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JP2009100354

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DESCRIPTION JP2009100354
The present invention provides an acoustic reproduction device for reproducing a sound field
including radiation directivity. SOLUTION: From the output signals of M systems of M
microphone groups directed to the sounding body from different directions, N speaker groups
having radiation directivity in different directions, and M systems of the microphone groups. The
audio processing unit has a speaker processing unit that generates speaker driving signals of N
systems for the speaker group, and the directivity of sound emitted from the sounding body for
each frequency is reproduced by the speaker group. More specifically, for the transfer function G
of N speaker groups obtained as a matrix, the inverse matrix H at the position of the microphone
group is found from the measured value of the transfer function G, and the sound processing unit
The input acoustic signal is arithmetically processed using the inverse matrix H and then output
as an acoustic signal of N systems, and the output of the N systems of the acoustic processing
unit is applied to the speakers of the speaker group to perform acoustics. Radiate. [Selected
figure] Figure 2
Omnidirectional frequency directional sound system
[0001]
The present invention relates to an omnidirectional frequency-oriented acoustic device for
inputting sound from a sound emitting body having radiation directivity and accurately
reproducing a sound field at the time of input.
[0002]
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1
As shown in FIG. 1, the frequency dependence of the radiation directivity of an actual speaker,
such as a violin, emits sounds of various frequencies in different directions with different
intensities.
As can be seen from FIG. 1, for example, in the horizontal plane, the radiation directivity of 300
Hz and 350 Hz is completely different. Also, it can be seen that the radiation directivity differs
similarly for the upper and lower. The same applies to other musical instruments, and the sound
source is not a point source and is not isotropic. In the stereo system and the omnidirectional
speaker technology so far, since it is considered as an isotropic point sound source, it is not
possible to provide a more natural and presence sound by providing frequency radiation
directivity. In order to provide a realistic sound, it is necessary to reproduce the radiation
directivity for each frequency of each sounding body in all directions.
[0003]
The conventional stereo type or multi-channel type sound device uses a loudspeaker having only
a fixed radiation directivity, and emits sound only in a specific direction. Although it is possible to
provide a fixed sound image to the viewer at the listening position to be caused to turn, it is not
possible to reproduce the directivity for each frequency.
[0004]
Further, Patent Document 1 discloses an electro-acoustic transducer which can obtain a good
point source with nondirectionality.
This is an omni-directional speaker device that emits an acoustic signal in all directions, and an
electro-acoustic transducer belonging to the breathing sphere system, and can generate spherical
wavefront sound. However, since this is a technique aimed at omnidirectionality, the abovementioned frequency directivity can not be provided.
[0005]
On the other hand, techniques have also been developed for the purpose of providing a realistic
sound by performing a speaker array device using a large number of speakers and acoustic
processing such as wavefront synthesis and an inverse filter. However, all these techniques do
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2
not have radiation directivity, and it is possible to give an accurate sound image only to a specific
viewer in a narrow listening position, and realize different frequency radiation characteristics.
The process is fundamentally different from the object of the present invention, which ideally
provides a sense of reality by having no optimal listening area.
[0006]
For example, Patent Document 2 discloses a recording and reproduction system using a method
of recording for reproduction by a plurality of loudspeakers or processing a sound for
reproduction by a plurality of loudspeakers. This is intended to provide a recording means for
reproduction via two (or more) loudspeakers, the reproduction of the recording by the
loudspeakers and the signal reproduced at the listener's intended position. , Using techniques to
minimize the error between the desired signal at the intended location.
[0007]
In Patent Document 2, inverse filter calculation using a head-related transfer function is
performed to provide a specific viewer with a sound image center. On the other hand, in the
present invention, using the transfer function using the directional characteristic coefficient of
the speaker without using the head transfer function makes a big difference.
[0008]
Patent Document 3 discloses a recording / reproducing apparatus capable of reproducing the
directivity of sound emitted from a sound source. This is because the multitrack recorder records
each waveform signal output from the plurality of microphones at the time of recording, and
generates sound from the plurality of speakers disposed corresponding to the arrangement
position of the microphones at the time of reproduction.
[0009]
In this case, a speaker for each microphone position is required. For example, in the case of a
large sound source such as a piano, the speaker is also large and it is difficult to use it widely.
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Moreover, in Patent Document 3, the Huygens principle is applied as it is, but in the present
invention, the size of the speaker system can be reduced even in the case of reproduction of the
sound of a large instrument by performing the convolution inverse operation on the speaker. Are
different. JP-A-2006-333441 JP-A-10-509565 JP-A-5-276592
[0010]
The present invention is a speaker apparatus having a plurality of speakers so as to have
different frequency radiation directivity, and calculates an acoustic signal to be reproduced,
thereby generating an acoustic signal matched to the size and overall shape of each speaker
Purpose is to provide realistic sound regardless of the viewer's position.
