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JP2002218583

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DESCRIPTION JP2002218583
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound synthesis method and apparatus suitable for use in, for example, video cameras and digital
cameras with sound. Specifically, the proximity effect can be corrected by extracting the close-up
sound using the proximity effect unique to the pressure gradient type microphone and
subtracting the close-up sound signal from the output signal from the same microphone, and the
wind included in the close-up sound Noise and touch noise can be reduced.
[0002]
2. Description of the Related Art In an apparatus in which a microphone (hereinafter referred to
as a microphone) is used, for example, a microphone incorporated in a video camera or a digital
camera with sound, the sound emitted from an object located in the forward direction of the
camera is simultaneously displayed. It is normal to use a microphone having directivity in the
same direction as the subject because of the need to record.
[0003]
In general, a directional microphone is a pressure gradient microphone, and the pressure
gradient microphone is a microphone that generates a voltage proportional to the sound
pressure difference between two closely spaced points in space.
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In such pressure gradient microphones, if the distance from the sound source is long, the
incident sound wave is regarded as a plane wave and a voltage proportional to the sound
pressure difference between the two points is output, but the distance from the sound source is
the wavelength of the sound wave At a near distance, the incident sound wave becomes a
spherical wave and the sound pressure difference between the two points increases.
[0004]
That is, a so-called proximity effect appears in which the sensitivity is increased as shown in FIG.
The proximity effect is a cause of disturbing the uniform frequency sensitivity characteristics of
the microphone, and in the device with a built-in microphone, noise generated in the vicinity of
the microphone such as touch noise to the device or wind noise is emphasized. It has become.
[0005]
However, it has not been easy to detect only these close sounds and perform low-pass sensitivity
correction. For example, a switch for a user to lower the low-pass sensitivity in consideration of
using it as a close-up sound source in a single high-grade microphone However, in general, in
devices with built-in microphones, it is often compromised by lowering the low frequency
sensitivity in advance by a fixed amount in this case, and in this case the low frequency
sensitivity also falls other than the sound wave at a short distance. And cause the sound quality
to be impaired.
[0006]
On the other hand, in Japanese Patent Laid-Open No. 5-207587, for example, the output levels
from the unidirectional microphone and the nondirectional microphone are compared, and a
plurality of high pass filters are controlled based on the comparison result. Although the
proposal to correct the sensitivity has been made, for example, in the case where the sound
waves of a short distance and a long distance come simultaneously, not only the sound wave of
the short distance but the low frequency level of the sound wave of long distance drops I can not
correct the sensitivity of only sound.
In addition, since the unidirectional microphone and the nondirectional microphone are
independent, there is a problem that accurate level comparison can not be performed if there is
sensitivity variation.
03-05-2019
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[0007]
Further, in Japanese Patent Laid-Open No. 4-58699, bi-directional microphones and nondirectional microphones are used, and in the case of near-field sound, the outputs of both are
synthesized using the proximity effect of the bi-directional microphones to achieve unidirectionality. In the case of far-field sound, low-frequency non-directionality and high-frequency
uni-directionality have been proposed. In this case, it is possible to correct the sensitivity of nearfield sound, but wind noise is possible in far-field sound. For normal sound other than that,
directivity changes between non-directivity and uni-directivity depending on the frequency, so
the sound quality changes depending on the sound source direction, and bi-directional
microphone and non-directional microphone become independent Therefore, if there is a
sensitivity variation, there is a problem that accurate sensitivity correction of close-up sound can
not be performed.
[0008]
SUMMARY OF THE INVENTION The present application has been made in view of such a point,
and the problem to be solved is that the conventional apparatus detects only the proximity sound
and detects the low range sensitivity. It is not easy to correct, and even if it is not a sound wave
in a short distance, low frequency sensitivity falls and it causes loss of sound quality, and if there
is variation in sensitivity of microphone, it is not possible to correct accurate sensitivity of close
sound etc That there was a problem with
[0009]
Therefore, in the present invention, a pressure gradient type microphone is formed by sound
field processing from two nondirectional microphones which are pressure type microphones, and
a signal from the nondirectional microphone is subtracted. The near-field sound is extracted by
the above-mentioned method. According to this, the low-pass sensitivity of the near-field sound is
corrected, and the near-field sound is further subtracted by using the extracted near-field sound
positively. This can also reduce touch noise and wind noise to the device with built-in
microphone.
