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JP2009010491

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DESCRIPTION JP2009010491
A speaker array device, a microphone array device, and a signal processing method capable of
performing directivity control in a wide range of frequency bands by a process with low load. A
speaker array device (1) of the present invention divides an audio signal (Sin) input from a signal
input unit (5) into a plurality of frequency bands in a signal dividing unit (4). By emitting an
audio signal that has been subjected to amplification processing based on the window function
set in each of the amplification units of the signal processing unit 3, desired directivity
characteristics can be obtained in a wide frequency band. . Further, since it is not necessary to
finely divide the frequency band, the amount of calculation of signal processing in the signal
processing unit 3 can be reduced, and directivity control in a wide frequency band can be
performed by a process with a small load. [Selected figure] Figure 1
Speaker array device, microphone array device, and signal processing method
[0001]
The present invention relates to a technique for improving the directivity of a speaker array.
[0002]
As a speaker system capable of improving directivity, that is, a speaker system having so-called
narrow directivity, for example, there is a speaker array.
The speaker array can control the directivity of the sound by controlling the amplitude, phase,
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and the like of the sound emitted from the individual speakers, and can emit the beamed sound
to a desired location. By beaming the sound, it is possible to transmit the sound with little
attenuation of the volume even at a distant place, so it is frequently used in a large hole or the
like.
[0003]
On the other hand, in the speaker array, the frequency band of sound tends to be narrow due to
the control of the directivity state. Therefore, in order to control the pointing state over a wide
frequency band, a technique for optimizing and controlling the phase and amplitude of the input
audio signal at each frequency point using FIR (Finite Impulse Response) is disclosed. (For
example, Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2). Patent
Document 1: Japanese Patent Application Laid-Open No. 2-239798 Tetsuguchi Taniguchi,
Kiyoshi Nishikawa, Masaki Amano, "Wide-band beam forming method by multiple band division
using a Dolph-Chebyshev spatial filter", Journal of the Institute of Electronics, Information and
Communication Engineers 1995/12 Vol. J78-A No. 12 p1576-p1584 Mitsuya Ohya, Kiyoshi
Nishikawa, “Any Beam Directional Directional Array Speaker with Band Division Design”, 10th
Digital Signal Processing Symposium 1995 / 11-2 p59-p64
[0004]
However, when the phase and amplitude are controlled at individual frequency points using an
FIR filter, the amount of calculation becomes enormous and the processing load on a DSP (Digital
Signal Processor) or the like becomes extremely large.
[0005]
The present invention has been made in view of the above-described circumstances, and provides
a speaker array device, a microphone array device, and a signal processing method that can
perform directivity control in a wide range of frequency bands with a process with low load. With
the goal.
[0006]
In order to solve the problems described above, the present invention divides a plurality of
divided audio signals having different frequency bands by dividing a plurality of sound emitting
means and an input audio signal according to one or more preset frequency characteristics. And
a signal processing unit having a plurality of amplifying unit groups each having a plurality of
amplifying units each set with an amplification factor based on a preset window function, each of
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the amplifying unit groups comprising: Among the plurality of divided audio signals generated by
the signal dividing means, divided audio signals of a predetermined frequency band and of a
frequency band different from that of the other amplification means group are supplied, and
each of the above-mentioned respective amplification means groups The amplification means is
configured to release the signal obtained by amplifying the divided audio signal supplied to the
amplification means group by the set amplification factor, connected to the amplification means.
The plurality of sound emitting means emit sound beams having predetermined directivity
characteristics by emitting the signals supplied from the respective amplifying means, and the
plurality of sound emitting means are preset to the respective amplifying means groups. The
window function is such that the number of intensity minima in the stopband of the directivity
characteristic increases in order from the amplification means group which is a frequency band
in which the frequency band of the divided audio signal supplied is low among the plurality of
amplification means groups. The speaker array device is characterized in that one or more
frequency characteristics of the signal dividing means are set such that the intensity of a
predetermined angle does not exceed a predetermined value in the directivity characteristics. .
[0007]
In another preferred embodiment, the apparatus further comprises control means for changing
the directivity characteristic, and each of the sound emitting means performs delay processing on
the signal supplied from each of the amplification means, and delay processing. The control unit
may change the directivity characteristic by controlling the delay amount of the delay means
constituting each of the sound emitting means.
[0008]
In another preferred embodiment, the apparatus further comprises control means for changing
the directivity characteristics, each amplification means group further comprises delay means
connected to each of the amplification means to perform delay processing, Each of the delay
means constituting each amplification means group supplies a signal obtained by delaying the
divided audio signal supplied to the amplification means group to amplification means connected
to the delay means which has performed the delay processing. The amplification means
constituting the amplification means group are replaced with the divided audio signals supplied
to the amplification means group, and the signals supplied from the delaying means are set at the
amplification factor set. The amplified signal may be supplied to the connected sound output
means, and the control unit may change the directivity by controlling the delay amount of the
delay means.
[0009]
Further, in another preferable aspect, when the directivity characteristic is changed by the
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control unit controlling each of the delay units, one or more frequency characteristics set in the
signal division unit are changed. The means may be further provided.
