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JPH08331696

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DESCRIPTION JPH08331696
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention enables, for
example, automatic adjustment of variations in sensitivity of a microphone (hereinafter referred
to as a microphone) mounted on a camcorder or the like on a manufacturing line. The present
invention relates to a microphone sensitivity automatic adjustment device capable of eliminating
a sensitivity difference between a plurality of sets due to variation or a sensitivity difference
between left and right microphones in one set.
[0002]
2. Description of the Related Art In many cases, microphone capsules incorporating small
microphones are mounted on camcorders and portable audio equipment. Such a microphone
capsule has a sensitivity difference of about ± several dB itself, and the gain variation of the
circuit system to which this microphone capsule is connected is added as well, thereby
incorporating such a microphone capsule in a camcorder or the like. And, the sensitivity
difference larger than the above-mentioned ± several dB will be produced. Therefore, at present,
for example, in a production line such as a camcorder, a microphone whose sensitivity is selected
in advance is used to change the gain of the microphone amplifier according to the microphone
sensitivity.
[0003]
01-05-2019
1
In the method of changing the gain of the microphone amplifier according to such microphone
sensitivity, the land on the printed wiring board on which the microphone amplifier is mounted is
shorted with solder, or the printed wiring board is fixed. It is made to short with the bis which
does. However, this work is always performed by a human hand, and therefore, only a few gain
distributions can be set, and the accuracy of the sensitivity correction is a little lacking.
[0004]
The present invention has been made in view of the above-described circumstances, and an
object of the present invention is to automatically and automatically correct variations in
microphone sensitivity on a manufacturing line, and to loop an automatic gain control circuit. It
is an object of the present invention to provide a microphone sensitivity automatic adjusting
device which can adjust the initial value in each of the microphones and can be easily combined
with the loop of the automatic gain control circuit of the digital recording device.
[0005]
Further, it is an object of the present invention to be able to adjust in advance the difference in
sensitivity of individual microphones prior to use of microphones having differences in sensitivity
characteristics in the normal use state mode, and microphones having differences in sensitivity
characteristics. However, it is an object of the present invention to provide a microphone
sensitivity automatic adjustment device which can be treated as a microphone having the same
sensitivity characteristic.
[0006]
In order to achieve the above object, the present invention comprises level adjusting means
capable of changing the level of an output signal of a microphone in a normal use state mode,
and an analog output signal of the level adjusting means. An automatic gain control circuit is
configured together with analog-digital conversion means for converting into digital signals, the
level adjustment means and the analog-digital conversion means, and according to the deviation
between the output signal of the analog-digital conversion means and the reference signal. A
microcomputer is provided which performs adjustment control of the output signal level of the
microphone with respect to the level adjustment means.
[0007]
Further, according to the present invention, it is possible to change the level of an adjustment
reference sound source generating a sound wave of a certain level and the output signal of a
microphone receiving the sound wave of the constant level of the adjustment reference sound
01-05-2019
2
source at the time of adjustment of variation in sensitivity characteristics. An automatic gain
control circuit comprising level adjustment means, analog-digital conversion means for
converting an analog output signal of the level adjustment means into a digital signal, the level
adjustment means and the analog-digital conversion means, the analog-digital conversion circuit
A microcomputer is provided which performs adjustment control of the output signal level of the
microphone with respect to the level adjustment means in accordance with the deviation between
the output signal of the conversion means and the reference signal.
[0008]
Furthermore, according to the present invention, the level adjustment means changes the control
voltage from the microcomputer according to an analog signal converted by the digital-analog
conversion means to change the gain to change the level of the output signal of the microphone.
It is characterized by being a voltage control amplifier.
[0009]
In addition, the present invention is characterized in that the level adjusting means is an
attenuator that changes the attenuation amount according to a control signal from the
microcomputer to change the level of the output signal of the microphone.
[0010]
Further, the present invention is characterized in that the reference signal and the output signal
of the analog-digital conversion means are stored in a memory.