[0010]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, nondirectional first and second pressure-type microphones are disposed facing the sound receiving
surface in opposite directions with a predetermined interval, and the first and second pressure
type microphones are provided. One output signal of the second pressure-type microphone is
attenuated by an arbitrary attenuation amount and subtracted from the other output signal, and
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an equalization means capable of controlling characteristics of the subtracted signal according to
an arbitrary attenuation amount is used. Forming a directional pressure gradient type
microphone device by outputting the signals, adding the output signals from the first and second
pressure type microphones, and outputting the added signal through the level conversion means
And a composite signal of both microphones is obtained.
[0011]
Further, in the present invention, nondirectional first and second pressure type microphones
disposed so as to face the sound receiving surfaces in opposite directions with a predetermined
interval are provided, and the first and second pressure type microphones are provided.
Equalization means having a subtractor for subtracting the amount of attenuation from the other
output signal via a controllable level attenuator at one output signal of the second stage, and for
controlling the characteristics according to the level attenuator at the output of the subtractor
Output a signal via a directional pressure gradient microphone device, and adding an adder for
adding output signals from the first and second pressure type microphones, and leveling the
signal from the adder A composite signal of both microphones is obtained by outputting through
the conversion means.
[0012]
Hereinafter, the present invention will be described with reference to the drawings. FIGS. 1 and 2
show a microphone arrangement example 1 and a microphone arrangement example 2 of an
embodiment of the present invention, respectively.
First, in the embodiment of FIG. 1, the nondirectional microphone 1 and the nondirectional
microphone 2 are linearly arranged side by side in the forward direction.
Further, in the embodiment of FIG. 2, it is a case where they are linearly arranged vertically in the
forward direction.
Both of these are disposed so that the sound receiving surfaces face in the opposite direction to
each other, and the distance between the sound receiving surfaces is set to, for example, several
mm.
03-05-2019
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[0013]
Generally speaking, to match the sensitivity and frequency characteristics of microphones, the
structure is the same in the same kind rather than between different kinds such as nondirectional microphone and unidirectional microphone, non-directional microphone and
bidirectional microphone, etc. It is easy to be.
Therefore, in these embodiments, two omnidirectional microphones can be used to easily use
microphones with uniform characteristics, and from these two omnidirectional microphones to
form a directional microphone having a sound pressure gradient. There is an advantage that the
characteristic variation between the microphones is smaller than the configuration of the prior
application in which the nondirectional microphone and the directional microphone are
independently configured.
[0014]
Next, one embodiment of the sound synthesis circuit of the present invention will be described
with reference to FIG.
The signals output from the two nondirectional microphones 1 and 2 arranged as shown in FIGS.
1 and 2 are amplified by the amplifiers (AMPs) 3 and 4 and the output of the amplifier 3 is
output from the adder 5. The output of the amplifier 4 is input to the other + side terminal of the
adder 5 and is added to the output of the previous amplifier 3 to obtain a 1/2 attenuator. The
signal is output from the terminal 11 through 9.
[0015]
Further, the output of the amplifier 4 is input to the negative terminal of the adder 7 via the
level-controllable attenuator (ATT) 6 and is subtracted from the output of the previous amplifier
3 to obtain the frequency characteristic adjusting equalizer (EQ) 8 It is outputted from the
terminal 10 through the terminal. Here, in FIG. 3, a signal having an average nondirectional
pattern obtained by adding the microphones 1 and 2 is output to the terminal 11, and by
subtracting 2 from the microphone 1 to the terminal 10, it is applied to both sound receiving
surfaces A directional pattern having a pressure gradient that is proportional to the sound
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pressure phase difference and that corresponds to the amount of attenuation set by the
attenuator 6 is output.
[0016]
At this time, since the directional pattern has a sensitivity characteristic proportional to the
frequency at this time, the equalizer 8 is inserted in order to make the frequency-sensitivity
characteristic constant. Then, although it is optimized according to the amount of attenuation set
by the attenuator 6, one example is a bass boost filter. Also, the 1⁄2 attenuator 9 need not always
be 1⁄2, and may be adjusted according to the characteristics of the equalizer 8. Thus, in the
embodiment of FIG. 3, the terminal 10 provides a signal with proximity effect and the terminal
11 provides a signal without proximity effect.
