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JP2001204092

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DESCRIPTION JP2001204092
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus for collecting only sound from a sound source in a desired zone using a plurality of
microphones.
[0002]
2. Description of the Related Art Conventionally, when collecting sound from a sound source in a
specific zone, a plurality of microphones are arrayed, and the output signal of each microphone is
from the point to be received (specific zone) to each microphone There is a sound receiving
method called a delay sum array, which gives a time delay according to the distance of and takes
out the output sum of each microphone. However, in this method, in order to use the same phase
addition of the microphone output, it is necessary to take a large microphone interval in order to
extract the sound from a specific zone at a high SN ratio, especially in a low frequency band.
There was a problem of getting bigger.
[0003]
On the other hand, there has also been proposed a method of collecting the sound from a specific
zone by reducing the number of microphones (Japanese Patent Application Laid-Open No. 10313497: "Source separation method, apparatus and recording medium"). In this method, a
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plurality of areas (zones) are formed by dividing an area by a bisector between two or more
microphones using two or more microphones, and an acoustic signal from one sound source is
generated. When the sound is picked up by two microphones, the output signal of each
microphone is used by taking advantage of the fact that the output signal of the microphone
closer to the sound source is higher in level than the output signal of the other microphone, and
the arrival time is earlier. Each band signal is small enough to be composed of the component of
the acoustic signal from one sound source, divided into a plurality of frequency bands, and
different by detecting the level difference or arrival time difference of the same band signal of
each microphone output signal The sound signal from the sound source present in the zone is
separated and taken out, that is, the frequency component from the sound source in the desired
zone with respect to the signal received by the microphone By extracting only, and extracts only
the sound from the sound source in a specific zone. Since this method does not use in-phase
addition of microphone outputs, it is possible to form a plurality of zones with a smaller number
of microphones compared to a delay-and-sum array.
[0004]
However, even with this method, it is possible to extract the sound coming from the direction of
the specific angle range, but it was difficult to pick up only the sound coming from the specific
distance. This is only the magnitude relationship of the sound pressure that enters the
microphone as a clue to know the distance between the microphone and the sound source, and
the sound pressure generally changes with time depending on the sound generation state of the
sound source. It is difficult to measure the distance of Also, in this conventional method, it was
not possible to simply change the zone.
[0005]
According to the present invention, a plurality of input / band division means for picking up
sound from a sound source in a specific direction by extracting only frequency components from
a sound source in a desired zone It is characterized in that only the signal of the sound source
coming from a specific distance and a specific direction is extracted. Also, the input / band
division means is extended to a plurality of units, and the selection of the frequency components
divided into bands is performed by the logical operation, and the sound collection is performed
by changing the method of the logical operation It is possible to change the specific distance or
specific direction of the zone of the sound source to be
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[0006]
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an embodiment of the present
invention. The input means 1 and 2 respectively pick up an acoustic signal from a sound source
and convert it into an electrical signal. In this embodiment, a directional microphone or the like is
used as the input means 1 and 2, for example, and a specific range (hereinafter referred to as a
zone) of the sound space which can be received is determined by using a microphone producing
a sensitivity difference depending on the direction of the sound source. It is something that can
be done. For example, the directions of the main beams of the directional characteristics of the
input means 1 and 2 composed of directional microphones respectively form zones 3 and 4
shown in FIG. 2A, and these zones 3 and 4 are made to intersect. The output signals of the input
means 1 and 2 are respectively supplied to the band dividing means 5. In the band dividing
means 5, the output signals from the directional microphones as the input means 1 and 2 are
respectively divided into a plurality of frequency band signals. This band division is finely divided
to such an extent that components included in one frequency band can be approximated if
generated only at the frequency from a single sound source. For example, Fourier transform is
used as a method of this band division. The input means 1 and 2 and the band dividing means 5
constitute an input / band dividing means 6. The band-divided signal from the input / band
division means 6 is supplied to the spectrum selection means 7 and the logic operation means 8.
[0007]
The logical operation means 8 determines new zones by defining logical operations (AND, OR,
NOT, etc.) for the zones determined for the respective input means 1, 2. For the two zones 3 and
4 shown in FIG. 2A, new zones can be determined, for example, by the following logical
operation. (Zone 3) ∩ (zone 4) (zone 3) ∪ (zone 4) (zone 3) ∩ (zone 4) 'where A ∩ B is the
logical product of A and B, A ∪ B is the logic of A and B The sum, A ', represents the negation of
A, respectively.
