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JP2018142886

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DESCRIPTION JP2018142886
Abstract: A filter setting device, a filter setting method and a filter setting program corresponding
to a situation in which a plurality of microphones are simultaneously used. A filter setting device
mixes a plurality of sound signals of a plurality of microphones with a gain according to the level
of each sound signal, and a plurality of filters adjust the frequency characteristics of the sound
signals of the plurality of microphones. The output side filter for adjusting the frequency
characteristic of the sound signal supplied to the speaker, and the sound signal of any of the
plurality of microphones output to the mixer to change the loop gain of each system However,
after setting the frequency characteristics of the plurality of input-side filters, the mixer is caused
to mix the plurality of sound signals, and the loop characteristics of the integrated system in
which the plurality of systems are integrated are changed while changing the loop gain of the
integrated system. And a setting unit for setting. [Selected figure] Figure 1
Filter setting device, filter setting method, and filter setting program
[0001]
The present invention relates to a filter setting device, a filter setting method, and a filter setting
program.
[0002]
If you want the sound acquired by the microphone to be loudened from the speaker, it is
necessary to take measures against howling.
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For example, Patent Document 1 discloses a configuration in which a transfer function is
measured for each combination of a microphone and a speaker to change the setting of the
system.
[0003]
Further, Patent Documents 2 and 3 disclose a configuration in which a howling frequency is
detected to suppress the frequency.
[0004]
JP-A-9-247787 JP-A-10-145888 JP-A-2005-341129
[0005]
However, when multiple microphones are used simultaneously, multiple feedback systems occur
simultaneously.
None of the howling measures according to the prior art documents takes into account howling
caused by interaction between a plurality of feedback systems.
Also in Patent Document 1, the transfer function is measured for each combination of the
microphone and the speaker, and only the optimum setting is performed for each system, and a
plurality of feedback systems simultaneously formed during actual use. The situation where they
interacted was not addressed.
[0006]
An object of the present invention is to provide a filter setting device, a filter setting method, and
a filter setting program corresponding to a situation in which a plurality of microphones are
simultaneously used.
[0007]
The filter setting device according to the present invention comprises a mixer for mixing the
sound signals of each of the plurality of microphones with a gain according to the level of each
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sound signal, and a plurality of frequency characteristics of the sound signals of each of the
plurality of microphones. An input-side filter, an output-side filter for adjusting the frequency
characteristic of a sound signal supplied to a speaker, and a sound signal of one of the plurality
of microphones output to the mixer to change the loop gain of each system After setting the
frequency characteristics of the plurality of input-side filters, the mixer mixes the plurality of
sound signals and sets the frequency characteristics of the output-side filter while changing the
loop gain of the integrated system in which the plurality of systems are integrated. And a setting
unit for
[0008]
As described above, the filter setting device first sets the frequency characteristics of the inputside filters individually, and then sets the frequency characteristics of the output-side filters.
When setting the output side filter, the filter setting device performs setting in a state in which
the inputs from the plurality of microphones are mixed, and therefore, a plurality of feedback
systems simultaneously formed during actual use interact with each other. Appropriate settings
can be made in these circumstances.
[0009]
The filter setting device of the present invention can cope with a situation in which a plurality of
microphones are used simultaneously.
[0010]
It is a top view of the room where a loud-speaker system was installed.
It is a block diagram showing composition of a loud-sound system.
It is a block diagram which shows the structure of the loud-sound system at the time of setting. It
is a flowchart which shows operation | movement of a loudspeaker system. It is a flowchart
which shows operation | movement of a loudspeaker system. It is a flowchart which shows
operation | movement of the loud-sound system which concerns on the modification 1. FIG. It is a
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block diagram which shows the structure of 4 A of signal processing apparatuses which concern
on the modification 2. FIG.
[0011]
FIG. 1 is a plan view of a room in which a loudspeaker system 1 is installed. FIG. 2 is a block
diagram showing the configuration of the loudspeaker system 1.