[0017]
Here, in the embodiment of FIG. 3, when the level-controllable attenuator 6 is varied from −0 to
0 dB, the maximum level at each frequency of the directional characteristic output from the
terminal 10 is output from the terminal 11 An example of directivity pattern change in the case
where the equalizer 8 and the 1⁄2 attenuator are optimized to coincide with the maximum level
at each frequency of the directivity characteristic will be described with reference to FIG.
[0018]
First, FIG. 4A shows the case where the attenuator 6 is set to −∞. At this time, since the
directivity characteristic of the microphone 1 is output as it is, it shows non-directivity, which
substantially matches the output of the terminal 11 Do.
Next, FIGS. 4 (b) to 4 (e) show the case where the attenuator 6 is changed from − 方向 to 0 dB,
which is generally referred to as a cardioid characteristic, and gradually in the forward direction
(0 ° direction). Narrow directivity. The characteristic shown in FIG. 4 (e) is called a
supercardioid.
[0019]
Further, FIG. 4 (f) shows the characteristic when the attenuator 6 is 0 dB. At this time, there is no
sound pressure difference in the sound waves from the left and right direction (270 ° and 90
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6
°), and microphones 1 and 2 output Since the phase and amplitude level of the signal to be
matched coincide with each other, the signal is canceled and loses sensitivity, resulting in socalled bi-directionality, which shows directivity characteristics only in the 0 ° and 180 °
directions.
[0020]
In each of the characteristics shown in FIG. 4, the broken line indicates the nondirectional
characteristic output from the terminal 11, and as described above, the maximum sensitivity of
each directivity pattern matches the maximum sensitivity of the nondirectionality. Although
optimized, particularly in the case of the present invention, it is characterized in that the
maximum sensitivity of each frequency is matched to the sound source distance where the
proximity effect does not occur.
[0021]
By the way, as shown in FIG. 14 described above, in the directional characteristic output from the
terminal 10, there is a proximity effect in which the sound source becomes closer to the
microphone and the output sensitivity increases as the frequency of the sound source becomes
lower.
Here, while each directivity characteristic of FIG. 4 described above shows directivity patterns in
the sound source distance and frequency at which the proximity effect is not shown, an example
of change of directivity patterns by proximity effect is shown in FIGS. 5 and 6. Show.
[0022]
That is, FIG. 5 shows an example of the directivity change of the directivity pattern of FIG. 4 (b)
to the proximity sound. FIG. 5 (a) shows the frequency of the sound source of 200 Hz, FIG. 5 (b)
shows 100 Hz, 5 (c) is the case of 50 Hz.
In these figures, as the frequency decreases, the directivity of the near sound is increased as
shown by the solid line with respect to the nondirectional sensitivity shown by the broken line
having no sound pressure gradient characteristic.
03-05-2019
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[0023]
Further, FIG. 6 shows an example of directivity change to the proximity sound of the directivity
pattern of FIG. 4C, and as in FIG. 5, FIG. 6A shows that the frequency of the sound source is 200
Hz, and FIG. FIG. 6C shows the case of 100 Hz and 50 Hz. In these figures, as the frequency
decreases, the directivity of the near sound is increased as shown by the solid line with respect to
the nondirectional sensitivity shown by the broken line having no sound pressure gradient
characteristic. In this case, however, the sensitivity increases in the forward direction (0 °) of
the main axis, and the sound wave is canceled behind (180 °), leaving almost no sensitivity.
[0024]
Here, in the present invention, the low-range rise of the near-field sound is extracted by
extracting the signal component in the region where the sensitivity exceeds the dashed line on
the solid line.
[0025]
Next, FIG. 7 shows a block diagram of the first embodiment according to the sound and tone
composition method and apparatus of the present invention.
In the present invention, close tones are extracted using the sound synthesis circuit shown in FIG.
3, but the same reference numerals are given to blocks having the same functions as those in FIG.
[0026]
In FIG. 7, microphones 1 and 2 are non-directional microphones arranged similarly to FIGS. 1 and
2, and their outputs are amplified by amplifiers 3 and 4, respectively. Here, the signal having no
directivity through the adder 5 and the 1⁄2 attenuator 9 is switched by the one terminal of the
control signal generation unit 20 and one of the cross fade switching unit 21 through the delay
circuit (DL) 27. Input to the terminal. Further, the signal having directional property processed
by the attenuator 6 and the adder 7 and the equalizer 8 is transmitted to the positive terminal of
the adder 22 through the delay circuit 25 and the other of the cross fade switching means 21
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through the delay circuit 26. And the other terminal of the control signal generation means 20.
