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JPS5883495

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DESCRIPTION JPS5883495
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone having a single directional characteristic configured by combining two single
directional microphone units. (Technical background of the invention) As indicated by the
directional characteristics of FIG. 1A, conventionally supplied unidirectional microphones are
generally highly sensitive to sound from the front direction, that is, the direction of Oo, It is
designed to cancel the sound from the side (90 ░, 270 ░) direction and the back (180 ?)
direction, and it is for vocals and musical instruments by using the advantage of reliably
collecting the target sound. , Are often used for interviews and the like. The A-directional
microphone is, in theory, an omnidirectional microphone having non-directional characteristics
as shown in the second prisoner and an intermediate microphone of a bi-directional microphone
having 80-character directional characteristics as shown in FIG. And obtained by combining an
omnidirectional microphone and a bi-directional microphone. FIG. 1 shows an ideal unidirectional characteristic obtained by theoretical light combination of an omnidirectional
microphone and a bi-directional microphone, and the response in the 180 ░ direction is zero.
(Problems of the Background Art) However, as can be seen from FIGS. 1a and 1b, although the
unidirectional microphone should theoretically have zero response in the 180.degree. Direction,
it is generally possible to use a single supplied microphone. In the so-called uni-directional
microphone, it has directivity characteristics (so-called polar pattern) in which resbons in the
180 ░ direction remain in the ring from the relationship of the structure, material, etc. of the
microphone, and the sensitivity in the back direction is suppressed to zero. I can not As a result,
the sound from the back direction can easily enter the microphone other than the target sound,
and there is a drawback that the original function of the unidirectional microphone can not be
sufficiently exhibited. Further, when this kind of unidirectional microphone is used as an 8 mm
camera, a microphone for a video camera or a microphone for broadcasting, it is difficult to pick
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up the device noise and to significantly deteriorate the S / N ratio. SUMMARY OF THE
INVENTION The present invention has been made to solve the above-mentioned drawbacks, in
which two unidirectional microphone units are arranged in the back and forth direction of each
other, and the output of the microphone unit directed rearward. Is synthesized with the output of
the microphone unit directed forward through the attenuation circuit to output a composite code,
a microphone capable of suppressing a feeling in the back (180 ░) direction to near zero. The
purpose is to provide. (Embodiments of the Invention) Embodiments of the present invention will
be described in detail below.
FIG. 3 is a circuit diagram showing an embodiment of the microphone of the present invention. In
the figure, the microphone unit 1 ░ 2 has, for example, a structure as will be described later, and
is a king of single-directionality in which frequency characteristics, directional characteristics and
structure 9 are aligned. It is a rectoret type microphone unit. One microphone unit 1 is disposed
forward, ie, in the direction of the sound source S, and the other microphone unit 2 is disposed
rearward, ie, in the back of the sound source S (in the direction of 180 ░ with respect to the
sound source). The output of one microphone unit 1 disposed forward is input to the synthesis
circuit 3, and the output of the microphone unit 2 disposed rearward is input to the synthesis
circuit 3 via the attenuator 4 formed of a variable resistor. The addition synthesis signal of both
microphone units 1.2 is output from the synthesis circuit 3 to the output terminal 5. Although
not shown, these microphone units 1.2 are accommodated in the microphone case together with
the synthesizing circuit 3 and the attenuator 4 with the pointing main axes parallel to each other,
and the electret shown in FIG. The concrete structure of the microphone part of the microphone
units 1 and 2 is shown. A fixed electrode 7 having an electret element formed on a back plate is
accommodated and fixed in the upper surface recess of the support 6 with the electret element
facing upward, and the fixed electrode 7 is mounted on a spacer ring 8 mounted on the upper
edge of the support 6 A thin film diaphragm 9 on which a metal film is vapor-deposited is fixed
on the front of the. A pressure plate 11 is attached to the lower surface of the support 6 via an
acoustic resistor 10, and lead wires 12 pass through the support 6 and the pressure plate 11 and
are led out from the fixed electrode 7. Reference numeral 13 is a weir ring. The microphone unit
1.2 shown in FIG. 3 is configured by connecting an impedance conversion circuit (not shown) to
the fixed electrode 7 and the thin film diaphragm 9 shown in FIG. Next, the operation of the
microphone of the present invention configured as described above will be described. In the
present invention, when sound waves propagate from the sound source S to the respective
microphone units 1.2, the respective microphone units 1.2 are arranged in opposite directions
from each other, and the respective microphone units 1.2 have substantially the same amplitude
and reverse to each other. An audio signal of a phase is output and input to the synthesis circuit
3. In this case, since the output of the microphone unit 2 disposed rearward is added to the
combining circuit 3 via the attenuator 4, the output level of the microphone unit 2 applied to the
combining circuit 3 is variable. As a result, the response in the 180 ? ? direction of the
microphone unit 1 placed forward and the O of the microphone unit 2 placed backward.