[0010]
Further, according to the present invention, there are provided a plurality of signal processing
means including a plurality of sound collecting means, and a plurality of amplification means
groups each having a plurality of amplification means each having an amplification factor set
based on a preset window function. A predetermined frequency band is set among a plurality of
frequency bands obtained by dividing in the above frequency characteristics, and a plurality of
band selection means for attenuating and outputting amplitudes of frequency bands other than
the frequency band of the supplied signal And signal dividing / synthesizing means having an
adding means for adding the signals output from the plurality of band selecting means, each of
the sound collecting means generates an audio signal based on the collected sound, and The
amplification means is supplied with an audio signal generated by the sound collection means
connected to the respective amplification means, and each amplification means group is adapted
to the supplied audio signal. The signals amplified at the set amplification factor are added by the
respective amplification means constituting the width means group, and the added signal is
supplied to the band selection means connected to the amplification means group, and the
plurality of the plurality of The predetermined frequency bands set in the band selection means
are respectively different frequency bands, and the sound collection performed by the plurality of
sound collection means has predetermined directivity characteristics, and the windows preset in
each of the amplification means The function is such that the number of intensity minima in the
stopband of the directivity characteristic increases in order from the amplification means group
connected to the band selection means which is a low frequency band and the frequency band
set among the plurality of band selection means The microphone is characterized in that one or
more frequency characteristics of the signal division and synthesis means are set such that the
intensity of a predetermined angle does not exceed a predetermined value in the directivity
characteristic. To provide a ray equipment.
[0011]
Further, the present invention is a signal processing method used in a speaker array device
having a plurality of sound emitting means, which divides an audio signal to be input into one or
more preset frequency characteristics, thereby to make the frequency band different. And a
signal processing step of generating a plurality of divided audio signals, and a plurality of
amplification step groups each including a plurality of amplification steps each having an
amplification factor set based on a preset window function. The process group is a
predetermined frequency band among a plurality of divided audio signals generated in the signal
division process, and a divided audio signal of a frequency band different from other
amplification process groups is supplied, and each of the amplification process groups In each of
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the amplification processes, the divided audio signal supplied to the amplification process group
is amplified by the set amplification factor. The plurality of sound emitting means are supplied to
sound emitting means corresponding to the amplification process, and the plurality of sound
emitting means emit an acoustic beam having a predetermined directivity characteristic by
emitting the signals supplied in the respective amplification processes, The window function
preset in each amplification process group is the intensity in the stopband of the directivity
characteristic in order from the amplification process group in which the frequency band of the
divided audio signal supplied among the plurality of amplification process groups is low. The
number of local minima is set to increase, and in the directivity characteristic, one or more
frequency characteristics in the signal division process are set such that the intensity at a
predetermined angle does not exceed a predetermined value. To provide a signal processing
method.
[0012]
Further, the present invention is a signal processing method for use in a microphone array
apparatus having a plurality of sound collection means, which comprises a plurality of
amplification processes each including a plurality of amplification processes each having an
amplification factor set based on a preset window function. A predetermined frequency band is
set among a plurality of frequency bands obtained by dividing a plurality of signal processing
steps and one or more preset frequency characteristics, and a frequency band other than the
frequency band of the supplied signal is set. A plurality of band selection processes for
attenuating and outputting the amplitude, and a signal division and synthesis process including
an addition process for adding the signals output from the plurality of band selection processes;
An audio signal is generated on the basis of the respective amplification processes, and the
respective amplification processes are supplied with audio signals generated by the sound
collection means corresponding to the respective amplification processes, The group adds the
signal amplified by the amplification factor set by the amplification process in the amplification
process group to the supplied audio signal, and adds the signal obtained by the addition to the
band corresponding to the amplification process group The predetermined frequency bands
supplied to the selection process and set in the plurality of band selection processes are
respectively different frequency bands, and the sound collection performed by the plurality of
sound collection means has a predetermined directivity characteristic, The window function set
in advance for each amplification process is, in order from the amplification process group
corresponding to the band selection process having a low frequency band among the plurality of
band selection processes, in the stopband of the directivity characteristic. The number of local
minima of the intensity is set to increase, and in the directivity characteristic, one or more
frequencies in the signal division and combining process such that the intensity at a
predetermined angle does not exceed a predetermined value. To provide a signal processing
method characterized by sex is set.
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[0013]
According to the present invention, it is possible to provide a speaker array device, a microphone
array device, and a signal processing method capable of performing directivity control in a wide
range of frequency bands by a process with low load.
[0014]
Hereinafter, an embodiment of the present invention will be described.
[0015]
Embodiment First, the configuration of the speaker array device 1 according to the present
embodiment will be described.
FIG. 1 is a block diagram showing the configuration of the speaker array device 1.
The sound output unit 2 includes non-directional speakers 2-1, 2-2,..., 2-n arranged linearly
facing the same direction, and the audio supplied from the signal processing unit 3 Sound the
signal.
The sound emitting unit 2 emits an audio signal subjected to signal processing as described later
from each of the speakers 2-1, 2-2,. The beam can be emitted.
[0016]
The signal processing unit 3 includes amplification units 31, 32, ..., 35 and an adder 30, as shown
in FIG.
Here, the configuration of each of the amplification units 31, 32, ..., 35 will be described using
the amplification unit 31 as an example.
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The amplification unit 31 has amplification circuits 31-1, 31-2, ..., 31-n as shown in FIG.
Each of the amplifier circuits 31-1, 31-2,..., 31-n amplifies the audio signal Sa-1 input from the
signal division unit 4 at the set amplification factor, and the amplifier circuit 31-1 The signal is
supplied to the speaker 2-1, and the amplification unit 31-2 is supplied to the speakers 2-1, 22,..., 2-n respectively connected to be supplied to the speaker 2-2.