[0027]
Furthermore, the control signal 24 generated from the control signal generation means 20 is
input to the cross fade switching means 21 and used for cross fade switching. Then, the output
signal appropriately switched by the cross fade switching means 21 is outputted from the
terminal 28 and also inputted to the negative side terminal of the adder 22 and is subtracted
from the signal having directivity from the previous equalizer 8 It is output from the terminal 23.
[0028]
Here, the operation of FIG. 7 will be described, but the cross fade switching means 21 and the
control signal generation means 20 will be described in more detail later. First, the
nondirectional signal and the directional signal synthesized by the same circuit as in FIG. 3 are
input to the cross fade switching means 21 and the control signal generating means 20, and the
control signal generating means 20 compares the signal levels of the two. The control signal 24
is generated so that the signal side where the level is always low is selected by the cross fade
switching means 21.
[0029]
The cross fade switching means 21 switches the two signals according to the control signal 24
and outputs the signal to the terminal 28 and the negative terminal of the adder 22. Here, in the
delay circuits 26 and 27, the delay is adjusted so that the phases of both signals input to the
cross fade switching means 21 become equal, and the delay amount due to the processing time
of the control signal generating means 20 is also given. The timing is switched in synchronization
with the compared signal. The delay circuit 25 is subjected to delay processing so that the phases
of the two signals input to the adder 22 match.
[0030]
Therefore, in the circuit of FIG. 7, for example, the attenuator 6 and the equalizer 8 are set so as
to generate a directional signal corresponding to FIG. Because the level of the directional signal is
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also lower than the level of the nondirectional signal, the crossfade switching means 21 selects
the directional signal side and subtracts it from the same directional signal at the adder 22.
Therefore, both are canceled from the terminal 23 and no signal is output.
[0031]
On the other hand, as shown in FIG. 5, in the case of close-up sound, the low-pass sensitivity is
increased due to the proximity effect, and cross-fades because the directional signal level exceeds
the omnidirectional signal level for sound waves from the same direction. Since the
nondirectional signal side is selected in the switching means 21 and the nondirectional signal is
subtracted from the directional signal by the adder 22, only the difference signal component of
the both, ie, the low range rising component of the near sound from the terminal 23. Is output,
and in the case of FIG. 5 (c), it can be extracted from almost all directions.
[0032]
At this time, a directional characteristic signal from which low-pass sensitivity increase due to the
proximity effect is removed is always obtained from the terminal 28, and the directivity pattern is
shown in FIG. 4 (b) at distances and frequencies other than the proximity sound source. It has the
indicated cardioid characteristics and exhibits non-directivity as the frequency decreases in the
low range of the close-in sound, which is effective in reducing wind noise.
[0033]
Similarly, the attenuator 6 and the equalizer 8 are set so as to generate a directional signal
corresponding to FIG. 4C, and if the distance and frequency of the sound source do not have the
proximity effect, the sound wave from any direction as well Also, since the directional signal side
is selected by the cross fade switching means 21 because the level of the directional signal is
smaller than the level of the omnidirectional signal, and subtracted from the same directional
signal by the adder 22, Both are canceled and no signal is output.
[0034]
However, as shown in FIG. 6, in the case of the low range of close sounds, the low range
sensitivity increases due to the proximity effect, and only the sound wave in the forward
direction exceeds the nondirectional signal level and the directional signal level exceeds the
crossfade switching. In the means 21, the nondirectional signal side is selected, and the
nondirectional signal is subtracted from the directional signal in the adder 22, so that only the
difference component between the two signals from the terminal 23, that is, the low range rising
component of the close-up sound In the case of a sound wave other than the forward direction,
the directional signal side is always selected and therefore not output, and in the case of FIG. 6, it
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can be extracted only from the forward direction.
[0035]
At this time, a directivity characteristic signal from which low-pass sensitivity increase due to the
proximity effect is removed is obtained from the terminal 28, and its directivity pattern is the
cardioid shown in FIG. 4 (c) at distances and frequencies other than the proximity sound source.
A signal having a characteristic, in which the sensitivity increase due to the proximity effect is
removed in the forward direction in the low range of the proximity sound, that is, a signal having
directional sensitivity characteristics in the area shared by the cardioid characteristic of solid line
and nondirectional characteristic of broken line Is output.
