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JPS5964995

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DESCRIPTION JPS5964995
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates mainly
to a microphone device suitable for howling measures in a loudspeaker such as a hall. The
configuration of the prior art and its problems In general, a loudspeaker and a microphone are
installed in the hall in a loudspeaker such as a hall, and a howling phenomenon occurs when the
first loudspeaker gain is increased by acoustic coupling between the loudspeaker and the
microphone. In order to prevent this howling phenomenon, it is necessary to reduce the acoustic
coupling between the speaker and the microphone. A common method of this purpose is to use
directional microphones to reduce the sensitivity to sound waves from sources other than the
sound source position to be collected, that is, the sensitivity to sound waves coming from the
speaker. However, it is very difficult to realize a microphone t having sharp directivity over the
entire frequency band. Therefore, a howling prevention system has been conceived which
combines signal components to be fed back from a speaker to a microphone by acoustic coupling
in a & pseudo circuit and reduces this from a microphone output. FIG. 1 shows a conventional
howling prevention system. In FIG. 1, 11 is a microphone, 12 is a subtractor, 13 is a gain
controller, 14 is a simulation circuit, 16 is an amplifier, and 16 is a speaker. The operation of the
conventional anti-wurling system configured as described above will be described below. 8! In
a conventional loudspeaker system without the pseudo circuit 14 and the reducer 12, a loop
based on a sound-pulling coupling between the microphone 11-gain controller 13-amplifier 15->
speaker 16-> microphone 11, microphone 11 and speaker 16 is formed. The formation of this
loop is the cause of howling. The simulation circuit 14 is provided between the microphone 11
and the amplifier 15, and the input of the amplifier 15 is fed back to the output of the
microphone 11 (v.sub.41.degree.). That is, the simulation circuit 14 having the transfer function
H (z) is provided in parallel to the feedback loop resulting from the acoustic coupling having the
transfer function H (z), and the characteristic of the simulation circuit 14 to be H (z) -Hz. To
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cancel the component of the sound from the speaker 16 included in the output of the
microphone 11. However, in the configuration as described above, i (z) needs to be set by
acoustic measurement in advance, and adjustment during use is impossible. This indicates that
there is a risk that the yawling prevention effect may be lost if the sound field conditions such as
the position and direction of the microphone change during use.
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional
problems, and its object is to provide a microphone device having a yawling preventing effect
sufficient for any change in sound field conditions. The microbon device according to the present
invention is arranged with one main microphone element and directivity axes different from each
other, and the directivity is adjusted to W114 so that the sensitivity of the sound wave position
to be picked up is 0. A plurality of (11-1 uJ variable directivity microphone elements, sound l &
(i.e. sound waves from a speaker) coming from other than the sound source position to be
collected which is included in the output of the main microphone element from the outputs of
these variable directional microphone elements And a subtractor for subtracting the output of
the generating means from the output of the main micro-bon device to obtain the howling
prevention effect. DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 shows an
embodiment of the microphone device of the present invention. In FIG. 2, using three
nondirectional microphone cartridges 21, 22 and 23, one main microphone element And two TiJ
variable directional microphones. That is, the microphone cartridge 21 is a main microphone
element, the first variable directional microphone element including the microphone cartridge
21, the directivity adjuster 24 and the microphone cartridge 22, the microphone cartridge 21,
the directivity adjuster 26 and the microphone The second variable directional microphone
element including the cartridge 23 is configured, and by sharing the microphone cartridge 21,
the number of microphone cartridges is reduced. Then, the outputs from the first and second two
microphone directional microphone elements are dedicated to the synthesis circuit 26, and the
output by the sound from the speaker 30 included in the output of the main microphone element
is synthesized to reduce 3 '. 1. An output component of the sound from the speaker in the main
microphone element is removed by the filter 27. 28 is a gain controller, 29 is an amplifier, and
3o is a speaker. FIG. 3 shows the main part of the same microphone device in detail, and in FIG.
