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JP2012050044

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DESCRIPTION JP2012050044
A sound collecting microphone for collecting sound signals of a reproduction sound field in a
multi-channel sound system, the sound collecting microphone collecting sounds with a number
of channels smaller than the number of reproduction channels, and a sound collecting device for
processing the collected sound signals. provide. A sound pickup microphone 10 according to the
present invention has a main microphone unit (Mc-FL, Mc-FC, Mc-FR) including a plurality of
directional microphones whose directivity is directed radially from a central point on a twodimensional plane. , Mc-SiR, Mc-BR, Mc-BC, Mc-BL, Mc-SiL), and an auxiliary located at a
predetermined distance on the normal line from the central point with respect to a twodimensional plane constituting the main microphone unit And a microphone unit (Mc-TpC). In
addition, the sound collection and reproduction apparatus 20 is configured to process the
collected sound signal. [Selected figure] Figure 2
Sound collecting microphone and sound collecting and reproducing apparatus
[0001]
The present invention relates to the technology of a multi-channel sound collection microphone,
and more particularly to a sound collection microphone that collects sound with less than the
number of reproduction channels and a sound collection device that processes the collected
sound signal.
[0002]
In an acoustic system in which speakers are three-dimensionally arranged, it is necessary to
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record sound according to the direction of the speakers.
For this reason, when it is necessary to transmit sound live, it is necessary to set up a number of
microphones corresponding to the speakers to be reproduced in a sound field to be picked up. In
addition, when it is not necessary to perform live transmission, the sound sources to be recorded
may be separated and recorded, and furthermore, the reproduction sound may be synthesized by
being located at an arbitrary location by off-line mixing processing for each of the recorded
sound sources. It has been done.
[0003]
In general, the sound is collected more than the number of reproduction channels, and is
intentionally edited in accordance with the sound field condition and the image at the time of
shooting (for example, see Patent Document 1).
[0004]
JP 2008-48355 A
[0005]
When installing the microphones of the number corresponding to the speaker to reproduce |
regenerate, in order to ensure isolation | separation of the sound reproduced | regenerated from
each speaker, it is necessary to mutually install many microphones in space enough distance
mutually.
In this case, the microphone system is distributed over a wide range in space, there are many
problems in real time and mobility, and it is extremely difficult to use in a program relay where
there are many restrictions on the installation position of the microphone.
[0006]
When the place to be installed is limited, there is a method of installing a microphone
corresponding to the direction of the speaker to be reproduced at one point in the space.
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In this case, it is necessary to point the directivity axis in each direction, and to pick up the sound
with individual microphones in which the width of the directional beam does not overlap with the
adjacent channel. At this time, in a system having a large number of channels, such as a 22.2
channel acoustic system, since the visual angle between the channels is small, it is necessary to
use a microphone having a very high directivity, which causes a problem that the system
becomes large.
[0007]
When live transmission is not required, it is possible to produce sound by off-line mixing
processing, but in this case the total number of microphones that generally picks up often far
exceeds the number of channels, and the collection It is a problem that the sound system
becomes large.
[0008]
SUMMARY OF THE INVENTION The object of the present invention is made in view of the abovementioned problems, and provides a sound collecting microphone which collects sound with less
than the number of reproduction channels and a sound collecting device which processes the
collected sound signal. It is in.
[0009]
The present invention relates to a sound collection method in an acoustic system in which
speakers are arranged three-dimensionally, such as a Super Hi-Vision (SHV) 22.2 channel audio
system, and integrates overlapping channels when the speaker arrangement is projected in a
plane. Sound is picked up with a smaller number of channels than the speaker arrangement at
the time of reproduction, and at the same time, the upper and lower directions of sound are
judged in combination with the auxiliary microphone for judgment in the vertical direction. By
combining the signals reproduced by the three-dimensionally arranged speakers from the
information in the above, sound is collected with the number of microphones smaller than the
number of reproduction channels.
Thereby, the number of microphones required for sound collection can be reduced, and the
sound collection microphone system can be simplified.
