JP4663159B2 - Stereo narrow directional microphone - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called gun-type stereo narrow directivity microphone having an acoustic tube, and more particularly to a stereo narrow directivity microphone based on the MS method of the intensity method.
[0002]
[Prior art]
The MS system is a stereo narrow directivity microphone devised by H, Lauridsen, where M is Middle, S is Side, M is a main signal, and S is a direction signal.
[0003]
Usually, in the MS system, the main signal M is obtained from the unidirectional microphone unit, and the direction signal S is obtained by the bidirectional microphone unit arranged so as to be orthogonal to the main signal M. Are input to a matrix circuit (sum differential circuit) to generate LR channel signals (M + S) and (MS).
[0004]
An example thereof will be described with reference to a longitudinal sectional view of FIG. 3A and a transverse sectional view of FIG. 3B (a sectional view taken along line AA of FIG. 3A). In this stereo narrow directional microphone, a unidirectional microphone unit 20 and a bidirectional microphone unit 30 are housed in the same acoustic tube 10, and the left side of the acoustic tube 10 is the tip side (not shown). If it is the sound source side), the microphone units 20 and 30 are both disposed on the rear end side of the acoustic tube 10.
[0005]
The unidirectional microphone unit 20 has the directivity pattern shown in FIG. 4A, and the bidirectional microphone unit 30 has the directivity pattern shown in FIG. The sound collection axis is arranged so as to be orthogonal to the sound collection axis of the unidirectional microphone unit 20.
[0006]
The main signal M of the unidirectional microphone unit 20 and the direction signal S of the bidirectional microphone unit 30 are input to a matrix circuit (sum differential circuit) (not shown), and from the matrix circuit, (M + S), (M− S) LR channel signals are output.
[0007]
According to this stereo narrow directivity microphone, each directivity pattern of the (M + S) signal and the (MS) signal is basically a symmetrical cardioid, so that two unidirectional microphones can be formed. Is synonymous with
[0008]
[Problems to be solved by the invention]
If there is a time difference between the unidirectional microphone unit 20 and the bidirectional microphone unit 30, when the LR signal is generated by the matrix circuit, a ripple occurs in the frequency response, so that there is no time difference between the two microphone units 20 and 30. Placed as close as possible.
[0009]
This type of stereo narrow directivity microphone is often mounted on a television camera. In this case, the microphone units 20 and 30 are arranged beside the viewfinder of the television camera.
[0010]
Then, since the sound collecting axis of the bidirectional microphone unit 30 is arranged to be orthogonal to the sound collecting axis of the unidirectional microphone unit 20, the sound collecting axis of the bidirectional microphone unit 30 is The head will be located.
[0011]
For this reason, when the cameraman speaks alone or raises a screaming voice or the like under a sudden situation, the bi-directional microphone unit 30 is close to the cameraman's mouth, so that sound is picked up at a large level.
[0012]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a stereo narrow directivity microphone that prevents the photographer's voice from being collected as much as possible when mounted on a television camera. is there.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a microphone main body in which two microphone units of a unidirectional microphone unit and a bidirectional microphone unit are housed in an acoustic tube, and is output from the unidirectional microphone unit. In a stereo narrow directivity microphone having a matrix circuit for obtaining LR channel signals (M + S) and (MS) from a main signal M and a direction signal S output from the bidirectional microphone unit, A bidirectional microphone unit is disposed closer to the distal end side of the acoustic tube than the unidirectional microphone unit, and the direction signal S output from the bidirectional microphone unit is transmitted from the position of the bidirectional microphone unit. Input to the matrix circuit through a delay circuit that delays the time difference of the sound reaching the position of the unidirectional microphone unit. It is characterized in that.
[0014]
The speed of the sound wave propagating in the acoustic tube is the time difference (delay time) of the sound from the position of the bidirectional microphone unit to the position of the unidirectional microphone unit because the characteristic impedance of the acoustic tube is the same as that in free space. T) is obtained by T = D / C, where D is the distance between the microphone units and C is the sound velocity, and a low-pass filter or BBD (Bucket Bridge Device) is preferably employed as the delay circuit.
[0015]
According to the present invention, since the bidirectional microphone unit is disposed on the distal end side of the acoustic tube, it is difficult for the photographer's voice to be collected. In addition, the direction signal S output from the bidirectional microphone unit is delayed by the distance between the microphone units via the delay circuit and input to the matrix circuit, so that a ripple is generated in the frequency response when obtaining the LR signal. Does not occur.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a stereo narrow directivity microphone according to the embodiment, and FIG. 2 shows a transverse sectional view (sectional view taken along line AA in FIG. 1) and a matrix circuit.
[0017]
In this stereo narrow directional microphone, the unidirectional microphone unit 20 and the bidirectional microphone unit 30 are housed in the same acoustic tube 10, but in this case, the unidirectional microphone unit 20 and the bidirectional antenna are both. The microphone unit 30 is separated in position.
[0018]
That is, in FIGS. 1 and 2, assuming that the left side of the acoustic tube 10 is the front end side (sound source side not shown), the unidirectional microphone unit 20 is disposed on the rear end side of the acoustic tube 10. On the other hand, the bi-directional microphone unit 30 is disposed on the distal end side of the acoustic tube 10 in order to make it difficult to pick up the voice of the cameraman.
