JP2006211230

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DESCRIPTION JP2006211230
PROBLEM TO BE SOLVED: To provide a speaker array system capable of generating an acoustic
beam having any directivity and direction and capable of being configured at low cost.
SOLUTION: A first delay process for directivity control in a first axial direction is applied to an
input audio signal IN, and a speaker unit array SP (i, 1) (i = 1 to m), SP (i, 2) Generate n first
delayed audio signals associated with each of (i = 1 to m),..., SP (i, n) (i = 1 to m). Next, a second
delay process for giving directivity in the second axial direction is selected, and the selected
second delay process is applied to each of the n first delay audio signals, thereby obtaining n The
x m second delay audio signals are supplied to the speaker units SP (i, j) (i = 1 to m, j = 1 to n).
[Selected figure] Figure 3
スピーカアレイシステム
[0001]
The present invention relates to a loudspeaker array system that outputs acoustic beams from a
plurality of loudspeaker units arranged in an array.
[0002]
A speaker system in which a large number of speaker units are arranged is called a "speaker
array".
In the speaker array, by controlling the delay and the gain given to the audio signal supplied to
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each speaker unit, the directivity of the speaker can be sharpened and the direction of the
acoustic beam can be controlled. When the directivity is enhanced, the same energy is emitted to
a narrower range, so that the distance attenuation of the sound pressure becomes smaller, the
sound can be clearly heard far away, and the acoustic radiation in unnecessary directions is
suppressed. be able to. In addition, since the direction of the acoustic beam can be controlled, the
speaker does not have to be directed to the listening position of the sound, so that there is an
advantage that the restriction on the installation method of the speaker is reduced. Patent
documents 1 and 2 are documents about this kind of speaker array. These documents disclose
techniques for generating a plurality of delayed audio signals from an audio signal by digital
filters, supplying these delayed audio signals to individual speakers of a speaker array, and
performing directivity control. JP-A-6-205496 JP-A-5-41897
[0003]
By the way, when the above-mentioned conventional speaker array system forms an acoustic
beam which converges to a focal point in front of the speaker array, for example, the delay audio
signal supplied to the speaker unit is supplied to each speaker constituting the speaker array. It
is necessary to calculate a delay time that is a phase delay with respect to the input audio signal,
delay the input audio signal by the delay time to generate a delayed audio signal, and supply the
signal to the speaker unit. The system has become expensive to secure a huge amount of
computing power. However, depending on the application of the speaker array, for example,
directivity control with high degree of freedom and resolution in the horizontal direction is
desired, while directivity control with high degree of freedom and high resolution in the vertical
direction is desired. It may not be necessary. Even in such a case, it is uneconomical to strictly
control the delay time of the delayed audio signal supplied to each speaker unit of the speaker
array at great cost.
[0004]
The present invention has been made in view of the above-described circumstances, and is
capable of generating an acoustic beam having any directivity and direction, and capable of being
configured at low cost. Intended to be provided.
[0005]
The present invention is a speaker array in which speaker lines consisting of n (n is an integer of
2 or more) speaker units arranged in a first axial direction are arranged in m rows (m is an
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integer of 2 or more) in a second axial direction. A first delay process for directivity control in the
first axial direction is applied to the input audio signal, and the speaker array corresponds to
each of the n rows of loudspeaker unit arrays aligned in the first axial direction Executing a
plurality of types of first delaying means for generating the attached n first delayed audio signals,
and second delay processing for giving predetermined directivity to the acoustic beam in the
second axial direction The m rows of loudspeakers in the second axial direction from each of the
n first delayed audio signals associated with each of the n rows of loudspeaker unit rows, which
are possible and selected by the second delay processing Each line A second plurality of m
second delayed audio signals associated with each of the plurality of second delayed audio
signals, and the generated n × m second delayed audio signals are respectively provided to
speaker units associated with each of the speaker arrays. Of the input audio signal and the n first
delayed audio signals in the first delay process to be executed by the first delay means based on
information designating the directivity of the acoustic beam and the delay means of And a
control means for selecting the second delay process to be executed by the second delay means,
and calculating a delay time between the two.