[0011]
In the present invention, after level adjustment to a predetermined level according to the output
signal level from the microphone input to the level adjustment means of the automatic gain
control circuit, it is converted to a digital signal by the analog-digital conversion means. Then, the
digital signal and the reference signal are compared by the macro computer, and the macro
computer causes the level adjusting means to adjust the level of the output signal of the
microphone according to the deviation between them.
[0012]
Therefore, variations in microphone sensitivity can be corrected easily and accurately in the
production line, and initial values in the loop of the automatic gain control circuit can be matched
for each microphone, and automatic gain control of the digital recording device It becomes easy
to combine with the loop of the circuit.
01-05-2019
3
[0013]
In the present invention, the microphone receives a sound pressure of a constant level from the
adjustment reference sound source, and the level is set to a predetermined level according to the
output signal level from the microphone input to the level adjustment means of the automatic
gain control circuit. After adjustment, the analog signal is converted to a digital signal by analogto-digital conversion means, and the digital signal and the reference signal are compared by the
microcomputer, and the microcomputer compares the level adjustment means with the
microphone The level adjustment of the output signal is performed, and even if there is a
difference in the sensitivity characteristic of the microphone, the output level of the analogdigital conversion means is not influenced by the sensitivity characteristic of the microphone.
[0014]
Therefore, prior to using the microphones having different sensitivity characteristics in the
normal use state mode, the sensitivity differences of the individual microphones can be adjusted
in advance, and microphones having the same sensitivity characteristics can be used even with
microphones having different sensitivity characteristics. It can be treated as
[0015]
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the microphone sensitivity automatic
adjustment device of this embodiment.
The embodiment of FIG. 1 shows the case where a voltage control amplifier (hereinafter referred
to as VCA) is used as a level adjustment means in an automatic gain control circuit (hereinafter
referred to as an AGC circuit).
[0016]
A microphone 1 in FIG. 1 is a microphone (hereinafter referred to as a microphone), and the
microphone 1 is mounted on, for example, a camcorder, and the sensitivity generally varies
01-05-2019
4
among the microphones.
In this embodiment, this variation can be automatically adjusted during, for example, a
microphone built-in manufacturing line to a camcorder.
A minute signal output from the microphone 1 is input to the fixed gain amplifier 2, and the
small signal temporarily output from the microphone 1 is amplified by the fixed gain amplifier 2.
The output signal of the fixed gain amplifier 2 is input to the VCA 3, and the VCA 3 is an
amplifier capable of changing the gain at the control voltage.
[0017]
The output signal of VCA 3 is sent to an analog signal recording circuit (not shown).
When the analog signal recording circuit is an analog recording circuit such as an 8 mm video
camera, the output signal of VCA 3 is sent as it is to the modulation circuit.
When a digital signal recording circuit is used instead of the analog signal recording circuit, the
output signal of VCA 3 is once converted to a digital signal by analog-to-digital conversion means
4 (hereinafter referred to as A / D conversion circuit). Then, the signal is sent to a digital signal
recording processing circuit (not shown) and then recorded by the digital signal recording circuit.
[0018]
Further, an output signal of the A / D converter 4 is simultaneously inputted to a microcomputer
5 (hereinafter referred to as a microcomputer).
The microcomputer 5 compares the output signal of the A / D converter 4 with the storage
content stored in the memory 7, and outputs an output signal corresponding to the deviation
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5
value as digital-analog conversion means 6 (hereinafter referred to as D / A conversion) Output).
The memory 7 is a non-volatile memory, and the memory 7 stores an AGC point 7a, D / A control
data 7b, a reference value 7c, and a switching flag 7d.
[0019]
The AGC point 7a represents a constant output level of an AGC circuit to be described later in the
normal mode of the microphone sensitivity automatic adjusting device 9 of the present invention,
and the memory 7 to the microcomputer 5 are in the normal mode of the microphone sensitivity
automatic adjusting device 9. It is supposed to be output.
The D / A control data 7 b is data for outputting to the microcomputer 5 to control the D / A
converter 6 in the normal mode of the microphone sensitivity automatic adjustment device 9.
