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DESCRIPTION JP2004193768

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DESCRIPTION JP2004193768
An audio apparatus to which a microphone can be connected requires some skill and experience
to adjust the level with a trim control volume while emitting voice toward the microphone. It is
difficult for a non-skilled or experienced operator to input a large level signal and see distortion
of the loud sound, or adjust to a proper level while observing the fluctuating needle of the level
indicator It is a good job. A microphone signal input level adjustment device includes an input
signal level adjustment unit 12, an average level detection unit 20, a comparison unit 31, and a
display unit 33. The input signal level adjusting means 12 can adjust the level of the input audio
signal by inputting the audio signal from the microphone. The average level detection means 20
detects the average level of the audio signal whose level has been adjusted by the input signal
level adjustment means 12. The comparison means 31 compares the average level detected by
the average level detection means 20 with the set reference value. The display means 33
performs different display according to the comparison result in the comparison means 31.
[Selected figure] Figure 2
Microphone signal input level adjustment device
TECHNICAL FIELD The present invention relates to a microphone signal input level adjusting
device capable of adjusting an input level of an audio signal from a microphone to an appropriate
level, and in particular, to the experience and skill of the present invention. The present invention
relates to a microphone signal input level adjusting device which can easily perform appropriate
level adjustment even by a non-adjuster. 2. Description of the Related Art Many sound
equipments are provided with input signal level adjustment means so that the level of the audio
signal from the microphone can be adjusted. FIG. 12 is a schematic block diagram of a
microphone mixer 101 which is a kind of such audio equipment. The microphone mixer 101
includes a plurality of systems of input modules 100M, which can input audio signals from the
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microphones. Although not shown, an amplifier and a speaker are connected to the rear stage of
the microphone mixer 101. An audio signal from the microphone is adjusted in level by a trim
control volume 112. The trim control volume 112 can change the level of the audio signal
continuously, that is, steplessly. The audio signal whose level is adjusted by the trim roll volume
112 is sent to the mixing circuit 151 further downstream. In the microphone mixer 101, if it is
intended to output an audio signal having a good S / N ratio from the output terminal, the audio
signal of the highest possible level is input to the mixing circuit 151 within a range that the
mixing circuit 151 can accept. Is desirable. That is, if the level of the signal sent from the input
module 100M to the mixing circuit 151 is too small, the S / N ratio will be worse, so even if the
volume is increased in the subsequent stage, distortion will occur in the loudspeaker sound. In
addition, if the level of the signal sent to the mixing circuit 151 is too large, the signal is clipped
at the input section of the mixing circuit 151, and distortion occurs in the loud sound from the
speaker. When a microphone is connected to the input module 100 M, the output signal level
also varies depending on the type and use state of the microphone, so the operator (adjuster) of
the microphone mixer 101 While saying "mike check, mike check", etc., while listening directly to
the loud sound reproduced from the speaker, or observing the level indicator when the
microphone mixer 101 is provided with a pointer type level indicator , Trim control volume 112
is adjusted.
However, adjusting the trim control volume 112 while emitting voice toward the microphone in
this manner requires some skill and experience. It takes a great deal of skill and experience to
input a large level signal and see distortion of its loud sound, or adjust it to the proper level while
observing the fluctuating needle of the level indicator Things are easily imagined. It is an object
of the present invention to provide a microphone signal input level adjusting device which
enables an appropriate level adjustment to be easily performed even by a particularly
experienced or skilled coordinator. SUMMARY OF THE INVENTION In order to solve the above
problems, a microphone signal input level adjusting device according to the present invention
comprises an input signal level adjusting means, an average level detecting means, and a
comparing means. And display means, the input signal level adjusting means being capable of
inputting an audio signal from the microphone, and capable of adjusting the level of the input
audio signal, the average level detecting means being capable of adjusting the input signal level
The average level of the audio signal whose level is adjusted by the adjustment means is
detected, and the comparison means compares the average level detected by the average level
detection means with the set reference value, and the display means performs the comparison
Different display is performed according to the comparison result in the means (claim 1). With
this structure, the coordinator can perform level adjustment in accordance with the display on
the display means. Since the display appears as a result of comparison of the average level of the
audio signal adjusted by the input signal level adjusting means with the reference value,
appropriate level adjustment can be performed by following the display. Further, even those who
are not particularly experienced or skilled can easily adjust by following the display of the
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display means. In the above microphone signal input level adjusting device, the input signal level
adjusting means may be capable of continuously adjusting the level of the audio signal from the
microphone (claim 2). With such a configuration, more appropriate level adjustment can be
performed. In the above microphone signal input level adjusting device, the comparison means is
set with a first reference value and a second reference value larger than the first reference value,
and the average level is set. When the average level detected by the detection means is less than
the first reference value, the display means performs a first display, and the average level
detected by the average level detection means is the first reference value. When the display
means performs a second display when the average level detected by the average level detection
means exceeds the second reference value, the display means performs a second display. A third
display may be provided (claim 3), wherein the first display is a display prompting the
coordinator to increase the level of the audio signal by the input signal level adjusting means,
The second indication is the input signal level It is a display for informing the coordinator that
the level of the audio signal adjusted by the adjustment means is proper, and the third display is
for the coordinator to reduce the level of the audio signal in the input signal level adjustment
means The display may prompt the user (claim 4).