Hereinafter, the aspect of the amplification factor set to each amplifier circuit 31-1, 31-2, ..., 31-n
is called a window function.
In this manner, each of the amplification units 31, 32,..., 35 transmits the five systems of audio
signals Sa-1, Sa-2,..., Sa-5 supplied from the signal division unit 4. The amplification processing is
performed based on the window functions set respectively, and is supplied to each of the
speakers 2-1, 2-2,.
Then, the audio signals output to the same speaker are added by each adder 30 and supplied to
the speaker.
Therefore, each of the speakers 2-1, 2-2,..., 2-n emits an audio signal obtained by adding the
audio signal output from each of the amplification units 31, 32,. It will be.
The window function is set by the control of the control unit 6, but the details will be described
later.
[0017]
Returning to FIG. 1, the description will be continued. The signal division unit 4 divides the audio
signal Sin input from the signal input unit 5 into a plurality of frequency bands to generate audio
signals Sa-1, Sa-2, ..., Sa-5, and a signal processing unit , And 35, respectively. Here, the
configuration of the signal division unit 4 will be described with reference to FIG. As shown in
FIG. 4, the signal dividing unit 4 includes an LPF (Low Pass Filter, low pass filter) 4-1, a BPF
(Band Pass Filter, band pass filter) 4-2, 4-3, 4-4, an HPF High Pass Filter, high pass filter) 4-5.
The LPF 4-1 attenuates the amplitude of the set frequency f1 or more with respect to the input
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audio signal Sin, and supplies the audio signal Sa-1 to the amplification unit 31 of the signal
processing unit 3 as the audio signal Sa-1. The BPFs 4-2, 4-3, and 4-4 set frequency bands for the
input audio signal Sin (for the BPF 4-2, for the frequency band from the lower limit frequency f1
to the upper limit frequency f2, BPF 4-3) Attenuates amplitudes other than the frequency band
from the lower limit frequency f2 to the upper limit frequency f3 and the frequency band from
the lower limit frequency f3 to the upper limit frequency f4 in the BPF 4-4 to attenuate as audio
signals Sa-2, Sa-3 and Sa-4 The signal is supplied to the amplification units 32, 33, 34 of the
signal processing unit 3. The HPF 4-5 attenuates the amplitude of the set frequency f4 or less
with respect to the input audio signal Sin, and supplies it to the amplification unit 35 of the
signal processing unit 3 as an audio signal Sa-5. Here, the relationship between the set
frequencies is f1 <f2 <f3 <f4, and if the audio signals supplied from the signal division unit are
arranged in order from the lower frequency band, the audio signals Sa-1 and Sa-2 are obtained. ,
..., Sa-5 in order. Although the frequency is set by the control of the control unit 6, the details will
be described later.
[0018]
Returning to FIG. 1, the description will be continued. The control unit 6 controls each unit of the
speaker array device 1 as described above. This control may be performed based on the input
setting value when the user operates the operation unit 7 or may be performed based on the
setting value stored in the storage unit 8. Here, the setting value is, for example, a window
function set in each of the amplification units 31, 32,..., 35 of the signal processing unit 3, and
frequencies f1, f2, f3 and f4 set in the signal division unit 4. , Directivity characteristics of an
acoustic beam, and the like. Note that the storage unit 8 combines these setting values and stores
a plurality of setting value sets as a table, so that the user operates the operation unit 7 and the
setting values stored in the storage unit 8 are stored. By selecting one set of set values from
among sets, the control unit 6 can also control each unit based on the set values of the selected
set.
[0019]
Next, the window function set in each of the amplification units 31, 32, ..., 35 of the signal
processing unit 3 under the control of the control unit 6 will be described. First, window
functions to be candidates set for each of the amplification units 31, 32,..., 35 are determined. A
plurality of candidate window functions are known using nonlinear optimization or the least
squares method at each frequency (preferably several Hz unit is desired) under predetermined
conditions in the speaker array device 1 such as the distance between speakers Filter design
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method (hereinafter, non-linear optimization will be described as an example, but it may be a
well-known filter design method using the least squares method or the like). For example, the
directivity characteristic of the acoustic beam in the case where the sound of 879 Hz is emitted
from the sound emitting unit 2 using the window function obtained by non-linear optimization at
879 Hz is the directivity characteristic as shown in FIG. . Here, FIG. 5 is a polar coordinate graph
in which the radial direction represents intensity (in dB when referred to the 0 degree direction)
and the angular direction is 0 degrees in the front direction of the speaker as shown in FIG.
Similarly, the directivity characteristics of the acoustic beam when the sound at 872 Hz is
emitted from the sound emitting unit 2 using the window function obtained by non-linear
optimization at 872 Hz is as shown in FIG. 5B. It becomes a characteristic.