Furthermore, the reference value 7c is output from the memory 7 in the mode of the microphone
sensitivity automatic adjustment device, and is added to the microcomputer 5 as a reference
value of the sensitivity level of the microphone 1 to the microcomputer 5. The switching flag 7d
is configured such that a signal of bit "1" is output from the memory 7 to the microcomputer 5
when the microphone sensitivity automatic adjustment device 9 is switched between the normal
mode and the adjustment mode.
[0020]
When the microphone sensitivity automatic adjustment device 9 is switched between the normal
mode and the adjustment mode, as described later, it is not limited to the case where the flags of
the memory 7 are set. It is also possible to switch by inputting a level or a low level. Furthermore,
this switching is performed by setting an address flag from the LANC (local area network control)
commander to the RAM (not shown in FIG. 1) in the microcomputer 5 as described later in detail.
It is also possible to switch between the normal mode and the adjustment mode.
[0021]
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6
Now, when the output of the microcomputer 5 is output to the D / A converter 6, the D / A
converter 6 converts the output data of the microcomputer 5 into an analog signal and then
changes the control voltage of the VCA 3, thereby changing the VCA 3 In this case, the variation
of the sensitivity of the microphone 1 can be adjusted by changing the gain. Thus, the AGC circuit
8 is constituted by the VCA 3, A / D converter 4, microcomputer 5 and D / A converter 6. The
AGC circuit 8, memory 7, microphone 1, gain fixed amplifier 2 Thus, the microphone sensitivity
automatic adjustment device 9 is configured. The microphone sensitivity automatic adjustment
device 9 is mounted on a camcorder or the like.
[0022]
FIG. 2 is a configuration explanatory diagram for explaining the operation in the adjustment
mode of the microphone sensitivity automatic adjustment device 9. The portions indicated by the
symbols 1 to 8 in FIG. 2 are the microphone sensitivity automatic adjusting device 9 shown in
FIG. 1, and in the description of the configuration, the same portions as those in FIG. Avoid the
explanation.
[0023]
Reference numeral 10 in FIG. 2 denotes an adjustment reference sound source, and the
adjustment reference sound source 10 is provided with a signal generation circuit 11. An output
signal of the signal generation circuit 11 is applied to the speaker 13 after being amplified by the
amplifier 12. The microphone 1 of the microphone sensitivity automatic adjustment device 9 is
disposed to face the front of the speaker 11. By doing this, the output signal from the signal
generation circuit 11 of the adjustment reference sound source 10 is amplified by the amplifier
12 and then drives the speaker 13. As a result, a sound wave of a constant sound pressure level
is generated from the speaker 13 and this sound is received by the microphone 1 of the
microphone sensitivity automatic adjustment device 9.
[0024]
Next, the operation of the microphone sensitivity automatic adjustment device of the present
invention will be described. First, the operation in the adjustment mode by the microphone
sensitivity automatic adjustment device 9 will be described. In the adjustment mode, as shown in
01-05-2019
7
FIG. 2, the speaker 13 of the adjustment reference sound source 10 is opposed to the
microphone 1 of the microphone sensitivity automatic adjustment device 9, and the output signal
of the signal generation circuit 11 of the adjustment reference sound source 10 is amplified by
the amplifier 12. After amplification, the speaker 13 is driven and a sound wave of constant
sound pressure is generated from the speaker 13. This sound wave is received by the
microphone 1 of the microphone sensitivity automatic adjustment device 9, converted into an
electric signal, amplified once by the fixed gain amplifier 2, and then input to the VCA 3. The
output signal of VCA 3 is converted to a digital signal by A / D converter 4.
[0025]
In this state, the process in the adjustment mode shown in the flowchart of FIG. 3 is performed.
In the flowchart of FIG. 3, the process in the adjustment mode starts, and the microcomputer 5
reads the reference value 7c from the memory 7 in step S1. Assuming that this reference value 7
c has no error or variation in the microphone 1, gain fixed amplifier 2, VCA 3, etc., the A / D
converter 4 when a certain constant sound level is added to the microphone sensitivity automatic
adjustment device 9 Theoretical output value of
[0026]
The microcomputer 5 compares the reference value 7c read from the memory 7 with the output
value of the A / D converter 4 in step S2. As a result of this comparison, (a). Reference value 7c>
Output value of A / D converter 4, (b). Reference value 7c <output value of A / D converter 4, (c).
