JPS5912239B2 - variable directional microphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable directional microphone, which has three primary sound pressure gradient single-directivity units that can obtain a first-order sound pressure gradient single-directivity from an omnidirectional one.
The axes of the directional microphones are placed on the same axis,
The purpose is to provide a small, lightweight microphone with a small diameter.

The present applicant previously published Japanese Patent Application No. 54-51691 entitled "Variable Directionality Microphone" with primary sound pressure gradient unidirectional (hereinafter referred to as 1)
A combination of three microphones (referred to as second-order unidirectionality) is arranged, and the directivity changes from omnidirectional to first-order unidirectionality to second order unidirectionality.
Next-order sound pressure gradient unidirectionality (hereinafter referred to as second-order unidirectionality)
We proposed a variable directional microphone that can be varied up to

As shown in the schematic diagram in FIG. 1, this device has a primary unidirectional microphone 1a and a primary unidirectional microphone 1c facing forward with their axes spaced apart by a distance d with respect to the sound source S. A primary unidirectional microphone 1b is arranged so that its diaphragm is in the same plane as the diaphragm of the microphone 1a, and a primary unidirectional microphone 1b is arranged so that its diaphragm is in the same plane as the diaphragm of the microphone 1a. It is fixed with a member.

Note that the outer diameters of the microphones 1a to 1c are all the same.

For example, when obtaining omnidirectionality, the interlocking variable resistor VR1,
Adjust vR2 so that the output of microphone 1b is maximum and the output of microphone 1c is minimum, and after adding the output of microphone 1a and the output of microphone 1b using adder 3, adjust the level using variable resistor ■R3. Adjust and take out the output from output terminal 4.

On the other hand, when obtaining primary unidirectionality, the microphone 1b,
Adjustments are made so that both outputs of Ic are minimized, and only the output of microphone 1a is taken out from terminal 4.

On the other hand, when obtaining secondary unidirectionality, microphone 1b
Adjust the output so that the output of the microphone Ia is the minimum and the output of the microphone 1c is the maximum, and the outputs of the microphones Ia and 1c are added and taken out from the terminal 4.

Compared to conventional microphones that combine two microphones and can vary from omnidirectional to first-order unidirectional to bidirectional, this device can vary the directivity over a wide range, and provides a sufficient sense of distance. By the way, this microphone 1a can achieve omnidirectional sound image zooming.
, 1b are installed so that their diaphragms are in the same plane, so the distances between the sound source S and each diaphragm are equal;
Although it is possible to obtain a distortion-free omnidirectional pattern that is theoretically faithful, the axes of the microphones 1a and 1b must be shifted from each other, so it is necessary to avoid increasing the outer diameter of the microphones. I can't do it.

That is, as shown in FIG. 2, the inner diameter of the microphone case 2 is at least the outer diameter of the microphone 1a and the microphone 1a.
It has to be larger than the sum of the outer diameter of b and has the problem that it is too large to be used as an attached microphone attached to a television camera or an 8 mm camera.

The present invention solves the above-mentioned problems, and each embodiment thereof will be described with reference to FIG. 3 and subsequent figures.

FIG. 3 shows a schematic diagram of a first embodiment of the variable directional microphone according to the present invention, and in the figure, the same components as in FIG. 1 are given the same numbers and symbols.

In the figure, the primary unidirectional microphone 1b' is located on the same axis as the microphones 1a and 1c, that is, facing backward with respect to the sound source S with the axis of the sound source S above, and behind the microphone 1a. The microphones 1a, 1b, and 1c are arranged at a distance ΔD from the rear surface of the microphone 1a to the diaphragm, and each of the microphones 1a, 1b, and 1c is fixed within the microphone case 5 with appropriate members.

Note that the outer diameters of the microphones la, 1b, and lc are all the same.

Microphone 1a. The circuits connected to the outputs of 1b and 1c are the same as those shown in FIG. 1, and their operations are also the same, so their explanation will be omitted.

Here, since the microphones 1a, 1b, and 1c are all arranged on the same axis, the inner diameter of the case 5 is 1a (lb') as shown in FIG.

Microphone 1a, 1 if the outer diameter is about the same as lc)
b'.