In the above-mentioned microphone signal input level adjusting device, the average level
detecting means may have a release characteristic for slowing down the attenuation at the time
of level attenuation (claim 5). With this configuration, the coordinator can easily confirm the
display content of the display means. Embodiments of the present invention will be described
with reference to the drawings. First, with reference to FIGS. 1 to 10, a basic structure of a
microphone mixer 1 adopting a microphone signal input level adjusting device according to an
embodiment of the present invention will be described. FIG. 1 is a schematic block diagram of an
acoustic system including a microphone mixer 1. The sound system includes a microphone 61, a
microphone mixer 1, an amplifier 62, and a speaker 66. The microphone mixer 1 is provided
with a plurality of (N) input modules M, and the microphone 61 is connected to one of them. The
signal output from the microphone mixer 1 is input to the amplifier 62, and the signal output
from the amplifier 62 is input to the speaker 66. Thus, the sound emitted toward the microphone
61 is output from the speaker 66. The microphone mixer 1 includes N input modules M, a mixing
circuit 51, an output signal level adjustment circuit 52, and an output terminal 53. The output
signals from the respective input modules M are mixed in the mixing circuit 51, and the mixed
signal is sent to the output terminal 53 after being level-adjusted in the output signal level
adjusting circuit 52. FIG. 2 is a block diagram of the input module M. The input module M
includes an input terminal 11, an input signal level adjusting circuit 12 which is an input signal
level adjusting means, a buffer amplifier 13, an average level detecting circuit 20 which is an
average level detecting means, a comparing circuit 31 which is a comparing means, and a
display. A drive circuit 32 and a panel-type display 33 as display means are provided. Among
them, the microphone signal input level adjusting device of the present invention mainly includes
the input signal level adjusting circuit 12, an average level detecting circuit 20, a comparison
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circuit 31, a display driving circuit 32, and a display 33. Ru. The microphone 61 is connected to
the input terminal 11 of the input module M. The audio signal from the microphone 61 is first
level-adjusted by the input signal level adjustment circuit 12.
The input signal level adjustment circuit 12 is mainly composed of a volume so that the level of
the input signal from the input terminal 11 can be adjusted continuously (steplessly). Therefore,
fine adjustment is also possible. The signal whose level has been adjusted by the input signal
level adjustment circuit 12 is sent to the mixing circuit 51 in the subsequent stage via the buffer
amplifier 13. The signal whose level is adjusted by the input signal level adjustment circuit 12 is
output not only to the buffer amplifier 13 but also to the average level detection circuit 20. The
average level detection circuit 20 outputs an average level signal of the input signal. Then, the
comparison circuit 31 at the subsequent stage compares the value of the average level signal
sent from the average level detection circuit 20 with a preset reference value. Then, the display
drive circuit 32 drives the display 33 such that a display corresponding to the comparison result
appears on the display 33. Next, the functions of the average level detection circuit 20, the
comparison circuit 31, the display drive circuit 32, and the display 33 will be described in more
detail. First, the function of the average level detection circuit 20 will be described. The average
level detection circuit 20 generates an average level signal of the audio signal sent thereto. The
average level detection circuit 20 can be configured by either an analog circuit or a digital circuit.
FIG. 3 is a block diagram of the average level detection circuit 20 configured by an analog circuit.
