Acoustic device

Abstract

To provide an acoustic device capable of detecting sound in a wide frequency band by a microphone.SOLUTION: In an acoustic device 1, a holder 10 having a through hole 11 is provided inside a support body 2, and a microphone 5 is housed inside the through hole 11 of the holder 10. Inside the through hole 11, a sound collection space 12 is formed in front of the front surface portion of the microphone 5 (the 6b of the front surface portion of the case 6 formed of a thin metal plate). The sound collection space 12 is a pipe line whose cross-sectional shape perpendicular to the center line O is uniform from the front surface part to the sound collection hole 12a, does not constitute a Helmholtz resonator, does not function as an acoustic low-pass filter, and can secure a wide frequency band of sound detected by the microphone.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an acoustic device that collects sound using a microphone supported by a support. [Background technology]

[0002] Figures 1 to 3 of Patent Document 1 describe an electronic device in which a microphone is housed within a housing. This electronic device has a microphone and a silicone rubber packing that covers the microphone held inside a sleeve that is integral with the housing. A thin film portion that is thin enough to be used as an electro-acoustic transducer is formed on the packing, and the opening area of ​​the microphone is covered with the thin portion. A small-diameter sound pickup hole is formed in the housing at a position opposite the thin portion, and a space is formed between the thin portion and the sound pickup hole. Air vibrations that enter the housing through the sound pickup hole vibrate the thin portion, and the air vibrations created by the vibration of the thin portion are detected by the microphone. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-179437 Summary of the Invention [Problem to be solved by the invention]

[0004] The electronic device described in Patent Document 1 has a Helmholtz resonator configured with a space located in front of the microphone and a small-diameter sound pickup hole that leads to the external space. This small Helmholtz resonator functions as an acoustic low-pass filter that attenuates sound energy in a certain wavelength band centered on the resonance frequency. Therefore, the electronic device described in Patent Document 1 has the problem that the frequency band of air vibrations that can be detected by the microphone is narrowed.

[0005] SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide an acoustic device that can sense sounds over a wide frequency range using a microphone and that is easy to assemble. [Means for solving the problem]

[0006] The present invention provides an acoustic device in which a microphone is supported by a support, A sound collection space is formed in front of the microphone, and a front end of the sound collection space is a sound collection hole that communicates with an external space, The sound pickup space is characterized in that the cross-sectional shape perpendicular to the center line extending forward and backward is uniform from the front portion to the sound pickup hole.

[0007] For example, the cross-sectional shape is circular.

[0008] In the acoustic device of the present invention, the support body is provided with a holder having a through hole formed therein, and the microphone is held in the through hole, The through-hole may be configured so that a region in front of the front surface of the microphone serves as the sound pickup hole.

[0009] The holder is preferably made of an elastic material.

[0010] In the acoustic device of the present invention, the sound pickup hole is preferably covered with a lid having a number of passage holes. [Effects of the Invention]

[0011] In the acoustic device of the present invention, the cross-sectional shape of the sound collection space formed in front of the microphone is uniform from the front of the microphone to the sound collection hole, so a Helmholtz resonator is not formed and the device does not function as an acoustic low-pass filter, thereby widening the frequency band of sounds that can be detected by the microphone.

[0012] In the acoustic device of the present invention, for example, a through hole with a uniform cross-sectional shape is formed in a holder made of an elastic material, and a microphone is held within this through hole, thereby making it possible to form a sound collection space with a uniform cross-sectional shape between the front part of the microphone and the sound collection hole through a simple assembly process. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a longitudinal sectional view showing the overall structure of an acoustic device according to an embodiment of the present invention; [Figure 2] 1 is an exploded perspective view showing the microphone and holder; [Figure 3] FIG. 2 is a longitudinal sectional view showing an acoustic device of a comparative example; [Figure 4] FIG. 1 is an explanatory diagram illustrating the difference in acoustic characteristics between an acoustic device according to an embodiment of the present invention and an acoustic device according to a comparative example; DETAILED DESCRIPTION OF THE INVENTION

[0014] 1, the Z1-Z2 direction is the front-to-rear direction, with the Z1 direction being the front and the Z2 direction being the downward direction. The acoustic device 1 has a support body 2. The support body 2 is a housing having a bottom wall 2a and a cylindrical side wall 2b rising from the bottom wall 2a. A front wall 2c is fixed to an opening in the front of the side wall 2b, covering part of it.