[0011]
According to the present invention, since it is possible to emit an acoustic signal having different
frequency radiation directivity emitted by the musical instrument, it is possible to provide an
original sound of the sounding body, so that a natural and more natural sound can be given to
anyone. Can be provided.
Further, the number of speakers to be used and the whole of the speakers can be arbitrarily
shaped.
[0012]
The present invention is an omnidirectional frequency directional acoustic device that
reproduces the sound emitted by a sounding body by a speaker group using a plurality of
speakers, including directivity of each frequency, from different directions around the sounding
body. A microphone group including M microphones directed to a sounding body, an acoustic
processing unit that performs arithmetic processing of an acoustic signal input from the
microphone group using a predetermined arithmetic processing method, and an acoustic signal
subjected to arithmetic processing And a speaker group including N (<M) speakers for converting
sound into sound.
[0013]
More specifically, the present invention provides M microphone groups directed from different
directions to the sounding body, N speaker groups having radiation directivity in different
directions, and M systems of the microphone groups. The acoustic processing unit for creating N
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speaker drive signals for the speaker group from the output signal, and for the transfer function
G of the N speaker groups obtained as a matrix, from the measurement value of the transfer
function G, the microphone group Find the inverse matrix H at the following position, the
acoustic processor performs arithmetic processing on the acoustic signal input from the
microphone group using the inverse matrix H, and outputs it as N series of acoustic signals, and
the acoustic The output of N systems of the processing unit is applied to each of the speakers of
the speaker group to emit sound.
[0014]
The speaker includes an amplifier, a transducer for converting an amplified electric signal to
mechanical vibration, and a diaphragm for converting mechanical vibration to sound, and the
number of the transducers and the diaphragm is three or more. And at least one of the
diaphragms emits sound in different directions.
This is because it is desirable that the wavefront of the sound emitted from the speaker not be
close to a plane.
[0015]
Let ω be the angular frequency, let X i (ω) be the sound signal recorded by the i-th microphone
of the microphone group, let Y j (ω) be the sound signal reproduced by the j-th speaker of the
speaker group, and Assuming that the elements of the matrix are H ij (ω), the acoustic signal Y j
(ω) is obtained according to the following equation;
[0016]
Furthermore, in the case where there is only one input acoustic signal, if there is the abovementioned inverse matrix obtained in advance, the acoustic signal emitted from the speaker
group is calculated according to the above equation (1).
[0017]
Since the processing time in the sound processing unit is long, it is desirable that the recording
be performed after the output of the sound processing unit.
[0018]
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Hereinafter, embodiments of the present invention will be described in detail.
First, FIG. 2 shows a system outline of the embodiment.
M microphones 2-1 to 2-M three-dimensionally arranged around a sound source 1, an acoustic
input unit 3 for inputting an acoustoelectric signal from the microphone, and arithmetic
processing of the acoustoelectric signal input The sound processing unit 4, the sound output unit
4 for outputting the calculated sound signal, the recorder 5 for recording the signal from the
sound output unit 4, and the speaker 6 for converting the output of the sound output unit 4 or
the recorder 5 into a sound signal It is comprised by -1 to 6-N and each speaker which drives
each speaker.
[0019]
The signal supplied to the speaker can be obtained as follows.
It is assumed that an acoustic signal X i (ω) is recorded by the ith microphone of M
microphones.
Here, in general, ω is a vector consisting of time, position, and frequency, but since it specifies
the microphone to be used by the subscript, it can be regarded as a function of frequency. At this
time, the acoustic electric signal Y j (ω) to be reproduced by the j-th speaker of the N installed
speakers is the above-described filter by the inverse filter H ij (ω) obtained from the directivity
coefficient of the speaker and the impulse response. It can be obtained by the convolution
operation according to Equation 1.
[0020]
Assuming that an acoustic electrical signal recorded by M microphones is to be subjected to the
operation of Equation 1, and a filter for providing reproduced sound using N speakers is a
speaker directivity characteristic and an impulse response Apply the inverse filter design method
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using, as the transfer function obtained from Thereby, the provided sound X ′ (ω) can be
represented by Here, to match the input signal with the reproduced sound, that is, to set X ′ (ω)
= X (ω), H (ω) can be obtained by obtaining the inverse matrix of G (ω). Become.
[0021]
In the case of this embodiment, when the impulse response of each speaker constituting the
speaker group is a matrix S, its element frequency characteristic S ji (ω) and the speaker
directivity characteristic of the j-th speaker are D j (ω Then, by obtaining the inverse operation
of G (ω), different frequency radiation directivity can be provided without limiting the position
and number of speakers.