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[0010]
That is, the sound collection microphone of the present invention is a sound collection
microphone that collects sound with a smaller number of channels than the number of
reproduction channels when generating an acoustic signal of a reproduction sound field in a
multi-channel sound system, and is on a two-dimensional plane. Main microphone comprising a
plurality of directional microphones whose directivity is directed radially from a central point,
and an auxiliary located at a predetermined distance on the normal line from the central point
with respect to a two-dimensional plane constituting the main microphone And a microphone
unit.
[0011]
Further, in the sound collection microphone of the present invention, the main microphone unit
includes a plurality of directional microphones configured to pick up sound with narrow
directivity in at least eight directions.
[0012]
In the sound collection microphone of the present invention, the lower limit value of the distance
is defined in accordance with a sampling frequency of sound representing the resolution of the
arrival direction determination of the sound in the vertical direction.
[0013]
Further, in the sound collection microphone of the present invention, the auxiliary microphone
unit has directivity capable of collecting both the sound arriving parallel to the plane constituting
the main microphone unit and the sound arriving from the upper side with respect to the plane
And the sound collection sensitivity in the upper arrival direction is higher than the sound
collection sensitivity in the lower arrival direction.
[0014]
Furthermore, the sound collection and reproduction apparatus according to the present invention
processes an acoustic signal of an original sound field picked up by the sound collection
microphone according to the present invention to generate an acoustic signal of a reproduction
sound field in the multi-channel sound system. The direction of arrival of sound by measuring the
cross-correlation function between the sound signal output from the main microphone unit and
the sound signal output from the auxiliary microphone unit to determine the time difference
between the sound signals And the amplitude of the acoustic signal from the main microphone
unit picked up based on the information on the direction of arrival of the sound determined by
the direction determination unit, and each of the multi-channel sound systems And an amplitude
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ratio adjusting unit that generates an acoustic signal of a reproduced sound field by assigning
and synthesizing the acoustic signal for a channel.
[0015]
Further, in the sound collection and reproduction apparatus according to the present invention,
the amplitude ratio adjustment unit is configured to set the sound to the plurality of speakers of
the multi-channel sound system at positions having different horizontal angles and equal
horizontal angles to the directional microphones. The acoustic signal of the reproduction sound
field in the direction corresponding to each directional microphone of the main microphone unit
is generated by distributing the output of the acoustic signal output from the main microphone
unit according to the information of the arrival direction. I assume.
[0016]
According to the present invention, in an audio system in which speakers are three-dimensionally
arranged, it is possible to collect sound with a smaller number of microphones than the speaker
arrangement at the time of reproduction.
[0017]
It is explanatory drawing of 22.2ch sound system.
(A), (b), (c) is the schematic of the sound collection microphone of one Example by this invention.
The sound signal of the original sound field collected in a plane consisting of one main
microphone and an auxiliary microphone when the sound collection microphone and sound
collection and reproduction apparatus of one embodiment according to the present invention is
applied to a 22.2 ch sound system FIG. 16 is a diagram showing an example of the configuration
of a sound collection system for converting into an audio signal of FIG.
It is a figure which shows the characteristic example of the narrow directivity of the main
microphone part in the sound collection microphone of one Example by this invention.
It is a figure which shows the frequency characteristic example of the main microphone part in
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the sound collection microphone of one Example by this invention.
[0018]
Hereinafter, a sound collecting microphone and a sound collecting and reproducing apparatus
according to an embodiment of the present invention will be described.
[0019]
The case where the sound collection microphone and the sound collection and reproduction
apparatus of this embodiment are applied to a 22.2 ch sound reproduction system will be
described.
FIG. 1 is an explanatory view of a 22.2 ch sound system.
The 22.2ch acoustic system is based on 8 channels (FL, FC, FR, SiR, BR, BC, BL, SiL) in the middle
layer in the horizontal plane, and is arranged in the upper layer in the same horizontal plane as
the channels of the middle layer. Eight channels (TpL, TpC, TpR, TpSiR, TpBR, TpBC, TpBL, TpSiL)
are installed, and in the center of the upper layer, one TpC channel is installed.
