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JPH11205889

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DESCRIPTION JPH11205889
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device and an audio acquisition method.
[0002]
2. Description of the Related Art FIG. 5 is a block diagram showing the configuration of a
conventional microphone device. Conventionally, the microphone of the MS system is configured
by a combination of a unidirectional microphone element called a mid microphone 101 and a bidirectional microphone element called a side microphone 102.
[0003]
In the microphone having such a configuration, a signal obtained by adding the output of the mid
microphone 101 and the output of the side microphone 102 at a ratio k is used as a left channel
signal, and the output of the mid microphone 101 and the output of the side microphone 102 are
subtracted at a ratio k. The signal can be taken out as the right channel.
[0004]
However, the above-mentioned conventional microphone devices have the following problems,
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and their improvement has been demanded.
That is, since the bi-directional microphone element is used for the side microphone, it is weak
against vibration and wind compared to other unidirectional microphone elements and nondirectional microphone elements due to its structure, and its response is low Many noises occur
in the sound range.
[0005]
Therefore, by inserting a high pass filter (HPF) at the output of each channel, the bass region
including noise components generated due to vibration and wind is attenuated. As a result, the
low-frequency component of the recorded audio is reduced, and the sound not only loses its
vigor, but also becomes hard and impairs the sound quality.
[0006]
Therefore, an object of the present invention is to provide a microphone device and an audio
collection method capable of high-quality recording without attenuating the low frequency range
of audio.
[0007]
In order to achieve the above object, a microphone device according to claim 1 of the present
invention is a microphone device having a unidirectional microphone element and a bidirectional
microphone element. Filter means for changing the frequency characteristic of the output signal
of the directional microphone element; addition means for adding the output signal of the filter
means to the output signal of the unidirectional microphone element at a predetermined ratio;
And subtracting means for subtracting the output signal of the filter means from the output
signal of the microphone element at the predetermined ratio, and outputting a stereo signal in
which the output signal of the adding means and the output signal of the subtracting means are
paired. It features.
[0008]
The microphone device according to claim 2 is a microphone device having a unidirectional
microphone element and a bidirectional microphone element, wherein the filter means changes
the frequency characteristic of the output signal of the bidirectional microphone element, and the
filter means. Selection means for selecting the output signal of the bidirectional microphone
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element and the output signal of the bidirectional microphone element; addition means for
adding the output signal of the selection means to the output signal of the unidirectional
microphone element at a predetermined ratio; And a subtracting means for subtracting the
output signal of the selecting means from the output signal of the unidirectional microphone
element at the predetermined ratio, and a stereo signal having the output signal of the adding
means and the output signal of the subtracting means as a pair It is characterized by outputting.
[0009]
The microphone device according to claim 3 is characterized in that in the microphone device
according to claim 2, the selection means is a selection switch operated manually.
[0010]
The microphone device according to claim 4, wherein the selection means in the microphone
device according to claim 2 comprises a low pass filter for extracting a low frequency component
of an output signal of the bi-directional microphone element, and an output signal of the low pass
filter. , A comparator for comparing the output voltage of the detector with a reference voltage,
and according to the output of the comparator, an output signal of the filter means and an output
signal of the bidirectional microphone element And a selection switch for selecting.
[0011]
The microphone device according to claim 5 is characterized in that the filter means is a high
pass filter in the microphone device according to claims 1 to 4.
[0012]
The microphone device according to claim 6 is a microphone device having a unidirectional
microphone element and a bidirectional microphone element, wherein the first equalizer means
changes a frequency characteristic of an output signal of the unidirectional microphone element.
Second equalizer means for changing the frequency characteristic of the output signal of the
bidirectional microphone element; addition means for adding the output signal of the second
equalizer means to the output signal of the first equalizer means at a predetermined ratio; And a
subtracting means for subtracting the output signal of the second equalizer means from the
output signal of the first equalizer means at the predetermined ratio, and a stereo signal in which
the output signal of the adding means and the output signal of the subtracting means are paired
It is characterized by outputting.