Three cases of reference value 7c = output value of A / D converter 4 are assumed. As a result of
this comparison, if the reference value 7c of (a)> the output value of the A / D converter 4, the
process proceeds from step S2 to step S3, and the microcomputer 5 outputs an output such that
the gain of VCA3 increases. The signal is supplied to the D / A converter 6. The D / A converter 6
receives the output signal from the microcomputer 5, converts the digital signal into an analog
signal, and applies the analog signal to the VCA 3 as a control voltage to increase the gain of the
VCA 3 To control.
[0027]
As a result, the output signal from the microphone 1 obtained by receiving the sound wave of
constant sound pressure from the speaker 13 of the adjustment reference sound source 10 is
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8
controlled so that the gain is increased by the VCA 3 through the gain fixed amplifier 2 Then, the
signal is outputted from the output end of the VCA 3 and inputted to the A / D converter 4. The
output signal of the A / D converter 4 is again compared with the reference signal 7c of the A / D
converter 4 in step S1 in the same manner as with the reference value 7c from the memory 7 in
step S1. The microcomputer 5 compares them. If the microcomputer 5 determines from the
result of this comparison that the reference value 7c of (b) is less than the output value of the A /
D converter 4, the process proceeds from step S2 to step S4. Outputs an output to the D / A
converter 6 such that the gain of the VCA 3 decreases.
[0028]
The D / A converter 6 receives the output signal from the microcomputer 5, converts the digital
signal into an analog signal, and applies the analog signal to the VCA 3 as a control voltage to
step the gain of the VCA 3 in the step. Contrary to the processing in S3, the gain of VCA 3 is
controlled to decrease. As a result, the output signal from the microphone 1 obtained by
receiving the sound wave of constant sound pressure from the speaker 13 of the adjustment
reference sound source 10 is controlled so that the gain is lowered by the VCA 3 through the
gain fixing amplifier 2 Then, the signal is outputted from the output end of the VCA 3 and
inputted to the A / D converter 4.
[0029]
The output signal of this A / D converter 4 is again compared with the reference signal 7c of the
A / D converter 4 in step S1 in the same way as with the reference value 7c from the memory 7
in step S2. The microcomputer 5 compares them. As a result of the comparison, when the
microcomputer 5 determines that the reference value 7c of (c) = the output value of the A / D
converter 4, the processing is shifted from step S2 to step S5. The output signal of the A / D
converter 4 at this time is stored in the memory 7.
[0030]
The data of the output signal of the A / D converter 4 stored in the memory 7 is the reference
value 7c of the sensitivity of the microphone 1 when the microphone sensitivity time adjusting
device 9 mounted on the camcorder is in the normal use mode. This is control data when the
VCA 3 is controlled so that the output signal of the A / D converter 4 becomes a preset constant
01-05-2019
9
value. That is, although the D / A converter 6 generates an analog voltage for determining the
gain of the VCA 3, it is digital data corresponding to the voltage. As described above, when the
microcomputer 5 stores the digital output signal of the A / D converter 4 in the memory 7, a
series of adjustment mode processing steps are completed.
[0031]
Next, the operation of the microphone sensitivity automatic adjustment device 9 in the normal
use state mode will be described along the flowchart of FIG. When the microphone sensitivity
automatic adjustment device 9 is mounted on a cam / coder or the like in the normal use state
mode of the microphone sensitivity automatic adjustment device 9, if there is a sensitivity
difference of the microphone 1, this sensitivity difference is automatically calculated. It
corresponds to the case of correction. In the flowchart of FIG. 4, the power is first turned on, and
the output signal of the A / D converter 4 stored in the memory 7 in the adjustment mode in step
S6 by the microcomputer 5, that is, the reference value 7 c of the sensitivity of the microphone 1
is stored. Read from
[0032]
The reference value 7c of the microphone 1 read out from the memory 7 by the microcomputer
5 is transferred from the microcomputer 5 to the D / A converter 6 in step S7, and the D / A
converter 6 converts the digital signal into an analog signal. This analog signal is a control
voltage for setting the reference gain of VCA 3, and the gain of VCA 3 is set by applying this
analog signal to VCA. When a sound wave is received by the microphone 1 with the gain of the
VCA 3 set, the output signal of the microphone 1 according to the intensity of the received sound
wave is input to the VCA 3 through the fixed gain amplifier 2 and amplified by the VCA 3 The
signal is recorded in the digital signal recording circuit through a modulation circuit (not shown)
and the like, and at the same time, is input to the A / D converter 4.
