JPH0520491U - Transmitter structure - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a microphone mounting structure for reducing wind noise generated in a microphone due to wind or air flow. [Structure] A small condenser microphone 1 is wrapped with a vibration-proof material such as silicone rubber 2, and an elongated hollow portion 6 leading to a front hole 5 is provided in the front portion of the silicone rubber 2. The drip-proof sheet 3 is sandwiched between the silicone rubber 2 and the housing 4, and the front hole 5 and the housing hole 7 are displaced from each other. The hollow portion 6 and the housing 4 form an elongated sound path, and the wind and the air flow are attenuated by viscous resistance while passing through the elongated sound path. Also,
Since the sound path is formed in the vibration-proof material, the mounting thickness is not increased, and a plurality of sound paths are formed to disperse the housing holes.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a microphone or a microphone mounting structure incorporated in a portable video camera or the like.

[0002]

[Prior Art]

 In a transmitter such as a telephone, it is desired that the speaker's voice is collected with high sensitivity and that it does not respond to the breath and wind of the speaker. In particular, a condenser microphone has a sufficiently high microphone sensitivity even in a low frequency band, and thus tends to respond to wind and air currents with low frequency components. Therefore, the wind noise reduction has been devised conventionally.

FIG. 8 is a cross-sectional view showing a conventional transmitter disclosed in, for example, Japanese Patent Publication No. 60-17191. In the figure, 11 is a transmitter, 12 is a microphone unit, 13 is a front hole, 14 is a cavity, and 15 is an opening. Next, the operation will be described. A sound wave such as a speaker's voice propagates through the opening 15, propagates in the cavity 14, further passes through the front hole 13, reaches the diaphragm of the microphone unit 12, and generates a voltage proportional to the sound pressure. Wind and airflow similarly enter the cavity 14 through the openings 15. Here, since the cross-sectional area and volume of the cavity 14 are configured to be larger than the cross-sectional area volume of the opening 15, the air velocity is reduced due to the viscosity and compliance of the air inside the cavity 14, etc. It is said to be effective in reducing In the conventional example, the cross-sectional area of the cavity 14 has a radius of 1 cm and a cavity height of 0.3 to 0.75 cm. On the other hand, recently, there is a strong demand for smaller and thinner mobile phones and the like, and a unit having a size of φ6 × t5 mm is also used for the microphone unit. The volume of this unit is 0.14 cm @ 3, and the volume of the cavity 14 is equivalent to 6.7 to 16 times this volume.

[0004]

[Problems to be solved by the device]

 Since the conventional transmitter is configured as described above, there is a problem that a large space is required to reduce wind noise and it is difficult to make the transmitter small and thin.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a transmitter structure which can reduce wind noise and can be downsized and thinned.

[0006]

[Means for Solving the Problems]

 The structure of the transmitter according to the present invention is one in which a recess is formed in the anti-vibration rubber that encloses the microphone unit to create a sound path, and the front hole of the microphone and the opening of the housing are mounted offset.

[0007]

[Action]

 In this invention, the sound path formed in the anti-vibration rubber reduces wind and air flow due to its viscosity.

Moreover, since a part of the vibration-proof rubber is used as a sound path, a new cavity having a large volume is not used.

[0009]

【Example】

 Example 1. FIG. 1 is a diagram showing a transmitter structure according to an embodiment of the present invention. FIG. 1 (a) is a cross-sectional view of a microphone attached to a housing, and FIG. 1 (b) is a silicone rubber used as an anti-vibration rubber. It is a perspective view of rubber. In the figure, 1 is a microphone, 2 is a silicone rubber used as an anti-vibration rubber, 3 is a breathable sheet that is permeable to sound waves but not water droplets, 4 is a mobile phone housing, and 5 is a microphone. Reference numeral 1 is a front hole, 6 is a recess formed by cutting a part of the silicone rubber 2 or formed by a molding die, and 7 is a housing hole opened in the housing 4 for receiving sound waves.

Next, the operation will be described. The voice of the speaker enters through the housing hole 7, passes through the breathable drip-proof sheet 3, and reaches the recess 6. The upper surface of the concave portion 6 is closed by the drip-proof sheet 3 and the housing 4, and a long sound path is formed from the housing hole 7 to the front hole 5. Therefore, the sound wave of the voice propagates through the elongated sound path, reaches the front hole 5, vibrates the diaphragm of the microphone 1, and generates a voltage proportional to the sound pressure.

Wind and airflow enter from the housing hole 7 and pass through the elongated sound path of the recess. Since the height of the sound path is equal to the thickness of the silicone rubber 2, the thickness of the anti-vibration silicone rubber 2 is about 1 mm.

It is known that the wind and the air flow passing through such a gap are attenuated by viscous resistance. According to the knowledge of fluid dynamics, the flow velocity u is u ∝ d2 / μ (1) d: sound path height, μ: viscous coefficient, and if the sound path height is low, the speed is small If the viscosity coefficient is large, the speed is also small. Since the velocity of the flow is proportional to the square of the height of the sound path, a sound path having a height of about 1 mm is sufficiently effective in reducing wind and air flow. In addition, it is known that wind noise is reduced if the gap or the length of the thin tube is long. In the embodiment, since the positions of the housing hole 7 and the front hole 5 are displaced, the length of the sound path is long. For example, as compared with the case where the housing hole 7 is formed right above the front hole 5, the length can be increased by about the radius of the microphone 1. Therefore, wind noise is further reduced.