[0008]
Among the newly determined zones, for example, (zone 3) ∩ (zone 4) is shown in zone 9 shown
by the hatched portion in FIG. 2B, that is, in the zone of the overlapping portion of zone 3 and
zone 4 Become. The type of zone determined by the logic operation means 8 is equal to the type
of zone generated when any logical operation is performed on each of the zones determined by
the input means 1 and 2. In order to extract the acoustic signal from the sound source present in
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the zone determined by the logic operation means 8 in the place, the respective output signals of
the input means 1 and 2 are respectively band signals S1i and S2i (i = 1, 1; , N and n are the
number of divided bands) are converted into logical values 1 or 0 depending on whether
the level (power) is above or below a predetermined value in the binarization unit 8 a. These
binarized band signals QS1i and QS2i are input to the logic operation unit 8b, and the logic
operation set in the logic operation unit 8b is a binary band signal for each same frequency band
of both input means 1 and 2 To be done. If the logical operation unit 8b is set to the logical
product (AND), QS1i ∩ QS2i is calculated respectively. The setting of the type of the logical
operation by the logical operation unit 8b is performed by a plurality of types of logic provided
in advance when configured by hardware so that the logical operation according to the setting
characteristic of the zone setting unit 8c is performed. A corresponding one of the arithmetic
circuits is selected and used, and when configured by software, one corresponding one of a
plurality of types of logical operation programs is selected.
[0009]
The spectrum selection means 7 selects frequency components from the sound source in the
zone determined by the logic operation means 8. For the purpose of explanation, it is assumed
that three sound sources A, B and C are arranged in the zone 9 and the zone 3 other than the
zone 9 and the zone 4 zone 9 other than the zone 9 as shown in FIG. 2C. For example, in order to
pick up only the sound from the sound source (sound source A in FIG. 2C) in (zone 3) ∩ (zone 4)
= (zone 9), the band signal (spectrum) from input means 1 and If only the frequency component
in which power exists (or has power over a certain magnitude) in the signals from both input
means in the same frequency band among the band signals (spectrum) from the input means 2,
that is, logical operation When the calculation result QS1i∩QS2i from the means 8 selects a
band signal of "1" (zone 3) ∩ (zone 4) = (zone 9), only an acoustic signal from a sound source (in
this case, sound source A) can be extracted. For example, as shown in FIG. 1, a gate 7G1i for
inputting the band signal S1i and a gate 7G2i for inputting the band signal S2i are provided in
the spectrum selection means 7, and these gates 7G1i and 7G2i are gate control signals GC1i
from the logic operation means 8. The gate 7G1i (7G2i) is opened when the gate control signal
GC1i (GC2i) is a logic "1", and the corresponding gate 7G1i (7G2i) is opened when the gate
control signal GC1i (GC2i) is a logic "0". Close it. The gate control signals GC1i and GC2i are
obtained by the logical operation result based on the zone set by the zone setting unit 8c.
[0010]
For example, in the example shown in FIG. 2C, when (zone 3) ∩ (zone 4) = (zone 9) is set by the
zone setting unit 8C, the frequency spectrum of the signal collected by the input means 1, that is,
The result of arranging the band-divided signals frequency-divided by the band-dividing means 5
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in the frequency order is shown by a thick solid line based on the acoustic signal from the sound
source A as shown in FIG. And the frequency spectrum of the signal picked up by the input
means 2 is shown by a thick solid line as that based on the acoustic signal from the sound source
A as shown in FIG. 3b. Also, if it is obtained in a state shown by a thin solid line based on an
acoustic signal from a sound source C, a spectrum (division band corresponding to a thick solid
line in FIGS. And only the logical product (QS1i∩QS2i) of the respective binary signals QS1i and
QS2i corresponding to V.2) becomes the logic "1", and the gate control signal GC1i or / and GC2i
of this logic "1" makes the corresponding gate 7G1i or And / or 7G2i, only the two spectra
(division band signals) shown by thick solid lines as shown in FIG. 3C, that is, the division band
signals of the acoustic signal from the sound source A only in the zone 9 are extracted from the
spectrum selection means 7 Ru.