[0012]
The sound amplification system 1 includes a plurality of microphones (two microphones M1 and
M2 in this example), a plurality of speakers (nine speakers S1 to S9 in this example), a signal
processing device 4, and an information processing device 5. There is.
[0013]
In the example of FIG. 1, the loudspeaker system 1 outputs sound downward from the room from
the microphones M1 and M2 suspended from the ceiling.
The speaker T is located below the microphone M1 or the microphone M2. Since the speaker T
talks while moving, the distance to each microphone changes. The number of microphones and
the installation position are not limited to the example shown in FIG.
[0014]
The microphone M1 and the microphone M2 pick up the sound spoken by the speaker T. The
microphone M1 and the microphone M2 output sound signals relating to the acquired sound to
the microphone amplifier 491 and the microphone amplifier 492, respectively. The microphone
amplifier 491 and the microphone amplifier 492 amplify the input sound signal and input it to
the signal processing device 4.
[0015]
As shown in FIG. 3, the signal processing device 4 includes an FBS (feedback suppressor) 450, an
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FBS 451, an auto mixer 420, an FBS 455, a matrix mixer 42, and a gain adjuster 43.
[0016]
The microphone M1 inputs a sound signal relating to the acquired sound to the FBS 440.
The microphone M2 inputs a sound signal relating to the acquired sound to the FBS 441.
[0017]
The FBS 440 and the FBS 441 correspond to the input side filter, respectively. The FBS 440 and
the FBS 441 include notch filters to attenuate the level of a specific frequency of the input signal.
The FBS 440 and the FBS 441 set the frequency characteristics (center frequency, level,
bandwidth, etc.) of the notch filter in the detection mode described later. The FBS 440 and the
FBS 441 input the processed sound signal to the auto mixer 420.
[0018]
The auto mixer 420 mixes sound signals input from the microphones M1 and M2 and outputs
the mixed sound signals to the FBS 445 in the subsequent stage. The auto mixer 420
automatically adjusts the gain of each microphone according to the level of the sound signal
input from the microphone M1 and the microphone M2.
[0019]
For example, the auto mixer 420 selects one of the sound signals input from the microphone M1
and the microphone M2 at the highest level, and outputs the sound signal of the selected
microphone to the subsequent stage. Alternatively, the auto mixer 420 sets the gain of the high
level system high, and sets the low gain of the low level system.
[0020]
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The FBS 445 corresponds to the output side filter. The FBS 445 also has a notch filter to
attenuate the level of a particular frequency of the input signal. The FBS 445 inputs the
processed sound signal to the matrix mixer 42.
[0021]
The matrix mixer 42 distributes the input sound signal to a plurality of systems (in this example,
the same 9 systems as the number of speakers).
[0022]
The gain adjuster 43 adjusts the gain of the input sound signal in the gain adjusters 431 to 439
of each system distributed by the matrix mixer 42, and outputs the result to the speaker
amplifier.
[0023]
The speaker amplifiers 451 to 459 amplify the input sound signals and output the amplified
sound signals to the speakers S1 to S9.
[0024]
The loudspeaker system 1 outputs sound from the plurality of speakers S1 to S9 embedded in
the ceiling toward the lower side of the room.
Note that the number of speakers and the installation mode in plan view are not limited to the
example shown in FIG.
[0025]
As described above, the loudspeaker system 1 amplifies the sound acquired by the microphone
M1 and the microphone M2 and delivers it to the listeners L1 to L9.
[0026]
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The information processing device 5 corresponds to the filter setting device of the present
invention, and includes, for example, a personal computer.
The information processing device 5 includes a CPU and a storage medium (not shown).
The CPU implements the setting unit 53 by executing a program stored in the storage medium.
[0027]
The setting unit 53 causes the auto mixer 420 to output sound signals of any of a plurality of
microphones, and sets the frequency characteristics of the FBS 440 and the FBS 441 while
changing the loop gain of each system. The sound signal is mixed, and the frequency
characteristic of the FBS 445 is set while changing the loop gain of the integrated system in
which a plurality of systems are integrated.
