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JP2016136656

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DESCRIPTION JP2016136656
Abstract: To provide a novel speaker system for generating a local sound field. According to the
present invention, there is provided a speaker system including a speaker array in which a
plurality of sub-speakers are dispersedly arranged on an array surface, and a signal processing
unit specific to each sub-speaker, and an input audio signal. And a main sound volume setting
unit for setting a main sound volume to each of the signal processing units, each of the signal
processing units having a predetermined main sound volume that has been set. A signal
amplification unit for amplifying an audio signal input from the signal distribution unit with an
amplification factor corresponding to a sub volume multiplied by a volume weighting coefficient,
and a phase of the audio signal amplified by the signal amplification unit as necessary A speaker
system is provided that includes a phase correction unit for performing a 180 degree delay
correction. [Selected figure] Figure 10
Speaker system and method for generating a local sound field
[0001]
The present invention relates to a speaker system, and more particularly to a speaker system for
generating a local sound field.
[0002]
The sound emitted from the speaker may be perceived as noise by those who do not need it.
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For example, the alarm sound of a level crossing is voice information that is important for people
who want to cross a level crossing or a car, but becomes an intolerable noise for residents living
near the level crossing. The sound of television and audio in communal residences such as
apartments and apartments is also true. That is, in many cases, it is desirable to make the sound
emitted from the speaker not be propagated as far as possible from the speaker.
[0003]
In this regard, various researches have been made on a speaker system for generating a so-called
"local sound field" in which sound maintains a large sound pressure only in a specific area and
the sound pressure sharply attenuates outside the area. There is. For example, Non-Patent
Document 1 discloses a speaker system that reproduces an evanescent wave having steep
distance attenuation characteristics using a speaker array in which bi-directional speakers are
arranged on a plane in order to generate a local sound field.
[0004]
On the other hand, Non-Patent Document 2 discloses a cancellation mechanism of vibration
radiation generated when a rectangular flat plate is vibrated.
[0005]
Hiroaki Ito, Kenichi Furuya, Yoichi Haneda, A Study of Evanescent Wave Reproduction Method
Using Flat Speaker Array, Technical Report of IEICE, Vol.131 (2011), pp29-34 Nobuo Tanaka,
Yoshihiro Kikushima, Masaharu Kuroda, Vibration Study on control of radiated sound,
Proceedings of the Japan Society of Mechanical Engineers (ed. C), Vol. 57, 537 (1991-5), pp. 94101
[0006]
The present invention has been made in view of the problems in the prior art, and an object of
the present invention is to provide a novel speaker system for generating a local sound field.
[0007]
The present inventor is keenly examining a new technique for localizing the sound field, paying
attention to the cancellation phenomenon of sound appearing on a rectangular plate (Non-Patent
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Document 2), and using the speaker array as the vibration mode of the rectangular plate. By
simulating, I got the idea that a local sound field of arbitrary frequency could be generated.
Then, from this idea, the following configuration was conceived, leading to the present invention.
[0008]
That is, according to the present invention, there is provided a speaker system including a
speaker array in which a plurality of sub-speakers are dispersedly arranged on the array surface,
and a signal processing unit unique to each sub-speaker and an input audio signal A signal
distribution unit for outputting to the signal processing unit, and a main volume setting unit for
setting a main volume to each of the signal processing units, each of the signal processing units
including an audio signal input from the signal distribution unit A signal amplification unit for
amplification; and a phase correction unit for performing a correction to delay the phase of the
audio signal amplified by the signal amplification unit by 180 degrees, and each of the signal
amplification units includes the array plane A value obtained by normalizing the representative
value of the amplitude of the vibration area of the sub-speaker corresponding to the vibration
plane of the sub-speaker when the VVC distribution is excited in the flat plate of the same size is
set as a volume weighting coefficient. According to the displacement direction of the vibration
area of the flat plate corresponding to the vibration plane of the sub-speaker in the case where
the VVC distribution is excited in the flat plate, one of the two groups related to the VVC
distribution is The signal amplification unit amplifies an audio signal input at an amplification
factor according to a sub-volume obtained by multiplying the set main volume by the volume
weighting coefficient, and the phase correction unit A speaker system is provided, which
performs the correction of the audio signal only when is set.
[0009]
As mentioned above, the present invention provides a novel speaker system for generating a
local sound field.
[0010]
The figure which shows the relationship between the acoustic radiation power at the time of
vibrating a rectangular aluminum flat plate and volume speed, and a vibration frequency.
The figure which shows vibration displacement distribution and radiation sound pressure
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distribution at the time of vibrating a rectangular aluminum flat plate.
(1,1)The figure which shows the numerical analysis result of the time average flow rate of the
energy of the sine wave sound of anti-resonance frequency 77 Hz in + (1, 3) VVC distribution.
BRIEF DESCRIPTION OF THE DRAWINGS The external view of the speaker system of this
embodiment.
FIG. 7 is a flow chart illustrating a method of generating a local sound field using a speaker array.