[0013]
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The microphone device according to claim 7, wherein in the microphone device according to
claim 6, the frequency characteristic of the output signal of the second equalizer means has a
bass level smaller than the frequency characteristic of the output signal of the first equalizer
means. It is characterized by
[0014]
The voice collecting method according to claim 8 is a voice collecting method for collecting voice
using a unidirectional microphone element and a bi-directional microphone element, wherein
frequency characteristics of an output signal of the bidirectional microphone element are
changed. An output signal obtained by changing the frequency characteristic is added to an
output signal of the unidirectional microphone element at a predetermined ratio, and an output
signal obtained by changing the frequency characteristic from an output signal of the
unidirectional microphone element The subtraction is performed at the predetermined ratio, and
a stereo signal in which the addition signal and the subtraction signal are paired is output.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the microphone device and
sound collection method of the present invention will be described.
The microphone device of the present embodiment is applied to an MS microphone (microphone)
having a mid microphone (Mid Mic) and a side microphone (Side Mic).
[0016]
First Embodiment FIG. 1 is a block diagram showing a configuration of a microphone device
according to a first embodiment.
In the figure, 1 indicates a mid microphone, 2 indicates a side microphone, 3 indicates an adder,
4 indicates a subtractor, and 5 indicates a high pass filter (HPF).
[0017]
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The signal output from the mid microphone 1 is divided into two, one of which is input to the
adder 3 and the other is input to the subtractor 4.
The output of the side microphone 2 is divided into two through the HPF 5, one of which is input
to the adder 3 and the other is input to the subtractor 4.
That is, to the adder 3 and the subtractor 4, a signal in which the bass range of the side
microphone 2 is attenuated by the HPF 5 is input.
[0018]
Assuming that the sensitivity of the mid microphone 1 is Lm, the sensitivity of the side
microphones 2 is Ls, and the angle between the sound source and each microphone is α, the
output signal L of the left channel and the output signal R of the right channel are mathematical
equations. It is given by (1) and (2).
[0019]
L = Lm (1 + cos α) / 2 + Ls · sin α (1) R = Lm (1 + cos α) / 2-Ls · sin α (2) where k = Ls / Lm
and Lm = 1 as regular Then, equations (1) and (2) are represented by equations (3) and (4),
respectively.
[0020]
L = (1 + cosα) / 2 + k · sinα (3) R = (1 + cosα) / 2−k · sinα (4) By changing the value of this
ratio k, the directivity axis angle of the stereo microphone is changed be able to.
The pointing axis angle θ is given by equation (5).
[0021]
θ = 2 arctan (2 k) (5) Usually, the directivity axis angle θ is set to about 90 to 120 degrees.
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The ratio k is given by equation (6). For example, when the directional axis angle θ is set to 90
degrees, k = 0.5.
When the directional axis angle θ is set to 120 degrees, k = 0.866.
[0022]
k = tan (θ / 2) / 2 (6) FIG. 2 is a graph showing the response to the vibration frequency of the
unidirectional microphone element and the bidirectional microphone element.
The bi-directional microphone element used in the side microphone 2 has a high influence level
of the bass range as compared with the unidirectional microphone element used in the mid
microphone 1.
Assuming that the level difference of the response at a certain frequency a is 20 dB and that the
response of the mid microphone 1 is an allowable level, the output signal of the left channel
when the level of the mid microphone 1 is 0 dB when k = 0.866. Since L does not enter with the
directionality of the sound wave as shown in Equation (3), the responses Lh and Rh can be
expressed by Equations (7) and (8), respectively.
[0023]
Lh = (mid microphone output level + side microphone output level) x 0.7 ... Rh = (mid microphone
output level-side microphone output level) x 0.7 ... phase of the output signal of each element
Since it can not be specified, it is assumed that the average is 3 dB lower.
Thus, the response Lh can be expressed by equation (9).
[0024]
Lh = (1 + 0.866 × 10) × 0.7 = 6.84 (9) In order to set this to a value of 1, that is, to make the
same value as the noise response of the mid microphone, A filter with an attenuation of 16.7 dB
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is required so that the response is 0.15, the reciprocal of 6.84.
[0025]
When this filter is inserted, the level of this frequency is attenuated by 16.7 dB at any angle.
[0026]
Here, consider a filter in which the same vibration is attenuated by inserting an HPF only in the
side microphone element.
This response Ls is expressed by equation (10).
[0027]
Ls = (output level of mid microphone + k × output level of side microphone × attenuation
amount of HPF) × 0.7 (10) Therefore, Ls = (1 + 0.866 × 10 × HPF) × 0.7 = 1 From the
equation of, HPF = 0.048.
That is, a filter with an attenuation of 26.4 dB is required.