[0020]
Thus, at near frequencies, the number of local minima at which the intensity of the stopband (an
angular region other than the main lobe having a large intensity in the 0 degree direction) in the
directivity characteristics of the acoustic beam becomes minimal (in FIG. If the number of local
minimum points from 4 degrees to 90 degrees is 4 or less, and simply referred to as the number
of local minimum points, the window function which formally means the number of local
minimum points from 0 degree to 90 degrees is the same can get. Among the window functions
obtained for each frequency in this manner, the window function obtained by the non-linear
optimization is set to one amplification unit at a frequency at which the number of local minima
in the directional characteristic becomes the same. Classify as a candidate. Then, among window
function candidates set in one amplification unit, a target directivity characteristic, for example, a
window function having a main lobe width close to the target width is selected from the window
functions as candidates, and this is selected. It is determined as a window function to be set in
the amplification unit. For example, when comparing the directivity characteristics of an acoustic
beam at 879 Hz and the directivity characteristics of an acoustic beam at 872 Hz, it is a window
function that can realize a state in which the main lobe width is narrow while the frequency at
872 Hz is lower. The window function determined at 872 Hz is determined as the window
function set in the amplification unit. Then, with respect to other window function candidates
related to directional characteristics with different numbers of local minimum points, the window
functions to be set to one amplification unit are determined in the same manner. By determining
the window function in this manner, the main lobe width can be made as narrow as possible
because the window function that most satisfies the condition can be used if the number of local
minima is the same. In addition, since the same window function can be used for the frequencies
having the same minimum number, the number of band divisions can be reduced.
[0021]
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As shown in FIG. 7, FIG. 8 and FIG. 9, the directivity characteristics of the acoustic beam in the
case where the sound of the frequency for which the window function is determined is emitted
from the sound emitting unit 2 using the window function thus determined. It uses a window
function whose frequency is determined at 126 Hz, 327 Hz, and 585 Hz, respectively. Here, FIG.
5 shows that the number of minimum points is 4 but FIG. 7 shows that the number of minimum
points is 1, FIG. 8 shows that the number of minimum points is 2 and FIG. 9 shows that the
number of minimum points is 3 The window function determined is used.
[0022]
Then, the frequency band of the input audio signal is set by the control unit 6 from the low
amplification unit in order from the window function relating to the directivity characteristic with
the smaller number of minimum points. For example, the window function obtained at 126 Hz
(the number of minimum points is 1) is set in the amplification unit 31, and the window function
obtained at 327 Hz (the number of minimum points is 2) is set in the amplification unit 32. In
this manner, the window function is set in each of the amplification units 31, 32, ..., 35 by the
control of the control unit 6. Each of the speakers 2-1, 2-2,..., 2-n in the present embodiment is a
nondirectional speaker, but may be a speaker having a directional characteristic. In this case, the
window function may be determined according to the directivity characteristics of each of the
speakers 2-1, 2-2,.
[0023]
Next, the frequencies f1, f2, f3, and f4 set in the signal dividing unit 4 by the control of the
control unit 6 will be described. The audio signal Sa-1 whose frequency band upper limit is
determined by the frequency f1 is supplied to the amplification unit 31. The window function set
in the amplifying unit 31 is a window function determined at 126 Hz, and when the sound of
126 Hz is emitted from the sound emitting unit 2, as a sound beam of directional characteristics
as shown in FIG. 7 as described above Released. When sounds of various frequencies are emitted
using this window function, the width of the main lobe widens at frequencies lower than 126 Hz
and the width of the main lobe narrows at high frequencies. On the other hand, on the high
frequency band side, disturbance of directivity characteristics such as an increase in intensity of
side lobes other than the main lobe occurs. For example, when a 2000 Hz sound is emitted from
the sound emitting unit 2 using a window function determined at 872 Hz, an acoustic beam
having a disordered directivity as shown in FIG. 10 is emitted.
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[0024]
As described above, when the intensity of the side lobes is increased, the directivity characteristic
of the acoustic beam is disturbed. Therefore, when using the window function set in each of the
amplification units 31, 32,. It is necessary to adjust the frequency characteristics at 31, 32, ..., 35.
Although there are various methods for this method, the frequency characteristic is determined
in the range in which the intensity in a predetermined angular direction does not exceed a
predetermined value. In the present embodiment, for example, the predetermined angle is 90
degrees, and the predetermined value is -10 dB. The predetermined angle and the predetermined
value do not have to be this value, and may be appropriately changed to obtain a desired
directional characteristic. The change may be made by the user operating the operation unit 7.
[0025]
Specifically, the frequency f1 is determined as follows. The directivity characteristics of the
acoustic beam when the sound of 130 Hz and 140 Hz is emitted from the sound emission unit 2
using the window function set in the amplification unit 31 are the directivity characteristics as
shown in FIG. 11 and FIG. 12. As described above, it can be seen that the width of the main lobe
is narrower at 130 Hz than at 126 Hz, and the width of the main lobe is narrower at 140 Hz. On
the other hand, it can be seen that the intensity of the side lobes increases as the frequency
increases. Since the intensity at 90 degrees is -14 dB in FIG. 11 and -10 dB in FIG. 12, the input
audio signal Sa-1 is obtained when the window function set in the amplification unit 31 is used.
The upper limit of the frequency band of is determined as 140 Hz. Thus, by the control of the
control unit 6, the frequency f1 in the signal division unit 4 is set to f1 = 140 Hz. In this case, at
the frequency f1, the output of the window function (corresponding to the amplification unit 31)
is slightly attenuated but includes the contribution of the output of the window function
(corresponding to the amplification unit 32) in the upper frequency band. There is. Therefore,
more strictly, in the frequency characteristic of the audio signal output from the signal dividing
unit 4 and the result of processing with each window function, the intensity in a specific angular
direction is taken into consideration, taking into consideration the directivity characteristic of the
speaker if necessary. The frequency characteristic of each filter in the signal dividing unit 4 may
be determined at the limit of the range in which the value does not exceed the predetermined
value. Here, when designing as a linear phase FIR filter using a method such as a window
function method or Fourier series approximation, the disturbance of the characteristic in the
transient region in the frequency characteristic of the audio signal divided by the signal division
unit 4 is reduced. Can.