The configuration of the average level detection circuit 20 is a configuration in which a rectifier
circuit 21 and a time constant circuit 22 are connected in series. The voice signal input to the
average level detection circuit 20 is rectified by the rectification circuit 21 and is sent to the time
constant circuit 22 in the subsequent stage. FIG. 4 is a circuit diagram of this time constant
circuit 22. As shown in FIG. The potential of the capacitor 24 of the time constant circuit 22
becomes an output signal of the time constant circuit 22. The resistance value of the resistor 25
is sufficiently larger than the resistance value of the resistor 23, so the charging rate is relatively
fast and the discharging rate is relatively slow. That is, the time constant circuit 22 is an attack /
release circuit in which the attack time is relatively short and the release time is relatively long.
The attack characteristic of the circuit 22 is mainly determined by the capacitor 24 and the
resistor 23, and the release characteristic is mainly determined by the capacitor 24 and the
resistor 25. FIG. 5 is an example of a flowchart executed by the average level detection circuit 20
when the average level detection circuit 20 is configured by digital circuits.
Signal processing substantially similar to that of the analog circuit of FIG. 3 is performed
according to the flowchart of FIG. In this flowchart, the input signal to the average level detection
circuit 20 is represented by Vi, and the output signal is represented by Vo. First, 0 is set as the
initial value of Vo (step 2). Next, the input voltage Vi is sampled at the sampling frequency fs
(step 3). Then, it is judged whether or not the absolute value | Vi | of the sampled input voltage
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Vi is larger (or equal) than Vo (step 4). When the absolute value | Vi | of the input voltage Vi is
larger than (or equal to) Vo, ie, at the attack time, a value obtained by subtracting Vo from the
absolute value | Vi | of the input voltage Vi is multiplied by a constant Ka Add something to Vo to
make this value a new Vo (step 5). If the absolute value | Vi | of the input voltage Vi is smaller
than Vo, that is, at the release time, Vo multiplied by Kr is set as a new Vo (step 6). Then, the new
Vo value calculated in step 5 or 6 is output as the output signal of the average level detection
circuit 20 (step 7). Such processing of steps 4 to 7 is performed each time Vi is sampled. As an
example of the constants Ka and Kr used in step 5 and step 6, Ka can be 0.020833333 and Kr =
0.9999792. The numerical value is as follows: sampling frequency fs = 48 kHz, attack time
constant Ta = 1 msec, release time constant Tr = 1 sec, Ka = (1 / (Ta · fs)), Kr = 1− (1 / (Tr · Fs))
It is a numerical value obtained from the equation. Next, the function of the comparison circuit
31 will be described with reference to FIG. Two reference values R1 and R2 are set in the
comparison circuit 31. R2 is greater than R1. The appropriate value of the signal level input to
the mixing circuit is No (dB), (No-6) (dB) is set as R1 and (No + 3) (dB) is set as R2. The
comparison circuit 31 compares the signal voltages input thereto with these reference values,
and outputs a signal according to the comparison result. That is, if the signal voltage input to the
comparison circuit 31 is less than R1, the comparison circuit 31 outputs a first signal. If the
signal voltage input to the comparison circuit 31 exceeds R1 and is less than R2, the comparison
circuit 31 outputs a second signal.
If the signal voltage input to the comparison circuit 31 exceeds R2, the comparison circuit 31
outputs a third signal. When the signal voltage input to the comparison circuit 31 matches R1,
the first signal or the second signal is output. When the signal voltage input to the comparison
circuit 31 matches R2, the second signal or the third signal is output. FIG. 6 is a diagram showing
the relationship between the signal input to the comparison circuit 31 and the reference values
R1 and R2. The horizontal axis of this figure shows time. It is assumed that a signal as shown by
a solid curve in FIG. 6 is input to the comparison circuit 31. Then, the first signal is output from
the comparison circuit 31 in the periods indicated by the arrows a1 and a5. During the periods
indicated by the arrows a2 and a4, the second signal is output from the comparison circuit 31.
During the period indicated by the arrow a3, the third signal is output from the comparison
circuit 31. Next, referring to FIG. 7, the functions of the display drive circuit 32 and the display
33 will be described. The display drive circuit 32 is a circuit that controls the display content of
the display 33. The display drive circuit 32 causes the display 33 to display the display content
corresponding to the signal input to the display drive circuit 32. When the first signal is sent
from the comparison circuit 31 to the display drive circuit 32, the display drive circuit 32
displays the display 33 so that the display "UP" as shown in FIG. 7A appears on the display 33.
