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JPS56111588

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DESCRIPTION JPS56111588
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a variable directional
microphone previously proposed by the present applicant, and FIGS. 2 and 3 are quadruple
variable resistors used in the microphone shown in FIG. The resistance change characteristic
diagram, FIG. 4 is a specific circuit diagram of the phase shift circuit shown in FIG. 1, FIG. 5 is a
phase shift characteristic diagram of the phase shift circuit, and FIG. 6 is obtained by the circuit
shown in FIG. FIG. 7 is a circuit diagram of an embodiment of the variable directional microphone
according to the present invention. -1a to 1c: microphone, 2: sound source, 4 ': frequency
characteristic correction circuit, 5: output terminal, 6: phase shift circuit, VH2, VRa: 2 with center
tap Series variable resistor, C3, C4 ... capacitor, R6-R9 ... resistor.
DETAILED DESCRIPTION OF THE INVENTION The present document relates to a variable
directional microphone, which uses a double variable resistor with a center tap as a variable
resistor for changing directivity, frequency characteristics and mixed output level, and is compact
and The object of the present invention is to provide a microphone whose circuit can be easily
configured. The present applicant has previously made three primary sound pressure gradients
in Japanese Patent Application No. 54-51691 "Variable Directional Microphone". Two directional
microphones (hereinafter referred to as “first-order uni-directional”) are arranged forward of
the sound source and one backward, and the outputs of these microphones are respectively
mixed and mixed. The directivity can be varied from omnidirectionality to primary
unidirectionality, to secondary acoustic pressure domain placement unidirectivity (hereinafter
referred to as “secondary unidirectivity”), and the directivity can be varied by changing the
ratio by a predetermined amount. Allow volume according to the change of Proposed a
microphone configured to be able to This is a conventional one to obtain directivity from nondirectionality to unidirectionality, (mi) bidirectionality by changing the mixing ratio of the
microphone output by making two primary unidirectional microphones face each other. Ratio 2.
Thus, the directivity can be varied widely, and sound zooming with sufficient sense of distance
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can be performed. On the other hand, the present person first connected the phase shift circuit to
one primary unidirectional microphone placed forward with 1F8 forward to the sound source by
means of “Kansei-Sho 54-1156644“ Desirable finger homosexual microphone ”. And the
output of the low frequency is in-phase added to the output of another microphone, while the
output of the high frequency is anti-phase added to the output of the other microphone, and the
mixing ratio is varied to make The microphones configured to be variable were 樟 M. This
configuration can reduce the amount of correction of the equalizer by preventing the loss of the
level particularly in the low range as compared with the frequency characteristic of the
conventional one. FIG. 111 shows a circuit diagram combining the two "variable directional
microphones" proposed above. In the open garden, the microphones la and lb are disposed
forward to the sound source 2 and the microphone lc is disposed rearward to the sound source
2. vR1 to VR4 are four sets of variable resistors, and when the respective sliders are in the
terminal ■, they are in non-directional (3) -ha, in the first child, in the primary unidirectionality,
in the child Sometimes it takes 10,000 to obtain secondary unidirectionality, and it is possible as
the slider is displaced from terminal ■ to terminal ■! By the term l′ ′ QVR, it is feared that
the output level will increase, and the resistance between the terminal ■ and the slider is the
second one in the variable resistors VR, VR. As shown in the figure, tear, fMK 6 VR ,, VR, '?
GflK3 as in icyr <f. Here, when nondirectionality is obtained, when the sliders of the variable
resistors 1 to vR4 are connected to the terminal 3, the outputs of the microphones la and lc are
added at the same level via the amplifiers 3a and 3c, respectively. It is output from the output
terminal 5 through the frequency characteristic correction circuit 4. At this time, the + W + wave
number characteristic correction circuit 4 maintains flat frequency characteristics. In order to
obtain primary uni-directionality, when the slider of variable resistor 1 to VR4 is connected to the
terminal 4, the output of microphone 1c is attenuated and only the output of microphone la is
amplified by amplifier 3a and frequency characteristic correction circuit 4 If the sliders of the
variable resistors 1 to VR4 are connected to the end (4), the microphones 1 m and 1 b are
connected. The outputs of 1 m and 1 lb are added at the same level via the phase shift circuit 6
whose specific phase is shown in the amplifiers 3a and 3b and the army 4 and the phase shift
characteristic is shown in FIG. The output level is bold (, Q), the WIf II number characteristic god
b 1 port, w 8 wave number justified in the road 4 is extracted. In the case of obtaining this
second-order single directivity, the angular frequency ω 8 of the 90 ° phase lag in the phase
shift circuit 6 is 50 Hz, the distance between the microphones la and lb is three countries,
microphone IR-IC and sound @ 2 The frequency characteristic diagram when the angle to be
made is OQ, 90 'is as shown in FIG. 6, and the response does not deteriorate as in the prior art
particularly at low and medium frequencies. For this purpose, the frequency characteristic
correction circuit 4 may be capable of correcting 13 dBJ [as apparent from the 0 °
characteristic shown in FIG. 6, and the correction amount is smaller than that of the conventional
'7). It is However, this is a variable resistor for changing directivity characteristics, v 、 2, a
variable resistor vR3 for changing the output level, and a variable resistor VB2 for correcting the
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frequency characteristic (5). It is necessary to use quadruple ones with special resistance change
characteristics, which makes it difficult to be small and secure, and requires a large torque to
drive it. There is a problem that the circuit can not be configured easily. The present invention
solves the above problems, and one embodiment will be described below with reference to FIG.