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[0026]
The frequency f2 related to the frequency characteristic of the audio signal Sa-2 is determined as
described above using the window function set in the amplification unit 32, and is set in the
signal division unit 4 by the control of the control unit 6. Ru. The frequencies f3 and f4 are
similarly set. Thus, under the control of the control unit 6, the signal division unit 4 sets the
frequencies f1, f2, f3 and f4.
[0027]
Next, for the operation of the speaker array device 1 in which the window function is set in the
signal processing unit 3 and the frequencies f1, f2, f3 and f4 are set in the signal division unit 4
as described above, an audio signal from the signal input unit 5 A description will be given until
Sin is input and sound is emitted from the sound emission unit 2.
[0028]
The audio signal Sin input from the signal input unit 5 is output to the signal division unit 4.
The signal dividing unit 4 distributes the audio signal Sin to the LPF 4-1, the BPF 4-2, 4-3, 4-4,
and the HPF 4-5, which are different based on the set frequencies f1, f2, f3, and f4. The audio
signals Sa-1, Sa-2, ..., Sa-5 divided into frequency bands are generated and supplied to the signal
processing unit 3.
[0029]
The audio signal Sa-1 supplied from the signal division unit 4 is supplied to the amplification unit
31 of the signal processing unit 3. The audio signal Sa-1 supplied to the amplification unit 31 is
amplified at each of the amplification circuits 31-1, 31-2, ..., 31-n based on the set window
function, and each speaker 2-1 , 2-2,..., 2-n. Similarly, the other audio signals Sa-2, Sa-3, Sa-4, Sa5 are amplified based on the window function set in the amplification units 32, 33, 34, 35,
respectively, and each speaker 2 -1, 2-2, ..., 2-n. At this time, the audio signals supplied from the
respective amplification units 31, 32, ..., 35 to the same speaker are respectively added by the
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adder 30 and emitted from the speaker.
[0030]
As described above, the audio signal Sin input from the signal input unit 5 is divided into a
plurality of frequency bands in the signal division unit 4, and the respective amplification units
31 of the signal processing unit 3 with respect to audio signals in different frequency bands. By
emitting an audio signal that has been subjected to amplification processing based on the
window function set to 32, ..., 35, desired directivity characteristics can be obtained in a wide
frequency band. . Further, since it is not necessary to finely divide the frequency band, the
amount of calculation of signal processing in the signal processing unit 3 can be reduced, and
directivity control in a wide frequency band can be performed by a process with a small load.
[0031]
Although the embodiments of the present invention have been described above, the present
invention can be implemented in various aspects as follows.
[0032]
<Modification 1> In the embodiment, the signal dividing unit 4 divides the audio signal Sin by the
frequencies f1, f2, f3, and f4 of 4 so that the audio signals Sa-1 and Sa-2 in the frequency band of
5 can be obtained. ,..., Sa-5, but the number of audio signals generated by division is not limited
to five, and may be any number as long as it is two or more.
In this case, the number of amplification units of the signal processing unit 3 may be increased
or decreased according to the number of divided audio signals, and the number of divisions of
the audio signal Sin and the number of amplification units are realized by the control of the
control unit 6 Just do it. This may be determined by calculating the required number of divisions
based on the desired directional characteristics, the number of speakers of the sound emitting
unit 2, the result of the non-linear optimization, and the like.
[0033]
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<Modification 2> In the embodiment, the directivity control is performed by amplification
processing based on the window function set in each of the amplification units 31, 32, ..., 35 of
the signal processing unit 3. Although it was not possible to control the direction of the lobe
(hereinafter referred to as the pointing direction), it is also possible to control the pointing
direction. In this case, as shown in FIG. 13, a delay unit 21 having delay circuits 21-1, 21-2,..., 21n is provided in the sound emitting unit 2, and each delay circuit 21-1, 21-2. ,..., 21-n may
perform delay processing of the delay amount set for the audio signal supplied from the signal
processing unit 3. Here, the control unit 6 calculates the delay amount based on the pointing
direction instructed by the user operating the operation unit 7, and the delay unit 21-1 of the
delay unit 21 is controlled by the control unit 6. , 21-2, ..., 21-n. The pointing direction does not
have to be a user's instruction, and information such as a change in pointing direction may be
stored in the storage unit 8 and the pointing direction may be set according to the information.
[0034]
In addition, when the pointing direction of the 126 Hz acoustic beam as shown in FIG. 7 is
changed by −5 degrees, for example, the intensity at 90 degrees may largely change as shown in
FIG. 14 by changing the pointing direction. is there. In this case, the frequencies f1, f2, f3, and f4
set in the signal dividing unit 4 may be changed so as to satisfy the conditions described above,
and in the case of changing them, the control of the control unit 6 The frequencies f1, f2, f3 and
f4 set by the above may be changed. The window function set in each of the amplification units
31, 32, ..., 35 of the signal processing unit 3 may be set again by the method described above.
Also in this case, the window function set by the control of the control unit 6 may be changed.