Although this filter has more attenuation than the above-described filter, the reason why the
sound quality is not impaired will be described below.
[0028]
The finished response Lf into which this filter is inserted is obtained by formula (11) by
substituting the HPF response coefficient 0.048 into formula (3).
[0029]
Lf = (1 + cos α) /2+0.048 k · sin α (11) Here, since the directional axis angle of this microphone
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is set to 120 degrees, the response of that angle is the largest.
Therefore, when the HPF coefficient is a value of 1, that is, when there is no HPF and when the
HPF is inserted, the difference in the finished response is calculated. The difference Dif (dB) is
given by equation (12).
[0030]
Dif = 20 · log (L−Lf) (12) When this is calculated, Dif = −5.6 (dB) is obtained. That is, while the
attenuation of the filter for removing the influence of vibration was 26.4 dB, the attenuation of
the finish is only 5.6 dB.
[0031]
In the conventional system inserted into the HPF in the mid microphone, the amount of
attenuation of the bass region is suppressed by 11 dB as compared to the case where the
attenuation is 16.7 dB. Moreover, since this number is the case of the most attenuating angle, the
amount of attenuation is further reduced as the incident angle of the sound wave changes. For
example, at an incidence angle of 0 degrees, the attenuation amount has a value of zero.
[0032]
Thus, the HPF is provided at the output of the side microphone, and the signal obtained by
adding the output signal of the HPF to the output signal of the mid microphone and the signal
obtained by subtracting the output signal of the HPF from the output signal of the mid
microphone By doing this, it is possible to attenuate the frequency characteristics of the low
frequency range of only the side microphones and reduce the effects of vibration and wind. As a
result, when the output signal of the microphone is recorded, high frequency sound recording is
possible because the low frequency range component necessary for sound collection is hardly
attenuated.
[0033]
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Second Embodiment FIG. 3 is a block diagram showing the configuration of a microphone device
according to a second embodiment. The same components as those in the first embodiment are
given the same reference numerals. In the first embodiment, the insertion of the HPF 5 into the
side microphone 2 shows a case where the attenuation of the bass region is reduced compared to
the conventional system, but in the second embodiment, in the state where there is no vibration
or wind. A selection switch 6 capable of switching between the output of the HPF 5 and the
through path output is provided so that the HPF 5 does not intervene in the output of the side
microphone 2. The selection switch 6 can be operated manually.
[0034]
Therefore, when the user switches the selection switch 6 according to the situation, voice
recording suitable for the situation is made possible.
[0035]
Third Embodiment FIG. 4 is a block diagram showing the configuration of a microphone device
according to a third embodiment.
The microphone of the third embodiment is configured to automatically turn on / off the
selection switch 6 in the second embodiment.
[0036]
In the figure, 7 is a low pass filter (LPF), 8 is a detector (DET), 9 is a reference voltage, and 10 is a
comparator (COMP).
[0037]
In the microphone having such a configuration, the low frequency component of the signal of the
side microphone 2 is extracted by the low pass filter 7, converted to a DC voltage by the detector
8, and converted to the reference voltage 9 which determines the preset operating point. When
the reference voltage 9 is exceeded, the selection switch 6 is switched to the HPF 5 side. When
the reference voltage is 9 or less, the selection switch 6 is returned to the through position side.
[0038]
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As described above, even when it is difficult for the user to determine the situation and perform
the switch operation, the microphone itself determines the situation and automatically switches
the insertion of the HPF, and when there is no noise, the frequency characteristics deteriorate In
a situation where noise is likely to occur, the filter enables noise-free recording.
[0039]
In the first to third embodiments, the collected output signal of the microphone is recorded on a
magnetic tape or the like, or is output as it is.
[0040]
In the first to third embodiments, the bass level of the output signal of the side microphone is
reduced by the high pass filter (HPF). Instead of using the HPF, the output of each of the mid
microphone and the side microphone is used. The same effect can be obtained even if the first
and second equalizers are provided.
In this case, the frequency characteristic of the output signal of the second equalizer is set so that
the bass level is lower than the frequency characteristic of the output signal of the first equalizer.