[0036]
Next, FIG. 8 shows a block diagram of the control signal generating means 20 in FIG. 7 and will
be described with reference to the explanatory view of FIG.
First, the input signal waveform shown in FIG. 9A and the inputs 1 and 2 shown in FIG. 9A are
input to the terminals 41 and 42, respectively, and are input to the absolute value conversion
processes 31 and 32, as shown by the solid line in FIG. Are converted into absolute values.
The signals subjected to the absolute value processing are further subjected to envelope
detection 33 and 34, and the envelopes of the respective signals are detected as shown by the
broken line in FIG. The output of envelope detection 34 is subtracted from the output of 33 to
compare the levels of the respective signals.
[0037]
Next, the output of the adder 35 is input to the code detection 36, and the codes + code,-code
and zero are detected.
That is, as shown in FIG. 9C, if the signal level is input 2> input 1, the − sign is detected, if input
2 <input 1, the + sign is detected, and if input 2 = input 1 it is zero Is detected.
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11
Further, the detected code is generated according to the code in the control signal generation 37.
Here, if the control signal is generated by the up-down counter of 16 bits in one example, 0 to 7
FFF (hex: hex outputs a coefficient in the range of hexadecimal notation as a control signal.
[0038]
This up / down counter continuously performs the counting operation of the previous value hold,
+ sign: up count-sign: down count zero, depending on the input sign.
[0039]
Specifically, as shown in FIG. 9 (d), if the code detected by the code detection 36 in the previous
stage is a minus code, it counts down by an arbitrary count value, and if it becomes a plus code,
an arbitrary count value Up counting is performed, and if it is zero, the operation of stopping the
counting operation and holding the previous count value is repeated.
Furthermore, although not shown, a limiter is provided when it exceeds the 0 to 7 FFF (hex)
range, so when the down count continues, the minimum value 0 is held, and the up count is
performed similarly. If continued, the maximum value 7FFF (hex) is held.
[0040]
The control signal generated by the control signal generation 37 as described above is input to
the time constant addition 38, and a time constant is added so as to be smooth to human hearing.
The time constant addition 38 is formed of, for example, an LPF (low pass filter), and specifically,
the high frequency component of the signal waveform is removed as shown in FIG.
In addition, the control signal generation may be optimized by changing the slope of the change
by changing the count values on the up side and the down side, or may be further optimized by
making the count values on the up side and the down side asymmetric. is there.
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[0041]
Next, a block diagram of the cross fade switching means 21 in FIG. 7 is shown in FIG. 10 (a), and
its characteristic diagram is shown in FIG. 10 (b). First, the inputs 1 and 2 are input to the
terminals 50 and 52, and the control signal 24 in FIG. 7, that is, the control signal generated by
the control signal generation means 20 is input to the terminal 51.
[0042]
This input 1 is input to one + terminal of the adder 56 through the attenuator 53 variably
controlled by the control signal, and the input 2 is variably controlled by the signal converted by
the coefficient inversion 55. The output of the adder 56 is output from the terminal 57 via the
attenuator 54 and the other positive terminal of the adder 56. Here, the coefficient inversion 55
executes (7FFF−k) if the control signal is 16 bits and the signal k is in the range of 0 to 7FFF
(hex).
[0043]
On the other hand, assuming that the attenuation levels of the attenuators 53 and 54 become −
で with a coefficient 0 and 0 dB with a coefficient 7FFF (hex), the control signal is shown on the
horizontal axis as shown in the characteristic diagram of FIG. If the attenuator attenuation level is
taken into consideration, the attenuator 53 becomes the attenuation level −∞ at the control
signal 0, and at this time the attenuation level becomes 0 dB because the attenuator 54 becomes
the coefficient 7FFF (hex) by the coefficient inversion 55 In the signal 7FFF (hex), the attenuator
53 has an attenuation level of 0 dB, and at this time the attenuator 54 has a coefficient of 0 due
to the coefficient inversion 55 so that the attenuation level is −∞.
[0044]
That is, in one example, the attenuators 53 and 54 described above can be configured by
multipliers using k and (7FFF-k) as multiplication coefficients.