[0033]
The output signal of the VCA 3 input to the A / D converter 4 is converted into a digital signal
there, and the digital signal is recorded in a digital signal recording circuit (not shown) and the
like and simultaneously input to the microcomputer 5. In step S8, the output signal of the A / D
converter 4 is compared with the data of the AGC point 7a stored in the memory 7 by the
01-05-2019
10
microcomputer 5 in step S9. The data of AGC point 7a represents the signal level at which the
AGC operation is started, and the level of the output signal of A / D converter 4 is less than the
level of the data of AGC point 7a (in A / D converter 4 If the level of the output signal <the level
of the data of AGC point 7a), the process returns from step S9 to step S8, and the step is
performed until the level of the output signal of A / D converter 4 and the level of the data of
AGC point 7a become equal. The processes of S8 and step S9 are repeatedly executed.
[0034]
When the result of determination by the microcomputer 5 in step S9 is that the level of the
output signal of the A / D converter 4 is equal to or higher than the level of the data of the AGC
point 7a (level of output signal of A / D converter 4> AGC point 7a data level), the process
proceeds from step S9 to step S10 to the AGC routine (the processing procedure of the AGC
routine will be described in detail later in FIG. 5) and returns from step S10 to step S8. The
process of step S10 is repeated until the level of the output signal of the A / D converter 4 and
the level of the data at the AGC point 7a become equal.
[0035]
That is, in the processes of steps S8 to S9, when the level of the output signal of the A / D
converter 4 is higher than that of the AGC point 7a, the microcomputer 5 decreases the gain of
VCA 3 to perform AGC operation, and step S8. In the process from step S10, the data output from
the microcomputer 5 to the D / A converter 6 is changed according to the level of the output
signal of the A / D converter 4 to perform AGC operation.
However, in this case, the data stored in the memory 7 is not changed.
[0036]
Next, the procedure of the AGC routine will be described in detail with reference to the flowchart
of FIG. First, the power is turned on to start the execution of the processing routine of FIG. 5. In
step S11, the microcomputer 5 reads the D / A control data 7b stored in the memory 7. In step
S12, the coefficient K = 1 is set. . The coefficient K is a value that is greater than "1" and less than
"0", and changes between "0" and "1". すなわち、0≦K≦1である。 The control data 7b is the
same as the data stored in the memory 7 in step S5 of the flowchart in the adjustment mode of
FIG. The processing from power on to step S12 in FIG. 5 is initialization processing, and the gain
01-05-2019
11
of VCA 3 is set to an initial value.
[0037]
Next, in step S13, the microcomputer 5 changes the gain of the VCA 3 by the coefficient K.
However, the D / A control data 7b read out from the memory 7 such that the gain of the VCA 3
becomes K times the current value. The value is changed and output to the D / A converter 6.
The D / A converter 6 inputs this output data from the microcomputer 5. The analog signal
converts the gain (G dB) of VCA 3 to KG dB, that is, 0 to G dB.
[0038]
In this state, if the power switch is turned off in step S14, the process proceeds to step S15, the
power is turned off, and the series of processing ends. In step S14, if the power switch is not
turned off, the process proceeds to step S16. In step S16, the microcomputer 5 determines
whether to switch to the adjustment mode. When switching to the adjustment mode, the step
S17. And the processing of the series of adjustment modes described in FIG. 3 is performed.
