JPS6228158Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a variable directional microphone, which uses a double variable resistor with a center tap as a variable resistor to vary the directivity, frequency characteristics, and mixed output level, and is compact and has a simple circuit. The purpose of the present invention is to provide a microphone that can be configured as follows.

The present applicant previously published Japanese Patent Application No. 54-51691 entitled "Variable Directionality Microphone," in which three microphones with primary sound pressure gradient unidirectionality (hereinafter referred to as primary unidirectionality) were used as a sound source. Two microphones are placed facing forward and one microphone is placed backward, and the outputs of these microphones are mixed and the mixing ratio is varied by a predetermined amount to change the directivity from omnidirectional to primary unidirectional. We have proposed a microphone configured to be able to vary the directionality, secondary sound pressure gradient, and even unidirectionality (hereinafter referred to as "secondary unidirectionality"), and to also be able to vary the volume as the directivity is varied. This device has two primary unidirectional microphones facing each other and changes the mixing ratio of the microphone output to change the directivity from omnidirectional to unidirectional.
Compared to conventional devices that obtain bidirectionality, the directivity can be varied over a wide range, and sound image zooming can be performed with a sufficient sense of distance.

On the other hand, the present applicant previously published Japanese Patent Application No. 54-145357 entitled "Variable Directional Microphone" by connecting a high-pass filter to one primary unidirectional microphone placed facing forward to the sound source. We proposed a microphone configured to add the output in reverse phase to the output of other microphones and vary the mixing ratio to vary the directivity. Compared to the frequency characteristics of conventional ones, this one can prevent loss of level especially in the low range and can configure the equalizer correction amount to be smaller.

FIG. 1 shows a circuit diagram combining the two "variable directional microphones" proposed above. In the figure, microphones 1a and 1b are arranged facing forward with respect to the sound source 2, and microphone 1c is arranged facing backward with respect to the sound source 2. VR ₁ to _{VR 4} are four variable resistors, and when each slider is at the terminal, it is omnidirectional, when it is at the terminal, it is primary unidirectional, and when it is at the terminal, it is secondary unidirectional. On the other hand, as the slider is displaced from terminal to terminal, the output level is increased by the variable resistor VR ₃ , and the resistance between the terminal and the slider is The variable resistors VR ₂ and VR ₃ are as shown in FIG. 2, and the variable resistors VR ₁ and VR ₄ are as shown in FIG. 3.

Here, if you want omnidirectionality, use variable resistor VR ₁
When the sliders of ~VR ₄ are connected to the terminals, the outputs of the microphones 1a and 1c are added at the same level via amplifiers 3a and 3c, respectively, and taken out from the output terminal 5 via the frequency characteristic correction circuit 4. When obtaining primary unidirectionality, when the sliders of the variable resistors VR ₁ to VR ₄ are connected to the terminals, the output of the microphone 1c is attenuated and only the output of the microphone 1a is connected to the amplifier 3a and the frequency characteristic correction circuit 4. When obtaining secondary unidirectionality by using a variable resistor
When the sliders VR ₁ to _{VR 4} are connected to the terminals, the outputs of the microphones 1a and 1b are connected to the amplifiers 3a and 3, respectively.
b and 3b' with opposite phases and the same level, the output level is increased by the variable resistor _VR3 , and the frequency is corrected by the frequency characteristic correction circuit 4, and then taken out. At this time, the cut-off frequency of the high-pass filter 6 composed of the capacitor C ₁ and the variable resistor VR ₁ is 100 Hz, the distance D between the microphones 1a and 1b is 3 cm, and the microphone 1a is
The frequency characteristic diagram when the angle between ~1c and the sound source 2 is 0° and 90° is as shown in Figure 4,
Particularly in the low and mid-range frequencies, the response does not deteriorate as in the conventional case. For this reason, the frequency characteristic correction circuit 4 only needs to be able to correct about 13 dB, as is clear from the 0° characteristic shown in FIG. 4, and the amount of correction is smaller than that of the conventional circuit.

However, this one uses special resistors as variable resistors VR ₁ and VR ₂ to vary the directional characteristics, variable resistor VR ₃ to vary the output level, and variable resistor VR ₄ to correct the frequency characteristics. It is necessary to use a four-unit circuit with variable characteristics, which makes it difficult to construct a compact and inexpensive circuit. Also, a large torque is required to drive the circuit, and the circuit cannot be constructed easily. There are problems such as not having one.