The figure which shows the array surface of the speaker system of this embodiment, and a flat
plate of the same dimension as this. The conceptual diagram for demonstrating the method to
define a volume weighting coefficient and to determine a group. The figure which shows the
histogram of the volume weighting coefficient defined about the sub speaker of the speaker
system of this embodiment. The figure which shows the radiation sound pressure distribution of
the sine wave sound (frequency 100 Hz) of the speaker system of this embodiment. The figure
which shows the mounting structure of the speaker system of this embodiment. The figure which
shows the radiation sound pressure distribution of the sine wave sound (frequency 400 Hz) of
the speaker system of this embodiment. The figure which shows the radiation sound pressure
distribution of the sine wave sound (frequency 400 Hz, 600 Hz, 800 Hz) of the speaker system of
this embodiment. The figure which shows the vibration displacement distribution of ten types of
VVC distributions excited to a rectangular aluminum flat plate. The figure which shows the
frequency characteristic of the acoustic radiation efficiency of ten types of VVC distributions
excited to a rectangular aluminum flat plate. The figure which shows the mounting structure of
the speaker system of this embodiment. The figure which shows the frequency characteristic of
the acoustic radiation power of three types of VVC distribution. The figure which shows the
mounting structure of the speaker system of this embodiment.
[0011]
Hereinafter, the present invention will be described with the embodiment shown in the drawings,
but the present invention is not limited to the embodiments shown in the drawings. In the
drawings referred to below, the same reference numerals are used for the common elements, and
the description thereof will be omitted as appropriate.
[0012]
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First, the basic concept of the speaker system of the present invention will be described.
[0013]
Fig. 1 (a) shows that when a center of a rectangular aluminum flat plate (0.575 m x 0.945 m x 2
mm, loss coefficient = = 0.001) is simply supported and the central point is vibrated, The
relationship between the acoustic radiation power and the volume velocity of the plate (the value
obtained by integrating the vibration velocity over the entire surface of the plate) and the
excitation frequency (the numerical analysis result) is shown.
As shown in FIG. 1 (a), in the vibration of a flat plate, a peak of acoustic radiation power is
observed at an excitation frequency that corresponds to a plurality of natural frequencies
possessed by the flat plate. Both the acoustic radiation power and the volume velocity are
minimized at the excitation frequency after the second order peak.
[0014]
Subsequently, FIG. 1 (b) shows the acoustic radiation power emitted from the flat plate and the
volume velocity of the flat plate when only the (1, 1) mode and the (1, 3) mode are excited in the
flat plate described above. The relationship between the vibration frequency and the excitation
frequency (numerical analysis result) is shown. In FIG. 1 (b), the acoustic radiation power is at an
excitation frequency of 77 Hz after the first peak showing the (1, 1) mode resonance and the
second peak showing the (1, 3) mode resonance. It can be seen that both and the volume velocity
are minimized. From this, it is considered that the phenomenon that both the acoustic radiation
power and the volume velocity are minimized in the vibration of the flat plate is due to the
coupling of two different odd order modes. In the following, this phenomenon is referred to as
"anti-resonance", the excitation frequency of the plate exhibiting anti-resonance is referred to as
"anti-resonance frequency", and the vibration distribution in which two different odd-order
vibration modes are coupled is referred to as "VVC It is called a distribution (VVC: Volume
Velocity Cancelled).
[0015]
Next, the attenuation of sound when only a VVC distribution is excited on a flat plate will be
discussed.
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[0016]
FIG. 2 (a) shows the vibration displacement distribution (upper stage) and the radiated sound
pressure distribution (a frequency of 77 Hz) when the (1,3) mode (eigen frequency 64 Hz) is
excited in the above-mentioned flat plate 2B shows the vibration in the case where the VVC
distribution (antiresonance frequency 77 Hz) in the (1,1) mode and the (1,3) mode is excited in
the above-described plate. The numerical analysis results of the displacement distribution (upper)
and the radiated sound pressure distribution (lower) of the sinusoidal sound (anti-resonance
frequency 77 Hz) are shown.
In the radiation sound pressure distribution of FIG. 2 (a), for comparison with the radiation sound
pressure of the VVC distribution, only the (1, 3) mode is used and the vibration is performed at
the same 77 Hz as the frequency at which the VVC distribution is excited. Indicates In the
following, the VVC distributions of the (1,1) mode and the (1,3) mode are referred to as (1,1) +
(1,3) VVC distributions (the same applies to combinations of other vibration modes).
[0017]
Comparing the upper part of Fig. 2 (a) and (b), the vibration displacement distribution of (1, 1) +
(1, 3) VVC distribution has the amplitude of the central nodal area compared with that of (1, 3)
mode. It can be seen that it is amplified and the volume velocity is zero. On the other hand, the
sound pressure of the 77 Hz sine wave sound emitted from the flat plate is 74 dB at the
observation point 0.3 m from the flat plate in the (1, 3) mode when comparing the lower part of
FIGS. A level of 67 dB is shown at an observation point of 1.3 m, and an attenuation of 7 dB
occurs at 1 m, whereas a distribution of (1,1) + (1,3) VVC is 0.3 m from a flat plate. It shows 74
dB at the observation point and 48 dB at the observation point 1.3 m, and it can be seen that an
attenuation of 26 dB occurs at 1 m.