[0039]
In step S16, when the mode is not switched to the adjustment mode, the microcomputer 5 shifts
from step S16 to step S18, and the microcomputer 5 determines whether the coefficient K is 1 or
not. If it is 1, the gain of VCA 3 is G dB. In the case where the coefficient K = 1, the process
proceeds to step S19, and it is determined whether the output of the A / D converter 4
corresponding to the gain control of VCA 3 when the coefficient K is 1 is larger than the AGC
point. Make a decision on
[0040]
As a result of this determination, when the output value of the A / D converter 4 is smaller than
the AGC point, the sensitivity of the microphone 1 is low, and the gain control of the VCA 3 in the
region 100 shown in FIG. It corresponds to FIG. 6 is a characteristic diagram showing the input
of VCA3 on the horizontal axis and the output of VCA3 on the vertical axis, and in the region
01-05-2019
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100, the output level of the A / D converter 4 rises with the gain of VCA3 as G dB. In order to do
so, the process returns from step S19 to step S13, and the process from step 13 to step S19 is
performed again. Conversely, if the microcomputer 5 determines in step 19 that the output value
of the A / D converter 5 is larger than the AGC point, the sensitivity of the microphone 1 is high,
and steps S19 to S20 are performed. Proceed to In step S20, the microcomputer 5 makes the
value of the coefficient K 1 / A times (A 1 1) and outputs it to the D / A converter 6, and the D /
A converter 6 outputs the output signal of the microcomputer 5 as an analog signal The control
voltage for reducing the gain is applied to the VCA 3 to reduce the gain of the VCA 3.
[0041]
On the other hand, when the microcomputer 5 determines that the coefficient K is not 1 in step
S18, the process proceeds from step S18 to step S21, and in step S21, the microcomputer 5
outputs an output signal of the A / D converter 4 It is determined whether it is larger than the
AGC point. As a result of this determination, if it is determined that the value is larger than the
AGC point, the process proceeds to step S19, the same process as described in step S19 is
performed, and the process returns to step S13. Further, in step S21, when the microcomputer 5
determines that the output signal of the A / D converter 4 is smaller than the AGC point, the
sensitivity of the microphone 1 is low. In the case of the area 200 in FIG. When the coefficient K
is K <1, the gain of VCVA3 is smaller than G dB, and the process proceeds to step S22.
[0042]
In step S22, the microcomputer 5 multiplies the value of the coefficient K by 1 / B (B 1 1) and
outputs it to the D / A converter 6, and the D / A converter 6 converts the output signal of the
microcomputer 5 into an analog signal. Convert to a signal, apply a control voltage to raise the
gain to VCA3, and raise the gain of VCA3. However, if K> 1 in this case, K = 1. When the process
of step S22 ends, the process returns from step S22 to step S13, and the processes of step S13
and subsequent steps are repeated again.
[0043]
As described above, even if the sensitivity of the microphone 1 is different, the output signal of
the A / D converter 4 is controlled to be constant by the control of the gain of the VCA 3. FIG. 7 is
shown to explain this state, as shown by the solid line a and the broken line b, in the case of
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performing gain control by VCA 3 when two microphones 1 having different microphone
sensitivities are individually used. The characteristic is shown, and the output level of the fixed
gain amplifier 2 is shown on the vertical axis. Assuming that the gain of the fixed gain amplifier 2
is AdB, the output signal in the case of either the solid line a or the broken line b of the
microphone 1 which has passed through the fixed gain amplifier 2 is amplified by AdB times and
sent to VCA3.
[0044]
The output of the fixed gain amplifier 2 input to the VCA 3 is amplified there, but the output of
the VCA 3 and hence the output of the A / D converter 4 are obtained regardless of whether the
microphone 1 has any sensitivity characteristic of solid line a and broken line b. The gain of the
VCA 3 is controlled by the microcomputer 5 through the D / A converter 6 so that the signal has
a constant value, as shown in FIG. 7, the sensitivity of the microphone 1 having the sensitivity
characteristic of the broken line b is a solid line a. If the gain of VCA 3 is BdB higher than the
sensitivity of the microphone 1 having the sensitivity characteristic of, the output of the AGC
circuit 8 as a whole is such that the sensitivity characteristic of the broken line b is BdB lower
than the sensitivity characteristic of the solid line a. The level is constant.
