JP2013093807

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DESCRIPTION JP2013093807
PROBLEM TO BE SOLVED: To provide sharp directivity over a wide frequency band even when
distances from a sound source to a microphone of a microphone array are different. SOLUTION:
Seven microphone units are configured by the microphones 8-1 to 8-8 in the microphone array
2, and the beam forming unit 12 receives audio signals from the seven microphone units, and
directivity of each microphone To output an audio signal having directivity. There are provided
delay circuits 10-1 to 10-8 whose delay amounts have been adjusted so as to match the delays
generated in the audio signals of the respective microphones based on the respective distance
differences between the sound source and the respective microphones. [Selected figure] Figure 1
Microphone device
[0001]
The present invention relates to a microphone device, and more particularly to one using a
microphone array.
[0002]
For example, when making speech, it may be amplified using a microphone, an amplifier and a
speaker.
In this case, a microphone may be placed around the speaker's mouth to be in an on-microphone
state in which sound is collected. In the on-mic state, the movement of the speaker may cause the
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sound volume and the sound quality to fluctuate sensitively, and a microphone at the speaker's
mouth may interfere with the speaker's speech. Therefore, there is also a case where an offmicrophone state in which a microphone is installed at a certain distance from the speaker to
pick up sound is set. However, in this case, noise around the speaker is also likely to be picked
up, the S / N is lowered, and the resistance to howling is also lowered. Therefore, it is conceivable
to use a microphone device having directivity as disclosed in Patent Document 1, for example, in
an off-microphone state.
[0003]
In the technique of Patent Document 1, the first to third three unidirectional microphones are
arranged in a row such that the distance D between adjacent microphones is a predetermined
distance, and the sound from the sound source is The first to third microphones are made to pick
up sound, the level of the audio signal of the second central microphone is adjusted, and the
audio signals of the second microphone and the audio signals of the first and third microphones
on both sides are It is based on combining and outputting a combined signal. This composite
signal shows sharp directivity having a directivity peak at a frequency determined by the
distance D. By changing the distance, it is possible to make sharp directivity in which the
frequency at which the directivity peak occurs is made different. Therefore, for example, the
fourth microphones are placed outside the first microphone at a distance 2D, and the first, third
and fourth microphones adjust the level of the audio signal of the central first microphone, The
voice signals of the second and fourth microphones are combined to output a combined signal.
The fifth microphone is placed outside the fourth microphone at a distance of 4D, and the third,
fourth and fifth microphones adjust the level of the audio signal of the fourth central
microphone, And the voice signal of the fifth microphone to output a composite signal. A
microphone device having sharp directivity over a wide frequency band can be obtained by
further combining composite signals having directivity peaks at different frequencies.
[0004]
Patent No. 3732041
[0005]
The technology of Patent Document 1 is based on the premise that the sound source is located
far from each microphone, and the sound arrives from each sound source to each microphone
without time difference to generate a sound signal.
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However, when the above microphone device is used for a speech such as a podium, the speaker
as a sound source is located relatively near to the microphone device. Then, the sound from the
sound source reaches each microphone with a time difference. If the microphone device is
sufficiently small with respect to the sound source, the time difference can not occur, but if it is
desired to cover a wide frequency band so that sound can usually be sufficiently collected, the
microphones of the microphone device must be sufficiently separated. Instead, each microphone
needs to have a certain distance to the speaker, resulting in a difference in distance. When the
microphone causes a difference in distance from the sound source as described above, when
synthesizing the voice signals of the plurality of microphones as described above, the voices with
out of phase are synthesized, or the voice signal cancels out due to the phase shift, If there is no
difference in distance from the sound source, the directivity effect can not be achieved in a
specific frequency band that has shown sharp directivity at a certain frequency. As a result, the
sound quality of the finally synthesized voice signal becomes different from the original sound
quality. In addition, every time the speaker as the sound source moves or shakes his head, the
difference in distance between the speaker and each microphone changes, and the sound quality
changes.
[0006]
An object of the present invention is to provide a microphone device having sharp directivity
over a wide frequency band even if the distance from a sound source to each microphone is
different.
[0007]
A microphone device according to an aspect of the present invention includes a microphone
array.