[0018]
On the other hand, FIG. 3 shows the result of numerical analysis of the time-averaged flow rate of
the energy of a sine wave sound with an antiresonance frequency of 77 Hz in the (1,1) + (1,3)
VVC distribution. It can be seen from FIG. 3 that in the (1,1) + (1,3) VVC distribution, the
phenomenon that the energy of the sound radiated from the central part of the flat plate is
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absorbed in the left and right regions of the flat plate occurs. That is, when the VVC distribution
is excited on the flat plate, the sound at the antiresonance frequency related to the VVC
distribution is significantly attenuated near the flat plate and does not propagate to the far field.
[0019]
Although this means that a local sound field is generated for the sound at the antiresonance
frequency related to the VVC distribution, it is usually impossible to excite only the VVC
distribution on the flat plate over a wide frequency, and it is actually natural In the phenomenon,
no local sound field is generated due to the influence of the sound related to other vibration
modes. In this regard, the present invention seeks to generate a local sound field of arbitrary
frequency by simulating the desired VVC distribution using a speaker array. In addition, although
the expression principle of the local sound field by VVC distribution was explained taking the
example of a rectangular flat plate here, the local sound field by VVC distribution is also a flat,
non-rectangular flat plate such as a circle, an ellipse, or a polygon. Note that it is expressed.
[0020]
The basic concept of the present invention has been described above, and subsequently, the
speaker system of the present invention will be described based on the embodiment.
[0021]
FIG. 4 shows the appearance of a speaker system 100 according to an embodiment of the
present invention.
The speaker system 100 according to the present embodiment includes a speaker array in which
a plurality of sub-speakers 10 are dispersedly arranged on a rectangular array surface 102, and a
mechanism (not shown) for independently controlling the volume and amplitude phase of each
sub-speaker ). In the example shown in FIG. 4, the speaker system 100 has 21 equivalent coneshaped sub-speakers 10 embedded in the enclosure in a 3 × 7 matrix. However, the present
invention does not limit the sub-speaker 10 to a cone type, and other types of speakers such as a
horn type and a flat type are adopted if the vibration surface is small and the vibration surface
does not divide and vibrate. May be Furthermore, the present invention does not limit the
number and arrangement of the sub-speakers 10, as long as a sufficient number of sub-speakers
10 are distributed substantially equally to achieve the object of the present invention.
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[0022]
The external configuration of the speaker system 100 according to the present embodiment has
been described above. Subsequently, a method for generating a local sound field using a speaker
array will be described based on the flowchart shown in FIG.
[0023]
(Step 1) In step 1, a flat plate having the same size as the array surface 102 of the speaker
system 100 is defined.
As shown in FIG. 6A, the array surface 102 of the speaker system 100 is a rectangular plane of
0.575 m × 0.945 m, and the sub-speakers 10 with a radius of 0.0275 m with respect to the
array surface 102 have a predetermined distance (long side In the case where the direction is
0.135 m and the long side direction is 0.27 m), in step 1, a flat plate 30 having the same area
and shape as the array surface 102 is defined as shown in FIG. . If the array surface 102 has a
shape other than a rectangle (such as a circle, an ellipse, or a polygon), a flat plate having that
shape is defined in step 1.
[0024]
(Step 2) In Step 2, the vibration displacement of the flat plate 30 is calculated by exciting the flat
plate 30 under a predetermined boundary condition to excite only the desired VVC distribution,
and the vibration displacement distribution of the flat plate 30 is determined. Hereinafter, the
calculation procedure of the vibration displacement of the flat plate 30 will be described with an
example in which the simple support is adopted as the boundary condition. Needless to say, the
boundary conditions are not limited to simple support.
[0025]
The plate's equation of motion when an excitation force acts on a simple support rectangular
plate embedded in an infinite large baffle can be described as the following equation (1).
[0026]
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[0027]
In addition, the bending rigidity D of a flat plate is calculated | required by following formula (2).
[0028]
[0029]
Here, when the external force f acts on the (波 1, 平板 1) point of a flat plate as a sine wave force,
the external force f can be described as the following equation (3), and the flat plate
displacement is also It can be described as equation (4).
[0030]
[0031]
Next, when the equations (3) and (4) are substituted into the equation (1), the equation of motion
is as shown in the following equation (5).
Therefore, the plate vibration displacement can be described as the following equation (6) as a
solution of the equation of motion, and the vibration velocity becomes the following equation (7).
[0032]
[0033]
Here, φ mn and ω mn in the above equation (6) are the (m, n) -order eigenfunction and its
natural angular frequency, and are expressed as the following equations (8) and (9), respectively.
[0034]
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[0035]
(Step 3) In step 3, a representative value of the amplitude of the vibration area of the flat plate
30 corresponding to the vibration plane of each sub-speaker 10 is calculated based on the
vibration displacement distribution of the flat plate 30 obtained in step 2.