[0028]
FIG. 3 is a block diagram of the loudspeaker system 1 at the setting time, and FIGS. 4 and 5 are
flowcharts showing the operation of the loudspeaker system 1 at the setting time.
The signal processing device of the loudspeaker system 1 at the time of setting includes a signal
detection unit 490 and an oscillator 470.
The signal detection unit 490 and the oscillator 470 may be realized by the software of the
information processing device 5. Therefore, the signal detection unit 490 and the oscillator 470
are not essential components in the present invention.
[0029]
First, the setting unit 53 selects a target system (for example, the system of the microphone M1)
(s11). Thereafter, the setting unit 53 sets the auto mixer 420 to a state in which the sound signal
of the target system (for example, the microphone M1) among the plurality of microphones is
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output (s12). After initializing the settings of the FBS 440 or FBS 441 corresponding to the target
system, the setting unit 53 shifts the FBS 440 or FBS 441 to the detection mode. The setting unit
53 sets all of the gain adjusters 431 to 439 in the gain adjuster 43 to −− dB and sets the gain
of the target system to the minimum (− 最小 dB). The gain of the target system can also be set
by setting the gain of the auto mixer 420 and the gain of the matrix mixer 42 to − ゲ イ ン dB.
[0030]
In addition, the setting unit 53 sets an oscillator (Gen. ) Stop the operation of 491. The oscillator
470 outputs measurement sound such as steady sound such as white noise or pink noise,
intermittent sound, or click sound (pulse sound). By the oscillator 470 outputting the
measurement sound into the room, the FBS 440, FBS 441, and FBS 445 can set the frequency
characteristics with high accuracy. Also, the measurement sound is input to the signal detection
unit 490. The signal detection unit 490 can measure the open loop gain by comparing the sound
signal relating to the measurement sound of the oscillator 470 and the input signal of the matrix
mixer 42. In addition, the signal detection unit 490 observes the input signal of the matrix mixer
42 to determine whether the level of the specific frequency is increased (that is, whether the loop
gain exceeds 0 dB at the specific frequency). To judge.
[0031]
Thereafter, the setting unit 53 operates the oscillator 470 (s13), and outputs, for example, an
intermittent sound. Further, the setting unit 53 increases the gain by a predetermined value ΔG
(for example, ΔG = 1 dB) (s14), and sets the FBS 440 or the FBS 441 (s15).
[0032]
The FBS 440 or FBS 441 adjusts the frequency characteristic of the notch filter in accordance
with the frequency characteristic of the input sound signal in the measurement mode. In the
detection mode, the FBS 440 or the FBS 441 converts the input sound signal into a frequency
signal, and detects a frequency that is likely to cause howling. The FBS 440 or FBS 441 is likely
to generate howling at the frequency when, for example, the signal level of each frequency
increases with the passage of time and the average value of all the frequencies exceeds a
predetermined value (for example +6 dB) Then, the center frequency, level and bandwidth of the
notch filter are set so that the level of the frequency is less than a predetermined value.
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[0033]
Thereafter, the setting unit 53 determines whether the setting of the FBS is completed or
whether howling has occurred (s16). The setting unit 53 determines that the setting of the FBS is
completed when the number of usable notch filters reaches the upper limit, such as when the
resource of the FBS 440 or the FBS 441 reaches the upper limit. The setting unit 53 determines,
through the signal detection unit 490, whether or not howling occurs by determining whether or
not the level of the specific frequency is increased. If the level of a particular frequency increases,
it can be considered that howling occurs because the loop gain exceeds 0 dB at that frequency. In
this case, since there is a loop gain that can not be suppressed by the notch filter by FBS440 or
FBS441, the setting of FBS440 or FBS441 is regarded as complete, and the detection mode of
FBS440 or FBS441 is turned off.
[0034]
If the resource of the FBS 440 or the FBS 441 has not reached the upper limit, or if howling does
not occur, the setting unit 53 increases the gain again by a predetermined value ΔG (for
example, ΔG = −1 dB) (s14). Or set the FBS 441 (s15).