The microphone array is configured by arranging a plurality of microphone units. Each
microphone unit is composed of a plurality of microphones arranged at intervals, and the
distance between the microphones is different for each microphone unit. The number of
microphones constituting the microphone unit can be any number of two or more, and the
number of microphones of each microphone unit can be the same, or can be different for each
microphone unit. The spacing between the microphones in each microphone unit may be the
same as, or different from, the spacing between the microphones in the same microphone unit.
The microphone directivity adjusting means has a synthesizing means for each microphone unit,
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and each synthesizing stage synthesizes an audio signal generated by collecting the sound from
the sound source by the one set of microphones in each microphone unit. Output a synthesized
signal. In the microphone directivity adjusting means, the combined signal outputted for each of
the microphone units obtained by each combining means is further combined by the recombining means and output. There is provided a delay means whose delay amount has been
adjusted so as to match the delay generated in the audio signal of each of the microphones based
on the distance difference between the sound source and each of the microphones. The delay
means may be provided between each microphone and each of the combining means, or may be
provided between each combining means and the re-combination means.
[0008]
According to this configuration, the audio signals generated by the microphones are adjusted by
the delay means so that the time difference with each sound source is all the same, and are
supplied to the microphone directivity adjustment means. The synthesized signal output from the
signal has sharp directivity over a wide frequency band.
[0009]
A filter may be provided downstream of each of the combining means.
Each filter extracts and outputs a composite signal of different frequency bands according to the
distance between the microphones constituting the microphone unit for each microphone unit,
and further combines the composite signals of different frequency bands by the recomposition
means. Output. By this, it is possible to further combine and output combined signals having
different frequency bands by the re-synthesis means, and it is possible to more reliably sharpen
the re-combined signal outputted from the re-combination means over a wide frequency band. It
can be possessed.
[0010]
The delay means may adjust the amount of delay so that the delay generated in the sound signal
of the microphone farthest from the sound source matches the delay generated in the sound
signal of the other microphones. Can. Since the delays of the audio signals of the other
microphones are made to coincide with the delays of the audio signals of the microphones
farthest from the sound source, the delay adjustment becomes easy.
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[0011]
The sound source may move. For example, the sound source is a speaker who makes a speech,
and movement includes movement of the speaker itself as well as movement of the face to the
audience at the time of speech, for example, from the center to a good side or a bad side . In this
case, the sound source position estimating means sequentially estimates the position of the
sound source according to the movement of the sound source. There are provided delay amount
adjustment means for adjusting the delay amounts of the respective delay means in accordance
with the position estimated by the sound source position estimation means.
[0012]
According to this configuration, even if the distance between the microphones and the sound
source changes with the passage of time as the sound source moves, the delay amount of each
delay means can be changed following the change, so the sound source moves. Also, the
synthesized signal output from the microphone directivity adjusting means has sharp directivity
over a wide frequency band.
[0013]
Further, an upper limit is provided for the position estimated by the sound source position
estimating means, and the delay amount adjusting means is arranged at a position estimated
beyond the upper limit when the sound source position estimating means estimates a position
exceeding the upper limit. It can be configured not to adjust the delay amount accordingly.
As the upper limit, for example, only a predetermined distance from the origin position
determined to estimate the sound source position is used, and the delay amount is not adjusted
when the sound source is at a position farther than this distance It is possible to use only a
predetermined angle with respect to the reference line passing through the origin position as the
upper limit, and adjust the delay amount when the sound source is at a position smaller or larger
than this angle Can also be done. Alternatively, two different first and second angles (second
angle> first angle) are set as upper limits, and the sound source angle is smaller than the first
angle or larger than the second angle. It is also possible not to adjust the delay amount.
Alternatively, the angle and the distance are combined so that the adjustment of the delay
amount is not performed regardless of the distance if the angle is smaller (or larger) than a
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certain angle, and the position of the sound source is more than one angle When the distance of
the sound source is larger than a predetermined distance when it is larger (or smaller), it is
possible not to adjust the delay amount. Alternatively, the angle range is set by the above first
and second angles, and the adjustment of the delay amount is not performed outside this angle
range, and the position of the sound source is farther than a predetermined distance within the
angle range. In this case, it is possible not to set the delay amount. With this configuration, it is
possible to prevent the sound of the sound source that you do not want to collect even if it is
around the sound source that you do not want to collect except the sound source you want to
collect. Can.