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If the response in the direction is adjusted equally by the attenuator 4, the outputs of the two
microphone units 1.2 are in opposite phase to each other, so that the synthesized signal which
canceled each other can be obtained from the synthesizing circuit 3. That is, as shown in FIG. 5A,
the directivity characteristic of the microphone unit 1 disposed forward is a characteristic in
which the response remains in the direction of 180 ░, and has the frequency characteristic
shown in FIG. 6A. Note that the curves of 0 ? ?, 90 ░ and 1800 in FIG. 6 show the
characteristics corresponding to 0 ░, 90 ░ and 180 ░ in the respective directions in FIG. When
the 0 ░ response of the microphone unit 2 directed backward is equal to the response of the
microphone unit 1 in the 1800 direction, the directivity characteristic as shown in FIG. 5B (based
on the direction in FIG. 5A) is obtained. The frequency characteristics are as shown in FIG. As a
result, when the output of the microphone unit 1 and the output of the microphone unit 2
attenuated by the attenuator 4 are combined by the combining circuit 3, the output signals of
both are canceled and the response in the direction of 180 ? ? as shown in FIG. 5C. It is
possible to obtain a directivity characteristic in which is reduced to zero or near zero. FIG. 7 is its
frequency characteristic diagram. Thus, the microphone of the present invention can suppress
the response in the 180 ░ direction back to zero or near zero, and therefore has a nearly ideal
single directivity characteristic as shown in FIG. It is difficult to pick up the noise from the
direction, and it can fully exhibit the advantages as a unidirectional microphone. Further, from
the frequency characteristic diagram of the microphone of the present invention shown by a
broken line in FIG. 7, the solid line with a large noise in the 180.degree. Direction shows the
180.degree. Response to FIG. Furthermore, since the attenuation in the low range is increased
compared to individual microphone units, it is possible to suppress the enhancement of the bass
produced by the proximity effect, and the sound quality is improved. In the microphone of the
present invention, since the output of the microphone unit 2 directed backward is added to the
combining circuit 3 through the attenuator 4 composed of a variable resistor, the directivity
characteristic can be continuously varied by varying the attenuation edge in the attenuator 4 It is
possible. For example, when the microphone of the present invention is used as a sound
collection microphone for a video camera or an 8 mm camera, the sensitivity of the microphone
unit 1 directed forward and the attenuation amount of the attenuator 4 can be synchronized to
be variable. Synchronization with the zooming of the lens provides ideal uni-directional
characteristics in accordance with zooming, and has the advantage of continuously obtaining the
depth of sound matched to the image.
In the microphone of the present invention, by reducing the attenuation * ii of the attenuator 4,
the outputs of the opposite phases from both microphone units 1.2 are synthesized at almost the
same level, as shown by the nondirectional characteristic in FIG. 2A. It can also be used as an
omnidirectional microphone. The attenuator 4 in the above-described embodiment is not limited
to the variable resistor, and an attenuation circuit using a conventionally known active element
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3
or the like can be used. (Effect of the Invention 5I) As described above, the microphone of the
present invention arranges two unidirectional microphone units having the same characteristics
in opposite directions to each other, and outputs the output of the microphone unit directed
forward. Since the output is synthesized with the output of the microphone unit directed
backward through the attenuation circuit, a conventional unidirectional microphone, that is, a
microphone whose response remains in the 180 ░ direction and does not become an ideal ? directional characteristic Using it, a uni-directional characteristic close to an ideal can be
obtained. Further, by making the attenuation amount in the attenuator circuit variable, it
becomes possible to continuously change the directivity characteristics from the omnidirectional
characteristics to the single directivity characteristics, and the microphone use range is
expanded.
[0002]
Brief description of the drawings
[0003]
Figures 1a and 1b show a single directional characteristic diagram and an ideal single directional
characteristic diagram showing a conventional unidirectional microphone, and Figures 2a and 2b
show omnidirectional microphones and bidirectional microphones. 3 is a circuit diagram showing
one embodiment of the microphone of the present invention, FIG. 4 is a cross-sectional view
showing the main part of the microphone unit in the microphone shown in FIG. 3, FIG. Is a
diagram for explaining the directivity characteristics of the microphone of the present invention
shown in FIG. 3, FIGS. 6A and 6B are frequency characteristics of the microphone unit of the
present invention shown in FIG. 3, and FIG. 7 is shown in FIG. It is a frequency characteristic
figure which the microphone of this invention shows.
1.2 ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии
иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии и Fixed electrode 8 ииииииииииииииииииииииииииииииииииииииии Thin film
diaphragm 12 иииииииии
ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии Fig. 1 0 ░ 18! J12 Figure AB Figure 4 Figure 6 Figure 8 8 (dB Figure 7 Oka y Il Number (KHz) Procedure
Amendment (Method) April 8, 1976 1. Display of the case Patent application No. 181493 No. 2,
name of the invention Microbon 3, relationship with the case making correction Patent applicant
4, agent 6, number of inventions increased by correction 07, correction On page 10, line 3 of the
subject's deposit box, delete ", a and b".
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