[0035]
<Modification 3> In the case where the delay unit 21 is provided as in the modification 2, the
delay circuits 21-1, 21-2, ..., 21-n are delayed so as to form the focal point of the acoustic beam.
By setting the amount, control of the directivity in the embodiment can also be performed, but in
that case, disturbance of the directivity of the main lobe may occur in a high frequency band. In
such a case, the signal input unit 5 may be frequency-dependent to have the function of an
equalizer capable of adjusting the amplitude, and the frequency dependence of the amplitude
may be adjusted so that the disturbance of the directivity characteristic does not occur. The
function of the equalizer is provided to the LPF 4-1, BPF 4-2, BPF 4-2, 4-3, 4-4, and HPF 4-5 of
the signal dividing unit 4, and the amplitude is adjusted in a predetermined frequency band not
to be attenuated. May be
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[0036]
<Modification 4> In the embodiment, the signal dividing unit 4 uses the LPF 4-1 to obtain the
audio signal Sa-1 of the lowest frequency band, and obtains the audio signal Sa-5 of the highest
frequency band. Although HPF 4-5 was used for this purpose, one or both of them may be BPF.
In this case, the lower limit of the frequency band needs to be determined for the BPF used
instead of the LPF 4-1, and the upper limit of the frequency band needs to be determined for the
BPF used instead of the HPF 4-5. The upper and lower limits may be determined based on the
audible range of sound, may be determined from the used frequency band based on the
frequency characteristic of the audio signal Sin, and may be a desired value. This value may be
determined in advance, or the user may designate a value by operating the operation unit 7.
Further, in the case of determining based on the frequency characteristics of the audio signal Sin,
the signal input unit 5 is provided with measurement means for measuring the frequency
characteristics of Sin of the audio signal, and the control unit 6 measures the frequency
characteristics measured by the measurement means It may be determined based on
[0037]
<Modification 5> In the embodiment, the window function set in each of the amplification units
31, 32, ..., 35 (in particular, the amplification unit in a high frequency band, and the amplification
unit 35 in the embodiment) The width of the main lobe of the acoustic beam may be too narrow.
In this case, as shown in FIG. 15, delay circuits 350-1, 350-2,..., 350-n for delaying the audio
signal input to the amplification unit 35 are provided to adjust directivity characteristics. You
may do so. In this way, delay processing can be performed for each frequency band. Note that
such a delay circuit may be provided not only in an amplification unit that amplifies an audio
signal in a high frequency band but also in a plurality of amplification units. Also, phase
interference occurs in the overlapping frequency band between the sound emitted and delayed
by the delay circuits 350-1, 350-2,..., 350-n and the sound emitted without the delay processing.
If this happens, as shown in FIG. 16, delay circuits 310, 320, 330, 340 for delaying the input
audio signal are provided to adjust the delay amount in each delay circuit 310, 320, 330, 340.
Thus, the influence of phase interference may be reduced. If the delay circuits as described above
are provided in all the amplification units, it is possible to change the directivity direction of the
acoustic beam as shown in the second modification. When the directivity characteristic is
disturbed, as described in the third modification, the signal input unit 5 or the like may have the
function of an equalizer to adjust the frequency dependency of the amplitude.
09-05-2019
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[0038]
<Modification 6> In the embodiment, each of the amplification units 31, 32, ..., 35 has the same
number of amplification circuits as the number of speakers included in the sound emission unit
2, but the windows set When the function has symmetry, the number of amplification circuits
can be reduced according to the symmetry, and the amount of calculation of processing in the
signal processing unit 3 can be reduced. For example, when the number of speakers is 11, and
the output is symmetrical with respect to the speakers 2-6, as shown in FIG. 17, the amplification
unit 31 includes amplification circuits 31-1, 31-2,. ..., to have a 31-6, respectively may be to also
output from the amplifier circuits with respect to the speaker to be symmetrical output, in this
way, the number of the amplifier circuit is reduced from 11 to 5 The processing load of the
signal processing unit 3 can be reduced.
[0039]
<Modification 7> In the embodiment, although the speakers 2-1, 2-2,..., 2-n of the sound emitting
unit 2 used the same speaker, each speaker 2-- of the sound emitting unit 2 1, 2-2,..., 2-n, for
example, small diameter speakers 2-1, 2-2,. A speaker different from, for example, the largediameter speakers 2-m + 1, 2-m + 2,. In this case, as shown in FIG. 18, for example, the audio
signals Sa-1 and Sa-2 of a relatively low frequency band are supplied to the amplification units
31 and 32 of the signal processing unit 3, so the speaker 2 The amplified audio signal is supplied
to −m + 1, 2-m + 2,..., 2-n, and audio signals Sa-3, Sa of relatively high frequency bands are
supplied to the amplification units 33, 34, 35. Since -4 and Sa-5 are supplied, the amplified audio
signal may be supplied to the speakers 2-1, 2-2,..., 2-m. In this way, the width of directional
control of the acoustic beam can be expanded, and for example, the width of the main lobe can
be further narrowed even for an acoustic beam in a low frequency band.
