JP2017118391A - Stereo boundary microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stereo boundary microphone in which mutual sound collection axes of right and left microphone units are formed at an appropriate opening angle in a lateral direction without affecting a directional property even if an elevation angle of the sound collection axes is changed.SOLUTION: A stereo boundary microphone comprises: a first unit mounting case 21L and a second unit mounting case 21R in which unidirectional microphone units 1L and 1R for left and right channel sound collection are housed; and a boundary plate 20 which is disposed while making the unit mounting cases adjacent to its top face. The first and second unit mounting cases are axially rotated, thereby changing the elevation angle of the microphone units. Further, in the unit mounting cases, side face openings 25L and 25R communicating to back face sound guide holes 5 of the microphone units are formed towards the outside of both the neighboring unit mounting cases.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a stereo boundary microphone in which the angle of elevation of a sound collection axis in left and right microphones arranged on a boundary plate can be varied.

Boundary microphones (surface pickup microphones) are often used in conference tables, television studios, and the like.
The boundary microphone is used by being placed on the desk surface at a conference table or the like, and is mainly used by being placed on the floor surface at a television studio or the like.

For example, as disclosed in Patent Documents 1 and 2, the above-described boundary microphone includes a boundary plate and a microphone placed on the boundary plate.
In this case, since the microphone is disposed close to the boundary plate, the direct sound and the reflected sound from the boundary plate arrive at the microphone. However, there is almost no time difference (phase difference) between the direct sound arriving at the microphone and the reflected sound by the boundary plate, and thus an audio signal having a higher clarity than the microphone can be obtained efficiently.

JP-A-8-65786 Special table 2013-527995 gazette

In many cases, the above-described boundary microphone is fixed and attached so that the sound collection axis of the unidirectional microphone is parallel to, for example, the upper surface of the boundary plate.
Therefore, when the sound source is off the sound collecting axis of the boundary microphone, it is difficult to pick up sound with good sound quality.
That is, when this boundary microphone is used, for example, at a conference table, there is a problem that the frequency response characteristics of the speaker facing the boundary microphone placed on the desk are greatly different between the seated state and the standing state. Occur.

  Therefore, it is conceivable to employ a configuration in which the microphone unit is mounted on a boundary plate so that the elevation angle of the sound collection axis in the unidirectional microphone unit can be varied. According to this configuration, since the elevation angle can be set so that the sound collection axis of the microphone unit is appropriately oriented in the direction of the sound source, it is possible to prevent the frequency response characteristics from being deteriorated due to the deviation of the sound collection axis.

By the way, when an operation for changing the sound collection axis of the microphone unit arranged on the boundary plate is performed, there arises a problem that the directivity characteristic of the microphone unit is changed for the following reason.
4A to 4C show the external configuration of a unidirectional electret condenser microphone unit 1 used as a boundary microphone. The microphone unit 1 is shown in a front view, a side view, and a rear view, respectively. Yes.

  In the unidirectional electret condenser microphone unit 1, as shown in the figure, a cylindrical unit case 2 made of, for example, an aluminum material forms an outer shell, and the front wall of the unit case 2 is shown in FIG. 4A. A plurality of front sound guide holes 3 in which the front acoustic terminals of the microphone unit 1 are formed are formed.

Although not shown, in the unit case 2, as is well known, a diaphragm and a fixed pole or the like facing the back surface of the diaphragm are disposed, and the sound waves introduced into the plurality of front sound guide holes 3 are The diaphragm will be vibrated.
On the back side of the unit case 2, a circuit board 4 on which an FET or the like functioning as an impedance converter is mounted as shown in FIG.
The circuit board 4 is provided with a plurality of back sound introduction holes 5 that communicate with the back surface of the diaphragm and form rear acoustic terminals on the back surface of the unit case 2.

  Note that the above-described acoustic terminal refers to a position of air that effectively applies sound pressure to the microphone unit 1. In other words, the acoustic terminal is the center position of the air that moves simultaneously with the diaphragm included in the microphone unit 1. Since the microphone unit 1 is unidirectional, the acoustic terminals are present at the front and rear portions of the diaphragm.

5A and 5B explain the technical problems of the boundary microphone.
That is, the unidirectional microphone unit 1 described above is disposed on the boundary plate 20 as schematically shown in FIG. 5A, thereby forming a boundary microphone. The microphone unit 1 has a boundary plate with an appropriate means so that the sound collection axis D can be varied from a state where the elevation angle where the sound collection axis D is parallel to the upper surface of the boundary plate 20 is 0 degrees to 90 degrees in the vertical direction. 20 is mounted on.

