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Industrial Application Field The present invention relates to a microphone device that is strong in
howling and difficult to pick up ambient noise for loud-sounding or recording. The structure of
the prior art and its problems FIG. 1 shows the prior art, which will first be described. This is to
arrange single-directional microphone units 1 to 7 having directivity as indicated by 8 in a
straight line with directivity axes in the o0 direction in the figure, and these single-directional
microphones uninot 1 to The outputs of 7 are added by the adder 9 and output. FIG. 2 shows the
characteristics of the above conventional example. In the figure, 11 indicates the output in the
direction of 0 ░, 12 in the direction of 900, and 13 in the direction of 180 ░ in FIG. 1, and
14.15 indicates the directivity pattern of low and high frequencies. From these, in the
conventional one, very sharp directivity can be obtained in the high region, but in the low region
it becomes unidirectional, but the directivity in the low region becomes insufficient, which is a
serious problem. SUMMARY OF THE INVENTION The object of the present invention is to
improve the above-described conventional low-pass directivity and to provide a microphone
device having sharp directivity over the entire band. Configuration of the Invention The present
invention arranges a plurality of uni-directional microphones Unisoto in a straight line
perpendicular to the directivity axis or in an arc shape close to the straight line and adds the
outputs of the uni-directional microphones Unisoto , And four nondirectional microphone units
on the same arrangement line as the unidirectional microphones, of which the inner two output
sums and the outer two output sums A second microphone for outputting the difference between
It is a microphone apparatus comprised with the circuit which synthesize | combines the output
of a 2nd microphone. Description of an Actual Sister Example An embodiment of the present
invention will be described below with reference to FIGS. In FIG. 3, the unidirectional
microphones 21 to 27 and the adders 28 and 28 have the same configuration as that of the
conventional example shown in FIG. 1 and become the first microphone. 31 to 341 / j:
nondirectional microphone units arranged on the same straight line as the unidirectional
microphones 21 to 27. A second microphone is configured by the nondirectional microphone
units and the adder / subtractor 35. This first one. The output of the second microphone is
combined by a combining circuit consisting of a filter 36 and a subtractor 29 and output. FIG. 4
shows the characteristics of the embodiment of FIG. 3. 41 indicates the output in the direction of
0 ░, 42 indicates the direction of 9?Oo, 43 indicates the direction of 180 ░, and 44.45
indicates the low band. And the high-frequency directivity pattern is shown.
It can be seen from FIG. 4 that the microphone according to the present invention has a
significantly improved low-pass directivity. The principle will be described in detail below. Now,
assuming that the sound source is at the ? angular position in FIG. The low frequency output of
the second microphone can be obtained by the following equation. First microphone output crab
E1 = F ? (B (10 cos ?) second microphone output crab E2 = F ? ? (o (S1n2?)) where F ? (f)
is the sensitivity of the first microphone and It is a function showing frequency dependence, and
F / (, is a function showing sensitivity and frequency dependence of the second microphone.
Now, if a filter having the characteristics of F '(f) / F "(f) is inserted into E2, the next output crab
E2' is obtained. Subtracting this F ? 2 from El gives the following output: Eout two F (q (10 cos
?-5 in 2 (1) = F '(f) (1 + cos ?) cos ? The directivity of this E Out:, (1 + cos) cos ? is the second
sound IJ, E high directivity of the gradient form The directivity shown in FIG. 4 can be obtained
more sharply, that is, the directivity pattern shown in FIG. 4 can be obtained. In the embodiment
of FIG. 3, the filter 36 is adjusted to have the characteristics of F (f) / F '(B), and E, -E.ltoreq.
Although the microphones are arranged in a straight line in the above embodiment, as shown in
FIG. 5, even if they are arranged in an arc shape centered on one point, the directivity of the low
band becomes; I can do it. As described in detail in the invention, the present invention is capable
of sharpening its low-pass directivity without losing the appearance of the conventional example,
and can realize a microphone with extremely excellent directivity. By using this microphone, it is
possible to perform loud-sounding with less howling, and also possible to pick up sound with still
less ambient noise.
Brief description of the drawings
1 is a block diagram showing a conventional example, FIG. 2 is the same frequency characteristic
diagram, FIG. 3 is a block diagram showing one embodiment of the present invention, FIG. 4 is
the same frequency characteristic diagram, FIG. It is a figure which shows the example of
arrangement | positioning of the microphone of another Example.
21 to 27 ииииииииииииииииииии Unidirectional microphone unito, 31 to 34 ииииии Non-directional microphone
unit, 28 ииииии Adder, 29 ииииииииииии Vessel 35 .....-adder-subtractor, 36 ..... filter.
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