[0015] A support protrusion 3 is provided inside the bottom wall 2a of the support 2, and a circuit board 4 is fixed in front of the support protrusion 3. A microphone 5 is mounted on the front surface of the circuit board 4. As shown in Figure 2, the microphone 5 has a case 6 made of a thin metal plate. The case 6 has a cylindrical portion 6a and a front portion 6b that covers the front of the cylindrical portion 6a. Numerous detection holes 7 are formed in the front portion 6b. The front portion 6b is the "front portion" of the microphone 5. The microphone 5 is a capacitor type, and the case 6 contains an insulator, a back plate fixed to the insulator, and a diaphragm located between the back plate and the detection holes 7. The back plate is a fixed electrode, and terminals extending rearward from the back plate are inserted into through holes formed in the circuit board 4 and soldered to an electrode layer formed on the circuit board 4. The capacitor type microphone 5 detects changes in electrostatic capacitance between the back plate and the diaphragm, which vibrates due to sound pressure.

[0016] A holder 10 is housed inside the support body 2. The holder 10 is made of an elastic material, such as natural rubber, synthetic rubber, or a foamed resin such as polyolefin or polystyrene. As shown in Fig. 2, a through-hole 11 is formed in the holder 10, penetrating it in the front-to-rear direction. The through-hole 11 has a circular cross section, and its inner diameter D is uniform over its entire length in the front-to-rear direction (Z1-Z2 direction).

[0017] As shown in Figure 2, microphone 5 is mounted on circuit board 4 and inserted into through-hole 11 of holder 10 from below. The outer diameter of case 6 of microphone 5 is formed to be approximately the same as or slightly larger than the inner diameter of through-hole 11. Therefore, case 6 of microphone 5 is housed in through-hole 11 with almost no gap. It is also possible to mount microphone 5 on circuit board 4 after fitting microphone 5 inside through-hole 11 of case 6.

[0018] 1 and 2, a cushioning material 8 is interposed between the circuit board 4 and the holder 10. The cushioning material 8 is intended to attenuate external vibrations acting on the case 6 so as not to adversely affect the detection operation of the microphone 5. For this reason, the cushioning material 8 is preferably made of a material with a smaller elastic modulus than the holder 10. However, if the holder 10 is made of a material with a small elastic modulus, such as foamed resin, the cushioning material 8 may not be used.

[0019] 1, after the circuit board 4, microphone 5, and holder 10 are housed and fixed inside the support body 2, a front wall 2c is fixed to the front of the support body 2. The inner diameter of a front opening 2d formed in the front wall 2c is sufficiently larger than the inner diameter dimension D of the through-hole 11 of the holder 10. The front opening 2d is closed by a lid 9 having a number of passage holes 9a.

[0020] Inside through hole 11 of holder 10, the space extending forward (in the Z1 direction) from the front portion of microphone 5 (front portion 6b of case 6) constitutes sound collection space 12. Front end portion 11a of through hole 11 constitutes sound collection hole 12a, which is located at the front end of sound collection space 12. Sound collection space 12 communicates with the external space from sound collection hole 12a. Sound collection space 12 extends from front portion 6b to sound collection hole 12a, and the length dimension L of sound collection space 12 in the front-to-back direction (Z1-Z2 direction) is greater than the inner diameter dimension D. FIG. 1 shows the center line O of through hole 11 extending in the front-to-back direction. This center line O is the center line extending front-to-rear of sound collection space 12. The cross-sectional shape of storage space 12, perpendicular to center line O, is uniform from front portion 6b of microphone 5 to sound collection hole 12a, and the cross-sectional shape is a perfect circle with inner diameter dimension D. The cross-sectional area of ​​the sound collection space 12 is also uniform from the front surface 6b to the sound collection hole 12a.

[0021] In the acoustic device 1 of the embodiment, sound pressure applied from the outside enters the inside of the support body 2 through the passage hole 9a of the lid body 9, passes through the sound collection space 12 from the sound collection hole 12a, and is applied to the microphone 5, where the sound pressure is detected by the microphone 5.