[0035]
If the resources of the FBS 440 or the FBS 441 reach the upper limit or howling occurs, the
setting unit 53 determines whether the setting of all the microphone systems is completed (s17).
When there is a microphone whose setting has not been completed, the setting unit 53 returns to
s11, changes the target system, and repeats setting again.
[0036]
When setting of the systems of all the microphones is completed, the setting unit 53 turns on all
the systems of the auto mixer 420 and sets the auto mixer 420 in the operation mode, as shown
in FIG. 5 (s22). In the operation mode, the auto mixer 420 automatically adjusts the gain of each
microphone according to the level of the sound signal input from the microphone M1 and the
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microphone M2. That is, the auto mixer 420 integrates a system of a plurality of microphones in
the operation mode.
[0037]
In addition, after initializing the setting of the FBS 445, the setting unit 53 shifts the FBS 445 to
the detection mode. The setting unit 53 sets all of the gain adjusters 431 to 439 in the gain
adjuster 43 to −∞ dB and sets the gain of the integrated system to the minimum (−∞ dB).
Alternatively, the gain of the integrated system can also be set by setting the gain of the matrix
mixer 42 to −∞ dB. In addition, the setting unit 53 sets an oscillator (Gen. ) Stop the operation
of 491.
[0038]
Next, the setting unit 53 operates the oscillator 470 (s23) to output an intermittent sound.
Further, the setting unit 53 raises the gain by a predetermined value ΔG (for example, ΔG = + 1
dB) (s24). The setting unit 53 uniformly raises all of the gain adjusters 431 to 439 in the gain
adjuster 43 by ΔG.
[0039]
Then, the setting unit 53 sets the FBS 445 (s25). Like the FBS 440 and the FBS 441, the FBS 445
adjusts the frequency characteristic of the notch filter according to the frequency characteristic
of the input sound signal in the measurement mode. In the detection mode, the FBS 445 converts
the input sound signal into a frequency signal to detect a frequency that is likely to cause
howling. For example, the FBS 445 determines that the possibility of howling to occur is high
when the signal level of each frequency increases from the average value of all frequencies to a
predetermined value (for example, +6 dB) or more as time passes. Then, the center frequency,
level and bandwidth of the notch filter are set so that the level of the frequency is less than a
predetermined value.
[0040]
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After that, the setting unit 53 determines whether the setting of the FBS 445 has been completed
or whether howling has occurred (s26). When the resource of the FBS 445 has reached the
upper limit or howling occurs, the setting unit 53 turns off the detection mode of the FBS 445
and sets the operation mode (S 28). Fix the frequency characteristics of the notch filter.
Thereafter, the setting unit 53 measures the open loop gain (s27).
[0041]
At the time of measurement of the open loop gain, the matrix mixer 42 distributes the
measurement sound input from the oscillator 470 to all the speakers at the same level. Further,
at the time of measurement of the open loop gain, the matrix mixer 42 outputs the input signal
to the signal detection unit 490 and does not output it to the gain adjuster 43 in the subsequent
stage.
[0042]
In addition, the setting unit 53 stops the operation of the oscillator 470. Further, the setting unit
53 sets the gain of the gain adjuster 43 based on the measured open loop gain so that the loop
gain of the integrated system becomes a predetermined value (for example, -6 dB). As a result,
since the loop gain of the integrated system is at most -6 dB, the occurrence of howling can be
prevented more appropriately.
[0043]
Thus, the loudspeaker system 1 first sets the frequency characteristics of the FBS 440 and the
FBS 441 separately, and then sets the frequency characteristics of the FBS 445. When
performing the setting of the FBS 445, the loudspeaker system 1 turns on the automatic mixer
420 to perform the setting in a state where the inputs from the plurality of microphones are
mixed. The automatic mixer 420 forms an integrated system in which a plurality of feedback
systems are integrated in order to automatically adjust the gain of each microphone according to
the level of the sound signal input from the microphone M1 and the microphone M2. The
loudspeaker system 1 sets the frequency characteristics of the FBS 445 in this integrated system.