[0040]
<Modification 8> In the embodiment, although amplification processing is performed on audio
signals of all frequency bands in the signal processing unit 3, amplification processing is
performed only on audio signals of some frequency bands. You may do so. In this case, for audio
signals in the frequency band for which amplification processing is not performed in the signal
processing unit 3, signal processing is performed to change the phase and amplitude with the FIR
filter, thereby performing directivity control of the acoustic beam in the frequency band. May be
For example, when the signal processing is performed only on the audio signal Sa-5 by the FIR
09-05-2019
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filter, the signal processing is further performed with frequency dependency and the height of
the audio signal output to the speaker located at the end is high. Frequency components can also
be attenuated. As described above, by performing signal processing with the FIR filter, it is
possible to change the frequency characteristics of the audio signal to be output for each
speaker, so it is possible to obtain more desired directional characteristics.
[0041]
<Modification 9> In the embodiment, the window function set in each of the amplification units
31, 32, ..., 35 of the signal processing unit 3 is a candidate classified according to the number of
local minimum points of directivity characteristics. The window function is determined for each
classification, and the frequency band of the supplied audio signal is set by the control unit 6 in
order from the window function relating to the directional characteristic with the smaller number
of local minima. At this time, the number of local minimum points is assumed to increase by one
since the window functions relating to the directivity characteristic having a small number of
local minimums are sequentially set, but may not necessarily increase by one. For example, the
window function set in the amplification unit 32 may not be the window function determined at
327 Hz (the number of minimum points is 2), but may be the window function determined at
585 Hz (the number of minimum points is 3). As a result, the frequency band of the audio signal
Sa-2 becomes a frequency band (frequency f1 to f3) obtained by combining the audio signals Sa2 and Sa-3 in the embodiment, and the audio signal has a wide frequency band. In the window
function related to 585 Hz, since the upper limit of the frequency band is originally the
frequency f3, there is no influence of the disturbance of the directional characteristics. In this
way, the frequency band handled by one amplification unit becomes wide, so the number of
amplification units can be reduced, and the processing load of the signal processing unit 3 can be
reduced.
[0042]
<Modification 10> In the embodiment, the control unit 6 controls the signal processing unit 3
based on the setting value input by the user operating the operation unit 7 and the setting value
stored in the storage unit 8. The division unit 4 is controlled to set the window function to the
signal processing unit 3 and the frequencies f1, f2, f3 and f4 to the signal division unit 4, but as
described above based on the desired directivity characteristic The window function and the
frequencies f1, f2, f3 and f4 may be calculated and set as In this case, the desired directional
characteristic may be input by the user operating the operation unit 7. As described above, if the
window function and the frequency for dividing the audio signal are calculated by the method as
09-05-2019
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described in the embodiment, the value calculated in advance may be set as the setting value, and
the control unit 6 may The calculated value may be used as the setting value.
[0043]
<Modification 11> In the embodiment, although the speaker array device 1 that emits an acoustic
beam having a desired directional characteristic is used, the microphone array device 100 may
be a directional microphone having a desired directional characteristic. In this case, the
configuration as shown in FIG. 19, FIG. 20, FIG. 21, and FIG. 22 may be adopted. Hereinafter, the
microphone array device 100 will be described.
[0044]
As shown in FIG. 19, the sound collection unit 9 having omnidirectional microphones 9-1, 9-2,...,
9-n includes the microphones 9-1, 9-2,. An audio signal relating to the sound picked up by -n is
generated and supplied to the signal processing unit 13. The signal processing unit 13 has
amplification units 131, 132,..., 135 as shown in FIG. The amplification unit 131 includes
amplification circuits 131-1, 131-2,..., 131-n and an adder 1310 as shown in FIG. Each of the
amplifier circuits 131-1, 131-2, ... 131-n is a microphone 9-1, 9-2, ..., with an amplification factor
based on the window function set as described in the embodiment. The audio signal supplied
from 9-n is amplified and output. Then, the audio signal output from each of the amplifier
circuits 131-1, 131-2,... 131-n is added in the adder 1310, and is added to the signal division
combining unit 14 as the audio signal Sb-1.
[0045]
The signal division combining unit 14 includes an LPF 14-1, BPFs 14-2, 14-3, 14-4, an HPF 14-5,
and an adder 140, as shown in FIG. The LPF 14-1, BPF 14-2, 14-3, 14-4, and HPF 14-5 are set in
the same manner as the LPF 4-1, BPF 4-2, 4-3, 4-4, and HPF 4-5 described in the embodiment.
Signal processing based on the frequencies f1, f2, f3 and f4 is performed on the supplied audio
signal. Here, the audio signal Sb-1 output from the signal processing unit 13 is supplied to the
LPF 14-1, the audio signal Sb-2 to the BPF 14-2, and the audio signal Sb-3 to the BPF 14-3. -4 is
supplied to the BPF 14-4, and the audio signal Sb-5 is supplied to the HPF 14-5. Then, by being
subjected to signal processing by the LPF 14-1, BPF 14-2, 14-3, 14-4, and HPF 14-5, audio
signals having different frequency bands are added by the adder 140 and output as an audio
09-05-2019
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signal Sout. It is output from the unit 15.
[0046]
Hereinafter, the window functions set in the respective amplification units 131, 132,..., 135 of
the signal processing unit 13 and the frequencies f1, f2, f3, and f4 set in the signal division
combining unit 14 will be described in order. First, the window function set in each of the
amplification units 131, 132,..., 135 of the signal processing unit 13 under the control of the
control unit 6 will be described. As in the description of the embodiment, window functions to be
candidates set for each of the amplification units 131, 132,..., 135 are determined. A plurality of
candidate window functions are determined by non-linear optimization at each frequency under
predetermined conditions in the microphone array device 100 such as the distance between
microphones. Then, at a frequency at which the number of local minima points of the directional
characteristic of the sound pickup is the same among the window functions obtained for each
frequency, the window function obtained by nonlinear optimization is set to one amplification
unit Classified as a candidate for Then, among window function candidates set in one
amplification unit, a target directivity characteristic, for example, a window function having a
main lobe width close to the target width is selected from the window functions as candidates,
and this is selected. It is determined as a window function to be set in the amplification unit.