[0022] The sound collection space 12 located in front of the microphone 5 is a duct with a uniform cross-sectional shape and cross-sectional area from the front part 6b of the microphone 5 to the sound collection hole 12a, and does not constitute a Helmholtz resonator. Therefore, the resonant frequency of a Helmholtz resonator does not exist in the operating frequency band detected by the microphone 5. Although the sound collection space 12, which is a duct, also has a resonant frequency, the sound collection space 12 is a 1 / 4 wavelength resonant tube, so if the length dimension L of the sound collection space 12 is 5 mm or less, the resonant frequency in the sound collection space 12 will not fall within the operating frequency band detected by the microphone 5. Furthermore, by setting the length dimension L of the sound collection space 12 to 5 mm or less, a small acoustic device 1 can be constructed.

[0023] Fig. 3 shows an acoustic device 101 of the comparative example. In the acoustic device 101 of the comparative example, a sound collection space 112 is formed in front of the front part 6b of the microphone 5, and the storage space 112 communicates with the external space via a sound collection hole 113. The sound collection hole 113 has a smaller diameter than the inner diameter of the sound collection space 112. Because the sound collection hole 113 functions as a duct, the sound collection hole 113 and the sound collection space 112 form a Helmholtz resonator. The acoustic device 101 of the comparative example is the same type as that described in Patent Document 1 in that it forms a Helmholtz resonator.

[0024] FIG. 4 shows the difference in characteristics between the acoustic device 1 of the embodiment and the acoustic device 101 of the comparative example. The horizontal axis indicates the frequency of the sound pressure detected by the microphone 5, and the vertical axis indicates the sound pressure level detected by the microphone 5. FIG. 4 does not show measurements of actual acoustic devices, but rather shows general characteristics derived from the structure of each acoustic device. The solid line (i) in FIG. 4 indicates the general characteristics of the acoustic device 1 of the embodiment, and the dashed line (ii) indicates the general characteristics of the acoustic device 101 of the comparative example. In the comparative example, the small Helmholtz resonator composed of the sound collection hole 113 and the sound collection space 112 functions as an acoustic low-pass filter that attenuates sound energy in a certain wavelength band centered on the resonant frequency, so the frequency band of sound detected by the microphone 5 is narrowed, as shown by the dashed line (ii). In contrast, in the embodiment, the sound collection space 12 does not function as an acoustic low-pass filter in the used frequency band, so a wide frequency band of sound can be detected by the microphone 5.

[0025] 1, sound collection space 12 is covered with lid 9 having a plurality of passage holes 9a, which makes it difficult for dust and moisture to enter sound collection space 12 from the outside. Furthermore, because length L of sound collection space 12 is greater than inner diameter D, even if dust or moisture does enter sound collection space 12, it is difficult for it to reach front surface 6b of microphone 5.

[0026] 2, in the acoustic device 1 of the embodiment, a through hole 11 with a uniform cross-sectional shape and cross-sectional area is formed in a holder 10, and by simply inserting a microphone 5 into the through hole 11 from below, a sound collection space 12 with a uniform cross-sectional shape can be formed in front of the microphone 5. Therefore, the relative positions of the microphone 5 and the sound collection space 12 can be determined with high precision through a simple assembly process, and the sound collection space 12 with a uniform cross-sectional shape perpendicular to the center line O can be easily formed in front of the microphone 5.

[0027] Furthermore, because holder 10 is made of an elastic material, when microphone 5 is inserted into and held in through-hole 11 of holder 10, a gap is unlikely to form between the microphone and the inner surface of through-hole 11. Furthermore, if the inner surface of sound collection space 12 is made of foamed resin, holder 10 can also eliminate noise. [Explanation of symbols]

[0028] 1 Sound equipment 2 Support 5 Microphone 6 cases 6b Front of the case (front of the microphone) 9 Lid 9a Passing hole 10 holders 11 Through holes 12 Sound recording space 12a sound pickup hole O center line

Claims

1. In an acoustic device in which a microphone is supported on a support, A sound collection space is formed in front of the microphone, and a front end of the sound collection space is a sound collection hole that communicates with an external space, An acoustic device characterized in that the cross-sectional shape of the sound pickup space perpendicular to a center line extending forward and backward is uniform from the front portion to the sound pickup hole.

2. 2. The acoustic device of claim 1, wherein the cross-sectional shape is circular.

3. a holder having a through hole formed therein is provided on the support, and the microphone is held in the through hole; 2. The acoustic device according to claim 1, wherein the through-hole has a region extending forward from the front surface of the microphone as the sound pickup hole.

4. 4. The acoustic device according to claim 3, wherein the holder is made of an elastic material.

5. 5. The acoustic device according to claim 1, wherein the sound pickup hole is covered with a lid having a number of passage holes.

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