The present invention solves the above problems, and one embodiment thereof will be described below with reference to FIG. 5.

FIG. 5 shows a circuit diagram of an embodiment of the variable directional microphone according to the present invention, in which the same parts as in FIG. 1 are designated by the same numbers and symbols. In the same figure,
VR ₅ and VR ₆ are two variable resistors with a center tap, and the terminal of the variable resistor VR ₅ is connected to the phase inversion amplifier 3b' via the capacitor _C1 , and the terminal is grounded at the center tap. The terminal is connected to an amplifier 3c. Between the terminal of the variable resistor VR ₆ and the center tap terminal, there are capacitors C ₄ , C ₅ for correcting the frequency characteristics.
Resistors R ₈ and R ₉ are connected, and the terminal is connected to resistor R ₇
It is connected to the terminal of the amplifier 4a via R6, and is grounded via a resistor _R6 . VR ₅ ,
When each slider of VR ₆ is at the terminal, you can obtain omnidirectionality, when it is at the terminal, you can obtain primary unidirectionality, and when it is at the terminal, you can obtain secondary unidirectionality. The output level is configured to increase by the variable resistor VR ₆ as it moves toward the terminal.

Here, if you want omnidirectionality, use a variable resistor
Connect the sliders of VR ₅ and VR ₆ to the terminals. As a result, the output of the microphone 1c becomes the maximum, while the output of the microphone 1b becomes the minimum, is mixed with the output of the microphone 1a, and is taken out from the output terminal 5 via the frequency characteristic correction circuit 4'.
At this time, the capacitor of the frequency characteristic correction circuit 4'
The circuit consisting of C ₄ , C ₅ and resistors R ₈ and R ₉ is a variable resistor
Since it is short-circuited at the slider of VR ₆ , the frequency characteristic of the frequency characteristic correction circuit 4' is flat.

When obtaining primary unidirectionality, variable resistor VR ₅ ,
Connect the slider of VR ₆ to the terminal. This results in
The outputs of microphones 1c and 1b are both variable resistors.
Since it is grounded through the center tap of the VR ₅ , it is not taken out from the slider, and only the output of the microphone 1a is taken out from the output terminal 5 via the frequency characteristic correction circuit 4'. At this time, since the circuit for varying the frequency characteristic of the frequency characteristic correction circuit 4' is short-circuited by the slider as in the above case, the frequency characteristic is flat. Note that when the slider is displaced from terminal to terminal, the output of microphone 1c gradually decreases due to the change in the resistance value of variable resistor VR ₅ , so the directivity gradually becomes unidirectional. , the feedback amount of the amplifier 4a changes as the resistance value of the variable resistor VR ₆ changes, so that the mixed output level of the microphones 1a and 1c gradually increases.

When obtaining secondary unidirectionality, variable resistor VR ₅ ,
Connect the slider of VR ₆ to the terminal. This results in
The output of the microphone 1c becomes the minimum, and the output of the microphone 1a and the output of the microphone 1b are added in reverse phase. At this time, a high pass filter 6' is constituted by the capacitor _C1 and the variable resistor _VR5 , and the microphones 1a and 1b are
The outputs of the microphones are mixed in opposite phases and at the same level, making it possible to obtain a secondary unidirectional pattern.On the other hand, at low frequencies below the cutoff frequency, only the output of the microphone 1a is taken out, resulting in a primary unidirectional pattern. Unidirectionality can be obtained, and the cutoff frequency is
The frequency characteristics in the case of 100 Hz are as shown in FIG. 4, similar to those in FIG.

Furthermore, when the slider is displaced from terminal to terminal, microphone 1 is controlled by variable resistor VR ₅ .
As the output level from microphone b increases continuously, the mixing ratio of microphones 1a and 1b changes from small to large, changing from primary unidirectional to secondary
The range up to the next unidirectionality can be varied continuously.