On the other hand, since the width of the sound path can be made large in the circumferential direction of the silicon rubber 2, it is possible to secure the cross-sectional area necessary for the propagation of sound waves. Since the front hole 5 has a radius of about 1 mm and the required area of the housing hole 7 is about 2 × 1 mm, when the sound path width is set to 3 to 5 mm, the sound path cross-sectional area becomes about twice that of the housing hole 7, and Attenuation can be reduced. Furthermore, if the recessed portion 6 and the housing hole 7 are filled with open-cell urethane material, wind noise will be further attenuated.

FIG. 2 shows an example in which the shape of the recess 6 of the silicon rubber 2 is changed. The recess 6 a has a narrow width near the housing hole 7 and a wide width near the front hole 5. The cross section of the sound path is small at the end of the housing hole 7 near the entrance, and gradually increases toward the front hole 5. Therefore, the wind and the airflow entering from the housing hole 7 are diffused in the sound path, which has the effect of reducing the speed.

Example 2. FIG. 3 shows another embodiment. In the figure, a housing hole 7 is provided outside the radius of the microphone 1 to lengthen the sound path. Therefore, the damping effect of wind noise is increased. The recess 6 of the silicone rubber 2 extends to the circumferential edge of the silicone rubber, and the length of the sound path is long. Reference numeral 8 is a recess formed in the housing 4. When a plurality of housing holes 7 and dents 8 are provided in a circular arc shape of a circle center, it is difficult to distinguish which dent is the housing hole 7 of the transmitter, so that the opening of the transmitter cannot be seen clearly. There are advantages.

Example 3. FIG. 4 shows a third embodiment. In the figure, 7a and 7b are housing holes a and b, respectively. In the figure, two housing holes having substantially the same size are provided. By using two housing holes 7a and 7b, the acoustic resistance of the microphone 1 to the sound waves is halved, the sound wave attenuation due to the sound path is reduced, and the sound pressure sensitivity of the microphone 1 can be increased. Further, since there are two housing holes for one recess 6, the fluctuation pressure of the wind or airflow that enters from one housing hole escapes from the other housing hole and is applied to the front hole 5. The pressure drops. Therefore, the effect of reducing the fluctuating pressure strongly applied to either of the two housing holes is great.

Example 4. FIG. 5 shows a fourth embodiment. The figure is a mounting cross-sectional view, and housing holes 7a to 7d are provided at asymmetrical positions with respect to the microphone 1. FIG. 6 shows the arrangement of the housing holes as seen from above the housing 4 in the fourth embodiment. The four housing holes 7a to 7d are arranged point-symmetrically in a concentric circular arc shape, but are arranged so as to be different in distance from the front hole 5 of the microphone 1.

FIG. 7 is a diagram for explaining the operation of the fourth embodiment. Consider a case where parallel winds and air flows along the housing 4 as shown in the figure. The flow away from the housing 4 passes without affecting, but the flow near the surface of the housing enters the housing holes 7a and 7b to generate new pressure fluctuations.

Since the casing surface is flat and the casing holes 7a and 7b have the same size, the flow inflow state is almost the same, so that the generated fluctuating pressure is in phase and at the same level. .. The generated fluctuating pressure reaches the front hole 5 through the sound path 9. Since the fluctuating pressure in the housing hole 7a is transmitted in the sound path by the distance La and the fluctuating pressure in the housing hole 7b is transmitted in the distance Lb, a phase difference occurs in the fluctuating pressure due to the transmission distance difference Lb-La. Therefore, in the vicinity of the front hole 5, the fluctuating pressures of the both cancel each other out. Since the fluctuating pressure is considered to be transmitted along the wind flow, the transmission speed becomes almost equal to the wind speed. For example, assuming that a microphone having a diameter of 6 mm in FIG. 7 has a distance difference of 6 mm and a wind speed of 4 m / sec, the 333 Hz component has a reverse phase and is canceled. Similarly, the frequency component corresponding to the difference in distance from the other housing holes 7c and 7d is also canceled. On the other hand, since the propagation speed of the speaker's voice is about 340 m / sec, the voice band component does not cancel at a distance difference of about 6 mm.

By arranging the plurality of housing holes with different distance differences, the component of wind noise is reduced. Although the example in which the number of the housing holes is four is shown, it is clear that the same effect can be obtained even when the number of the housing holes is two or three or five or more.

[0021]

[Effect of the device]

 As described above, according to the present invention, the anti-vibration rubber is provided with the concave portion to configure the sound path, and the microphone front hole and the housing hole are displaced from each other, so that the wind noise is reduced in the thin housing. There is an effect that a transmitter can be configured.

[Brief description of drawings]

FIG. 1 is a diagram showing a transmitter structure according to an embodiment of the present invention.

FIG. 2 is a view showing the structure of another modified example of the present invention.

FIG. 3 is a view showing a structure according to another embodiment of the present invention.

FIG. 4 is a diagram showing a structure according to a third embodiment of the present invention.

FIG. 5 is a view showing a structure according to a fourth embodiment of the present invention.

FIG. 6 is a view showing an arrangement of housing holes according to a fourth embodiment of the present invention.

FIG. 7 is a diagram for explaining the operation of the fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a conventional transmitter.

[Explanation of symbols]

 1 Microphone 2 Anti-vibration rubber 3 Drip-proof sheet 4 Case 5 Front hole 6 Recess 7 Case hole

Claims (2)

[Scope of utility model registration request] 1. A microphone unit is wrapped with anti-vibration rubber, and a recessed portion communicating with a front hole of the microphone unit is provided outside the anti-vibration rubber, and a sound path is formed between the recessed portion and the housing. A transmitter structure characterized in that the housing is provided with an opening communicating with one end of the sound path. 2. The transmitter structure according to claim 1, wherein the housing is provided with a plurality of openings which are located at different distances from the front hole of the microphone unit and communicate with the sound path.