[0022]
Although it is desirable to realize the coincidence between X '(ω) and X (ω) above in the entire
space, it is impossible. Therefore, in the present invention, the input signal and the reproduced
sound are matched at the position of the microphone. Let
That is, by setting X ′ (ω) = X (ω) at the position of the microphone, it is possible to
approximately match in the entire space. By determining the position in this manner, ω in G (ω)
or H (ω) is a function of frequency and has no position coordinates.
[0023]
Further, G (ω) under the condition X ′ (ω) = X (ω) can be obtained as follows. 1) If the
microphone group for inputting X (ω) in FIG. 9 (a) and the microphone group for measuring G
(ω) in FIG. 9 (b) are the same including the arrangement, the obtained G ( ω) can be used as it is.
2) If the microphone group for inputting X (ω) in FIG. 10 (a) is different from the microphone
group for measuring G (ω) in FIG. The function form of ω) can be obtained, and then the value
of the element of G (ω) at each microphone position of the microphone group to which X (ω) is
input can be obtained. At this time, in order to make the function form of G (ω) accurate, it is
desirable that the number of microphones used be more than the number of microphone groups
that input X (ω). However, in this case, it is necessary to correct the frequency characteristics of
each microphone.
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[0024]
Also, methods for actually determining the frequency characteristics of G (ω) are already well
known: 1) applying a step-like signal to a sound source and inputting its output from a speaker
group with a microphone to perform frequency analysis It can be determined by 2) It can also be
determined by applying signals of various frequencies to the sound source and detecting the
output intensity with a microphone to obtain input / output characteristics for each frequency.
[0025]
FIG. 3 is an overhead view of the speaker apparatus according to the first embodiment which is
the simplest embodiment of the present invention. Although the viewer's position is only in the
direction in which the speakers are arranged, it is possible to provide a more realistic sound than
in the conventional type by realizing different frequency radiation directivity. In the case of using
the speaker device of the first embodiment, since it is not necessary to consider diffraction from
the back side, G ji (ω) is implemented by a general inverse filter design, and the inverse matrix
calculation thereof is performed on sufficiently large discrete frequencies. It can be implemented
using the least squares method in the discrete Fourier transform frequency domain.
[0026]
Here, the speaker includes an amplifier, a transducer for converting an amplified electric signal
to mechanical vibration, and a diaphragm for converting mechanical vibration to sound, and for
example, a normal loudspeaker Good. In addition, a speaker provided with a plurality of
diaphragms can be used. In this case, the number of transducers and the number of diaphragms
are three or more, and at least one of the diaphragms emits sound in different directions. This is
because it is desirable that the wavefront of the sound emitted from the speaker not be close to a
plane.
[0027]
FIG. 4 is an overhead view of the speaker device of the second embodiment. In the case of using
the speaker device according to the second embodiment, it is necessary to design the speaker
directivity characteristic D j (ω) in consideration of the diffraction of the speaker device.
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However, in the second embodiment, a sufficient number of speaker devices are provided around
the speaker device. By providing measurement points so as to surround the speaker device, G ji
(ω) including all of the diffraction and the speaker directivity was designed. The inverse matrix
calculation of G ji (ω) is performed by the same calculation method as the inverse matrix
calculation of the first embodiment.
[0028]
In the most versatile embodiment 2 of the present invention, it is considered that the larger
number of speakers in the speaker device is more effective, but in view of productivity and
spreadability, as shown in FIG. , A speaker apparatus in which 26 loudspeakers are mounted on a
spherical housing. These arrangements are arranged such that the centers of all three speakers
are at the same distance.
[0029]
(1) The signal input from the microphone is transmitted from the sound input unit to the sound
processing unit, (2) the sound processing unit performs processing for matching the acoustic
characteristics, and (3) the signal is transmitted to the sound output unit 4) Each acoustic signal
from the acoustic transmission unit is amplified by an amplifier, and (5) the above 26 speakers
reproduce the sound. When recording a signal input from a microphone, it is desirable to place
many microphones in the direction in which the radiation characteristic is prominent to increase
the accuracy of the recorded signal. At this time, the sound signals recorded by the 30
microphones are subjected to calculation using the number 1 incorporating the position of the
microphone and the directivity characteristic information of the speaker device as described
above, and then each of the 26 speakers described above Distribute to
[0030]
For example, the recorded signal of the first microphone is distributed to 26 speakers, and the
sound is synthesized by all 26 speakers at the first microphone position. This is done for all 30
microphones, and the same sound as the final recorded state is synthesized.