To drive. When the second signal is sent from the comparison circuit 31 to the display drive
circuit 32, the display drive circuit 32 displays the display 33 so that the display "OK" as shown
in FIG. To drive. When the third signal is sent from the comparison circuit 31 to the display drive
circuit 32, the display drive circuit 32 displays the display 33 in such a manner that the display
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33 displays "DOWN" as shown in FIG. 7C. To drive. The functions of the average level detection
circuit 20, the comparison circuit 31, the display drive circuit 32, and the display 33 of the input
module M have been described above. Next, the operation of the average level detection circuit
20 and the like when a voice is input to the microphone 61 will be described based on FIG. 8,
FIG. 9, and FIG. FIG. 8 is a perspective view of the microphone mixer 1. The microphone mixer 1
is provided with a knob 12a which is a rotation operation means, and by operating this knob, the
input signal level adjustment circuit 12 of FIG. 2 is controlled.
A microphone 61 (not shown in FIG. 8) is connected to the input module M of the microphone
mixer 1, and the coordinator issues voices such as “microphone check, microphone check” etc.
toward the microphone 61, Operate the knob 12a. FIG. 9 is an input / output signal diagram of
the average level detection circuit 20. FIG. 9A shows the average level detection circuit 20 when
a voice “microphone check, microphone check” is emitted toward the microphone. It is a
figure of the signal (audio | voice signal) input, (b) is a figure of the signal (average level signal)
output at that time. In (a) and (b), the horizontal axis indicates time. In (b), a curve indicated by a
solid line indicates the output signal of the average level detection circuit 20. In addition, the
curve shown with a dashed-two dotted line in (b) is an envelope (envelope) of the audio | voice
signal of (a). If the release time of the average level detection circuit 20 is very short, the output
signal of the average level detection circuit 20 roughly matches the two-dotted line curve. In FIG.
9B, since the average level detection circuit 20 outputs the first signal in the period of the arrows
a11 and a13, the display 33 displays “UP”. In the period of the arrow a12, since the average
level detection circuit 20 outputs the second signal, the display 33 displays "OK". As described
above, when an indication “OK” appears on the display 33 when the voice “microphone
check, microphone check” is emitted toward the microphone 61, the coordinator looks at this to
obtain the input signal level. It can be known that the adjustment of the adjustment circuit 12 is
appropriate. As shown in FIG. 9B, since the time during which the output signal of the average
level detection circuit 20 is maintained at R1 or more is stretched due to the release
characteristic of the average level detection circuit 20, the adjustment is performed. The person
can surely confirm the display of "OK" on the display 33. It has been described above that if the
release time of the average level detection circuit 20 is very short, the output signal of the
average level detection circuit 20 substantially matches the two-dot chain line curve of FIG. 9B.
At this time, the display of “UP” and the display of “OK” are repeated several times in the
period of the arrow a12, and it is determined whether the adjustment of the input signal level
adjustment circuit 12 is appropriate for the adjuster It becomes difficult to distinguish
FIGS. 10A and 10B show signals (average level signal) output from the average level detection
circuit 20 when the signal level adjustment by the input signal level adjustment circuit 12 is not
appropriate. (A) shows a signal (average level signal) output from the average level detection
circuit 20 when the signal level sent from the input signal level adjustment circuit 12 is too large.
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In the period of the arrows a23 and a25, since the display 33 displays "DOWN", the coordinator
knows that the signal level is too high. The coordinator may decrease the signal level adjusted by
the input signal level adjustment circuit 12 by operating the knob 12 a according to the
indication of “DOWN”. (B) shows a signal (average level signal) output from the average level
detection circuit 20 when the signal level sent from the input signal level adjustment circuit 12 is
too small. Even if a voice is emitted toward the microphone 61, the display 33 displays only "UP",
so that the coordinator knows that the signal level is too small. The coordinator may increase the
signal level adjusted by the input signal level adjustment circuit 12 by operating the knob 12 a
according to the indication of “UP”. The operation of each circuit when a voice is input to the
microphone 61 has been described based on FIG. 8, FIG. 9, and FIG. As understood from the
above description, the coordinator can perform the signal level adjustment by the input signal
level adjustment circuit 12 based only on the display content of the display 33. Therefore, even
the coordinator who is not skilled or experienced can properly adjust the signal level by the input
signal level adjusting circuit 12. One embodiment of the present invention has been described
above based on FIGS. In the above embodiment, the average level detection circuit 20 generates
the average level signal by averaging the absolute value (rectification value) of the input signal
voltage with the time constant of the attack / release circuit. 20 is not limited to such a
configuration. For example, it may be configured by a squaring circuit and a low pass filter
circuit, and an envelope signal obtained by squaring an input signal and passing through a low
pass filter may be output as an average level signal. Further, although the average level detection
circuit 20 of the above embodiment uses an attack / release circuit (time constant circuit) having
a release time longer than the attack time, the release time may be the same as the attack time, It
may also be short.