In addition, FLc and FRc for in-screen localization reinforcement as a lower layer, BtFL, BtFC and
BtFR three channels for reinforcement at the lower part of the screen, and LFE1 and LFE2 for
low-frequency reproduction (also called Low Frequency Effect). I own a channel.
[0020]
In such a 22.2ch sound reproduction system, for example, for collecting sound in the original
sound field where the installation place of the microphone such as an acoustic hall is limited, the
directivity axes are directed in each direction using the microphones for the number of
reproduction channels, The sound is collected by individual microphones in which the width of
the directional beam does not overlap with the adjacent channel, and the sound collection system
has become large in the prior art.
[0021]
Therefore, the sound collection microphone of the present embodiment has a configuration in
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which the number of microphones required for sound collection is reduced, and the sound
collection and reproduction apparatus of the present embodiment has a smaller number of
acoustic signals than the number of reproduction channels collected by the sound collection
microphone. The reproduction is performed by adjusting the amplitude ratio of the sound signal
of the number corresponding to the number of reproduction channels.
[0022]
FIG. 2 is a schematic view of a sound collection microphone according to an embodiment of the
present invention.
Fig.2 (a) is a top view of the sound collection microphone of an Example, FIG.2 (b) is a side view
of the sound collection microphone of an Example, FIG.2 (c) is a sound collection of an Example.
It is a bird's-eye view (perspective view) of a microphone.
[0023]
As shown in FIG. 2, in the sound pickup microphone 10 of this embodiment, a main microphone
unit including a plurality of directional microphones whose directivity is directed radially from a
central point on a two-dimensional plane, and upper and lower arrival directions are determined.
For this purpose, the auxiliary microphone unit (Mc-TpC) is located at a predetermined distance
on the normal line from the central point with respect to the two-dimensional plane constituting
the main microphone unit.
More specifically, the main microphone unit has a narrow directivity in at least eight directions
disposed equiangularly with respect to the central point in a two-dimensional plane, and the
number of channels smaller than the number of reproduction channels (Mc-FL, Mc It consists of
a plurality of directional microphones picked up with FC, Mc-FR, Mc-SiR, Mc-BR, Mc-BC, Mc-BL,
Mc-SiL).
[0024]
In the 22.2ch sound reproduction system, the middle layer and the upper layer 8ch are the bases
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of the speaker arrangement described in FIG. 1, so here, the sound collection microphone 10 of
this embodiment is used for the sake of explanation. A point A located at the center of the plane
of the middle layer 8 channel shown in FIG. 1 and on the normal to the plane of the upper layer
center 1 channel to the middle layer 8 channel is set as the center point of the sound collection
microphone 10 It is assumed that sounds of layer 8 channels, upper layer 8 channels and upper
layer center 1 channel are picked up.
In addition, since the environment of the sound field which is actually picked up is picked up on
the assumption that the case of reproducing with the 22.2ch sound reproduction system, the
installation position with respect to the original sound field of the sound pickup microphone 10
of this embodiment is It can be determined appropriately.
[0025]
More specifically, in a multi-channel sound reproduction system such as 22.2 ch, it is considered
desirable to reproduce the sound in each direction that arrives at one point in the original sound
field from the corresponding speaker in the reproduction sound field.
For this purpose, it is desirable that a directional microphone whose main axis is the direction of
each speaker of the reproduction sound field be installed in the original sound field and that the
directivity of each microphone be narrow directivity so that they do not overlap each other.
Ideally, it would be desirable to install as many narrow directional microphones as there are
loudspeakers, but if the directional beams do not overlap each other, the more directional
channels there are, the more directional beams. In general, the size of the microphone is
increased. The present invention can solve the problem of an increase in the size of the
microphone and an increase in the number when applied to a multi-channel sound system.
[0026]
In addition, it is known that human ears have only two right and left ears in the horizontal plane,
and thereby, the horizontal resolution in the horizontal plane is superior to that in the vertical
direction. Therefore, in the present embodiment, as the main microphone unit, narrow directional
microphones (Mc-FL, Mc-FC, Mc-FR, Mc-SiR, Mc) corresponding to eight channels in a plane
(horizontal plane in this example) are used. -BR, Mc-BC, Mc-BL, Mc-SiL) as an auxiliary
microphone unit, the auxiliary microphone (Mc-TpC) at a position separated by a fixed distance
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in the vertical direction from the plane (in this example, the horizontal plane) Set up one channel.