[0045]
Next, the procedure for switching between the adjustment mode described in FIG. 3 and the
normal use state mode described in FIG. 4 will be described with reference to the flowchart of
FIG.
The difference between the adjustment mode and the normal use state mode can be dealt with
only by the software of the microcomputer 5. Therefore, for example, the program in the
adjustment mode is made into a subroutine, and the subroutine is executed only when a
predetermined condition is satisfied. In this case, for example, as in the embodiment of FIG. 1,
"switching flag 7d" stored in the memory 7 is set. In the description of FIG. 8, the description will
be made in the case where the switching flag 7 d is set.
[0046]
In the flowchart of FIG. 8, the power is first turned on, and the microcomputer 5 reads the data to
the D / A converter 6 stored in the memory 7 in step S23, that is, the D / A control data 7b. Is
output to the D / A converter 6 in step S24, and the D / A converter 6 converts the D / A control
data 7b into an analog signal, sets it as a control voltage of VCA3, and applies it to VCA3. Set the
01-05-2019
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gain of.
[0047]
By setting the gain of VCA 3, the output signal of microphone 1 passes through gain fixed
amplifier 2, is amplified by VCA 3 according to the set gain, and is converted into a digital signal
by A / D converter 4.
The digital signal is monitored by the microcomputer 5 in step S25. In this monitoring state, the
microcomputer 5 determines from the monitoring result whether or not to switch in the
adjustment mode (step S26). This determination is made by the microcomputer 5 depending on
whether the switching flag 7d stored in the memory 7 is set, that is, whether the bit "1" is input
to the microcomputer 5 or not. As a result of this determination, when switching to the
adjustment mode, the process proceeds to the processing of the subroutine in the adjustment
mode in step S27. The processing of the subroutine in this adjustment mode follows the
processing procedure already described in FIG.
[0048]
If the adjustment mode is not selected in step S26, the process proceeds from step S26 to step
S28. In step S28, the microcomputer 5 outputs the output signal of the A / D converter 4 and the
AGC stored in the memory 7 Compare with the data of point 7a. As a result of the comparison,
when the output signal of the A / D converter 4 is smaller than the data of the AGC point 7a, the
process returns from the step S28 to the process of the step S25, and the process from the step
S25 to the step S28 is executed again.
[0049]
If the result of the determination in step S28 is that the output signal of the A / D converter 4 is
larger than the data of the AGC point 7a, the process proceeds from step S28 to step S29 to
execute the AGC routine. The processing of the AGC routine is as already described in the
flowchart of FIG. 5, and when the processing of the AGC routine is executed, the processing is
returned from step S29 to step S25 again.
01-05-2019
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[0050]
Although the determination at the time of transition to the adjustment mode in step S26 of FIG. 8
has been described based on whether or not the microcomputer 5 determines whether the
switching flag 7d of the memory 7 is set, the present invention is limited thereto For example, as
shown in FIG. 9, depending on whether the predetermined input port of the microcomputer 5
becomes “H” level or “L” level, the adjustment mode is set or the normal use state It may be
determined whether to switch to the mode. In this case, as shown in FIG. 9, the resistor R1 and
the switch S1 are connected in series between the power supply and the ground, and a
predetermined input terminal of the microcomputer 5 is connected to the connection point of the
resistor R1 and the switch S1. When the switch S1 is on, the predetermined input terminal of the
microcomputer 5 is set to the "L" level to switch to the normal use state mode. Conversely, when
the switch S1 is off, the predetermined input terminal of the microcomputer 5 may be at the "H"
level, and the adjustment mode may be selected.
[0051]
Furthermore, as shown in FIG. 10, the LANC commander 14 is connected to the microcomputer
5, and the LANC commander 14 switches to the adjustment mode by setting a flag to a specific
address in the RAM 5a in the microcomputer 5. Good.
[0052]
Although the embodiment of FIG. 1 exemplifies the case of using VCA 3 as the level adjustment
means, the present invention is not limited to this, and the attenuator 15 may be used instead of
VCA 3. Good.