Therefore, assuming that the output signal Y of the terminal 57 is represented by Y = kA + (7FFFk) B when the input 1 is A and the input 2 is B, Y is a control signal k of 0 and the signal B is
03-05-2019
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output. When the signal K is 7FFF (hex), the signal A is output, and when the control signal k is at
an intermediate value, a composite signal of the inputs 1 and 2 according to the ratio is output.
[0045]
That is, in the present invention, the switching between the signal A and the signal B is
characterized by cross-fading switching in this manner, and by setting the cross-fading time to
about several ms in one example, noise at the time of switching is generated. There is almost no
sense of incongruity in hearing, and it is possible to switch.
[0046]
In the block diagram of FIG. 7 configured as described above, the output of the equalizer 8, that
is, the directional signal, is input to the input 2 of the control signal generation means 20, and
the cross fade switching means via the delay circuit 26. Input to input 1 of 21.
The output of the half attenuator 9, that is, the nondirectional signal, is input to the input 1 of the
control signal generating means 20 and to the input 2 of the cross fade switching means 21 via
the delay circuit 27.
[0047]
Thus, for example, when the level of the directional signal is higher than the level of the nondirectional characteristic signal, as in the low-frequency proximity sound, the code detection 36
in FIG. 8 becomes a − code and the control signal 24 in FIG. As it approaches, in the cross fade
switching means 21, cross fade selection is made to the input 2, that is, the nondirectional signal
side.
[0048]
Conversely, since the level of the nondirectional signal is higher than the level of the directional
signal except in the low-range proximity sound, the code detection 36 in FIG. 8 becomes a plus
code and the control signal 24 in FIG. 7 approaches 7FFF (hex) In the cross fade switching means
21, cross fade selection is performed on the input 1, that is, the directional signal side.
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In this way, the signal with the lower level is always selected to achieve the purpose.
[0049]
Therefore, in this embodiment, a pressure gradient type microphone is formed by sound field
processing from two nondirectional microphones which are pressure type microphones, and a
close sound is extracted by subtracting a signal from the nondirectional microphone. Thus, it is
possible to correct the low-pass sensitivity in the near-field sound and also to reduce the touch
noise and the wind noise to the device with built-in microphone by further subtracting the nearfield sound using the extracted near-field sound positively. it can.
[0050]
By this, it is not easy to detect only near-field sound and perform low-pass sensitivity correction
with the conventional device, and low-pass sensitivity may be degraded even at a short distance
sound wave to cause loss of sound quality, and microphone sensitivity According to the present
invention, these problems can be easily solved according to the present invention, in which there
is a problem that accurate proximity sound sensitivity correction can not be performed if there is
a variation in.
[0051]
Further, the block diagram of the second embodiment according to the tone-simulation
processing method and apparatus of the present invention will be described using FIG. 11 while
giving the same reference numerals to blocks having the same function as in FIG. .
In FIG. 11, proximity sound is extracted by the proximity effect in the same manner as in FIG. 7,
and the extracted proximity sound signal is used to be input to a microphone incorporated in, for
example, a camera integrated VTR or digital camera. Wind noise, and touch noise and switch
click noise generated when the function switch is operated are actively canceled.
[0052]
First, directional signals with proximity effect synthesized similarly to FIG. 7 are output from the
equalizer 8 from the microphones 1 and 2 arranged similarly to FIGS. 1 and 2, and control signal
generation configured as in FIG. 10 is input through the input 2 of the means 20 and the delay
circuit 26 to the positive terminal of the adders 22 and 61 through the input 1 of the cross fade
switching means 21 and the delay circuit 25 which are configured similarly to FIG.
03-05-2019
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[0053]
Similarly, nondirectional signals synthesized from the microphones 1 and 2 are outputted from
the 1⁄2 attenuator 9 and input 1 of the control signal generation means 20 and input 2 of the
cross fade switching means 21 through the delay circuit 27. Is input to
Furthermore, the control signal 24 from the control signal generation means 20 is used as a
control signal for cross fade switching of the cross fade switching means 21. Therefore, from the
output of the cross fade switching means 21, the low frequency rise of the near sound is similar
to FIG. A suppressed directional signal is obtained.
[0054]
Further, this signal is input to the negative side terminal of the adder 22 and is subtracted from
the directional signal including the close range sound input to the positive side terminal, whereby
the output of the adder 22 is increased in the low frequency range of the close range sound. Is
extracted.