[0011]
Further, in the example shown in FIG. 2C, in the case of selecting divided band signals (spectra)
from all the sound sources present in the sound collection zones 3 and 4 of the input unit 1 and
the input unit 2, the zone setting unit 8c A synthesis zone of zone 3 and zone 4 is set, logical OR
8 calculates logical sum of QS1i and QS2i, and at least one of band division signal S1i from input
unit 1 and band division signal S2i from input unit 2 On the other hand, gate control signal GC1i
(and GC2i) = QS1iiQS2i = 1 for a band where power is present (or having power of a certain
magnitude or more), and gate 7G1i or / and 7G2i is opened.
The split band signals of all the sound signals from the sound sources A, B, C in zones 3 and 4 are
extracted.
[0012]
Furthermore, if zones other than zone 4 in zone 3 (zones hatched in FIG. 2C) are set in zone
setting unit 8c in the example in FIG. 2C, logical operation means 8 reverses QS1i and QS2i. The
logical product is calculated, and the gate 7G1i where QS1i∩QS2i '= 1 is opened, and from the
divided band signal (spectrum) S1i from the input means 1, the divided band signal from the
input means 1 and the divided from the input means 2 A split band signal from which a split
band signal in which power is present in both of the band signals (or having a power greater than
a certain magnitude) is removed is selected from the spectrum selection means 7.
[0013]
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In FIG. 1, in the signal combining means 11, only the band split signals from the sound source in
the setting zone selected by the spectrum selecting means 7 are collected and combined, and are
returned to the time waveform as required.
For example, an inverse Fourier transform is used as an operation of returning to the time
waveform. Band division signals from the sound source of the setting zone may be collected and
synthesized, and may be used for acoustic signal analysis, for example, for speech recognition
without converting into time domain signals.
[0014]
In the embodiment shown in FIG. 1, for example, only the sounds in zones 3 and 4 can be
accurately collected only when it can be assumed that the sound from the sound source in zones
other than zones 3 and 4 shown in FIG. Sound is possible. Specifically, it is particularly effective
in an ideal environment such as a superdirective microphone having a particularly sharp
directivity, when used in a place where free space can be assumed, such as outdoors or in an
anechoic room. However, in practice, when sound is collected indoors, as shown in FIG. 4A, the
sound coming from the sound sources D other than the zone 3 and the zone 4 often has an
unignorable magnitude. Therefore, only the sound from the sound source in the set zone can be
collected. An embodiment will be described with reference to FIG.
[0015]
For example, a plurality of microphones are used as the input units 1 and 2. For example, as
shown in FIG. 4B, two microphones M1-1 and M1-2 are used as the input means 1 and 2,
respectively. As shown in FIG. 4B, for example, when the sound source (speaker) A is closer to the
microphone M1-1 than the microphone M1-2, the sound from the sound source A is compared to
the microphone M1-2 compared to the microphone M1-2. Reach quickly and with a large sound
pressure. The output signals of the microphones M1-1 and M1-2 are respectively divided by the
band dividing means 5 into a plurality of band signals S1-11 to S1-1n and S1-21 to S1-2n as in
the case of FIG. The parameter value difference detection means 21-1 calculates the arrival time
difference or arrival level difference between the microphones M1-1 and M1-2 for the same
frequency band of each band signal divided into frequency bands.