[0014]
Alternatively, when the sound source position estimating means estimates the position exceeding
the upper limit, the delay amount adjusting means does not adjust the delay amount according to
the position estimated beyond the upper limit, and the delay amount adjusting means does not
adjust the delay amount within the upper limit. The delay means may be configured to continue
the delay amount corresponding to the estimated position. For example, the amount of delay can
be adjusted such that the sound source is stopped at the position of the sound source estimated
immediately before the upper limit is exceeded. According to this configuration, the sound of the
sound source desired to be collected can be sufficiently collected.
[0015]
Alternatively, when the sound source position estimating means estimates the position exceeding
the upper limit, the delay amount adjusting means does not adjust the delay amount according to
the position estimated beyond the upper limit, and the position of the upper limit It is also
possible to configure to set the delay amount according to the delay means. For example, the
delay amount is adjusted so that the sound source is stopped at the upper limit position. Also
when configured in this way, the sound of the sound source to be collected can be sufficiently
collected.
[0016]
The position of the sound source is virtually determined in advance, and the delay means
matches the delay occurring in the audio signal of each of the microphones based on the distance
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difference between the virtually determined sound source and each of the microphones. The
amount of delay can also be adjusted to By setting the position of the sound source virtually in
this manner, it is possible to ensure that the sound that you do not want to collect is not
collected, and it is sufficient to estimate the sound source position only once.
[0017]
As described above, according to the present invention, even if the distance from the sound
source to each microphone is different, the microphone device can have sharp directivity over a
wide frequency band, and even if the sound source moves. However, sharp directivity can be
provided over a wide frequency band.
[0018]
It is a block diagram of the microphone device of one embodiment of the present invention.
It is a perspective view of the state which attached the microphone array of the microphone
apparatus of FIG. 1 to the podium. It is a block diagram of the beam forming part of the
microphone apparatus of FIG. It is explanatory drawing of the estimation principle of the position
of the sound source in the sound source position estimation part of the microphone apparatus of
FIG. It is explanatory drawing of the determination principle of the delay amount in the sound
source position estimation part of the microphone apparatus of FIG. It is a figure which shows
the directivity adjustable range in the microphone apparatus of FIG.
[0019]
The microphone system of one embodiment of the present invention has a microphone array 2
as shown in FIG. The microphone array 2 is formed by arranging a plurality of, for example, eight
unidirectional microphones in a line in the main body 4. These unidirectional microphones have
the same unidirectionality. For example, as shown in FIG. 2, this microphone array 2 is disposed
at one end of a pod 6 mounted on the stage, and collects voices of speakers using the pod 6. That
is, in this embodiment, the speaker is a sound source.
[0020]
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In the microphone array 2, first and second microphones 8-1 and 8-2 are disposed at intervals D
along the length direction of the main body 4. A third microphone 8-3 is disposed at the center
of the microphones 8-1 and 8-2. The distance between the microphones 8-1 and 8-3 and the
distance between the microphones 8-2 and 8-3 are respectively D / 2.
[0021]
In addition, a fourth microphone 8-4 is disposed between the first and third microphones 8-1 and
8-3. The distance between the microphones 8-1 and 8-4 and the distance between the fourth
microphone 8-4 and the third microphone 8-3 are each D / 4.
[0022]
A fifth microphone 8-5 is disposed at the center of the fourth microphone 8-4 and the third
microphone 8-3. The distance between the fourth microphone 8-4 and the fifth microphone 8-5
and the distance between the third microphone 8-3 and the fifth microphone 8-5 are D / 8.
[0023]
A sixth microphone 8-6 is disposed at the center of the fifth microphone 8-5 and the third
microphone 8-3. The distance between the fifth microphone 8-5 and the sixth microphone 8-6
and the distance between the third microphone 8-3 and the sixth microphone 8-6 are D / 16.
[0024]
A seventh microphone 8-7 is disposed at the center of the sixth microphone 8-6 and the third
microphone 8-3. The distance between the seventh microphone 8-7 and the sixth microphone 86 and the distance between the seventh microphone 8-7 and the third microphone 8-3 are D /
32.
[0025]
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An eighth microphone 8-8 is disposed at the center of the seventh microphone and the third
microphone 8-3. The distance between the seventh microphone 8-8 and the seventh microphone
8-7 and the distance between the third microphone 8-3 and the eighth microphone 8-3 are D /
64.