[0027]
Each narrow directional microphone in the main microphone unit directs the directivity of
collecting the sound in the middle direction between the middle layer speaker and the upper
layer speaker in order to cope with incoming sound having horizontal angles of the microphone
and different elevation angles. It shall be. For example, as a narrow directional microphone, there
are microphones having, for example, the directivity characteristic of FIG. 4 and the frequency
characteristic as shown in FIG. 5 (see, for example, patent publication 6-233371). In this
embodiment, it is possible to use a narrow directional microphone in which a band in which a
half value width of -6 dB or less can be obtained in 45 directions which are adjacent channel
positions is 1 kHz or more.
[0028]
In addition, since the auxiliary microphone unit needs to cover both the arrival direction of the
plane that constitutes the main microphone unit and the arrival direction for determination of the
upper and lower directions of arrival, it should be an omnidirectional microphone. Although
preferred, it is also possible to use a unidirectional microphone whose main axis is directed in the
upper arrival direction, if the influence of sound reflection from the lower arrival direction
adversely affects the direction estimation. In this case, the auxiliary microphone unit has
directivity capable of picking up sound in both of the arrival direction of the sound in the plane
constituting the main microphone unit and the arrival direction of the sound from the upper side
with respect to the plane, and the upper arrival direction It is more preferable that the sound
collection sensitivity of is 20 dB or more higher than the sound collection sensitivity in the lower
arrival direction.
[0029]
FIG. 3 shows an acoustic signal of an original sound field collected in a plane consisting of one
main microphone and an auxiliary microphone when the sound collection microphone and sound
collection and reproduction apparatus of one embodiment according to the present invention is
applied to a 22.2 ch sound system. 1 is a diagram showing an example of the configuration of a
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sound collection system for converting a sound signal into an acoustic signal of a reproduction
sound field. The sound pickup microphone 10 picks up the sound of the original sound field.
[0030]
The sound pickup / reproduction device 20 receives an acoustic signal from the picked up main
microphone unit (for example, Mc-SiL) and an acoustic signal from the auxiliary microphone unit
(Mc-TpC), and outputs the sound signal from the main microphone unit. A direction in which
information on the direction of arrival of sound (information in the height direction) is
determined by measuring the cross-correlation function between the sound signal and the sound
signal output from the auxiliary microphone unit and determining the time difference between
the sound signals. The amplitude of the acoustic signal from the main microphone unit (for
example, Mc-SiL) collected based on the information on the direction of arrival of the sound
determined by the determination unit 201 and the direction determination unit 201 is adjusted,
and And an amplitude ratio adjusting unit 202 which generates an acoustic signal of a
reproduced sound field by assigning and synthesizing the acoustic signal for each channel.
[0031]
Specifically, with reference to FIG. 3, among the main microphones in the horizontal plane of the
intermediate layer, description will be given focusing on Mc-SiL.
The sound component collected by Mc-SiL and the sound component collected by the auxiliary
microphone Mc-TpC are input to the direction determination unit 201. The direction
determination unit 201 can obtain information on the direction of arrival of the sound
(information on the height direction) by comparing the outputs of the main microphone Mc-SiL
and the auxiliary microphone Mc-TpC in the horizontal plane of the intermediate layer,
Information on the direction of arrival of the sound is sent to the amplitude ratio adjusting unit
202.
[0032]
Here, although there are a plurality of methods for obtaining information on the direction of
arrival of the sound (information on the direction of height), here, a method for obtaining a
correlation function of both signals will be described.
[0033]
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<img class = "EMIRef" id = "205147885-000003" />
[0034]
[0035]
From the equation (1), the arrival direction can be obtained from τd obtained by calculation of
the correlation function.
[0036]
[0037]
Note that the direction determination unit 201 uses the auxiliary microphone Mc-TpC used for
determination when determining from which direction the sound component input to the main
microphone Mc-SiL in the horizontal plane of the intermediate layer is mainly a component.
