 3b shows the cross-section of the cap portion 1 and the head portion 2 along the cross-section line A - A of Fig. 2a1. As shown in the figure, the cap portion 1 is connected to the head portion 2 in such a way that only the MEMS microphone unit 22 and the microphone holding portion 211 are housed within the space enclosed by the cap connecting portion 212 and the cap portion 1. The front end surface and side surfaces of the cap portion 1, which form the boundary wall of the aforementioned space, are approximately made of a mesh with high acoustic transparency (for example, a metal mesh). Unwanted acoustic signals (sound waves) that pass through the cap portion 1 from the front, travel into the space, and proceed behind the MEMS microphone unit 22 are reflected outward by the side surfaces of the microphone holding portion 211 as described above, and continue to the outside of the cap portion 1. Therefore, the degradation of the microphone's characteristics due to the reflection of these unwanted acoustic signals (sound waves) is suppressed. In Figures 3a and 3b, the mesh portion of the cap 1, indicated by the grid-like shading, represents the mesh part, while the white portion represents the rigid frame part. However, the cap portion 1 may consist only of a rigid frame, or it may have a shape similar to the protective grid of a typical measuring microphone.

[0019] Here, Figures 4a, b, and c are diagrams to illustrate the effects of this embodiment by comparison. These diagrams show the case where the MEMS microphone unit 22 is fixed so that it fits within the front end surface of the microphone holder 211 when viewed in the front-rear direction, in order to facilitate comparison. Figure 4a shows a perspective view and a side view of the head unit body 21 when the microphone holding part 211 is frustoconical in shape, as in this embodiment. Figures 4b and 4c show a perspective view and a side view of the head unit body 21 when the microphone holding part 211 is cylindrical. As shown in Figure 4b, when the microphone holder 211 is cylindrical with the same diameter as the front end of the cap connecting portion 212, the structure around the MEMS microphone unit 22 is larger compared to when the microphone holder 211 in this embodiment shown in Figure 4a is truncated cone-shaped, resulting in a larger peak value of the resonant frequency and a deterioration in the microphone characteristics compared to this embodiment.

[0020] On the other hand, as shown in Figure 4c, if the microphone holder 211 is cylindrical with a smaller diameter than the front end of the cap connecting portion 212, the surrounding structure of the MEMS microphone unit 22 can be made smaller. However, unlike this embodiment in which reflection is directed outward as described above, reflection of the acoustic signal (sound wave) directed forward by the front end surface of the cap connecting portion 212, as well as reflection in unspecified directions due to the presence of edges and corners, occurs, resulting in a larger component of the acoustic signal due to reflection acting on the MEMS microphone 222, leading to a deterioration of the microphone's characteristics.

[0021] Hereinafter, the shape of the microphone holder 211 that fixes the MEMS microphone unit 22 was set to a frustoconical shape as shown in Figure 4a. However, as shown in the perspective view and side view in Figure 5a, it may also be a shape in which a cylinder of the same diameter as the front end face of the frustoconical is coaxially connected to the front end face of the frustoconical.

[0022] Alternatively, the shape of the microphone holder 211 may be changed to a shape in which the side surface of the frustum of the cone is curved inward to form a smooth surface, as shown in Figure 5b; or to a shape in which the side surface of the frustum of the cone is curved outward to form a smooth surface, as shown in Figure 5c; or to a shape in which part of the shape of the side surface of the frustum of the cone is curved outward and the other part is curved inward to form a smooth surface, as shown in Figure 5d.

[0023] Furthermore, in the above embodiment, the body 3 may be provided with a correction filter along with the preamplifier section to correct the input or output signal of the preamplifier section so that the microphone characteristics become the desired characteristics. Furthermore, although the above embodiments have described the MEMS microphone unit 22 being fixed to the microphone holder 211 with adhesive or the like, the method of fixing is arbitrary. For example, if the cap portion 1 is fixedly connected to the head portion 2, the MEMS microphone unit 22 may be fixed to the microphone holder 211 by sandwiching the MEMS microphone unit between the cap portion 1 and the front end surface of the microphone holder 211.