When the attenuator 15 is used, the microcomputer 5 compares the output signal of the A / D
converter 4 with the reference value stored in the memory 7, and the microcomputer 5 performs
D / A according to the deviation value. The control data is output to the attenuator 15 to control
the attenuation amount of the attenuator 15, and the level control of the output signal of the
microphone 1 amplified by the fixed gain amplifier 2 is performed.
[0053]
As apparent from the above description, according to the present invention, the level adjusting
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means capable of changing the level of the output signal of the microphone in the normal use
state mode, and the analog output signal of the level adjusting means are digital signals. Together
with the level adjusting means and the analog to digital converting means, the automatic gain
control circuit is configured, and the level is adjusted according to the deviation between the
output signal of the analog to digital converting means and the reference signal. Since the
adjustment means is provided with a microcomputer for adjusting and controlling the output
signal level of the microphone, variations in sensitivity of the microphone can be easily and
accurately corrected automatically on the production line, and The initial value in the loop of the
automatic gain control circuit can be matched for each microphone, digital recording Easily loops
and combinations of the automatic gain control circuit of the location.
[0054]
Further, according to the present invention, it is possible to change the level of an adjustment
reference sound source generating a sound wave of a certain level and the output signal of a
microphone receiving the sound wave of the constant level of the adjustment reference sound
source at the time of adjustment of variation in sensitivity characteristics. An automatic gain
control circuit comprising level adjustment means, analog-digital conversion means for
converting an analog output signal of the level adjustment means into a digital signal, the level
adjustment means and the analog-digital conversion means, the analog-digital conversion circuit
Since the level adjustment means is provided with a microcomputer that performs adjustment
control of the output signal level of the microphone according to the deviation between the
output signal of the conversion means and the reference signal, the microphone having a
difference in sensitivity characteristic Prior to use in normal use mode, sensitivity differences
between individual microphones can be Can be integer, it can be treated as a microphone of the
same sensitivity in the microphone with a difference in sensitivity characteristics.
[0055]
Brief description of the drawings
[0056]
1 is a block diagram showing the configuration of an embodiment of the microphone sensitivity
automatic adjustment device of the present invention.
[0057]
2 is a block diagram in the case of applying the microphone sensitivity automatic adjustment
device of the present invention in the adjustment mode of the microphone.
01-05-2019
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[0058]
3 is a flowchart showing a processing procedure in the adjustment mode in the case of applying
the microphone sensitivity automatic adjustment device of FIG. 2 in the adjustment mode of the
microphone.
[0059]
4 is a flowchart showing a processing procedure in the normal use state of the microphone
sensitivity automatic adjustment device of the present invention.
[0060]
5 is a flowchart showing the processing procedure of the AGC routine of the microphone
sensitivity automatic adjustment device of the present invention.
[0061]
6 is an operation explanatory diagram of VCA at the time of processing of the AGC routine of the
microphone sensitivity automatic adjustment device of the present invention.
[0062]
7 is an explanatory view of a state of absorbing the sensitivity difference of the microphone in
the microphone sensitivity automatic adjustment device of the present invention.
[0063]
8 is a flowchart showing a processing procedure when switching between the adjustment mode
and the normal use mode of the microphone sensitivity automatic adjustment device of the
present invention.
[0064]
9 is a circuit diagram of an embodiment of the switching means applied when switching between
the adjustment mode and the normal use mode, the microphone sensitivity automatic adjustment
device of the present invention.
[0065]
10 is a block diagram showing the configuration of another embodiment of the switching means
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applied when switching between the adjustment mode and the normal use mode, the microphone
sensitivity automatic adjustment device of the present invention.
[0066]
11 is a block diagram showing the configuration of another embodiment of the microphone
sensitivity automatic adjustment device of the present invention.
[0067]
Explanation of sign
[0068]
1 microphone 2 fixed gain amplifier 3 VCA 4 A / D converter 5 microcomputer 6 D / A converter
7 memory 7 a AGC point 7 b D / A control data 7 c reference value 7 d switching flag 8 AGC
circuit 9 microphone sensitivity automatic adjustment device 10 for adjustment Reference sound
source 11 Signal generation circuit 12 Amplifier 13 Speaker 14 LANC commander 15 Attenuator
R1 Resistance S1 switch
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