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JPS61219298

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DESCRIPTION JPS61219298
[0001]
Industrial Applicability The present invention can arbitrarily cut the low band or the high band.
FIG. 7 is a cross-sectional view of a conventional electret condenser microphone. The
configuration of this conventional example will be described below with reference to FIG. In FIG.
7, 1 is a drawing cloth, 2 is a cylindrical metal case having a sound hole 2a on the top surface, 3
is a film ring formed by uniformly stretching a vibrating film 4 having a metal surface by metal
deposition or the like, 5 is Reference numeral 6 denotes a fixed electrode, 7 denotes a pot-like
insulator, 8 denotes a FET, 9 denotes a printed circuit board, 10 denotes a back air chamber, and
11 denotes a front air chamber. In this description, a wheel electret type using an electret
material for the vibrating membrane 4 is taken as an example, but the same is true for a pack
electret type where an electret material is provided on the fixed electrode side. The fixed
electrode 6, the insulator 7, the FET 8, and the printed circuit board 9 can be considered as one
amplifier block, and the above-described portions are fixed to the metal case 2 by the caulking
portion 2b after being inserted into the metal case 2. In the electret condenser microphone
constructed as above, the typical frequency characteristic is shown in FIG. 8, but theoretically the
low band is substantially flat and the high band is the diaphragm. There is a Q near the
resonance frequency, and this point is a reproducible band. In recent years, electret condenser
microphones are mass-produced as built-in microphones for cassette tape recorders or
telephones etc. However, the frequency characteristic shown in FIG. 8 requires a wider band due
to AGC level, intelligibility and other reasons. In the past, low cut or high cut was used outside
the required band in the electric circuit. Therefore, there is a disadvantage that the number of
circuit parts increases, leading to an increase in cost. An object of the present invention is to
eliminate the above-mentioned drawbacks and to provide an electret condenser microphone
which does not require band limitation on the circuit side. Means for Solving the Problems In
order to achieve the above object, according to the present invention, the back air chamber can
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be ventilated to the front air chamber in front of the vibrating membrane to perform low-pass
cutting or high-pass cutting. It is something like that. Operation Therefore, according to the
present invention, an electric circuit can be used (although band limitation can be performed
acoustically). Implementation 9 ′ ′! The configuration of an embodiment of the present
invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view
of one embodiment, and the same parts as FIG. 7 are indicated by the same reference numerals.
In FIG. 1, reference numeral 7a denotes one or a plurality of notches provided in the insulator 7.
The back air chamber 10 acoustically ventilates the metal case 2 and the gap 10a such as an
amplifier block.
A front equalizer 12 is provided between the metal case 2 and the membrane ring 3 and has one
or a plurality of ventilating notches 12a near the outer periphery as shown in FIG. There is a
sound hole 12b near the center. Therefore, the back air chamber 10 ventilated to the gap portion
10a is ventilated to the front air chamber 11 by the notching portion 12a. A simple acoustic
equivalent circuit diagram when configured as described above is shown in FIG. The same
reference numerals as in FIG. 1 denote equivalent constants of the same parts. By setting the
acoustic constants of the A block and the B block appropriately from FIG. 3, it is possible to cut
the high band of the A block and cut the low band of the B block to perform band limitation. FIG.
4 is an example of the frequency characteristic in the case of the present embodiment, and the
range of band limitation is arbitrary. FIG. 5 is another embodiment of the present invention. The
same parts as in FIG. 1 are indicated by the same numbers. In FIG. 5, the difference between FIG.
1 and FIG. 1 is that the front equalizer 12 has a boundary portion 2d near the top surface side
wall inside the metal case 2 and one or a plurality of notched portions 2c. The boundary portion
2 d works the same as the front equalizer 12. Therefore, the same results as in FIG. 1 can be
obtained. FIG. 6 is a perspective view of the metal case 2. Although not shown in the present
embodiment, it is the main purpose of the present invention to vent the back air chamber 10 to
the gap 10a inside and to ventilate the front air chamber 11; And the like are the same as in the
subject matter of the present application even if they are configured similarly. As described
above, according to the present invention, since an electret condenser microphone capable of
acoustically arbitrary band restriction can be provided at low cost, band restriction on the
electric circuit side is unnecessary, and a tape recorder, The total cost of telephones and the like
can be reduced, and further, the performance such as recording and clarity can be improved.
Further, in the case of the present invention, there is also an advantage that an additional part is
attached to the outside of the microphone unit and acoustically configured (it is performed
internally, so a small band-limited microphone unit can be supplied.
[0002]
Brief description of the drawings
04-05-2019
2
[0003]
1 is a cross-sectional view of an electret condenser microphone according to an embodiment of
the present invention, FIG. 2 is a perspective view of the front equalizer in FIG. 1, FIG. 3 is a
simple acoustic equivalent circuit diagram in FIG. 5 is a cross-sectional view showing another
embodiment of the present invention, FIG. 6 is a perspective view of the metal case in FIG. 5, FIG.
7 is a perspective view of a conventional example, FIG. FIG. 8 is a frequency characteristic
diagram of FIG.
7a ······ notch, IOa ······ gap portion, 10 and old ... back air chamber, 11 ... ... before air chamber, 12
...... front equalizer 12a. Name of agent Attorney Nakashima Toshio et al. 1 person Fig. 2 Fig. 3
Fig. 4 □ F 歿) Fig. 6 Fig. 7 Fig. 8 + 1 orchid
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