[0024] Furthermore, the microphone holder 211 may be made from a synthetic / chemical resin that has been molded. Alternatively, the MEMS microphone unit 22 may be fixed to the microphone holder 211 by integrating it with the microphone holder 211 and performing the molding process. In this embodiment, the diameter of the microphone is preferably 1 inch, 1 / 2 inch, or 1 / 4 inch, in accordance with the IEC 61094-4:1995 standard for measuring microphones. [Explanation of Symbols]

[0025] 1...Cap part, 2...Head part, 3...Body part, 21...Head part main body, 22...MEMS microphone unit, 23...Cable, 211...Microphone holder part, 212...Cap connector part, 213...Body connector part, 221...Circuit board, 222...MEMS microphone, 2111...Hole for mounting MEMS microphone unit, 2112...Support part, 2113...Support material, 2114...Hole for cable, 2211...Sound hole, 2221...MEMS sensor, 2222...Detection circuit chip.

Claims

1. A microphone that picks up sound, The microphone has a mounting section at its front end to which an electroacoustic conversion element, which converts acoustic signals into electrical signals, is fixed, with the microphone's sound pickup direction being forward and the opposite direction being backward. The microphone is characterized in that the holding portion has a larger size at the rear end than at the front end in the direction perpendicular to the front-rear direction, and at any position in the front-rear direction between the front end and the rear end, the size at that position in the direction perpendicular to the front-rear direction is greater than or equal to the size at a position further forward in the front-rear direction.

2. A microphone that picks up sound, The microphone has a mounting section at its front end to which an electroacoustic conversion element, which converts acoustic signals into electrical signals, is fixed, with the microphone's sound pickup direction being forward and the opposite direction being backward. The microphone is characterized in that the holding portion has a shape in which the rear end is larger in the direction perpendicular to the front-rear direction than the front end, and the area between the front end and the rear end is a smooth surface.

3. A microphone according to claim 2, The microphone is characterized in that the holding portion has a shape in which the size gradually increases from the front end to the rear end in both the front-to-back direction and the direction perpendicular to it.

4. A microphone according to claim 2, The microphone is characterized in that the holding portion has the shape of a frustoconical pyramid, with the front-to-back direction as its axial direction, and the diameter increasing from front to back.

5. A microphone according to claim 1, The microphone is characterized in that the holding portion comprises a rear portion having a shape in which the size gradually increases in the front-to-rear direction and in the direction perpendicular to the front-to-rear direction from the front end to the rear end, and a front portion having a cylindrical shape that extends in the front-to-rear direction and is connected to the rear portion without any steps.

6. A microphone according to claim 1, 2, 3, 4, or 5, It has a main body and a cap, The main body portion has a holding portion and a cap connecting portion connected to the rear end of the holding portion. The cap portion is connected to the front of the cap connecting portion of the main body, and the space between the cap connecting portion and the holding portion on which the electroacoustic conversion element is fixed is housed there, and the holding portion on which the electroacoustic conversion element is fixed is shielded in the forward direction and in the direction perpendicular to the front-rear direction, The cap portion of the microphone is characterized by high acoustic transparency in the forward direction and in directions perpendicular to the front-to-back direction.

7. A microphone according to claim 6, The microphone is characterized in that the cap portion has a cylindrical shape, and the cap portion has a frame that forms the framework of the cylindrical shape, with gaps on the front end surface and sides of the cylindrical shape, and a mesh that closes the gaps on the front end surface and sides of the frame.

8. A microphone according to claim 1, 2, 3, 4, or 5, The aforementioned electroacoustic conversion element is a microphone characterized by being a MEMS (Micro Electro Mechanical Systems) microphone.

9. A microphone according to claim 6, The aforementioned electroacoustic conversion element is a microphone characterized by being a MEMS (Micro Electro Mechanical Systems) microphone.

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