In the following, the case where the vibration displacement distribution in the case where only
the (1, 1) + (1, 3) VVC distribution is excited in the flat plate 30 in step 2 will be examined.
[0036]
FIG. 7B shows the vibration displacement distribution at the maximum amplitude when only the
(1,1) + (1,3) VVC distribution is excited in the flat plate 30.
Here, as the vibration displacement distribution, positive and negative values are defined in the
Z-axis direction, and the positive direction of the Z-axis corresponds to the sound output
direction of the speaker system 100.
The vibration displacement distribution shown in FIG. 7B represents the displacement
distribution at the moment when the left and right regions of the flat plate 30 are displaced in
the negative direction as much as possible and the central region is displaced in the positive
direction as much as possible. After the cycle, the directions of displacement of the left and right
regions and the central region are reversed.
[0037]
In step 3, first, 21 vibration regions corresponding to the vibration planes of the 21 sub-speakers
10 of the speaker system 100 are placed on the flat plate 30 as shown by a broken line circle on
the flat plate 30 in FIG. Define to
For example, in the case of the fifth sub-speaker 10 of the speaker system 100, the vibration area
of the flat plate 30 corresponding to the vibration plane of the sub-speaker 10 is a circular area
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R5 of the same size as the opening of the cone of the sub-speaker 10 It corresponds to
[0038]
Next, the amplitude (z) at a plurality of observation points S (x, y) in each of the defined vibration
regions is obtained from the vibration displacement distribution shown in FIG. 7 (b), and a
representative of the obtained plurality of amplitudes (z) Calculate the value.
Here, the representative value is, for example, an average value of a plurality of obtained
amplitudes (z).
[0039]
(Step 4) In step 4, the sub-speakers 10 corresponding to the vibration area are divided into two
groups according to the displacement direction of the vibration area obtained in step 3.
Specifically, when the representative value of the amplitude of each vibration region is calculated
based on the vibration displacement distribution shown in FIG. 7B, the representative value of
the vibration region R5 corresponding to the fifth sub speaker 10 is a negative value. Since the
displacement direction of the vibration region R5 is negative and the representative value of the
vibration region R11 corresponding to the eleventh sub-speaker 10 takes a positive value, the
displacement direction of the vibration region R11 is positive. .
In this case, for example, the attribution of the eleventh sub-speaker 10 is taken as a first group,
and the attribution of the fifth sub-speaker 10 is taken as a second group.
The other sub-speakers 10 are also divided into either the first or second group from the same
viewpoint.
[0040]
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(Step 5) In step 5, the representative value of the amplitudes of the 21 vibration regions obtained
in step 3 is normalized by an appropriate method to define the volume weighting coefficient α
of the sub speaker 10. Specifically, positive and negative signs are taken from the representative
value of each vibration region to obtain an absolute value. For example, each absolute value is
divided by the maximum value among 21 absolute values to be normalized, and the normalized
value is The volume weighting coefficient α of the sub-speaker 10 corresponding to the
vibration area is used.
[0041]
(Step 6) In step 6, a value obtained by multiplying the main sound volume set in the speaker
system 100 by the sound volume weighting coefficient α of each sub speaker 10 is determined
as the sound volume of the sub speaker 10. For example, when the main volume of the speaker
system 100 is set to “1”, the volume of the sub-speaker 10 whose volume weight coefficient α
is defined to “0.5” is set to “1 × 0.5 = 0.5”. In the following, the volume of the sub speaker
10 is referred to as "sub volume".
[0042]
(Step 7) Finally, in step 7, sound is output from the sub speaker 10 at the volume set in step 6. At
this time, control is performed such that the phase of the input audio signal to the sub speaker
10 belonging to the first group and the input audio signal to the sub speaker 10 belonging to the
second group are 180 degrees out of phase, Output.
[0043]
FIG. 8 shows a histogram of the volume weighting factor α defined for the 21 sub-speakers 10
that make up the speaker array of the speaker system 100. Note that FIG. 8 can also be viewed as
a histogram of sub-volumes that are set to the volumes of the 21 sub-speakers 10 when the main
volume of the speaker system 100 is set to “1”. In FIG. 8, the bar graph extends above and
below the zero plane, but this corresponds to the input audio signals to the nine sub-speakers 10
(symbols 7 to 12) belonging to the first group (G1) It represents that the phases of the vibrations
of the twelve sub-speakers 10 (symbols 1 to 6, symbols 16 to 21) belonging to the two groups
(G2) are 180 degrees out of phase.
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[0044]
FIG. 9 shows the result of numerical analysis of the radiation sound pressure distribution of a
sine wave sound with a frequency of 100 Hz when the speaker system 100 shown in FIG. 6A is
controlled by the method described above. Note that the black circles shown in FIG. 9 correspond
to the arrangement positions of the sub-speakers 10 (the same as in the following FIGS. 11 and
12). As shown in FIG. 9, the sound pressure of a sine wave sound with a frequency of 100 Hz
radiated from the array surface of the speaker system 100 is attenuated to 67 dB at an
observation point 0.3 m away from the array surface and to 43 dB at an observation point 1.3 m
away It can be seen that the local sound field is generated. Here, it should be noted that in the
case of the speaker system 100, a local sound field is generated for a sound with a frequency of
100 Hz that deviates from the antiresonant frequency of 77 Hz according to the (1,1) + (1,3) VVC
distribution That is the point.