[0019]
The sound collection axis of the unidirectional microphone unit 20 is oriented parallel (coaxial) to the axis of the acoustic tube 10, whereas the sound collection axis of the bidirectional microphone unit 30 is the unidirectional microphone unit 20. It is oriented so as to be orthogonal to the sound collection axis of the above, and this point is the same as the conventional example described above. Note that the reference numeral 11 attached to the acoustic tube 10 is a slit.
[0020]
The main signal M output from the unidirectional microphone unit 20 and the direction signal S output from the bidirectional microphone unit 30 are given to the matrix circuit 40 which is a sum differential circuit, and the matrix circuit 40 (M + S). , (MS) LR signal is output. In the present invention, the direction signal S of the bidirectional microphone unit 30 is input to the matrix circuit 40 through the delay circuit 41.
[0021]
That is, since the bidirectional microphone unit 30 is disposed away from the unidirectional microphone unit 20, a sound propagation time difference occurs between the microphone units 20 and 30 if left as it is. When the signal is used, a ripple occurs in the frequency response.
[0022]
In order to prevent this, in the present invention, the delay circuit 41 is employed so that the unidirectional microphone unit 20 and the bidirectional microphone unit 30 are electrically arranged close to each other.
[0023]
The speed of the sound wave propagating through the acoustic tube 10 is a sound from the position of the bidirectional microphone unit 30 to the position of the unidirectional microphone unit 20 because the characteristic impedance of the acoustic tube 10 is the same as that of free space. Is obtained by T = D / C where D is the distance between the microphone units and C is the speed of sound.
[0024]
In the present invention, the direction signal S of the bidirectional microphone unit 30 is electrically delayed by the delay time T by the delay circuit 41 and input to the matrix circuit 40. Although various circuits can be applied to the delay circuit 41, a low-pass filter or a BBD is preferably employed from the viewpoint that the configuration is simple and that the circuit can be obtained at low cost.
[0025]
Regarding wind noise, in general, in a line microphone (gun type microphone) having an acoustic tube, wind noise tends to occur at the tip of the acoustic tube. In addition, since the bidirectional microphone unit 30 is also vulnerable to wind noise, conventionally, the windshield design has been made with emphasis on the front and rear ends of the acoustic tube.
[0026]
On the other hand, according to the present invention, since the amphibious microphone unit 30 is disposed on the distal end side of the acoustic tube 10, it is only necessary to design a windshield mainly on the distal end side of the acoustic tube 10. Thus, the present invention is also effective in this respect.
[0027]
【The invention's effect】
As described above, according to the present invention, the unidirectional microphone unit and the bidirectional microphone unit are accommodated in the acoustic tube, and the main signal M and the bidirectional microphone output from the unidirectional microphone unit. In the stereo narrow directivity microphone that receives the LR channel signals (M + S) and (MS) by inputting the direction signal S output from the unit to the matrix circuit, the bidirectional microphone unit is unidirectional. The time of sound from the position of the bidirectional microphone unit to the position of the unidirectional microphone unit when the direction signal S is arranged at the distal end of the acoustic tube relative to the bidirectional microphone unit and output from the bidirectional microphone unit By inputting to the matrix circuit through a delay circuit that delays the difference, the voice of the cameraman can be heard as much as possible, especially when installed in a TV camera. It is possible to not be sound.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a stereo narrow directional microphone according to an embodiment of the present invention.
FIG. 2 is a diagram showing a cross-sectional view and a matrix circuit of a stereo narrow directivity microphone according to the embodiment.
FIG. 3 is a longitudinal sectional view and a transverse sectional view of a conventional stereo narrow directivity microphone.
FIG. 4 is a characteristic diagram showing directivity patterns of a unidirectional microphone unit and a bidirectional microphone unit.
[Explanation of symbols]
10 acoustic tube 20 unidirectional microphone unit 30 bidirectional microphone unit 40 matrix circuit (sum differential circuit)
41 Delay circuit

Claims (3)

A microphone main body in which two microphone units of a unidirectional microphone unit and a bidirectional microphone unit are housed in an acoustic tube, a main signal M output from the unidirectional microphone unit, and the bidirectional microphone unit In a stereo narrow directivity microphone having a directional signal S output from a matrix circuit for obtaining LR channel signals (M + S) and (MS) from
The bidirectional microphone unit is disposed closer to the distal end side of the acoustic tube than the unidirectional microphone unit, and the direction signal S output from the bidirectional microphone unit is used as the position of the bidirectional microphone unit. A stereo narrow directional microphone that is input to the matrix circuit through a delay circuit that delays a time difference of sound from the position to the position of the unidirectional microphone unit. With the distance between the unidirectional microphone unit and the bidirectional microphone unit as D and the sound speed as C, the signal delay time T by the delay circuit is:
T = D / C
The stereo narrow directivity microphone of Claim 1 calculated | required by these. The stereo narrow directivity microphone according to claim 1, wherein a low-pass filter or a BBD is used as the delay circuit.

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