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JPS5888994

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DESCRIPTION JPS5888994
[0001]
As a means for giving a sharp single directional characteristic (directivity) to the microphone,
conventionally, a method of adding an acoustic tube in front of the microphone, a method of
installing the microphone at the focal position of the parabolic reflector, plural Shown in FIG. 1 in
addition to each method such as arranging the microphone units having the single directivity in a
plane perpendicular to the sound source and calculating the output from each microphone unit
to obtain the output. As described above, a method is known in which microphone units having
unidirectionality are arranged in the front-rear direction, and an output from each microphone
unit is processed to obtain a required output. The sound pressure gradient type unidirectional
microphone according to the construction principle shown in the present invention has a smaller
microphone configuration than a unidirectional microphone according to the other method
described above. It has a feature that can be. In FIG. 1, S is a sound source, MI I MI is a
microphone unit having unidirectionality, SUB is a subtractor, 囮 is an equalizer, 0 is an output
terminal, and M1 is the one for the whole band. Using the unidirectional microphone units,
microphone units M and microphone units are disposed in the front-rear direction at a distance d
apart, and each microphone unit M1. The output signal from is subtracted by a subtracter SUB.
The output from the subtractor SUB is maximum when the wavelength 172 of the sound wave is
equal to the distance d between the two microphone units Mt, and is 0 when the wavelength of
the sound wave is an integral fraction of the above-mentioned distance. FIG. 2 is a frequencycharacteristic curve of the output signal of the subtracter SUB in the sound pressure gradient
type unidirectional microphone shown in FIG. 1. The output signal of the subtracter SUB is 6 db
from low frequency to high frequency. The output is increasing at a slope of / octave. Therefore,
it is necessary to flatten the frequency characteristic in the used band by correcting the
frequency characteristic of the output signal of the subtractor SUB by the equalizer circuit EQ
and sending it to the output terminal O. FIG. 3 is a curve diagram showing an example of
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equalizer characteristics of the equalizer circuit EQ, and FIG. 4 is an output signal sent from the
equalizer circuit EQ to the output terminal 0, that is, the sound pressure gradient of the
configuration shown in FIG. Front view of the front frequency characteristic curve of the singledirectional microphone. In order to make the frequency characteristic of the sound pressure
gradient type unidirectional microphone having the configuration shown in FIG. 1 flat as shown
in FIG. For example, as shown in FIG. 3, correction should be performed significantly in the low
frequency band, but such a large increase in signal components in the low frequency band is
obtained. When done, it becomes a problem that it becomes weak with respect to wind noise, socalled blowing, etc. in which a habit worsens.
As means for solving the above-mentioned problems, FIG. 5 (a). (B) A secondary sound pressure
gradient type mono-directional microphone p-phone with a configuration in which band division
is performed as shown in the figure was tried. That is, in FIG. 5W, S is a sound source, W. Wlh +
Ma4, Mai, etc. are each a unidirectional microphone unit, and LPF is a low pass filter, HPF is a
high pass filter, 5UBt, 5UBh is a subtractor, M ° C is an adder, 0 is an adder The microphone
unit Maz is disposed at a distance dz from the microphone unit cigar as an output terminal, and
the microphone unit Mh is disposed at a distance 4 dh in front of the microphone unit Mah
disposed on the same plane as the microphone unit Mat. The output signal of the microphone
unit W is passed through the low pass filter LPF and the output signal of the microphone unit
Mhj to the subtractor, and the output signal obtained from the subtractor 5UBt is added to the
adder ADD Supply the output signal of the microphone unit Mh as The signal passed to the filter
HPF and the output signal of the microphone unit Mah are applied to the subtracter SUB h, and
the output signal obtained from the subtractor 5UBh is supplied to the adder ADD as the other
input signal thereof. The microphone output is sent from the adder ADD to the output terminal 0,
and the distance dt between the microphone unit w and the microphone output m described
above, and the distance dh between the microphone unit Mh and the microphone unit Mah. Are
selected as in dz) d), the microphone unit M117 + Ma h is used as a microphone unit for the
entire band, and the microphone unit W is low due to the band limiting function of the low pass
filter LPF. Used as a microphone unit for Further, the microphone unit 胤 is used as a high-pass
microphone unit by the band-limiting function of the high-pass filter HPF, whereby a secondary
sound pressure gradient type uni-directional microphone is configured as a whole. Next, in FIG. 5
(FIG. 5 (b1), microphone units Ma L + Ma h for two full bands used in FIG. The output signal of
the low-pass filter LPF and the output signal of the high-pass filter HPF are added by the adder
ADD and then given to the subtractor SUB, and the output signal of the microphone unit for
whole band Ma from the subtractor SUB Although the output signal of the adder ADD is
subtracted and the output signal of ~ 岬 is sent to the output terminal 0, the secondary sound
pressure gradient type single signal shown in FIG. 5 (b) is used. The directional microphone pphone is equivalent to the secondary sound pressure gradient type mono-directional microphone
shown in FIG. 5 (a) described above.