1c, and the outer diameter of the case 5 can be configured to be approximately Σ of the outer diameter of the case 2 shown in FIG. 1, and can be configured smaller than that shown in FIG. 1. Ideal as an accessory microphone for 8mm cameras.

Note that the microphones 1a and 1b that obtain omnidirectional
' are arranged with the same axis line above, so their respective diaphragms are not on the same plane, but a certain distance (D+△D-d)
I have no choice but to set them apart.

For this reason, as shown in Figure 6, the omnidirectional characteristic cannot provide a theoretically faithful directivity pattern (■) without distortion, but instead results in a slightly distorted directivity pattern (■). There is no problem in handling it as a directional microphone.

Also, since the microphone 1b is placed behind the microphone 1a, the overall length is slightly longer by △D than the length D shown in FIG. Since the outer diameter of the case is approximately Σ of the outer diameter of the case 2, the overall shape of the case can be made smaller than that shown in FIG.

FIG. 5 shows a schematic diagram of a second embodiment of the microphone of the present invention, in which the same components as in FIG. 1 are given the same numbers and symbols.

In the same figure, microphones 1a and 1b that obtain omnidirectional
is placed in front of the microphone 1c, at a distance similar to that shown in FIG. 3, with the axis of the sound source above, and is fixed to the case 5'.

Note that the outer diameters of the microphones 1a, 1b, and 1c are all the same.

The circuits connected to the outputs of the microphones 1a', 1'', 10' are the same as those shown in FIG. 1, and their operations are also the same, so their explanation will be omitted.

Here, since the microphones 1a, 1b, and 1c are all arranged on the same axis as shown in FIG.
The outer diameter of the case 5' can be made smaller than that shown in FIG.

On the other hand, since the distance between the diaphragms of microphones 1a and lc is d, and microphone 1' is placed between these microphones 1a and 1c, the overall length is less than that shown in Figure 3. can also be made shorter and configured to have the same length D as shown in FIG.

Further, the circuit from the microphone 1c to the adder 3 in FIG. 3 or the circuit from the microphone 1c to the adder 3 in FIG. 69990, Japanese Patent Application Laid-open No. 56-69991, and Utility Model Application No. 56-56289, the phase shift circuit and variable resistor, variable bypass filter, bypass filter and variable resistor, variable It may also be configured with a phase shift circuit.

As mentioned above, the variable directional microphone according to the present invention has the following features:
Three primary sound pressure gradient unidirectional microphones are arranged with their respective axes on the same axis, two facing forward and one facing backward with respect to the sound source, and the outputs from these microphones are By mixing the mixture and changing the mixing ratio, the directivity can be varied from omnidirectional to primary unidirectional to secondary unidirectional, so the inner diameter of the microphone case is approximately the same as the outer diameter of one microphone. All the microphones can be accommodated sufficiently if the diaphragm is placed in the same plane, making it possible to configure the case to be approximately ↓ the outer diameter of a conventional variable directional microphone case, which is smaller and lighter than the conventional one. can be configured,
It has features such as being ideal as an accessory microphone for television cameras and 8mm cameras.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 and 2 are a schematic diagram and a vertical cross-sectional view of the main parts of an example of a variable directional microphone previously proposed by the applicant, and FIGS. 3 and 4 are respectively FIG. 5 is a schematic diagram of a first embodiment of the variable directional microphone according to the present invention and a vertical cross-sectional view of its essential parts, FIG. 5 is a schematic diagram of a second embodiment of the microphone according to the present invention, and FIG. This is a pattern of theoretical and measured values. 1a, 1a', 1b', 11r, 1c, 1c'...1
Next unidirectional microphone, 3... Adder, 4...
Output terminal, 5, 5'...Microphone case, VR1
~vR3...variable resistor, S...sound source, t...axis line.

Claims (1)

[Claims] Three 11th-order sound pressure gradient unidirectional microphones are placed on the same axis, with two facing forward and one facing backward relative to the sound source, and the outputs from these microphones are By mixing and varying the mixing ratio, the directivity changes from omnidirectional to primary sound pressure gradient single-directivity to secondary sound pressure gradient single-directivity.
A variable directional microphone characterized by being configured so that even the directivity can be varied.