Furthermore, the extracted signal is input to the amplifier 60 and amplified. The amplification
gain of the amplifier 60 is the same level as the low-pass component due to the proximity effect
of the directional signal input to the + side terminal of the adder 61. Since the setting is
performed as follows, when subtraction is performed by the adder 61, a directivity signal from
which the low frequency component of the near-field sound is removed is obtained at the
terminal 62 of the output.
[0055]
The signal to be removed here is only a low frequency component from several Hz to several
hundreds Hz, but generally the signal component of the wind noise is mostly 1 kHz or less, and
the energy is concentrated in the low frequency region. Is the wind noise of a wire mesh or
cabinet around the microphone, so it is a close-up sound near the microphone. Also, since touch
noise and the like are close tones transmitted from the cabinet to the microphone and there is
03-05-2019
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much energy in the low range, most noise components can be reduced by removing the close
range sounds in the low range.
[0056]
As a secondary effect of the apparatus according to FIG. 11, the sound level emitted by the
photographer during shooting may be suppressed. Generally, the voice level at a short distance is
recorded larger than that at a long distance, so that it is possible to avoid the problem that the
voice of the photographer at a short distance is more prominent than the voice at a long distance.
[0057]
Further, the block diagram of the third embodiment according to the tone and tone composition
method and apparatus of the present invention will be described with reference to FIG. 12, and
the blocks having the same functions will be assigned the same reference numerals as in FIG. Do.
In FIG. 12, a microphone 70 having directional characteristics such as cardioid is further added
to the microphones 1 and 2 to remove wind noise, touch noise and the like input to the
microphone 70.
[0058]
First, the output signal of the microphone 70 is amplified by the amplifier 71 and input to the +
side terminal of the adder 73 through the delay circuit 72. Next, as in the case of FIG. 11, the
low-frequency close-tone component extracted from the microphones 1 and 2 is output to the
output of the adder 22 and amplified to a predetermined level by the amplifier 74. Input to and
subtracted from the signal of the microphone 70 of the + side terminal. Here, the delay circuit 72
is inserted in order to match the phase of the low frequency close-tone signal to be subtracted by
the adder 73.
[0059]
Therefore, since the gain of amplifier 74 is set to be the same level as the proximity sound of the
directional signal including the low-pass rise due to the proximity effect from microphone 70, the
output of adder 73 is the proximity sound from the signal from microphone 70. The removed
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signal is obtained and output from the terminal 75.
[0060]
Thus, in the embodiment of FIG. 12, it is possible to remove, for example, wind noise, touch noise
and the like input to an external telephoto microphone or the like attached to an accessory shoe
of a camcorder.
Also, in this case, the attenuator 6 and the equalizer 8 are optimized to the setting that
approximates the directivity pattern of the external microphone from the directivity pattern
change example shown in FIG. It is possible.
[0061]
The block diagram of the fourth embodiment according to the tone and tone composition method
and apparatus of the present invention will be described with reference to FIG. 13 while
assigning the same reference numerals to blocks having the same functions as in FIG. . The
embodiment of FIG. 13 is a case where band limitation is provided to the processing of the
embodiment of FIG.
[0062]
In FIG. 13, first, the sound synthesis circuit 80 is the sound synthesis circuit shown in FIG. 3, and
from the terminal 10, a directional signal including low tone close-tone components is obtained,
and from the terminal 11 a non-directional signal Sex signal is obtained. Therefore, the output
signal of the terminal 10 is input to the + side terminal of the adder 61 through the delay circuit
83 and is input to the low pass filter (LPF) 81 to be band-limited. Similarly, the output signal of
the terminal 11 is also input to the low pass filter (LPF) 82 to be band-limited.
[0063]
Further, the signals band-limited by the low-pass filters 81 and 82 are processed in the same
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manner as in FIG. 7, so that the low band extracted from the band-limited microphones 1 and 2
at the output of the adder 22 The close-tone component is output, amplified to a predetermined
level by the amplifier 60, input to the negative terminal of the adder 61, subtracted from the
signal of the positive terminal not band-limited, and output from the terminal 85. Here, the delay
circuit 83 is inserted in order to match the phase of the low frequency close-tone signal to be
subtracted by the adder 61.
[0064]
Therefore, if the gain of the amplifier 60 is set to the same level as the close-tone component of
the directional signal input to the + side terminal of the adder 61, the signal from which the
close-tone is removed from the terminal 85 is the same as FIG. However, in the present
embodiment, since the processing is further band-limited by the low pass filters 81 and 82, it is
possible to reduce only the low frequency component of the near-field sound having a band up
to, for example, 1 kHz. Further, it is also possible to remove only a specific band by replacing the
low pass filters 81 and 82 with another band limiting means such as a band pass filter or a high
pass filter.