FIG. 5B shows a state where the elevation angle of the sound collection axis D of the microphone unit 1 is set to about 45 degrees. According to this state, the rear acoustic terminal of the microphone unit 1 approaches the boundary plate 20 and the space on the rear acoustic terminal side is the boundary plate as compared with the state where the elevation angle of the sound collection axis D shown in FIG. It is narrowed between 20.
In addition, when the elevation angle of the sound collection axis D is set to be larger in the vertical direction, the space on the rear acoustic terminal side is further narrowed between the boundary plate 20.

  Therefore, with the change in the above-described elevation angle of the sound collection axis D of the microphone unit 1, a restriction is imposed on the supply of the signal wave to the rear acoustic terminal side. For this reason, the microphone unit changes from a unidirectional characteristic to a characteristic close to omnidirectional characteristics, and if it is remarkable, it develops a problem of causing howling.

  Therefore, the present applicant has previously proposed a boundary microphone having a configuration that does not affect the rear acoustic terminal with respect to a change in the elevation angle of the sound collection axis D, and this has been proposed as Japanese Patent Application No. 2014-159372. I am doing.

  FIG. 6 shows the basic configuration, and a unit mounting recess 12 is formed on the peripheral side surface of a cylindrical unit mounting member 11 having a hollow portion 13 penetrating in the axial direction. The unidirectional microphone unit 1 shown in FIGS. 4A to 4C is mounted in the unit mounting recess 12, and the rear sound guide hole 5 of the microphone unit 1 is communicated with the hollow portion 13. According to this configuration, the rear acoustic terminals of the unidirectional microphone unit 1 are formed in the vicinity of the left and right openings of the hollow portion 13 formed in the unit mounting member 11.

The elevation angle of the sound collection axis D of the microphone unit 1 can be changed by mounting the cylindrical unit mounting member 11 on the boundary plate so that the shaft can be rotated.
In addition, according to the configuration shown in FIG. 6, there is no physical change between the rear acoustic terminal of the microphone unit 1 and the boundary plate 20 even when the unit mounting member 11 is axially rotated. Therefore, it is possible to provide a boundary microphone that does not affect the sound.

  By the way, the boundary microphone previously proposed by the applicant of the present application is considered as a monaural specification, and when sound is collected using this boundary microphone, stereo sound collection is often required.

Therefore, when two boundary microphones are used for stereo sound pickup, the boundary plate has a certain area, and therefore the left and right microphones must be spaced apart from each other. .
As described above, when the left and right microphones are spaced apart from each other, there arises a technical problem that the frequency response is not flat due to the time difference depending on the sound speed. Therefore, it is desirable that the left and right unidirectional microphone units be arranged in a state where the interval is narrow, that is, close to one boundary plate.

The present invention has been made based on the above technical viewpoint, and suppresses a physical change between the rear acoustic terminal of the microphone unit and the boundary plate when the elevation angle of the sound collection axis is changed. An object of the present invention is to provide a stereo boundary microphone capable of suppressing changes in directivity characteristics (sound collection characteristics) of a microphone unit.
In addition, the present invention is a stereo in which the left and right unidirectional microphone units are arranged close to each other on one boundary plate and the sound collecting axes are formed with appropriate opening angles in the left and right directions. It is an object to provide a boundary microphone.

  The stereo boundary microphone according to the present invention made to solve the above-described problems includes a first unit mounting case that houses a unidirectional microphone unit for first channel sound collection, and a second channel sound collection device. A second unit mounting case containing a unidirectional microphone unit, wherein the first unit mounting case and the second unit mounting case are disposed adjacent to the upper surface of a boundary plate, respectively, The mounting case and the second unit mounting case are each rotated on a single axis parallel to the surface of the boundary plate, thereby forming front surfaces formed on the first channel and second channel sound collecting microphone units. The first channel is disposed so that the elevation angle of the sound guide hole can be changed. A side opening formed in the first unit mounting case that communicates with the rear sound guide hole of the sound collecting microphone unit and a second unit mounting case that communicates with the rear sound guiding hole of the second channel sound collecting microphone unit. The formed side openings are respectively formed toward both outer sides in the one axial direction parallel to the surface of the boundary plate.

  In this case, it is desirable that the elevation angle of the front sound guide hole in the microphone unit for collecting the first channel and the microphone unit for collecting the second channel can be changed independently.

  In a preferred embodiment, the first unit mounting case and the second unit mounting case have side surfaces formed in a cylindrical shape, and a sound collection opening for exposing a front sound guide hole of the microphone unit on a part of the peripheral side surface. A configuration is employed in which one of the end faces of the unit mounting case is formed and closed, and the side opening is formed on the other end face of the unit mounting case.