[0045]
As mentioned above, although the method to produce | generate a local sound field using the
speaker system 100 of this embodiment was demonstrated, the 1st implementation form for
implement | achieving the method mentioned above next is demonstrated.
[0046]
FIG. 10 shows a first implementation configuration of the speaker system 100. As shown in FIG.
As shown in FIG. 10, the speaker system 100 includes a main sound volume setting unit 110 and
a signal distribution unit 120. Furthermore, the speaker system 100 is provided with a signal
processing unit 20 unique to the front stage of each of the 21 sub-speakers 10. Each signal
processing unit 20 includes a signal amplification unit 22, a phase correction unit 24, and a
power amplifier 26. Have.
[0047]
Here, in the present embodiment, the volume weighting coefficient α defined for the subspeaker 10 is set in the signal amplification unit 22 of the signal processing unit 20
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corresponding to each sub-speaker 10. Further, in the present embodiment, an identifier of the
group to which the sub speaker 10 belongs (hereinafter, referred to as a group identifier) is set in
the phase correction unit 24 of the signal processing unit 20 corresponding to each sub speaker
10.
[0048]
In the example shown in FIG. 10, [0.1] is set as the sound volume weighting coefficient α in the
signal amplification unit 22a of the signal processing unit 20 corresponding to the sub speaker
10a, and [2] is set in the phase correction unit 24a as the group identifier. There is. Similarly,
[1.0] is set as the volume weighting coefficient α in the signal amplification unit 22b of the
signal processing unit 20 corresponding to the sub speaker 10b, and [1] is set as the group
identifier in the phase correction unit 24b. [0.5] is set as the volume weighting coefficient α in
the signal amplification unit 22c of the signal processing unit 20 corresponding to 10c, and [2] is
set in the phase correction unit 24c as the group identifier.
[0049]
When the main volume of the speaker system 100 is set, in response to this, the main volume
setting unit 110 sets the set amount to the 21 signal processing units 20 simultaneously. On the
other hand, when an audio signal is input to the speaker system 100, in response to this, the
signal distribution unit 120 simultaneously outputs the same signal to the 21 signal processing
units 20.
[0050]
When the main volume is set to each signal processing unit 20 from the main volume setting unit
110, the signal amplification unit 22 determines a value obtained by multiplying the set main
volume by the volume weighting coefficient α as a sub volume. Then, the signal amplification
unit 22 amplifies the audio signal input from the signal distribution unit 120 at an amplification
factor according to the determined sub volume, and outputs the amplified audio signal to the
phase correction unit 24 in the subsequent stage.
[0051]
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In the example shown in FIG. 10, the signal amplification unit 22a of the sub-speaker 10a
generates the sub-speaker 10a with a value [0.5] obtained by multiplying the main sound volume
[5.0] input from the main sound volume setting unit 110 by the sound volume weighting
coefficient α [0.1]. It is decided as a sub volume of. Then, the signal amplification unit 22a
amplifies the audio signal input from the signal distribution unit 120 at an amplification factor
according to the determined sub volume [0.5], and outputs the amplified audio signal to the
phase correction unit 24a. Similarly, the signal amplification unit 22b of the sub speaker 10b
determines the value [5.0] obtained by multiplying the main sound volume [5.0] by the sound
volume weighting coefficient α [1.0] as the sub sound volume of the sub speaker 10b, and the
input audio signal is determined. The signal amplification unit 22a of the sub speaker 10c
multiplies the main sound volume [5.0] by the sound volume weighting coefficient α [0.5]. The
value [2.5] is determined as the sub volume of the sub speaker 10c, and the input audio signal is
amplified at an amplification factor according to the sub volume [2.5] and output to the phase
correction unit 24c.
[0052]
On the other hand, the phase correction unit 24 of each signal processing unit 20 performs
correction to delay the phase of the audio signal input from the signal amplification unit 22 as
necessary based on the group identifier set to itself. The audio signal is output to the power
amplifier 26 in the subsequent stage. In response to this, the power amplifier 26 amplifies the
current of the input audio signal and inputs it to the sub-speaker 10, and the sub-speaker 10
outputs audio based on the input audio signal.
[0053]
In the example shown in FIG. 10, the phase correction unit 24a and the phase correction unit 24c
in which [2] is set as the group identifier G performs correction to delay the phase of the input
audio signal by 180 degrees, and then performs correction. The audio signal is output to the
power amplifier 26a and the power amplifier 26c. On the other hand, the phase correction unit
24b in which [1] is set as the group identifier G does not perform correction, and outputs the
input audio signal as it is to the power amplifier 26b. As a result, the phase of the input audio
signal to the sub-speaker 10b belonging to the first group (G1) and the phase of the input audio
signal to the sub-speakers 10a and 10c belonging to the second group (G2) become 180 degrees
shifted. .