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In the secondary sound pressure gradient type mono-directional microphone shown in FIGS. 5 (a)
and 5 (b), the frequency band thereof is divided into high and low two bands so that the
frequency thereof is divided. The characteristics are, for example, as shown in FIG. 6, and the
directivity characteristics are as illustrated in FIG. As apparent from the side of the frequency
characteristic curve shown in FIG. 6, the secondary sound pressure gradient type monodirectional microphone having the configuration as shown in FIGS. Since the decrease in the
output in the band is small, it can be practically used sufficiently without using the equalizer
circuit, and therefore, FIG. 5 (a). (B) According to the secondary sound pressure gradient monodirectional microphone p-phone having the configuration as shown in the figure, the defects in
the conventional microphone described with reference to FIG. 1 can be eliminated well. However,
if the secondary sound pressure gradient type mono-directional microphone having the
configuration as shown in FIG. 5 (a) or (b1) is separated from the sound source by more than a
certain degree, Although it is possible to obtain frequency characteristics as shown in the figure,
when the sound source and the microphone are close to each other, the output of the signal
component in the low frequency band becomes abnormally high. As described above, when the
microphone is used in a state in which the sound source is in close proximity to the microphone,
the recorded sound has become an abnormally emphasized sound in the low range, and its
improvement has been demanded. The present invention, as shown in FIGS. 5 (a) and 5 (b), is a
secondary sound pressure gradient single type without the above-mentioned problems in a
secondary sound pressure gradient type single directional microphone in which band division is
performed as shown in FIG. -The purpose of the present invention is to provide a directional
microphone. Hereinafter, the specific content of the secondary sound pressure gradient type
mono-directional microphone ホ ン phone of the present invention will be described in detail
with reference to the attached drawings. explain. FIG. 8 is a block diagram showing the
configuration of a secondary sound pressure gradient type mono-directional microphone
according to the present invention. In FIG. 8, S is a sound source, and Mh is a unidirectional
microphone for high frequency band. Unit, Ma: Unidirectional microphone unit for all bands, W:
Unidirectional microphone unit for low band, HPF: high band filter, LPF: low band filter, ADD:
adder, SUB: subtraction 0 is an output terminal. The high-frequency microphone unit Mh is
disposed closer to the sound source S than the position of the full-band microphone unit Ma such
that the distance to the full-band microphone unit Ma is dh. In addition, the low-range
microphone unit W is disposed so that the distance between the above-described full-band
microphone unit Ma and the above-described full-band microphone unit Ma is a at a position
farther from the sound source S than the position of the full-band microphone unit Ma. There is.