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[0016]
The zone determination means 22-1 uses the time difference between microphones and the
inter-microphone level difference for each band signal calculated by the parameter value
difference detection means 21-1 to define the zone and the frequency components from the
sound sources in each zone (band Determine the signal). For example, as shown in FIG. 4C, when
the line dividing the distance between the microphones M1-1 and M1-2 into two equal parts is
the boundary line 23, and there is a sound source in the area on the microphone M1-1 side from
the boundary line 23, the sound is When the sound source reaches the microphone M1-1 faster
than the microphone M1-2 and with a large sound pressure, and the sound source is in a region
closer to the microphone M1-2 than the boundary line 23, the opposite is true. Therefore, when
the microphone M1-1 side is defined as the zone 31 and the microphone M1-2 side is defined as
the zone 4 from the boundary line 23, for each signal obtained by dividing the acoustic signal
input to the microphones M1-1 and M1-2, A split band signal whose power of the frequency
component (split band signal) entering the microphone M1-1 is larger than that of the
microphone M1-2 or whose arrival time is earlier is determined as a split band signal from a
sound source in the zone 31 Do. Similarly, the split band signal from the sound source in the
zone 32 is a split band signal whose power of the frequency component (split band signal)
entering the microphone M1-2 is larger than that of the microphone M1-1 or whose arrival time
is earlier Determine it as a signal. In this way, zones 31 and 32 can be defined, and sub-band
signals from sound sources in the zones can be determined. That is, divided band signals from
zone 31 are taken out as D1-1 to D1-m, and divided band signals from zone 35 are taken out as
D2-1 to D2-p. Here, divided band signals D1-1 to D1-m and D2-1 to D2-p for each zone are
signals of different divided bands.
[0017]
Similarly, the output signals of the two microphones of the input means 2 are divided into
divided band signals S2-11 to S2-1n and S2-21 to S2-2n, and the parameter value difference
between these corresponding bands is detected by the detecting means 21. -2 and each zone
signal is a signal from the sound source of which zone in zone determination means 22-2, each
zone signal of zone 33, 34 and each zone signal D3-1 to D3-k and D4-1. It is separated into D4-q.
The input means 1 and 2, the band division means 5, the parameter value difference detection
means 21-1 and 21-2, and the zone determination means 22-1 and 22-2 constitute an input /
band division means 6. The determination of which zone each sub-band signal is based on the
acoustic signal as described above is disclosed in the above-mentioned publication.
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[0018]
Similarly to the embodiment shown in FIG. 1, the band division signal for each zone from the
input / band division means 6 is input to the logic operation means 8 to set a new zone, and the
new zone is set. Only the split band signal from the sound source is selected by the spectrum
selection means 7, and the selected split band signals are collected and combined by the signal
combining means 11, converted into a time domain signal as necessary, and output. . Now, the
zones 31 and 32 shown in FIG. 6A are defined by the output signals of the microphone M1-1 of
the input means 1 by the respective output signals of M1-2, and as shown in FIG. 6B, the
microphones M2-1 and M2-2 of the input means 2 are Zones 33 and 34 are defined by each
output signal, and as shown in FIG. 6C, the zone between the zone 31 and 32 and the zone 33 or
34, that is, the overlapping area of the zone 32 and the zone 33 As zone 35.
[0019]
When zone 35 is set in logical operation means 8, the binary signal of the divided band signal
belonging to zone 32 in the divided band signal inputted to logical operation means 8 and the
binary value of the divided band signal belonging to zone 33 It is sufficient to take the logical
product of the same band with the conversion signal and to output only the divided band signal
whose result is the logic "1" from the spectrum selection means 7. Further, the sound source A is
present in the zone 35, the sound source B is present in the zone 34, the sound source C is
present in the zone 31, and those determined as the divided band signals from the sound source
of the zone 32 by the input means 1 are as shown in FIG. The solid line is the spectrum (split
band signal) from the sound source A, the thin solid line is the spectrum from the source B (split
band signal), and the divided band signal from the source of the zone 33 is shown in FIG. 7B. In
the case where the thick solid line is the spectrum from the sound source A (division band signal)
and the solid line is the spectrum from the sound source C (division band signal), when the zone
35 is set, in both spectra of FIG. Are simultaneously selected by the spectrum selection means 7
as shown in FIG. 7C, and only the split band signal of the sound source A of the zone 35 is
selected.
[0020]
Also, for example, as a frequency component (division band signal) of (zone 32) ∪ (zone 33), that
is, a division band signal from a sound source located in either zone 32 or zone 33 (shaded area
in FIG. 6D) Of the spectrum of the input means 1, the divided band signal determined to belong
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to the zone 32 in the zone determination means 22-1 and the spectrum of the input means 2 are
determined to belong to the zone 33 in the zone determination means 22-2. The spectrum
selection means 7 selects all of the divided band signals forming a union with the divided band
signals. By doing this, it is possible to select a frequency component from a sound source located
in a newly defined zone (a zone consisting of zone 32 and zone 33).