[0026]
As described above, in the microphone array, the distance D between the first and second
microphones 8-1 and 8-2 is divided by a factor (1, 2, 4,.. It is arranged. Based on the distance d
between the third microphone 8-3 and the eighth microphone 8-8, they are arranged at different
values (1, 2,... 64) times of multiples of 2 of the distance d It is done.
[0027]
The voices of the speakers picked up by the microphones 8-1 to 8-8 are output as voice signals
from the microphones 8-1 to 8-8, respectively. These audio signals are supplied to delay means
provided corresponding to each microphone 8-1, for example, variable delay circuits 10-1 to 108, given predetermined delays respectively, and directivity adjustment means, for example,
beams It is supplied to the forming unit 12.
[0028]
The beam forming unit 12 processes each audio signal as will be described later, and supplies it
as an audio signal having sharp directivity over a wide frequency band to an amplification means,
for example, an amplifier 14, where it is amplified and amplified. It is loudened from 16.
[0029]
In the beam forming unit 12, for example, as shown in FIG. 3, a first microphone unit is
configured by the first and second microphones 8-1 and 8-2 having the widest distance D as
shown in FIG. Level adjustment means, for example, amplifiers 20-1 and 20-2 are amplified, and
combining means, for example, adder 22 combines.
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The gains of the amplifiers 20-1 and 20-2 have the same value, for example 1, respectively. With
such a configuration, as disclosed in Patent Document 1, directivity is sharper than when the first
or second microphones 8-1 and 8-2 are used alone, and the directivity according to the interval D
is obtained. The frequency f1 at which is sharpened is determined.
[0030]
The second microphone unit is also configured by the first to third microphones 8-1, 8-2, 8-3 in
which the distance between adjacent ones is D / 2, respectively, and their audio signals are
amplified by the amplifier 24-1, The signals are amplified by 24-2 and 24-3 and synthesized by
the adder 26. The gains of the amplifiers 24-1, 24-2 and 24-3 are the same as those of the first
and second microphones 8-1 and 8 when the gain of the amplifier 24-3 for the audio signal of
the third microphone 34-3 is 1, for example. The gain of the amplifiers 24-1 and 24-2 for the
audio signal of -2 is set to 0.5, for example. With such a configuration, as described in Patent
Document 1, sharper directivity is obtained than in the case of the first microphone unit, and the
frequency f2 at which the directivity is the sharpest is determined by the interval D / 2, and The
frequency is higher than the frequency f1 of
[0031]
Similarly, a third microphone unit is constituted by the first, third and fourth microphones 8-1, 83, 8-4 in which the distance between adjacent ones is D / 4, respectively, and their audio signals
are , 28-1, and 28-3, and amplified by the adder 30. The gains of the amplifiers 28-1, 28-2 and
28-3 are the fourth microphone 8-4 located at the center of the first, third and fourth
microphones 8-1, 8-3 and 8-4. For example, the gain of the amplifier 28-2 is 1, for example, and
the gains of the amplifiers 28-1, 28-3 for the first and third microphones 8-1, 8-3 are set, for
example, to 0.5. According to this configuration, as disclosed in Patent Document 1, sharp
directivity substantially the same as that of the second microphone unit can be obtained, and the
frequency f3 at which the sharpest directivity can be obtained is higher than the abovementioned frequency f2 .
[0032]
A fourth microphone unit is constituted by the third, fourth and fifth microphones 8-3, 8-4 and
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8-5, each of which has an interval of D / 8 between adjacent ones. 1, 32-2, 32-3 and amplified by
the adder 34. The gains of the amplifiers 32-1, 32-2 and 32-3 are also, for example, 1 for the
gain of the amplifier 32-2 with respect to the fifth microphone located at the center, and the
gains of the other amplifiers 32-1 and 32-3, for example. It is set to 0.5. According to this
structure, as disclosed in Patent Document 1, sharp directivity substantially the same as that of
the second microphone unit can be obtained, and the frequency f4 at which the sharpest
directivity can be obtained is higher than the above-mentioned frequency f3. .