  In addition, a condenser microphone unit can be preferably used for each of the unidirectional microphone unit for collecting the first channel and the unidirectional microphone unit for collecting the second channel.

According to the stereo boundary microphone having the above-described configuration, by rotating the first unit mounting case and the second unit mounting case, the sound collecting shafts of the respective unidirectional microphone units housed in the unit mounting cases are rotated. The elevation angle can be changed.
In this case, since each side opening formed in each unit mounting case is formed toward both outer sides in one axial direction parallel to the surface of the boundary plate, the elevation angle of the sound collection axis is changed. However, there is no physical change between the rear acoustic terminal and the boundary plate of each microphone unit, and this can prevent the directivity characteristics of each microphone unit from changing.

  Also, with the above-described configuration, each microphone unit is formed with a sound collecting axis on a line connecting the rear acoustic terminal and the front acoustic terminal, so that each sound collecting axis is appropriately opened in the left-right direction. A stereo boundary microphone formed with an angle can be provided.

FIG. 3 is a top view of the stereo boundary microphone according to the present invention, with the unit mounting case cut away. It is the side view which fractured | ruptured and showed the unit mounting case similarly. It is the schematic diagram which showed the example which supports a unit mounting | wearing case so that rotation is possible. It is the front view which showed the example of the microphone unit used for a boundary microphone. It is a side view similarly. It is a back view similarly. It is the side view which showed the basic composition of the conventional boundary microphone. It is the side view which showed the example which changed the sound-collection axis | shaft similarly. It is a perspective view which shows the state which accommodated the microphone unit in the unit mounting case.

  A stereo boundary microphone according to the present invention will be described based on an embodiment shown in the drawings. 1 and 2 are sectional views showing unit mounting cases each accommodating a microphone unit. That is, the unit mounting case shown in FIG. 1 is a cross-sectional view as seen in the direction of the arrow from the aa line shown in FIG. 2, and the unit mounting case shown in FIG. 2 is from the bb line shown in FIG. It is sectional drawing of the state seen in the arrow direction.

As the unidirectional microphone unit 1 used for this stereo boundary microphone, the unidirectional electret condenser microphone unit 1 described above based on FIGS. 4A to 4C is used. Omitted.
In the following, the first channel is sometimes referred to as the left (L) channel, and the second channel is sometimes referred to as the right (R) channel, and the “L” and “R” are appended to the end of each code. I will identify it.

As shown in FIG. 1 and FIG. 2, a first unit mounting case 21L that accommodates a unidirectional microphone unit 1L for collecting the left channel and a unidirectional microphone unit 1R that accommodates the unidirectional microphone unit 1R for collecting the right channel. The two-unit mounting case 21 </ b> R is disposed adjacent to the upper surface of the boundary plate 20.
As shown in FIG. 2, each of the unit mounting cases 21L and 21R has a cylindrical side surface, and the microphone units 1L and IR are accommodated in a part of the peripheral side surface. Sound collecting openings 22L and 22R are formed through which the front sound guide holes 3 of the units 1L and IR are exposed.

Further, wall surfaces 23L and 23R are formed on the end surfaces of the unit mounting cases 21L and 21R adjacent to each other so as to be closed. Side openings 25L and 25R are formed on the other end surfaces of the unit mounting cases 21L and 21R, that is, on both outer sides of the adjacent unit mounting cases 21L and 21R, leaving part of the wall surfaces 24L and 24R.
As a result, the rear sound guide holes 5 (see FIG. 4C) of the microphone units 1L and IR communicate with both outer sides of the unit mounting cases 21L and 21R through the side openings 25L and 25R.

  With the above-described configuration, the front acoustic terminals of the left and right microphone units 1L and 1R are formed near the center of the sound collection openings 22L and 22R of the unit mounting cases 21L and 21R. Further, the rear acoustic terminals of the left and right microphone units 1L and 1R are formed near the center of the side openings 25L and 25R of the unit mounting cases 21L and 21R.

Therefore, the horizontal sound collection axis of the left channel sound collection microphone unit 1L is set in the direction indicated by the arrow DL, which is a line connecting the rear acoustic terminal and the front acoustic terminal.
Further, the horizontal sound collecting axis by the right channel sound collecting microphone unit 1R is set in a direction indicated by an arrow DR that is a line connecting the rear acoustic terminal and the front acoustic terminal.
Accordingly, it is possible to provide a stereo boundary microphone in which the sound collecting axes DL and DR are formed with an appropriate opening angle in the left-right direction.