[0021]
In each of the embodiments shown in FIGS. 1 and 5, the number of input means may be two or
more in the same manner. For example, as shown in FIG. 8A, three input means 1, 2 and 3 having
relatively sharp directivity characteristics are provided, and a sound collection zone 1, which is
determined by the main beam of each directivity characteristic of these input means 1, 2 and 3 It
can also be installed so that 2 and 3 cross each other. In this case, various zones can be selected
such as a zone determined by a combination of two zones (AND, OR, NOT) or a zone by a
combination of three zones. Zones 1, 2 and 3 may intersect each other two by two.
[0022]
Further, in the embodiment shown in FIG. 5, three or more microphones can be used for one
input means. For example, as shown in FIG. 8B, three microphones M1-1, M1-2, and M1-3 are
used in the input unit 1 to form zones 1-1, 1-2, and 1-3, and the input unit 2 is formed. Also,
three zones 2-1, 2-2, 2-3 are formed by using three microphones M2-1, M2-2, M2-3, and the six
zones 1-1, 1-1, 2-3 are formed by the logic operation means 8. It is also possible to select various
zones determined by two or more arbitrary combinations (AND, OR, NOT) of 1-2, 1-3, 2-1, 2-2, 23.
[0023]
Further, in the above embodiment, it is possible to pick up the sound from the sound source in
the zone of the specific direction and distance. However, for example, as shown in FIG. 9A,
directional microphones M1 and M2 for determining zones 1 and 2, respectively, are disposed,
and a sound collecting device capable of freely controlling the width of the overlapping zones
(zones hatched in the figure). It can also be done. In FIG. 9A, angles φ1 and φ2 are angles
formed by the perpendicular bisector p of the line connecting the two microphones M1 and M2
with the direction of the main beam of the directivity characteristic of the microphones M1 and
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M2, respectively. Here, it is assumed that zone 1 and zone 2 are respectively inside the ellipse. If
the direction of the main beam is changed so that φ1 and φ2 each become 90 degrees, if the
portion ((zone 1) / (zone 2)) shown by the hatched portion in FIG. The width of sex narrows. On
the other hand, if φ1 and φ2 are made smaller (zone 1) to (zone 2), the width of the sound
collection directivity becomes wider if sound is collected. This concept can be applied to other
zones as well. For example, if φ1 and 22 are made variable and a portion of (zone 1) ∪ (zone 2)
is picked up, it is possible to pick up a directional characteristic different from the previous one.
In addition, when φ1 and φ2 exceed 90 degrees, the characteristic is symmetrical to the case
where they change from 0 degrees to 90 degrees. Furthermore, as shown in FIG. 1, when the
sound collection zone is determined by the directivity characteristic of one input means itself, as
shown in FIG. 5, a plurality of microphones are used for one input means, resulting in the
microphone position. The sound pressure of the sound signal reaching the changing microphone,
the difference in parameter values such as arrival time, etc. are determined for the corresponding
ones of the divided band signals of each microphone output signal, and a plurality of sound
collection zones are defined. In the case of determining the sound source of which zone for each
divided band of the signal, that is, even if the input / band division means 6 in FIG. 1 and the
input / band division means 6 in FIG. Good.
[0024]
For example, as shown in FIG. 9B, while providing the input means 1 which determines zone 1 by
directivity characteristics and the input means 2 which determines zone 2 by directivity
characteristics, one microphone M3 is provided, and the input devices 2 and microphones M3
and Thus, the input means 3 shown in FIG. 5 can be configured, and a vertical bisector of a line
connecting the input means 2 and the microphone M3 can be used as a boundary and the
microphone M3 side can be used as the zone 3. In this way, the sound source D present in the
zone 3 can detect that the sound source D is present in the zone 3 by the input means 3, and for
example, the problem shown in FIG. 4A can be avoided.
[0025]
Furthermore, in the above embodiment, a new zone is defined in the acoustic space by the logical
operation calculation means 8 and any one of the zones is picked up, but it is not one but a
plurality of zones. The sound signal may be collected separately. For example, as shown in FIG.