[0033]
A fifth microphone unit is constituted by the third, fifth and sixth microphones 8-3, 8-5, 8-6 in
which the distance between adjacent ones is D / 16, respectively, and their audio signals are
amplified by the amplifier 36-. 1, 36-2, 36-3 and amplified by the adder 38. The gains of the
amplifiers 36-1, 36-2 and 36-3 are also, for example, 1 for the gain of the amplifier 32-2 and the
gains of the other amplifiers 36-1 and 36-3 for the sixth microphone located at the center, for
example. It is set to 0.5. Also in this case, a sharp directivity substantially the same as that of the
second microphone unit can be obtained, and the frequency f5 at which the sharpest directivity
can be obtained is higher than the frequency f4 described above.
[0034]
A sixth microphone unit is constituted by the third, sixth and seventh microphones 8-3, 8-6, 8-7
in which the spacing between adjacent ones is D / 32, respectively, and their audio signals are
amplified by the amplifier 40- 1, 40-2 and 40-3 and amplified by the adder 42. The gains of the
amplifiers 40-1, 40-2 and 40-3 are also, for example, one at the gain of the amplifier 40-2 for the
seventh microphone located at the center and the gains of the other amplifiers 40-1 and 40-3,
for example. It is set to 0.5. Also in this case, a sharp directivity substantially the same as that of
the second microphone unit can be obtained, and the frequency f6 at which the sharpest
directivity can be obtained is higher than the above-mentioned frequency f5.
[0035]
A seventh microphone unit is constituted by the third, seventh and eighth microphones 8-3, 8-7,
8-8 in which the intervals between adjacent ones are D / 64, respectively, and their audio signals
are amplified by the amplifier 44-. 1, 44-2, 44-3 and amplified by the adder 46. The gains of the
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amplifiers 44-1, 44-2 and 44-3 are also, for example, 1 when the gain of the amplifier 44-2 for
the eighth microphone located at the center and the gains of the other amplifiers 44-1 and 44-3,
for example. It is set to 0.5. Also in this case, a sharp directivity substantially the same as that of
the second microphone unit can be obtained, and the frequency f7 at which the sharpest
directivity can be obtained is higher than the frequency f6 described above.
[0036]
From the combined output of the adder 22, a low-pass filter 48 extracts frequency components
equal to or less than the frequency f1. The band pass filter 50 extracts a band component having
the frequency f2 as the center frequency and the predetermined frequency between the
frequencies f1 and f2 as the lower limit frequency and the predetermined frequency between the
frequencies f2 and f3 as the upper limit frequency from the combined output of the adder 26 .
The band pass filter 52 extracts a band component having the frequency f3 as the center
frequency, the predetermined frequency between the frequencies f2 and f3 as the lower limit
frequency, and the predetermined frequency between the frequencies f3 and f4 as the upper
limit frequency from the combined output of the adder 30 . The band pass filter 54 extracts a
band component having the frequency f4 as the center frequency and the predetermined
frequency between the frequencies f3 and f4 as the lower limit frequency and the predetermined
frequency between the frequencies f4 and f5 as the upper limit frequency from the combined
output of the adder 34 . The band pass filter 56 extracts a band component having the frequency
f5 as the center frequency, the predetermined frequency between the frequencies f4 and f5 as
the lower limit frequency, and the predetermined frequency between the frequencies f5 and f6 as
the upper limit frequency from the combined output of the adder 38 . The band pass filter 58
extracts a band component having the frequency f6 as the center frequency, the predetermined
frequency between the frequencies f5 and f6 as the lower limit frequency, and the predetermined
frequency between the frequencies f6 and f7 as the upper limit frequency from the combined
output of the adder 42 . A high pass filter 60 extracts a band component higher than the
frequency f 7 from the combined output of the adder 44. An audio signal having sharp directivity
over a wide band is obtained by combining the band components extracted by the filters 48, 50,
52, 54, 56, 58, 60 by combining means, for example, the adder 62. Can.
[0037]
As described above, the beamforming unit 12 using the technique of Patent Document 1 assumes
that the sound source is positioned so far away that the difference in distance from the sound
source to each of the microphones 8-1 to 8-8 can be ignored. And However, as shown in FIG. 2,
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when the microphone array 2 is installed on the podium 6, there is a difference in distance
between the speaker as the sound source and each of the microphones 8-1 to 8-8. There is a time
difference for the same voice to arrive at 8-3. Therefore, as described above, sharp directivity can
not be obtained at a specific frequency, and as a result, the sound quality of the combined signal
from the beam forming unit 12 may be different from the original sound quality.