[0031]
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FIG. 5 is a diagram of measurement of frequency sound pressure distribution in a horizontal
plane when the acoustic guitar is reproduced. 0 degree is the first speaker, 45 degrees is the
eighth speaker position. As can be seen from FIG. 5, the sound pressure distribution for each
frequency of the reproduced sound is not uniform, and it can be seen that the frequency has
directivity.
[0032]
FIG. 6 is an overhead view of the speaker device of the third embodiment. The arrangement of
this example is based on the arrangement of speakers directed to the viewer on a linear axis and
the outward speakers at both ends of the axis, and various directions around the axis. Six
speakers facing the are arranged. In the case of using the speaker device of the third
embodiment, as in the second embodiment, a sufficient number of measurement points are
provided to surround the speaker device, and design and inverse matrix calculation of G ji (ω)
are performed. Example 3 shows an arrangement suitable for reproducing a violin, but if
individual speaker drive devices are arbitrarily arranged and G ji (ω) is determined for each
arrangement, more diverse sounds can be provided. It becomes possible. However, if the spacing
between the speakers is too large, an error occurs in the calculation and the sound image is
blurred, so the arrangement can not be infinite. In general, it is desirable to keep the speaker
spacing within 50 cm in order to correlate the wavefronts.
[0033]
As described above, even when recording can not be substantially performed using a plurality of
microphones, it is possible to generate a realistic sound from one piece of recording information
by acoustic processing. This is because the frequency sound pressure distribution is unique to
each instrument. That is, even in the case of recording using a single microphone, if the direction
and distance of the position of the microphone viewed from the musical instrument are
determined, sounds in other directions can be reproduced based on the recording. Also, it is clear
that the direction and distance of the microphone position as seen from the above-mentioned
instrument can be specified by analyzing the spectrum of the recording.
[0034]
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For this reason, in order to perform realistic reproduction by recording using a single
microphone of the sound of an instrument whose frequency sound pressure distribution is clear,
the following procedure may be followed. (1) Conduct spectrum analysis to estimate the
positional relationship between the musical instrument and the microphone. If this positional
relationship is apparent in advance, this procedure can be omitted. (2) The positions of a plurality
of microphones are set so as to three-dimensionally surround the above-described musical
instrument. (3) According to the above-described frequency sound pressure distribution, the
above-mentioned recording is converted into acoustic signals at the positions of the abovementioned plurality of microphones. (4) The above recorded and converted acoustic signal is
applied to any one of the above-described first to third embodiments.
[0035]
As an example of the frequency sound pressure distribution of a musical instrument, FIGS. 7 and
8 show the frequency directivity characteristics of a violin. FIG. 7 shows a horizontal sound
pressure distribution of a violin, and FIG. 8 shows a vertical surface sound pressure distribution.
From this figure, it can be seen that the spectral distribution in each direction is characterized
and can be used to estimate the positional relationship between the instrument and the
microphone. Although FIGS. 7 and 8 show distributions for three types of frequencies, it is
apparent that using natural distributions in more detailed frequency divisions results in natural
acoustic signals.
[0036]
In order to obtain a more accurate solution and provide high quality sound, the calculation
method of Example 3 is used for the input signal X '(ω). Further, for the acoustic processing in
the discrete Fourier transform, a more natural sound with a sense of presence can be provided by
using an analysis method using the cepstrum method or a complex system Fourier transform.
[0037]
Although a normal loudspeaker unit is used in the description of the embodiment of the present
invention, it is apparent that other loudspeaker units can be used. For example, even if it
comprises a flat panel speaker etc., the same effect can be acquired.
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[0038]
It is a figure which shows the example of the frequency dependence of radiation directivity of a
violin. It is a figure which shows the outline of the omnidirectional frequency directivity acoustic
apparatus of this invention. FIG. 2 is a view showing an overhead view of the speaker device of
Example 1; It is a figure which shows the bird's-eye view of the speaker apparatus of Example 2.
FIG. It is the figure which measured the frequency sound pressure distribution in the horizontal
surface when reproducing an acoustic guitar. FIG. 10 is a view showing an overhead view of the
speaker device of Example 3; It is a figure which shows the horizontal surface sound pressure
distribution of a violin. It is a figure which shows the perpendicular surface sound pressure
distribution of a violin. (A) It is a figure which shows the case where arrangement ¦ positioning of
the microphone group which inputs X ((omega)), and the microphone which measures (b) G
((omega)) is the same. (A) It is a figure which shows the case where the microphone group which
inputs X ((omega)), and the microphone which measures G ((omega)) differ in arrangement ¦
positioning.
Explanation of sign
[0039]
1 microphone group 2 speaker group 3 sound processing unit
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