FIG. 7 shows a circuit diagram of an embodiment of a variable directional microphone according
to the present invention, in which the same reference numerals as in FIG. 1 denote the same
parts in FIG. In the figure, VR, VR are two series of variable resistors with center tap, and the
terminal ■ of variable resistor vRs is connected to the phase shift circuit 6 and the terminal ■ is
grounded at the center tap. , Terminal ■ is amplified J!
Connected to 63c. A capacitor 03.04 for correcting the frequency characteristic and resistors R8
and R are connected between the terminal ■ of the variable resistor ■ and the center tap 0,
which is a center tap, t], K Each of the sliders VR, VB is connected to the 端子 terminal of the
amplifier 4a via a resistor R7 and connected to the 端子 terminal of the amplifier 4a via a resistor
R7 and grounded via a resistor R6. When the terminal ■ is (6) 1 nondirectional, when it is at the
terminal ■ primary unidirectionality, when it is at the terminal ■ secondary unidirectivity can
be obtained while the slider is a terminal The output level is increased by the variable resistor VR
as the potential from the terminal to the terminal 2 is increased. Here, if you get annoyance, you
can have f resistance! l! VB、。 Set s4 of VR to terminal s4. As a result, the output of the
microphone lc is maximized, while the output of the microphone 1b is minimized, mixed with the
output of the microphone 1a, and taken out from the output terminal 5 via the frequency
correction circuit 4 '. At this time, to the capacitor C4 of the frequency characteristic correction
circuit 4 ', the OS% resistance. The circuit consisting of R9 is short-circuited by the slider of the
variable resistor VR, {circle around (5)} around tl! The frequency characteristic of the
characteristic correction circuit l is flat. Variable resistor ■, when obtaining primary unidirectionality. Connect the VR, slider to one child. As a result, the outputs of the microphones lc
and lb are both grounded via the center tap of the variable resistor 3, so they are not taken out
from the slider, and only the (1) output of the microphone la has dark wave number
characteristics It is taken out from the output terminal 5 through the divine regular turn # 14 '.
At this time, the frequency l of the frequency inertia circuit 4 '! The turn to change the
characteristics is the case of one period and r8 '! Since it is short-circuited by the slider to the
fence, w4al ai III is flat. When the slider is displaced from the terminal 端子 to the terminal O, the
output of the microphone lc gradually decreases with the change of the resistance 1 of the
variable resistor VR, so the directivity gradually goes to the primary unidirectivity On the other
hand, the variable resistor n R changes the amount of feedback of the amplifier 4a due to a
change in resistance value, so that the microphone 1a. The mixed output level of lc gradually
increases. When obtaining second-order uni-directionality, f-resistor VR ,. Connect the VR, slider
to terminal ■. As a result, the output of the microphone lc is minimized, and the output of the
microphone la and the output of the microphone lb are added. At this time, the output of the
microphone lb is subjected to 180 ° phase inversion in the phase shift circuit 6 and added to
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the output of the microphone la at a high frequency extremely higher than ω and -1, and
substantially reverse phase addition is performed. As a result, the output of the microphone lb is
an output of the microphone 1a at a very low number C of transmissions which is 4 much lower
than ω / 4 + 1 = 1, while it is possible to obtain a second-order unidirectionality (8) As shown in
Fig.6, the frequency of 41 $ in the case of 50 Hz of the angular frequency 伽 is obtained in the
case of IEI figure and that of the barrel in order to obtain the primary unidirectivity in order to be
added in phase with W. It is.
In addition, when the slider is in potential across the ladder terminal, etc., the mixed output level
of the microphones la and lb gradually increases due to the resistance 4 @ change of the variable
resistor ■, while the B7 variable resistance i The variation of the impedance of X4 connected
between the terminals {circle over (1)} and {circle over (6)} of the unit VR changes the frequency
characteristic of the frequency characteristic correction circuit 4 '. In this case, the frequency
characteristic of the mixed output of each microphone is only lowered by about 13 dB at the mid
frequency as shown in FIG. 6E, so the correction amount of the frequency characteristic
correction circuit 4 'is a characteristic opposite to that of FIG. The correction amount is smaller
than that of the conventional one, the SN ratio can be improved, and wind noise and the like are
less likely to occur. In the dark wave number characteristic correction circuit 4 ', the resistance
value of the resistor R6 (9) R1 is larger than the resistance value of the variable resistor aVR, the
resistance (R, ◆ l'L), and the capacitance of the capacitor C1. The value is selected to be smaller
than that of the capacitor C4. In addition, variable resistor ■ 6, resistors KR ,, R, capacitor 01 *
Ca, medium and high frequency ll1a! The number characteristic is determined, and the frequency
characteristic in the low range is determined by the variable resistor 6, the resistors R to R0, and
Conden + Cs + 04. As described above, the variable directional microphone to be the present
event is a two-stage variable resistor with center tap via the phase shift circuit at the output of
the microphone of the directional umbrella of the pair of microphones distributed in opposite
directions to each other. Connect one end of one of the resistors, and connect the other end of
the resistor to the output of the backward microphone of the one pair of microphones to ground
its center tap, A mixer circuit for mixing the output from the slider and the output of the other
microphone to the other slider other than the one pair of microphones, Since the other resistor is
connected to the connected frequency characteristic correction (lO) IC '1 abbreviation, as t:
another fIrf resistor which changes directivity, III prime number factor characteristic mixed
output level It's two sets Small, inexpensive and insularly divided into four, and the power to
rotate is also small, and the father, the circuit can be configured simply, and furthermore, the
change characteristic of the resistance value is the general +1 罐It is easy to obtain because it can
be used in the common phase, and furthermore, it is possible to perform anti-phase addition at
high frequencies and in-phase addition at low frequencies since the phase shift circuit is used.
Therefore, the correction amount of the pigeon S number correction circuit can be reduced, and
the 8N ratio can be improved.
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