[0038]
In order to improve this point, in this embodiment, the audio signals of the first to eighth
microphones 8-1 to 8-8 are supplied to the variable delay circuits 10-1 to 10-8, and the audio
signal is most delayed. Also, the same delay as that of the microphone which has arrived is given
to the audio signals from other microphones and supplied to the beam forming unit 12. Thus,
even when there is a difference in distance between the sound source and each of the
microphones 8-1 to 8-8, it is possible to output from the beam forming unit 12 a composite
signal having a sharp directivity over a wide frequency band. .
[0039]
In order to determine the delay amount in each of the variable delay circuits 10-1 to 10-8, first,
the position of the sound source, that is, the position of the speaker is estimated, and the first to
eighth microphones 8-1 are determined from the estimated position. It is necessary to determine
the distance to 8-8. In addition, the speaker may move while giving a speech, or may shake the
face from the center toward the upper or lower side of the stage during the speech. In such a
case, the distance between the speaker and the first to eighth microphones changes. When the
distance changes in this manner, it is necessary to change the delay amount of each of the
variable delay circuits 10-1 to 10-8 in accordance with the new distance.
[0040]
Therefore, in this embodiment, delay amount setting means, for example, a sound source position
estimation unit 64 is provided. The sound source position estimation unit 64 receives, for
example, audio signals of the first, second, and third microphones 8-1, 8-2, and 8-3. The sound
source position estimation unit 54 first obtains the cross correlation of the audio signals of the
second and third microphones 8-2 and 8-3, and the second and third microphones 8-2 and 8-3
from the cross correlation. The time difference δT23 between them is determined. The distance
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difference δL23 is obtained from this time difference. This distance difference .delta. L23 is
determined by the hyperbola A which is divided into the audience side and the speaker side in
the rows of the first, second and third microphones 8-1, 8-2 and 8-3 as shown in FIG. expressed.
In this case, only the sound source is found on the hyperbola A, and the position of the sound
source can not be identified. Therefore, the sound source position estimation unit 64 also obtains
the cross-correlation of the audio signals of the first and third microphones 8-1 and 8-3, and the
first and third microphones 8-1 and 8 are obtained based on this cross-correlation. Calculate a
time difference δT13 of -3. The distance difference δL13 is obtained from this time difference.
The distance difference δL13 is represented by a hyperbola B shown in FIG. This hyperbola B is
also divided into an audience side and a talker side by a row of first, second and third
microphones 8-1, 8-2, 8-3. The intersection point C of the hyperbola B and the hyperbola A
described above can be estimated as the position of the sound source. It should be noted that
although there are two intersections of hyperbola A and B on the stage side and the audience
side, it is obvious that when the microphone unit 2 is installed on the above mentioned podium 6,
the intersections made on the audience side are not sound sources Therefore, only the
intersection on the speaker side is estimated as the position of the sound source.
[0041]
When the position C of the sound source is estimated in this manner, the distances from the
sound source to the first to eighth microphones 8-1 to 8-8 can be determined as shown in FIG.
Then, among these distances, in FIG. 5, with the distance from the sound source position C to the
second microphone 8-2 as a radius, an arc centered on the sound source position C is
determined. The line segments connecting the microphones 8-1, 8-3 to 8-8 and the position C of
the sound source are extended toward the circular arc, each intersection point is determined, and
each microphone 8-1, 8 corresponding to each intersection point The distance from -3 to 8-8
corresponds to the delay amount for causing the audio signal to reach the other microphones 81, 8-3 to 8-8 simultaneously with reaching the microphone 8-2. These extended distances are
respectively calculated, converted to delay amounts, and set in corresponding variable delay
circuits 10-1, 10-3 to 10-8. As a result, the microphones farthest from the sound source, the
delay generated in the audio signal of the microphone 8-2 in this embodiment, and the audio
signals of the other microphones 8-1 and 8-3 to 8 in this embodiment The delay that occurs is
the same.
[0042]
As described above, since the position of the sound source may change, the above-described
estimation of the position of the sound source is performed each time a predetermined time
elapses, and if the position of the sound source changes, the position of the sound source is
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newly determined. Based on the above, a new delay amount is set as described above.