10, from the input / band dividing means 6 (or a combination thereof) in FIG. 1 or FIG. It is
digitized and supplied to the logic operation circuits 8b1 and 8b2, and for the logic operation
circuits 8b1 and 8b2, binarization division of a plurality of zones respectively corresponding to
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the zones set by the zone setting units 8c1 and 8c2 The logical operation between the band
signals is performed, and the divided band signals of each zone from the input / band dividing
means 6 are respectively selected by the spectrum selecting means 7-1 and 7-2 according to the
logical operation results of the logical operation circuits 8b1 and 8b2. The divided band signals
for each setting zone are collected and synthesized by the signal synthesizing means 11-1 and
11-2, respectively, and converted into time domain signals as necessary. It is. In this way, it is
also possible to extract more zone-specific acoustic signals separately.
[0026]
The function of each unit in the above may be obtained by decoding and executing a program by
a DSP (digital signal processor) or the like. In the above description, although various logical
operations and zones to which divided band signals to be used belong can be selected and
changed in the logical operation means 8, one or both of them may be fixed.
[0027]
According to the present invention, since it is not necessary to add the signals of a plurality of
microphones in phase, it is possible to collect sound in a specific zone with a small device scale
as compared with the conventional delay-and-sum array. Furthermore, a new zone different from
the sound collection zone by the conventional input means is defined by the plurality of input
means and the logical operation means, and the frequency component from the sound source in
the new zone can be selected. For this reason, it is also possible to pick up the sound in the space
in a specific direction and a specific distance with respect to the input means.
[0028]
In addition, since a new zone is formed by performing a logical operation on the zones defined by
each input means, for example, sound is collected from zones of complex shapes in which only
sounds within a specific range are not collected. It is possible. In addition, if it is possible to
change the pointing direction of the input means, it is possible to collect sounds for controlling
the width of the directivity freely, from extremely narrow to wide directivity. Furthermore, by
using a plurality of microphones as the input means and using the difference between the
divided band signals of the microphone output, the frequency component from the sound source
in each zone is accurately determined, and from other than the desired sound collection zone By
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suppressing the unwanted sound, the sound from the desired zone can be collected at a high S /
N.
[0029]
Brief description of the drawings
[0030]
1 is a block diagram showing a functional configuration of an embodiment of the zone-specific
sound collection device of the present invention.
[0031]
FIG. 2A is a view showing an example of zone formation by the directional characteristics of the
directional microphone, B is an example of a newly defined zone (zone 9) = (zone 3) ∩ (zone 4),
and C is in each zone It is a figure which shows the example of arrangement ¦ positioning of
sound source A, B, C. FIG.
[0032]
3A shows an example of the spectrum of the output signal of the input means 1, B shows an
example of the spectrum of the output signal of the input means 2, and C shows the spectrum of
sound collection from (zone 3) 3 (zone 4) FIG.
[0033]
FIG. 4A is a diagram for explaining an influence from a sound source located in a place other
than zone 1 and zone 2, B is a diagram for explaining a parameter value difference between
output signals generated by using a plurality of microphones, and C is a plurality It is a figure
which shows the example of the zone which can be produced ¦ generated by using the output
signal parameter value difference of a microphone.
[0034]
5 is a block diagram showing a functional configuration of another embodiment of the present
invention.
[0035]
6A shows an example of zones defined for the input means 1 in FIG. 5, B shows an example of
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zones defined for the input means 2, C shows (zone 32) ゾ ー ン (zones) 33 shows a zone (shaded
area) defined in 33), and D shows a zone (shaded area) defined by (zone 31) / (zone 34).
[0036]
7A shows a spectrum belonging to zone 32, B shows a spectrum belonging to zone 33, and C
shows a spectrum belonging to (zone 32) ス ペ ク ト ル (zone 33).
[0037]
FIG. 8A shows an example of zone formation when three directional input means are used, and
FIG. 8B shows an example of zone formation when three microphones are used as each input
means 1 and 2 using a plurality of microphones. is there.
[0038]
FIG. 9A is a diagram for explaining the relationship between the angle of the microphone and the
width of the directivity characteristic of the zone overlapping area, and B is another directional
input means by combining a plurality of directional input means and one of the microphones. It
is a figure which shows the zone structural example at the time of comprising.
[0039]
10 is a block diagram showing a functional configuration of still another embodiment of the
present invention.
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