Therefore, the loudspeaker system 1 can perform appropriate setting in the situation where a
plurality of feedback systems simultaneously formed in actual use interact with each other. In
addition, since the auto mixer 420 automatically adjusts the gain of each microphone according
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to the level of the sound signal input from the microphone M1 and the microphone M2, the gain
of the integrated system is the highest (howling tends to occur). Therefore, since the loudspeaker
system 1 sets the frequency characteristic of the FBS 445 in a state in which howling is most
likely to occur, the occurrence of howling can be appropriately prevented.
[0044]
Next, FIG. 6 is a flowchart showing an operation of the sound amplification system 1 at the time
of setting according to the first modification. In the first modification, the loudspeaker system 1
performs resetting (s51) after the setting of the FBS 445 is completed.
[0045]
That is, since changing the frequency characteristic of the FBS 445 and changing the frequency
characteristic on the output side changes the transfer characteristic of the feedback system
including the input side, the loudspeaker system 1 changes in FIG. Perform the settings for FBS
440 and FBS 441 shown again. Thus, the loudspeaker system 1 can prevent the occurrence of
howling with higher accuracy.
[0046]
In addition, although the loud sound system 1 may fix the settings of the FBS 440, the FBS 441,
and the FBS 445 with the content set last, even when setting is performed multiple times, even if
any one setting is selected Good.
[0047]
In this case, the sound amplification system 1 selects, for example, a setting that maximizes the
volume (power) of the input signal of the matrix mixer 42. The sound amplification system 1
selects, for example, a setting that minimizes loop gain, or The frequency characteristics of the
FBS 440, FBS 441, and FBS 445 are set according to any criteria such as selecting the setting
with the best sound quality.
The setting with the best sound quality is one that is less limited by the notch filter. For example,
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the loudspeaker system 1 integrates the frequency characteristics of the FBS 440, the FBS 441,
and the FBS 445, and selects the one with the smallest restriction by the notch filter by making
the integral value the largest.
[0048]
FIG. 7 is a block diagram showing a configuration of a signal processing device 4A according to
the second modification. The signal processing device 4A includes an automatic FBS (FBS Auto)
481, an automatic FBS 482, and an automatic FBS 483. The signal processing device 4A includes
an automatic FBS 481 at the rear of the FBS 440, an automatic FBS 482 at the rear of the FBS
441, and an automatic FBS 483 at the rear of the FBS 445.
[0049]
The automatic FBS 481, the automatic FBS 482, and the automatic FBS 483 each have a notch
filter. The automatic FBS 481, the automatic FBS 482, and the automatic FBS 483 detect the
frequency at which the howling is likely to occur. For example, automatic FBS 481, automatic FBS
482, and automatic FBS 483 increase as time passes, and when the signal level of each frequency
exceeds a predetermined value (eg, +6 dB) from the average value of all frequencies, howling
occurs at that frequency It is determined that the possibility of occurrence is high, and the center
frequency, level and bandwidth of the notch filter are set so that the level of the frequency is less
than a predetermined value. Therefore, the signal processing device 4A can further prevent the
occurrence of howling.
[0050]
The description of the present embodiment is illustrative in all respects and not restrictive. The
scope of the present invention is indicated not by the embodiments described above but by the
claims. Further, the scope of the present invention is intended to include all modifications within
the scope and meaning equivalent to the claims.
[0051]
L1: Listener M1, M2: Microphone S1 to S9: Speaker T: Speaker 1: Loudspeaker system 4, 4A:
Signal processing device 5: Information processing device 42: Matrix mixer 43: Gain adjuster 53:
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Setting unit 420: Auto Mixers 431 to 439 ... Gain adjusters 440, 441 and 445 ... FBS 451 to 459
... Speaker amplifiers 470 ... Oscillators 481, 482 and 483 ... Automatic FBS 490 ... Signal
detection unit 491 and 492 ... Microphone amplifiers
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