[0043]
If the directivity of the microphone array 2 is adjusted following the movement of the sound
source, for example, as shown in FIG. When a person moves near any one of the speaker boxes
200, the microphone array 2 may pick up the loud sound from the speaker box 200 as well.
In this case, howling occurs. In order to prevent this, in this embodiment, the directivity
changeable range 202 in which the directivity of the microphone array 2 is changed as the sound
source moves is limited. An origin defined appropriately, for example, the position of the
microphone 8-3 is taken as an origin, and a straight line r passing this origin on a horizontal
plane is considered, for example, angles α and β with respect to the r axis are set. The positions
of distances D and D determined in advance from the origin are set above, and the range
surrounded by connecting these two positions is set as the directivity changeable range 202. The
angles α, β and the distance D are changed by the user according to the place where the
microphone array 2 is installed.
[0044]
If it is estimated that the sound source position 204 has come out of the directivity changeable
range 202 as a result of estimation by the sound source position estimation unit 64, the
directivity is stopped following the sound source, in which case the directivity is For example, it is
fixed to the position 206 of the sound source estimated immediately before leaving the
directivity changeable range 202, or on the boundary of the directivity changeable range close to
the sound source position 204, eg on the boundary having the same distance as the sound source
position 204. Position 208 of FIG. The directivity changeable range 202 is restricted by the two
angles α and β and the distance D, but can be restricted by the reference line r and one angle,
for example, β and the distance D.
[0045]
Although the above description is premised on processing an analog audio signal, the analog
audio signal of each of the microphones 8-1 to 8-8 is converted into a digital audio signal using
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an A / D converter. Can also be processed. In that case, the variable delay circuits 10-1 to 10-8,
the beam forming unit 12, and the sound source position estimating unit 64 can all be digital
circuits, and all of them can be configured by, for example, one DSP. . When digital processing is
performed, the mutual phase for estimating the sound source position in the sound source
position estimation unit 64 is, for example, each time a predetermined number of continuous
digital audio signals are obtained, the predetermined number of obtained digital numbers is
obtained. It is also possible to obtain an audio signal as a target.
[0046]
<Modifications> (1) In the above embodiment, an example in which a microphone unit is
configured by two microphones like the first and second microphones 8-1 and 8-2, and the first
to third microphones Although the example which comprised the microphone unit by three
microphones like 8-1, 8-2, 8-3 was shown, the number of the microphones which comprise a
microphone unit shall be two or more arbitrary numbers. For example, one microphone unit can
be configured by five microphones and seven microphones. Further, in the microphone unit
configured by three microphones, the example in which the distance between the microphones is
doubled is shown, but this is only an example, and the distance can be arbitrarily extended. In
addition, when the microphone unit is configured by three microphones, the gain of the central
microphone is doubled, but this is only an example, and the gain can be changed to any value.
[0047]
(2) In the above embodiment, in order to cope with the case where the position of the sound
source moves in the sound source position estimation unit 64, the estimation of the sound source
position is repeated each time a predetermined time elapses, and the variable delay circuit 10
Although the delay amount of -1 to 10-8 has been updated, it is not limited thereto. That is, when
the position of the sound source hardly changes, the sound source position estimating unit 64
estimates the position of the sound source only once or for a predetermined time to determine
the delay amount of the variable delay circuits 10-1 to 10-8. After that, the estimation process of
the sound source position may not be performed, and the delay amount may be maintained. Also,
at the manufacturing stage or shipping stage of the microphone 2, the sound source position is
virtually determined in advance, and the delay amount is set to match the directivity of each of
the microphones 8-1 to 8-8 with this virtual sound source position. It is possible not to perform
sound source position estimation at the time of operation of. In this case, specifically, as in the
case of the embodiment, the delay generated in the sound of the microphone farthest from the
predetermined position of the virtual sound source and the delay generated in the sound signal
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of the other microphone The delay amount to be matched may be set.
[0048]
(3) In the above embodiment, the first to eighth microphones 8-1 to 8-8 are linearly arranged in
a row, but may be arranged, for example, in an arc. Further, although eight microphones are used
in the above embodiment, the present invention is not limited to this, and various numbers can
be used.
[0049]
Reference Signs List 2 microphone array 8-1 to 8-8 microphone 10 variable delay circuit (delay
means) 12 beam forming unit (microphone directivity adjustment means)
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