[0065]
Also in the embodiment of FIG. 7 and the embodiment of FIG. 12, it is possible to provide a band
limiting means as in this embodiment, and similarly, extraction and reduction can be performed
targeting close sound in a specific band. However, I omit it because the explanation is duplicated.
[0066]
Thus, according to the above-described sound-field synthesis method, non-directional first and
second pressure-type microphones are provided with the sound-receiving surfaces facing in
opposite directions with a predetermined interval, and the first and second pressure-type
microphones are provided. The output signal of one of the pressure-type microphones of 2 is
attenuated by an arbitrary attenuation amount and subtracted from the other output signal, and
an equalization means capable of controlling characteristics of the subtracted signal according to
an arbitrary attenuation amount is used. The output forms a directional pressure gradient
microphone device, and the output signals from the first and second pressure microphones are
added, and the added signal is output through the level conversion means. By obtaining a
composite signal of both microphones, the low-pass sensitivity of the near-field sound is
corrected, and the extracted near-field sound is positively utilized to further subtract the nearfield sound, thereby reducing the sensitivity to the built-in device. Noise and wind noise are also
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those that can be reduced.
[0067]
Further, according to the above-described sound field synthesis arithmetic device, the
nondirectional first and second pressure type microphones disposed so that the sound receiving
surfaces face each other in the opposite direction with a predetermined interval are provided. A
subtractor that subtracts the amount of attenuation from the other output signal to the output
signal of one of the second pressure-type microphones via a controllable level attenuator, and the
characteristics are matched to the level attenuator at the output of the subtractor While forming
a directional pressure gradient microphone device by outputting through controllable equalizing
means, it has an adder for adding output signals from the first and second pressure type
microphones, and adding By outputting the signal from the signal converter via the level
conversion means to obtain a composite signal of both microphones, the low-pass sensitivity of
the near-field sound is corrected, and the extracted near-field sound is actively used to generate a
near signal. Distance sound Touch noise or wind noise to the microphone device housing by
subtracting the al also as it can be reduced.
[0068]
The present invention is not limited to the above-described embodiment, and various
modifications can be made without departing from the spirit of the present invention.
[0069]
Therefore, according to the present invention, a pressure gradient type directional characteristic
is generated from two identical nondirectional microphones, and a low-pass signal component
due to the proximity effect is extracted. The characteristic variation can be suppressed compared
to the case of using different types of microphones, and it can be easily realized in camcorders
and digital cameras that generally use non-directional microphones as built-in microphones, thus
reducing the size and cost of the device. It can be implemented without much impact.
[0070]
Also, by subtracting the extracted low-pass rising signal component from the directional signal
having the proximity effect, a directional microphone in which the proximity effect is suppressed
is obtained, and further amplification is performed with a predetermined gain and subtraction is
performed. Because it is possible to obtain a directional microphone that removes low-pass closeup sound, wind noise in the built-in microphone such as a camcorder or digital camera, touch
noise to the vicinity of the microphone, camera function switches (eg zoom switch, exposure,
shutter speed Etc.) can be easily reduced from the picked up audio signal.
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[0071]
Furthermore, even with an external microphone such as a telephoto microphone attached
separately to the accessory shoe of the camera, the proximity is achieved by subtraction using
low-frequency proximity sound extracted from the two nondirectional microphones similarly
placed in the vicinity. While being able to suppress an effect, it is possible to reduce the wind
noise to input, the touch noise to the microphone vicinity, etc.
[0072]
Also, the voice level of the photographer can be suppressed relative to the voice level emitted by
the subject, making it easier to hear when playing.
[0073]
Furthermore, since the switching between the nondirectional signal and the directional signal is
performed by the cross fade addition, no noise is generated at the time of switching, and the
discomfort of the sound can be suppressed.
[0074]
Also, functional blocks such as cross fade switching means and control signal generation means
can be configured by analog circuits, but digital processing makes it easy to realize with
hardware by DSP or LSI, software by microcomputer, etc. With the miniaturization of
semiconductors, the increase in density, and the increase in memory capacity, an increase in
circuit scale can be realized with almost no problems.
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