The microphone unit for high frequency band Mh and the microphone unit HM for low
frequency band have the same characteristics as the microphone unit for full frequency band Ma,
and the microphone unit for high frequency band is Mh The filter HPF performs its band
limitation, and the low-pass microphone unit conflicts its band limitation by the low pass filter
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LPF. The output signal from the high-pass microphone unit Mh passing through the high-pass
filter HPF and the output signal from the low-pass microphone unit ML passing through the lowpass filter LPF are added by the adder ADD The subtractor SUB is supplied as a subtraction signal
to the subtractor SUB, and the subtractor SUB is supplied with the output signal of the
microphone unit Ma for the entire band. The output signal from the subtractor SUB is sent to the
output terminal O as the output signal of the microphone. The secondary sound pressure
gradient type mono-directional microphone of the present invention having the above-described
configuration includes the high-frequency microphone unit Mh, the low-frequency microphone
unit Mt, and the full-band microphone unit for band division. As an aspect of the arrangement
with Ma), as shown in FIG. 8, the microphone unit Mh for high frequency is arranged in the side
closest to the sound source S, and all the microphone units Mh for high frequency are located at
the distance dh A microphone unit Ma for the band is disposed, and further, from the position of
the distance a from the microphone unit for the whole band Ma, that is, the position of the
microphone unit for the high frequency region Mh, the position of the distance (dh + dt) is low By
arranging the microphone lephone unit for the area, even if the sound source S approaches the
microphone no matter how close the microphone source for the sound source S and the bass
microphone Since the distance to the dot Mt is at least (dh + dt ') or more, in the secondary sound
pressure gradient type uni-directional microphone of the present invention, the output signal
level is abnormal in the bass region even if the sound source S is close to the microphone In the
present invention, according to the present invention, FIG. 5 (a) already described. (The problems
with the secondary sound pressure gradient type mono-directional microphone having the
configuration shown in FIG. B1 are well solved. Fig. 9 shows the characteristics of the secondary
sound pressure gradient type mono-directional microphone of the present invention and the
secondary sound pressure gradient type mono-directional microphone of the configuration
shown in Figs. 5 (a) and 5 (b). FIG. 9 is a frequency characteristic curve diagram for explaining
the above difference, and in FIG. 9, curve work is a secondary sound pressure gradient singledirectional microphone of the configuration shown in FIGS. 5 (a) and 5 (b). A p-phone (where d or
150 m, dh = 40 m) and the secondary sound pressure gradient type mono-directional
microphone of the present invention shown in FIG. 8 (where dt = 150, dh = 40.
And FIG. 9 is a frequency characteristic curve diagram obtained when their frequency
characteristics are measured in a sound field that can be regarded as a plane wave field, and the
frequency characteristic curve shown by curve I in FIG. It is obtained when the distance between
the microphone and the sound source S is 1 meter. Also, in FIG. 9, the curve {circle over (2)}
represents the secondary sound pressure gradient type mono-directional microbon (where dt =
150 m, dh = 40 mm) and the sound source of the configuration shown in FIGS. 5 (a) and 5 (b).
The distance to s is 100. The curve ■ in FIG. 9 is the secondary sound pressure gradient type
mono-directional microphone p-phone of the present invention shown in FIG. 8 (where dt = 150
wa, d h). It is a frequency characteristic curve figure in case the distance of = 40 tran) and the
sound source S is 100 degrees. FIG. 10 shows curve I in FIG. 10 based on the characteristic curve
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shown by curve I shown in FIG. 9, and curves n and m in FIG. It is a curve diagram shown by
curves 1 and 2. As can be understood from the curves 1 to 6 in FIGS. 9 and 10, in the secondary
sound pressure gradient type mono-directional microphones having the configuration shown in
FIGS. 5 (a) and 5 (b), the sound source S is used. The output level of the low-pass signal
component rises abnormally when the signal approaches the microphone, but in the secondary
sound pressure gradient type mono-directional microphone p phone of the present invention, the
low-pass is generated even if the sound source S approaches the microphone. It is apparent that
the rise of the output level of the signal component is small, and by adopting the arrangement
relationship of the microphone units in the present invention, the problems of the prior art
described above are well solved.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of an example of a conventional unidirectional microphone, FIG. 2 is a
frequency characteristic diagram of a subtractor output of the microphone shown in FIG. 1, FIG.
3 is an equalizer characteristic diagram, FIG. 6, FIG. 9, and FIG. 10 are frequency characteristic
curve diagrams, and FIG. 5 (a).
(Figure b1 is a block diagram showing a configuration example of a conventional band division
type secondary sound pressure gradient type mono-directional microphone p-phone, FIG. 7 is a
directional characteristic curve side view, and FIG. 8 is a second order of the present invention It
is a block diagram of a sound pressure gradient type | mold uni-directional microphone p-phone.
Side: microphone unit for low band, Mh: microphone unit for high band% Ma: microphone unit
for all bands, SUB: subtractor, ADD: adder, HPF · · ·・ High-pass filter, LPF ・ ・ ・ Low-pass
filter, 0 ... output terminal Patent applicant Nippon Victor Co., Ltd.% 1 寛 2 Fig f → 3 3 4 H7) →
3030 minutes. 060090
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