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[0054]
In order to achieve the same purpose, it is needless to say that the phase correction unit 24b may
perform the correction without the phase correction unit 24a and the phase correction unit 24c
performing the correction. . In short, in the present embodiment, only the phase correction unit
24 in which one of the two group identifiers is set performs the correction, and the phase
correction unit 24 in which the other group identifier is set is the correction Should not be
implemented. As a further alternative, the phase correction unit 24 in which the group identifier
that is not to be corrected is set may not be provided from the beginning.
[0055]
The first implementation of the speaker system 100 has been described above. Next, the second
implementation will be described.
[0056]
FIG. 11 shows the radiated sound of a sine wave sound with a frequency of 400 Hz when
simulating a (1,1) + (1,3) VVC distribution with an antiresonance frequency of 77 Hz using the
speaker array shown in FIG. 6 (a) The numerical analysis result of pressure distribution is shown.
As shown in FIG. 11, the sound pressure of a 400 Hz sine wave sound emitted from the array
surface of the speaker system 100 shows 71 dB at an observation point 0.3 m away from the
array surface and 50 dB at an observation point 1.3 m away from the array surface. It can be
seen that the damping action is reduced compared to the result (attenuation of 26 dB at 1 m)
according to the sine wave sound of frequency 100 Hz shown in FIG. It is considered that such a
decrease in the damping action is caused by the directivity becoming stronger as the wavelength
of the sound becomes shorter than the wavelength of the bending wave of the (1,1) + (1,3) VVC
distribution to be simulated. Be
[0057]
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On the other hand, FIG. 12 shows three types of sine wave sounds (frequency) when simulating
(1, 5) + (1, 7) VVC distribution of anti-resonance frequency 470 Hz using the speaker array
shown in FIG. The numerical analysis results of the radiation sound pressure distribution at 400
Hz, 600 Hz and 800 Hz) are shown. The results shown in FIG. 12 mean that local sound fields in
a high frequency band (400 Hz to 800 Hz) are generated by simulating the (1, 5) + (1, 7) VVC
distribution.
[0058]
On the other hand, FIG. 13 shows the vibration displacement distribution in the case where 10
different VVC distributions are excited on the flat plate 30 shown in FIG. 6B, and FIG. 14 shows
the frequency characteristics of the acoustic radiation efficiency of each VVC distribution. . As
shown in FIG. 14, as the coupled odd-order mode becomes higher, the acoustic radiation
efficiency is notched at the higher frequency side.
[0059]
This means that local sound fields of different frequency bands are generated depending on the
type of VVC distribution to be simulated, and furthermore, if two or more VVC distributions are
simulated at the same time, a wider frequency band can be obtained. It is derived that a local
sound field is generated.
[0060]
In this regard, an implementation of the speaker system 100 for simulating two or more VVC
distributions simultaneously will be described below.
[0061]
FIG. 15 shows a first VVC distribution (eg, (1,1) + (1,3) VVC distribution at an antiresonance
frequency of 77 Hz) corresponding to a low frequency band and a second VVC distribution
corresponding to a high frequency band. An implementation of the speaker system 100 for
simultaneously simulating (e.g., (1, 5) + (1, 7) VVC distribution at anti-resonance frequency 470
Hz) is shown.
In the following, the description of the contents common to the elements shown in FIG. 10 will be
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omitted appropriately.
[0062]
As shown in FIG. 15, the speaker system 100 includes a band separation unit 130 in addition to
the main sound volume setting unit 110 and the signal distribution unit 120.
Furthermore, each signal processing unit 20 includes a signal superposition unit 28 in addition
to the signal amplification unit 22, the phase correction unit 24, and the power amplifier 26.
[0063]
The band separation unit 130 separates the audio signal input to the speaker system 100 into a
low frequency band component corresponding to the first VVC distribution and a high frequency
band component corresponding to the second VVC distribution, and outputs the signal to the
signal distribution unit 120. Output. In response to this, the signal distribution unit 120
simultaneously outputs the low frequency band component and the high frequency band
component to the 21 signal processing units 20.
[0064]
Here, each signal processing unit 20 includes two signal amplification units 22 corresponding to
two types of VVC distributions (that is, two types of frequency band components), and the first
signal amplification unit 22 The volume weighting coefficient α defined based on the vibration
displacement distribution according to the VVC distribution of 1 is set, and the second signal
amplification unit 22 is configured with the sound volume defined based on the vibration
displacement distribution according to the second VVC distribution. The weighting factor α is
set.
[0065]
In addition, each signal processing unit 20 includes two phase correction units 24 corresponding
to two VVC distributions (that is, two types of frequency band components), and the first phase
correction unit 24 performs the first phase correction. The identifier of the group determined
based on the vibration displacement distribution related to the VVC distribution is set, and the
identifier of the group determined based on the vibration displacement distribution related to the
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first VVC distribution is set in the second phase correction unit 24 It is set.