In the above embodiment, the display content “UP” is displayed as a prompt for the
coordinator to increase the signal level, and the signal level adjusted by the input signal level
adjustment circuit 12 is adjusted to be appropriate. Although the display content "OK" is
displayed as a display for informing the user and the display content "DOWN" is illustrated as a
display prompting the coordinator to reduce the signal level, the display content is not limited to
this, for example, " It may be something like "Please raise the input volume", "It is the appropriate
level", "Please lower the input volume". In the above embodiment, the panel type display 33 is
adopted as the display means, but the configuration of the display means is not limited to this.
For example, as shown in FIG. 11, three LEDs 41, 42 and 43 are disposed on the front panel of
the microphone mixer 40, and the adjustment degree of the input signal level adjustment circuit
12 is indicated depending on which of these lights. Good. For example, as shown in FIG. 11, on
the front panel of the microphone mixer 40, print “UP” “OK” “DOWN” on the top of each
LED 41, 42, 43, and adjust the input signal level adjustment circuit It may indicate how 12
should be adjusted. Further, in the above-described embodiment, there are cases in which each
circuit is clearly described as an analog circuit or a digital circuit, and also in other cases. In the
present invention, it is not particularly important whether each circuit is an analog circuit or a
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digital circuit, and any method may be adopted. In the above embodiment, the input module M is
provided with the input signal level adjustment circuit 12 capable of continuously adjusting the
input signal level immediately after the input terminal 11. For example, the input terminal 11
and the input Between the signal level adjustment circuit 12, a switched attenuator may be
provided which can adjust the input signal level stepwise (for example, in three steps of -20 dB, 40 dB, -60 dB). In the above embodiment, two reference values are set in the comparison circuit
31 and three types of display on the display 33 are set. However, more reference values may be
set to increase the number of display types. Alternatively, only one reference value may be set
and only two types of display may be performed. In the above embodiment, the microphone
signal input level adjustment device is applied to the microphone mixer 1, but the present
invention can be applied to other acoustic devices.
Industrial Applicability The present invention is carried out in the mode as described above, and
even a coordinator who is not particularly experienced or skilled can easily perform appropriate
level adjustment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of
an acoustic system including a microphone mixer. FIG. 2 is a schematic block diagram of an input
module. FIG. 3 is a block diagram of an average level detection circuit configured by an analog
circuit. FIG. 4 is a circuit diagram of a time constant circuit. FIG. 5 is a flowchart executed by the
average level detection circuit when the average level detection circuit is configured by digital
circuits. FIG. 6 is a diagram showing the relationship between a signal input to a comparison
circuit and a reference value. FIGS. 7A and 7B are front views of the display, showing three
display modes by (a), (b) and (c). FIG. 8 is a perspective view of a microphone mixer. FIG. 9 is an
input / output signal diagram of the average level detection circuit, where (a) is a diagram of the
input signal, and (b) is a diagram of the output signal. FIG. 10 is a diagram of an output signal
from the average level detection circuit, and FIG. 10A is a diagram of an output signal of the
average level detection circuit when the signal level sent by the input signal level adjustment
circuit is too large; b) is a diagram of the output signal of the average level detection circuit when
the signal level sent by the input signal level adjustment circuit is too small. FIG. 11 is a
perspective view of a microphone mixer. FIG. 12 is a block diagram of a microphone mixer
adopting a conventional microphone signal input level adjusting device. [Description of the code]
1 microphone mixer 11 input terminal 12 input signal level adjustment circuit 13 buffer
amplifier 20 average level detection circuit 21 rectification circuit 22 time constant circuit 23
resistor 24 capacitor 25 resistor 31 comparison circuit 32 display drive circuit 33 display 51
Mixing circuit 52 Output signal level adjustment circuit 53 Output terminal 61 Microphone 62
Amplifier 66 Speaker M input module
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