Then, with respect to other window function candidates related to directional characteristics with
different numbers of local minimum points, the window functions to be set to one amplification
unit are determined in the same manner. Each of the microphones 9-1, 9-2, ..., 9-n in the present
modification is a nondirectional microphone, but may be a microphone having directional
characteristics. In this case, the window function may be determined in accordance with the
directivity characteristics of each of the microphones 9-1, 9-2, ..., 9-n.
[0047]
Next, the frequencies f1, f2, f3, and f4 set in the signal division and synthesis unit 14 by the
control of the control unit 6 will be described. As described in the embodiment, when sounds of
various frequencies are picked up using the window function set in one amplification unit, the
strength of the side lobes other than the main lobe increases in the high frequency band side, etc.
Disturbance of the directional characteristics of Therefore, the upper limit frequency of each of
the audio signals Sb-1, Sb-2, ..., Sb-4 output from each of the amplification units 131, 132, ..., 134
is set in a range where the disturbance of the directional characteristics does not occur. decide.
Although there are various methods for determining the upper limit of the frequency, the upper
limit of the frequency is determined within the range in which the intensity in a predetermined
09-05-2019
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angular direction does not exceed a predetermined value.
[0048]
In this way, the microphone array device 100 can be made capable of performing sound
collection with a predetermined directional characteristic, and the amount of calculation of signal
processing can be reduced to achieve a wide range of frequencies, as in the effects of the
embodiment. It becomes possible to perform directional control in a band by a process with low
load. The modification 11 may apply a modification according to another modification to the
microphone array apparatus 100.
[0049]
It is a block diagram showing composition of a speaker array device concerning an embodiment.
It is a block diagram which shows the structure of the signal processing part which concerns on
embodiment. It is a block diagram showing composition of an amplification part concerning an
embodiment. It is a block diagram which shows the structure of the signal division part which
concerns on embodiment. FIG. 7 is an explanatory view showing directivity characteristics in
which the number of minimum points is 4 in directivity characteristics of an acoustic beam. It is
explanatory drawing which shows the angle direction in the directional characteristic of an
acoustic beam. It is explanatory drawing which shows the directional characteristic in which the
number of the minimum points is 1 in the directional characteristic of an acoustic beam. FIG. 7 is
an explanatory view showing directivity characteristics in which the number of minimum points
is 2 in directivity characteristics of an acoustic beam. FIG. 7 is an explanatory view showing
directivity characteristics in which the number of minimum points is 3 in directivity
characteristics of an acoustic beam. It is explanatory drawing which shows the state in which the
directivity of the acoustic beam was disturbed. It is explanatory drawing which shows the
directional characteristic in which the number of the minimum points is 1 in the directional
characteristic of an acoustic beam. It is explanatory drawing which shows the directional
characteristic in which the number of the minimum points is 1 in the directional characteristic of
an acoustic beam. It is a block diagram which shows the structure of the sound emission part
which concerns on the modification 2. FIG. FIG. 18 is an explanatory view showing directivity
characteristics in which the number of minimum points is 1 in the directivity characteristics of an
acoustic beam according to Modification 3; FIG. 16 is a block diagram showing a configuration of
an amplification unit according to a fifth modification. FIG. 16 is a block diagram showing a
configuration of connection of a signal division unit, a delay circuit, and a signal processing unit
according to a fifth modification. FIG. 18 is a block diagram showing a configuration of an
09-05-2019
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amplification unit according to a modification 6; FIG. 18 is a block diagram showing the
configuration of a signal processing unit according to Modification 7; FIG. 18 is a block diagram
showing the configuration of a microphone array device according to a modification 11; FIG. 18
is a block diagram showing the configuration of a signal processing unit according to
Modification 11. FIG. 16 is a block diagram showing the configuration of an amplification unit
according to a modification 11; FIG. 18 is a block diagram showing the configuration of a signal
division and synthesis unit according to Modification 11.
Explanation of sign
[0050]
DESCRIPTION OF SYMBOLS 1 ... Speaker array apparatus, 2 ... sound emission part, 2-1 to 2-n ...
Speaker, 21 ... Delay part, 21-1 to 21-n, 310, 320, 330, 340, 350-1 to 350-n ... Delay circuit 3, 13
... Signal processing unit, 30, 1310, 140 ... Adder, 31-35, 131 to 135 ... Amplification unit, 31-1
to 31-n, 35-1 to 35-n, 131- 1-131-n ... Amplifier circuit, 4 ... Signal division unit, 4-1, 14-1 ... LPF,
4-2 to 4-4, 14-2 to 14-4 ... BPF, 4-5, 14-5 ... HPF, 5 ... Signal input unit, 6 ... Control unit, 7 ...
Operation unit, 8 ... Storage unit, 9 ... Sound collection unit, 9-1 to 9-n ... Microphone, 14 ... Signal
division synthesis unit, 15 ... Signal Output unit
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