[0066]
In the example shown in FIG. 15, regarding the sub speaker 10a, [1.0] is set as the volume
weighting coefficient α in the first signal amplification unit 22a-1, and [1] as the group identifier
in the first phase correction unit 24a-1. Is set, [0.5] is set to the second signal amplification unit
22a-2 as the volume weighting coefficient α, and [3] is set to the second phase correction unit
24a-2 as the group identifier.
Similarly, for the sub-speaker 10b, [0.5] is set in the first signal amplification unit 22b-1 as the
volume weighting coefficient α, and [2] is set in the first phase correction unit 24b-1 as the
group identifier, [1.0] is set to the second signal amplification unit 22b-2 as the volume
weighting coefficient α, and [4] is set to the second phase correction unit 24b-2 as the group
identifier.
[0067]
When the main volume of the speaker system 100 is set, in response to this, the main volume
setting unit 110 simultaneously sets the set amount in the 21 signal processing units 20.
The two signal amplification units 22 of each signal processing unit 20 determine the sub
volume based on the main volume input from the main volume setting unit 110.
[0068]
Then, each of the first and second signal amplification units 22 amplifies the input audio signal at
an amplification factor according to the determined sub volume, and outputs the amplified audio
signal to the phase correction unit 24 in the subsequent stage.
[0069]
In the example shown in FIG. 15, the first signal amplification unit 22a-1 related to the sub-
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speaker 10a has a low frequency [5.0] obtained by multiplying the main volume [5.0] by the
volume weighting coefficient α [1.0] set in advance. The sub-volume of the band is determined,
and the audio signal in the low frequency band input from the signal distribution unit 120 is
amplified by the amplification factor according to the determined sub-volume [5.0] and output to
the first phase correction unit 24a-1 doing.
On the other hand, the second signal amplification unit 22a-2 related to the sub-speaker 10a
uses the value [0.5] obtained by multiplying the main volume [5.0] by the preset volume
weighting coefficient α [0.1] as the sub-volume of the high frequency band. The audio signal in
the high frequency band, which is determined and input from the signal distribution unit 120, is
amplified at an amplification factor corresponding to the determined sub volume [0.5], and is
output to the second phase correction unit 24a-2.
[0070]
Similarly, the first signal amplification unit 22b-1 related to the sub-speaker 10b sets the main
volume [5.0] to a value [0.5] obtained by multiplying the volume weighting coefficient α [0.1]
set in advance as a low frequency band component sub The audio signal of the low frequency
band, which is determined as the sound volume, is amplified at an amplification factor according
to the determined sub sound volume [0.5] and output to the first phase correction unit 24b-1 .
On the other hand, the second signal amplification unit 22b-2 related to the sub-speaker 10b is a
sub-volume of the high frequency band component with a value [5.0] obtained by multiplying the
main volume [5.0] by the preset volume weighting coefficient α [1.0]. The audio signal in the
high frequency band input from the signal distribution unit 120 is amplified by the amplification
factor according to the determined sub volume [5.0], and is output to the second phase
correction unit 24a-2.
[0071]
On the other hand, when the first and second phase correction units 24 of each signal processing
unit 20 receive the amplified audio signals from the first and second signal amplification units
22, respectively, the groups set in themselves are generated. After the correction for delaying the
phase of the input audio signal is performed based on the identifier as necessary, the audio signal
is output to the signal superimposing unit 28 in the subsequent stage.
[0072]
In the example illustrated in FIG. 15, the phase correction unit 24 a-2 and the phase correction
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unit 24 b-1 in which [2] is set as the group identifier G performs correction to delay the phase of
the input audio signal by 180 degrees. Therefore, the phase correction unit 24a-1 and the phase
correction unit 24b-2 in which [1] is set as the group identifier G do not perform correction, and
output the input audio signal as it is to the signal superposition units 28a and 28b. Do.
[0073]
The signal superimposing unit 28 of each signal processing unit 20 superimposes the voice
signal of the low frequency band input from the first phase correction unit 24 and the voice
signal of the high frequency band input from the second phase correction unit 24. , And output
the superimposed audio signal to the power amplifier 26.
[0074]
In the example shown in FIG. 15, the signal superimposing unit 28 a is the voice signal of the low
frequency band input from the first phase correction unit 24 a-1 and the high frequency band of
the high frequency band input from the second phase correction unit 24 a-2. An audio signal is
superimposed and output to the power amplifier 26a.
In response to this, the power amplifier 26a amplifies the current of the input audio signal and
inputs it to the sub-speaker 10a, and the sub-speaker 10a outputs audio based on the input audio
signal.
Similarly, the signal superimposing unit 28 b superimposes the audio signal in the low frequency
band input from the first phase correction unit 24 b-1 and the audio signal in the high frequency
band input from the second phase correction unit 24 b-2 Output to the power amplifier 26b.
In response to this, the power amplifier 26b current-amplifies the input audio signal and inputs it
to the sub-speaker 10b, and the sub-speaker 10b outputs audio based on the input audio signal.