On the other hand, the cylindrical first unit mounting case 21L and the second unit mounting case 21R are each rotated on a single axis Ax parallel to the surface of the boundary plate 20, whereby the left channel The elevation angle of the front sound conduction hole 3 formed in the microphone unit 1L for sound collection (the elevation angle of the sound collection axis DL) and the elevation angle (collection angle) of the front sound conduction hole 3 formed in the microphone unit 1R for sound collection on the right channel. The elevation angle of the sound axis DR) can be changed individually.
FIG. 2 shows that when the sound collecting axis DR by the right channel sound collecting microphone unit 1R is parallel to the upper surface of the boundary plate 20, the elevation angle θ of the sound collecting axis DR is 60 degrees. The state set to the degree is shown.

FIG. 3 shows an example of a support that rotatably supports the first and second unit mounting cases 21L and 21R on the boundary plate 20. In FIG. 3, the support is hatched. This is shown in the longitudinal sectional view.
This support includes a central support frame member 31 disposed between adjacent first and second unit mounting cases 21L and 21R, and both axial sides of the first and second unit mounting cases 21L and 21R. The pair of ring-shaped outer support frame members 32 disposed along the peripheral side surface of the base plate 33 and the base plate 33 for fixing the pair of outer support frame members 32 on the boundary plate 20. .

  That is, the central support frame member 31 is interposed between the first and second unit mounting cases 21L and 21R, and a pair of outer support frame members 32 are provided from both sides of the first and second unit mounting cases 21L and 21R. Sandwich. Subsequently, by fixing the base plate 33 on the boundary plate 20, the two unit mounting cases 21 </ b> L and 21 </ b> R can be rotatably mounted on the boundary plate 21.

  Then, as shown in FIG. 3, the first and second unit mounting cases 21L and 21R are attached by attaching rod-shaped handles 34 to part of the side surfaces of the first and second unit mounting cases 21L and 21R, respectively. The shafts can be rotated, and the elevation angles θ of the sound collecting axes DL and DR in the left and right microphone units 1L and 1R attached to each unit mounting case can be individually adjusted. The first and second unit mounting cases 21L and 21R are rotated together to adjust the elevation angles θ of the sound collecting axes DL and DR in the left and right microphone units 1L and 1R by the same angle. May be.

  As described above, according to the stereo boundary microphone according to the present invention, even if the elevation angle θ of the sound collection axes DL and DR is changed, the sound collection axes of the left and right microphone units do not affect the directivity characteristics. It is possible to provide a stereo boundary microphone in which DL and DR are formed with an appropriate opening angle in the left-right direction.

1L, 1R Microphone unit 3 Front sound guide hole 5 Back sound guide hole 20 Boundary plate 21L, 21R Unit mounting case 22L, 22R Sound collection opening 23L, 23R Wall surface 25L, 25R Side opening 31 Central support frame member 32 Outer support frame member 33 Base plate 34 Handle Ax axis DL, DR Sound collection axis

Claims (4)

A first unit mounting case containing a unidirectional microphone unit for collecting a first channel; and a second unit mounting case containing a unidirectional microphone unit for collecting a second channel;
The first unit mounting case and the second unit mounting case are arranged adjacent to the upper surface of the boundary plate, respectively.
The first unit mounting case and the second unit mounting case are respectively rotated on a single axis parallel to the surface of the boundary plate, so that the first channel and second channel sound collecting microphone units are provided. It is arranged so that the elevation angle of the formed front sound guide hole can be changed,
And a side opening formed in the first unit mounting case that communicates with the back sound introduction hole of the first channel sound pickup microphone unit, and a second opening that communicates with the back sound introduction hole of the second channel sound collection microphone unit. A stereo boundary microphone, wherein a side opening formed in the unit mounting case is formed toward both outer sides in the one axial direction parallel to the surface of the boundary plate.   2. The elevation angle of the front sound guide hole in the microphone unit for collecting the first channel and the microphone unit for collecting the second channel can be changed independently of each other. Stereo boundary microphone.   Each of the first unit mounting case and the second unit mounting case has a side surface formed in a cylindrical shape, and a sound collection opening for exposing the front sound guide hole of the microphone unit is formed in a part of the peripheral side surface. 3. The stereo boundary microphone according to claim 1, wherein one end face of the mounting case is closed, and the side opening is formed on the other end face of the unit mounting case.   The unidirectional microphone unit for collecting the first channel and the unidirectional microphone unit for collecting the second channel are each constituted by a condenser microphone unit. 4. The stereo boundary microphone according to any one of 3 above.

Images