[0041]
According to the microphone device of the present invention, the frequency characteristic of the
output signal of the bi-directional microphone element is changed by the filter means, and the
uni-directional microphone element is obtained by the addition means. The output signal of the
filter means is added to the output signal at a predetermined ratio, and the subtraction means
subtracts the output signal of the filter means from the output signal of the unidirectional
microphone element at the predetermined ratio, and Since a stereo signal in which the output
signal and the output signal of the subtraction means are paired is output, high-quality recording
can be performed without attenuating the bass range of the audio.
[0042]
Thus, a filter means (HPF) is provided at the output of the output signal of the side microphone,
and a signal obtained by adding the output signal of the filter means (HPF) to the output signal of
the mid microphone and a filter means (HPF) from the output signal of the mid microphone By
making the signal obtained by subtracting the output signal of) into the output signal of the
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microphone, it is possible to attenuate the low frequency characteristic of only the side
microphone and to reduce the influence of vibration and wind.
[0043]
Therefore, it is possible to suppress vibration noise and wind noise levels, which are
conventionally considered to be weak points of MS-type stereo microphones, and to minimize
high frequency range components required for sound collection, thus enabling high-quality
recording. .
The same effect can be obtained by the voice collection method according to claim 8.
[0044]
According to the microphone device of the second aspect, the frequency characteristic of the
output signal of the bi-directional microphone element is changed by the filter means, and the
output signal of the filter means and the output signal of the bi-directional microphone element
are selected by the selection means. And adding the output signal of the selecting means to the
output signal of the unidirectional microphone element at a predetermined ratio by the adding
means, and subtracting the output signal of the unidirectional microphone element by the
subtracting means. And the output signal of the addition means and the output signal of the
subtraction means are paired to output a stereo signal, so that no filter means is used in the
absence of vibration or wind. This makes it possible to record audio that is suitable for the
situation.
[0045]
According to the microphone device of the third aspect, since the selection means is a selection
switch operated manually, the user can select the use of the filter means according to the
situation.
[0046]
According to the microphone system of claim 4, the low pass component of the output signal of
the bi-directional microphone element is extracted by the low pass filter, the output signal of the
low pass filter is detected by the detector, and the comparator detects the output signal of the
low pass filter. The user compares the output voltage of the detector with the reference voltage
and selects the output signal of the filter means and the output signal of the bidirectional
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microphone element by the selection switch according to the output of the comparator. Even
when it is difficult to judge the situation and perform the switch operation, the microphone itself
judges the situation and automatically switches the insertion of the filter means, and when there
is no noise, there is no deterioration of the frequency characteristic and noise occurs In situations
where it is likely to do so, the filter enables noise-free voice recording.
[0047]
According to the microphone device of the fifth aspect, since the filter means is a high pass filter,
the high pass filter can reduce the bass range of the bi-directional microphone.
[0048]
According to the microphone device of the sixth aspect, the frequency characteristic of the
output signal of the unidirectional microphone element is changed by the first equalizer means,
and the frequency of the output signal of the bidirectional microphone element is changed by the
second equalizer means. The characteristic is changed, the adding means adds the output signal
of the second equalizer means to the output signal of the first equalizer means at a
predetermined ratio, and the subtracting means adds the output signal of the first equalizer
means to the second equalizer means Output signal of the adding means and the output signal of
the subtracting means and the output signal of the subtracting means are output as a stereo
signal, so that the frequency characteristic of the equalizer is adjusted to reduce the side
microphones only The frequency characteristics of the region can be attenuated to reduce the
effects of vibration and wind.
[0049]
According to the microphone device of the seventh aspect, the frequency characteristic of the
output signal of the second equalizer means has a bass level smaller than the frequency
characteristic of the output signal of the first equalizer means. The equalizer can reduce the bass
range of the bi-directional microphone.
[0050]
Brief description of the drawings
[0051]
1 is a block diagram showing a configuration of a microphone device in the first embodiment.
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[0052]
2 is a graph showing the response to the vibration frequency of the unidirectional microphone
element and the bidirectional microphone element.
[0053]
3 is a block diagram showing the configuration of the microphone device in the second
embodiment.
[0054]
4 is a block diagram showing a configuration of a microphone device in the third embodiment.
[0055]
5 is a block diagram showing the configuration of a conventional microphone device.
[0056]
Explanation of sign
[0057]
1 Mid Microphone 2 Side Microphone 3 Adder 4 Subtractor 5 High Pass Filter (HPF) 6 Selection
Switch 7 Low Pass Filter (LPF) 8 Detector 9 Reference Voltage 10 Comparator
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