[0075]
As a result, the phase of the low frequency component of the input audio signal to the sub
speaker 10a belonging to the first group (G1) and the phase of the low frequency component of
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the input audio signal to the sub speaker 10 b belonging to the second group (G2) are It will shift
180 degrees. Similarly, the phase of the high frequency component of the input audio signal to
the sub speaker 10b belonging to the first group (G1) and the phase of the high frequency
component of the input audio signal to the sub speaker 10a belonging to the second group (G2)
are 180 You will be tempted.
[0076]
As described with reference to FIG. 10, the present invention is not limited to the abovedescribed embodiment, and only the phase correction unit 24 in which one of the group
identifiers is set may perform correction, and the group in which the correction is not performed
The phase correction unit 24 in which the identifier is set may not be provided from the
beginning.
[0077]
Further, FIG. 15 shows a mode in which the band separation unit 130 separates the audio signal
into two frequency bands for convenience of the paper, but the band separation unit 130
includes N audio signals (N is an integer of 2 or more). In the case where the signal processing
unit 20 separates into N frequency band components, N signal amplification units 22 for
amplifying each of the N frequency band components, and a frequency band amplified by the N
signal amplification units. N phase correction units 24 are prepared to perform correction to
delay the respective phases of the components by 180 degrees.
The contents of the signal processing in that case are understood by the person skilled in the art
as a priori understood from the above-described contents of the description, and thus the further
description is omitted.
[0078]
The second implementation of the speaker system 100 has been described above. Next, the third
implementation will be described.
[0079]
FIG. 16 shows the frequency characteristics of the acoustic radiation power when the VVC
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distribution is simulated by the above-mentioned speaker array, and FIGS. 16 (a), (b) and (c) show
(1, 1) + (1) respectively. 3) VVC distribution, (1, 3) + (1, 5) VVC distribution, and (1, 5) + (1, 7)
VVC distribution are simulated.
As shown in FIG. 16, it can be seen that the acoustic radiation power at the time of simulating the
VVC distribution by the speaker array increases as the frequency increases, and the sound
attenuation effect decreases as the frequency increases.
[0080]
In this regard, an implementation of the speaker system 100 for leveling the output signal
according to the frequency characteristic of the acoustic radiation power related to the simulated
VVC distribution will be described below.
[0081]
FIG. 17 shows a third implementation of the speaker system 100.
In the following, the description of the contents common to the elements shown in FIG. 15 will be
omitted as appropriate.
[0082]
As described above in FIG. 15, each signal processing unit 20 includes two signal amplification
units 22 corresponding to two VVC distributions (that is, two types of frequency band
components), but in this embodiment, A leveling unit 29 is provided at the front stage of each
signal amplification unit 22. Here, the leveling unit 29 is a functional unit for suppressing
variation in the sound attenuation action for each frequency component, and the sound
according to the VVC distribution to be simulated with respect to the input signal input from the
signal distribution unit 120. It functions as a filter that multiplies the inverse of the frequency
characteristic of the radiation power.
[0083]
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For example, when the local sound field in the low frequency band (50 to 400 Hz) is realized by
simulating the (1, 1) + (1, 3) VVC distribution, the leveling unit 29a-1 and the leveling unit 29b-1
The inverse of the value obtained by dividing the value of the acoustic radiation power shown in
FIG. 16A by the value of 400 Hz (maximum value) is multiplied by the input signal input from the
signal distribution unit 120. For example, when the local sound field in the high frequency band
(400 to 800 Hz) is realized by simulating the (1, 5) + (1, 7) VVC distribution, the leveling unit
29a-2 and the leveling unit 29b-2 are The inverse of the value obtained by dividing the value of
the acoustic radiation power shown in FIG. 16C by the value of 800 Hz (maximum value) is
multiplied by the input signal input from the signal distribution unit 120.
[0084]
According to the third embodiment described above, the output signal output from the signal
amplification unit 22 is leveled, so that variation in sound attenuation effect is suppressed for
each frequency component. Although FIG. 17 exemplarily shows a configuration in which the
leveling unit 29 is provided at the front stage of the signal amplification unit 22, the leveling unit
29 may be provided at the rear stage of the signal amplification unit 22. It may be provided in
the latter stage of the phase correction unit 24.
[0085]
As described above, according to the present embodiment, the speaker array can be used to
generate a local sound field of any frequency.
[0086]
As mentioned above, although this invention was demonstrated with embodiment, this invention
is not limited to embodiment mentioned above, As long as the effect | action and effect of this
invention are exhibited within the range of the embodiment which those skilled in the art may
think about. , Are included in the scope of the present invention.
[0087]
DESCRIPTION OF SYMBOLS 10 ... Sub speaker 20 ... Signal processing part 22 ... Signal
amplification part 24 ... Phase correction part 26 ... Power amplifier 28 ... Signal superposition
part 29 ... Leveling part 30 ... Flat plate 100 ... Speaker system 102 ... Array surface 110 ... Main
volume setting part 120: Signal distribution unit 130: Band separation unit
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