3, the speaker 31, ie, the sound source to be picked up, is at a distance of r.sub.1 r.sub.2 r.sub.3
from the respective microphone cartridges 21. , And the speaker 30 is at a distance r from the
microphone cartridge 21. The two variable directional microphone elements are arranged such
that their directivity i11 + deviates by 0 °. Further, it is assumed that the distance between the
acoustic terminals of the 02 variable directional microphone elements in which the speaker 30 is
in the direction shown by the angle θ in the drawing, that is, the distance between the
microphone cartridges 21 and 22 and 21 is d.
Then, assuming that sound pressures incident on the microphone cartridges 21, 22, 23 are
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P1P2P3, respectively, this sound pressure can be obtained by the following equation. Here, Pv is
the sound pressure reaching the micro bon cartridge 21 from the speaker 31, Pr is the sound
pressure reaching the microphone cartridge 21 from the speaker 30, and k is the wave number.
In the present embodiment, the directivity of the two variable directional microphone elements is
adjusted so that the sound pressure component from the speaker 31 is not included in the
output. That is, the directivity regulator 24.25 can perform the following operation. Normally r
':):> r r r d holds 1 2 3 or 3, and if rl, r 2 and r 3 are given, U's of each variable directivity
microphone element U' R 12 R 13 from speaker 31 It is possible not to include the sound
pressure PV. したがって、とのP12. If P13 is properly processed by the synthesis circuit 26,
Pr can be obtained, and Pv-Pr is executed to obtain Pv, that is, the speaker 2 and θ satisfying
this equation. Further, it is a method of performing an operation of 2 to obtain Pr. The above
describes the case of a planar arrangement in which one main microphone element and two
variable directional microphone elements are combined, and there is no howling preventing
effect when the speaker 3 o is not on this arrangement plane. Therefore, in this case, three
variable directional microphone elements may be three-dimensionally arranged as shown in FIG.
In FIG. 4, each of 41.42 and 43.44 is a lts 1 ((directional micro-bon cartridge, microphone
cartridge 41.42 and directional The second variable directivity microphone element is connected
by the microphone cars 11 and 41 and the directivity adjustment device 46, and the microphone
cartridge 41.44 and the directivity adjustment "V setter 4 end. The variable directional
microphone element of Then, the output of each variable directional microphone element is
added to the synthesis circuit 48 to create an output component from all other than the sound
source position included in the output of the microphone cartridge 41 as the main microphone
element, and the generated output Are configured to be added to the enemy calculator 49. If
more variable directional microphone elements are used, it is possible to average them as needed
to improve the calculation accuracy of Pr. In the above embodiment, the main micro-bon element
is shared as one of the two microphone cartridges which are uj variable directional microphone
confectionary 4'rQ components, but these are separated Is also possible.
Small, variable directional micro-bon element Shi L1. If the sensitivity of the position of lll 得 る
can be controlled to 0, the microphone element of another method, ie, 1 ° on the front surface?
It is also possible to construct one micro pon cartridge with holes and back holes. It is even more
effective if used in combination with the 610 distance system, which is the size of r1 r2 r3.
Effects of the Invention As described above, according to the present invention, unlike the
conventional method, the reaching sound from the speaker can be automatically obtained by
calculation and eliminated according to the change in the blind field, so that howling Has the
advantage of being able to prevent effectively.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a block diagram showing a conventional howling preventing system, FIG. 2 is a block
diagram showing an embodiment of the microphone J phone apparatus according to the
present invention, and FIG. 3 is a configuration showing the main part of the apparatus d FIG. 4
is a block diagram showing another embodiment of the same apparatus.
21.22.23
·······································································································································································································
·································· Subtractor , 28..., Gain controller, 29..., Amplifier, 30 .., speaker 41.degree. 42,
43, 44. 45.46.47
········································································································································································ Reduced Vunit. Name of agent Attorney Nakao Toshio 1 person Figure 1 / J figure 2 figure 3
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