Also, when the slider is displaced from terminal to terminal, the mixed output level of microphones 1a and 1b gradually increases due to the change in the resistance value of variable resistor VR ₆ , and on the other hand, the mixed output level of microphones 1a and _1b gradually increases. The frequency characteristics of the frequency characteristic correction circuit 4' change due to changes in the impedance of the terminals and the circuits connected therebetween. In this case, the frequency characteristics of the mixed output of each microphone are in the mid-range frequency as shown in Figure 4.
Since the amount of correction is only about 13 dB or less, the correction amount of the frequency characteristic correction circuit 4' only needs to have a characteristic opposite to that shown in Fig. 4, and the amount of correction is smaller than that of the conventional one, and the SN ratio is In addition, wind noise is less likely to occur.

In addition, in the frequency characteristic correction circuit 4', the resistor
The resistance values of R ₆ and R ₇ are variable resistor VR ₆ and resistor (R ₈ +
The resistance value of capacitor C ₄ is much smaller than that of R ₉ ).
The capacitance value of is selected to be extremely smaller than that of capacitor _C5 . Also, variable resistor VR ₆ , resistance
R ₈ , R ₉ capacitors C ₄ , C ₅ determine the frequency characteristics in the middle and high frequencies, and variable resistor VR ₆ , resistors R ₆ to _{R 9} , and capacitors C ₄ and C ₅ determine the frequency characteristics in the low frequency range. decide.

Further, in the above embodiment, the phase inverting amplifier 3b' is connected only to the output side of the microphone 1b, but it may be configured to connect the amplifier 3b' only to the output side of the microphone 1c and the output side of the microphone 1a. , in short, take out the outputs of microphones 1b and 1c in opposite phases, and
Any configuration is sufficient as long as the outputs of a and 1b are taken out in opposite phases.

As mentioned above, the variable directional microphone according to the present invention connects both ends of one resistor of a dual variable resistor with a center tap to the outputs of a pair of microphones arranged in opposite directions, and also connects the center tap to the ground. A mixing circuit for mixing the output from the slider and the output from the other microphone is connected to the slider of this one resistor and the other microphone other than the pair, and a mixing circuit is connected to this circuit. Since the other resistor of the variable resistor is connected to the frequency characteristic correction circuit, two sets of variable resistors are required to vary the directivity, frequency characteristics, and mixed output level, and four sets are sufficient. It is smaller and cheaper than the conventional one, requires less rotation force, and can be easily configured as a circuit.Furthermore, the resistance value change characteristic can be a general linear one. It is easy to obtain, and since it uses a high-pass filter, it can prevent level loss, especially in the low range, so it has the advantage of reducing the amount of correction in the frequency characteristic correction circuit and improving the SN ratio. .

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a variable directional microphone previously proposed by the applicant, Figs. 2 and 3 are resistance change characteristic diagrams of a four-set variable resistor used in the microphone shown in Fig. The figure is a frequency characteristic diagram in the 0° direction and 90° direction obtained by the circuit shown in FIG. 1, and FIG. 5 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'...High pass filter, VR ₅ , VR ₆ ...Double variable resistor with center tap, _C1 , _C4 , _C5 ...
Capacitor, _R6 to _R9 ...Resistance.

Claims (1)

[Claims for Utility Model Registration] Three primary sound pressure gradient unidirectional microphones are arranged in combination, two facing forward and one facing backward with respect to the sound source, and these microphones are connected to each other. Connect both ends of one of the variable resistors with a center tap to the outputs of a pair of microphones arranged in opposite directions, respectively, and ground the center tap of the two variable resistors with a center tap. A mixing circuit that mixes the output from the slider and the output from the other microphone is connected to the slider and another microphone other than the pair of microphones, and the mixing circuit is connected to the two-unit variable with center tap. A variable directional microphone that is connected to a frequency characteristic correction circuit connected to a variable resistor with a center tap on the other side of the resistor. A part of the variable resistor with a center tap has one end connected to the center tap, and a resistor and a capacitor on one side form a high-pass filter, and the center tap of the other variable resistor with a center tap is connected to the center tap. The frequency characteristic correction circuit is connected to an element that varies the frequency characteristics, and the high-pass filter side of the one center-tapped variable resistor is connected to the forward-facing microphone. Connect the other side to the rear-facing microphone,
The outputs of the microphones connected to one of the variable resistors with a center tap are taken out in opposite phases to each other, and the outputs of the two microphones arranged forward are taken out in opposite phases to each other. A variable directional microphone according to claim 1 of the utility model registration claim.