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Description of the Invention Bi-directional condenser microphone 1, first and second sound-toelectricity conversion units comprising a vibrating film and a back electrode opposite thereto,
vibration of the first acousto-electric conversion unit The membrane is composed of electrets,
and the back electrode of the second acousto-electric conversion unit is attached to the back
electrode of the electret so that a signal can be taken out between the two diaphragms and the
back electrode. Bidirectional condenser microphone.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bi-directional
microphone using a condenser microphone unit. The co / de / sa mic a phone unit originally has
a rate directivity, but as a configuration for obtaining a bi-directional microphone using this, a
book as shown in FIG. 1 is considered Be And 9 are briefly described as + (1 m) (lb) #i
respectively, the first and second acoustic-electrical conversion units (hereinafter simply referred
to as conversion units). First, this conversion unit (11) K will be described. (2) is a vibrating
membrane, (3a) is a back electrode, and electrets (5 m) are attached to the surface opposite to
the vibration M (2) of the back electrode (31). Also, vent holes (acoustic holes) (4a) are formed at
a plurality of locations on the back electrode (3 m) and the electret C5m). The distance W1 is
determined by the back electrode (3 m) and the vibrating membrane (21 by the spacer (6 m). In
this case, the back electrode (3a) K is coated with the electrets (5a) as described above, so that
the vibration-(2) is formed of the thin metal plate itself, of the vibrating film such as thin or resin
It is possible to use one having a metal layer (conductive layer) deposited on the surface. As is
well known, the back electrode (3M) 11 is formed of a conductive material, and signals are taken
out from the back electrode (3a) and the vibration (EndPage: 1 moving film 12). The conversion
unit (1b) is configured in the same manner, and in this case, the diaphragm (2) is configured to
be used in common to the angle conversion unit (la) (lb). Therefore, for the conversion unit (1b),
the suffix b is substituted for the portion corresponding to the conversion unit (1a) instead of the
suffix breath, and the description thereof is omitted. Thus, the back electrodes (3a) and (3b) are
connected to each other, and in this case, the frame (7) is also electrically connected by forming
the frame (7) with a conductive material), the diaphragm (2) and Lead wires (8) and (9) are
respectively derived from the back poles (3a) and (3b). In such a configuration, the electret (5a)
of the conversion unit (1a) and the electret (5b) of the conversion unit (1b) are used as a
entanglement by using a book in which their polarities are opposite to each other. A
characteristic having bi-directionality as shown in FIG. 2 is obtained. In the figure, line a
represents an axis in the direction facing the microphone, and b represents an axis in the
direction facing the side surface of the microphone. In this way, the bi-directionality is obtained
in the microphone shown in FIG. 1 in the book, but there is a drawback that the frequency
characteristic of the low band thereof is greatly reduced.
This is because the vibrating film 12+ of the conversion unit (U) (lb) is made common, so that the
low frequency signal has almost no phase difference with the front and back surfaces of the
vibrating film (2) It turned out that it occurs because it can not be obtained. Also, according to
such a microphone, there is a disadvantage that the characteristics of the angle conversion parts
(1a) and (1b) will not match unless the air gaps Wa and wb of the conversion parts (1a) and (1b)
are equal to each other. Combining these also has the disadvantage of being a very difficult task
in the prior art. In the present invention, such drawbacks are avoided. Therefore, the frequency
characteristic does not deteriorate even in the low frequency range, and it is also desirable to
obtain a condenser microphone which can be configured as a relatively good product compared
to the prior art. An example of the bi-directional microphone according to the invention will be
described with reference to FIG. 2. The same reference numerals as in FIG. 1 denote the same
parts as in FIG. 1, and a description thereof will be omitted. In the present invention, having the
first and second conversion parts (1a) and (1b) is the same as the case of FIG. 1, but the
conversion parts (1a) and (1b) in the present invention Is a book with vibrating membranes (2a)
and (2b) respectively. In the first conversion unit (1a), the vibrating membrane (2m) is
constituted by an electret, the back electrode (3m) faces this, and the second converting unit (1b)
is the vibrating membrane (2b) itself A thin vibrating film such as a thin metal plate or a
synthetic resin with a conductive material deposited is used, and an electret (5) is deposited on
the surface of the back electrode (3b) facing the vibrating film (2b). That is, in one of the
conversion parts, the vibrating membrane (2a) itself is used as an electret, and in the other
conversion part, the electret (5) is attached to the back electrode (3b). In this case, electrets
having the same polarity with respect to the angle conversion parts (1a) and (1b) are used, and it
is possible to use negative charges as the electret charge. Then, since the conductive layer is
attached to the vibrating membrane (2a) of the conversion unit (1m), the vibrating membranes
(2a) and (2b) are electrically connected directly, and the back electrode (3a) and (3b) are directly
connected electrically and lead wires (8) and (9) from each other. As the vibrating membrane (2a)
and the electret (5), conventionally known ones can be used. According to such a table
configuration, each of the conversion parts (1a) and (1b) has a unidirectional characteristic as
shown in FIG. 4, so that the directivity directions thereof have an angle of The
microphones having the bi-directional characteristics shown in FIG. 2 can be obtained by being
combined with each other.
In the present invention, since the vibrating membranes (2a) and (2b) are positioned outward
with respect to the back electrodes (3a) and (3b), these vibrating membranes (2a) and (2b) There
may be a distance W between them, for example it can be configured 12-. Therefore, as
compared with the case of the microphone shown in FIG. 1 for the low frequency tube
replacement, the phase difference is sufficiently generated with respect to both the diaphragms
(2a) and (2b) compared to the case of the microphone shown in FIG. It is a turtle having a feature
that can reliably prevent EndPage: 2 from deteriorating as compared with the condenser
microphone shown in FIG. Also, by using one with negative charge as the vibrating membrane
(2a) and the electret (5), the charge holding time can be made sufficiently longer than the time of
positive charge, K, It is a demon that also has% armor that can be used for a long time. FIG. 5
shows another embodiment of the capacitor i according to the present invention, and in the
configuration shown in FIG. 3, the back electrode, (3) and (3b) are integrally formed in advance.
Are the same, and the operation 4 is the same, so the corresponding parts are given the same
reference numerals and the explanation thereof is omitted.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of an example
of a conventionally considered bi-directional capacitor microphone, FIG. 2 is its directivity
characteristic diagram, and FIG. 3 is a route of a bi-directional capacitor microphone according to
the present invention FIG. 4 is a directional characteristic view, and FIG. 5 is a cross-sectional
view showing another embodiment. (La) (lb) Fi First and t1g2 acoustic-electric conversion parts,
(2a) (2b) Fi vibrating membrane, (3a) (3b) Fi back electrode, (5) are electrets. ・ "Pa" agent Ito
voice "EndPage: 3
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