Although the sound in each direction in the horizontal plane of the intermediate layer is input,
since the main microphone has narrow directivity, the influence of sounds other than the
direction of interest can be suppressed to a small degree in the determination of the sound
arrival direction.
[0038]
From equation (1), it is considered that when the distance d is too small, the time difference to be
detected becomes small and the accuracy is deteriorated, but when the distance d is made large,
the overall size of the sound collection microphone 10 increases and the sound collection
Unfavorable from the viewpoint of mobility as a system.
Therefore, when the sound comes from the 45 degree direction, which is intermediate between
the main microphone unit and the auxiliary microphone unit, it can be considered as the
minimum value that can accurately detect the time difference between the sounds detected by
the main microphone unit and the auxiliary microphone unit. Considering a value that can obtain
a time difference of about 0.5 ms, it is calculated from equation (1) that d ≒ 24 cm.
This value is a value that can be sufficiently realized as the size of a portable microphone.
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It should be noted that detection of the time difference itself is possible even with a time
difference of 1 ms or less, and it is considered possible to further reduce the distance d, but when
the sampling frequency of sound is 48 kHz, the time per sample is about 20 μs Therefore,
although the time difference is detectable, the resolution of the detectable time difference is
reduced, and as a result, the resolution of the estimated angle is reduced, the distance d is
determined in consideration of the required angle resolution.
Therefore, it is preferable to define the lower limit value of the distance d in accordance with the
sampling frequency of sound representing the resolution of the direction of arrival determination
of sound in the vertical direction. More specifically, the distance d is preferably 12 cm or more. It
is.
[0039]
The amplitude ratio adjustment unit 202 adjusts the sound collected by the main microphone
Mc-SiL with an amplitude ratio based on the information (information in the height direction) of
the arrival direction of the sound obtained from the direction determination unit 201, An
acoustic signal for reproduction is generated from both the main microphone and the speaker
Sp-SiL in the corresponding direction and the speaker Sp-TpSiL immediately above it.
When it is determined that the direction of arrival is above Sp-TpSiL, an appropriate amplitude
ratio is given between Sp-TpSiL and Sp-TpC to reproduce sound.
The amplitude ratio adjustment unit 202 also obtains information on the direction of arrival of
sound with respect to the acoustic signal of the original sound field obtained by similarly
collecting sound in the seven directions in the plane of the main microphone other than Mc-SiL
(height direction Information is adjusted with an amplitude ratio based on the information to
generate an acoustic signal of a reproduced sound field. The acoustic signal of the reproduction
sound field thus obtained can efficiently collect the sound of the reproduction sound field
corresponding to the three-dimensional speaker arrangement by the two-dimensional
arrangement of the main microphone unit .
[0040]
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In the above embodiment, the direction determining unit 201 has been described as an example
of performing processing of distributing the amplitude ratio of the acoustic signal collected to the
upper and lower speakers in the direction corresponding to the main microphone using sound in
the entire band. It is also possible to perform this process for each frequency band.
[0041]
Furthermore, the direction determination of the direction determination unit 201 needs to follow
the change in the direction of arrival of the sound, but in order to avoid an unnatural feeling of
movement of the sound, a change in the parameter that determines the amplitude ratio of the
sound should have a time constant. It is also possible to loosen the movement.
[0042]
In the above description, although the description has been given focusing on one main
microphone Mc-SiL in the horizontal plane, the same processing is performed in seven directions
other than Mc-SiL to generate a synthesized acoustic signal. It goes without saying that you can
[0043]
Further, in the present embodiment, the case has been described in which the acoustic signal of
the reproduction sound field is generated for two layers of eight channels and nine channels in
the upper layer in the horizontal direction of the intermediate layer. It is applicable also when the
number of layers of direction differs.
[0044]
According to the present invention, since it is possible to collect sound with a smaller number of
microphones than the number of reproduction channels, it is useful for a multi-channel sound
system in which speakers are three-dimensionally arranged.
[0045]
DESCRIPTION OF SYMBOLS 10 sound collection microphone 20 sound collection reproducing
apparatus 201 direction discrimination | determination part 202 amplitude ratio adjustment part
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