In a preferred embodiment, the second delay means is constituted by a plurality of analog delay
lines each having an output tap of a plurality of delayed audio signals. In another preferred
embodiment, the first delay means is constituted by a digital filter which convolutes a filter
coefficient sequence determined according to a designated delay time into a past number of
samples of the input audio signal. In another preferred embodiment, the first delay means
comprises a ring buffer which sequentially stores the samples of the input audio signal and
outputs the samples previously stored for a designated delay time as the first delayed audio
signal. It is done. In another preferred embodiment, the input audio signal is composed of audio
signals of a plurality of channels, and the control means is based on the information specifying
the directivity of the acoustic beam given to each channel, and the delay in the first delay
processing. The time is calculated for each channel and selection of the second delay processing
applied commonly to all the channels is performed, and the first delay means independently
performs the processing for the audio signal for each channel. A plurality of channel delay
processing units that execute one delay process and generate n delayed audio signals associated
with each of the n speaker unit strings aligned in the first axial direction; The delayed audio
signals output from the delay processing unit of FIG. 6 are mixed with ones corresponding to the
same speaker It includes an n-number of mixing unit for outputting the extended audio signal.
[0006]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. FIG. 1 is a front view showing a configuration example of a speaker array 10 in a
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speaker array system according to an embodiment of the present invention. As shown in FIG. 1,
in the speaker array 10, a speaker line formed by arranging n speaker units SP (i, j) (j = 1 to n) in
the horizontal direction (first axial direction) is vertical It is a planar speaker array formed by
arranging m lines in the direction (second axial direction). Each speaker unit SP (i, j) (i = 1 to m, j
= 1 to n) constituting the speaker array 10 is a wide directional speaker such as a cone type
speaker, and each speaker axis is a speaker The direction is perpendicular to the plane formed by
the array 10.
[0007]
The speaker array system according to the present embodiment generates m × n delayed audio
signals from the input audio signal IN based on the information specifying the directivity of the
acoustic beam to be output, and the speaker unit is generated by these delayed audio signals. By
driving SP (i, j) (i = 1 to m, j = 1 to n), an acoustic beam having directivity as specified is formed
on the speaker array 10.
[0008]
Here, with reference to FIG. 2 and FIG. 3, the feature of directivity control of an acoustic beam in
the present embodiment will be described.
In the present embodiment, as shown in FIG. 2 and FIG. 3, the directivity of the acoustic beam is
determined by the first axial directivity, which is a strict request for directivity control and
resolution, and the second, which is not so strict. The directionality control of the first axis
direction and the directionality control of the second axis direction are performed separately. In
the present embodiment, a large amount of computing power is allocated to the directivity
control in the first axial direction, and the directivity control in the second axial direction is
performed by a simple process. In the present embodiment, an example in which the first axial
direction is the horizontal direction and the second axial direction is the vertical direction will be
described, but these may be reversed.
[0009]
As shown in FIG. 3, in this embodiment, a first delay process for directivity control in the first
axial direction is applied to the input audio signal IN, and speaker units of n columns arranged in
the first axial direction It corresponds to each of the columns SP (i, 1) (i = 1 to m), SP (i, 2) (i = 1
to m), ..., SP (i, n) (i = 1 to m) Generating n first delayed audio signals.
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[0010]
Here, a specific example of the first delay processing will be described by taking the case of
forming an acoustic beam that converges to the focal point P in front of the speaker array 10 as
an example.
In this embodiment, assuming a horizontal plane including any k-th speaker line SP (k, j) (j = 1 to
n), an acoustic beam converging on the projection point of the focal point P in this virtual
horizontal plane is a speaker line The conditions for forming by SP (k, j) (j = 1 to n) are
determined. That is, when n first delayed audio signals obtained by delaying the common input
audio signal IN are supplied to n speaker units SP (k, j) (j = 1 to n), radiation is generated from
each speaker unit The delay time between the input audio signal IN required for the received
sound wave to reach the projection point in phase and each of the n first delayed audio signals is
determined. Then, in the first delay processing, n first delayed audio signals are generated by
performing delay processing on the input audio signal IN which is delayed by each delay time
thus obtained. The above is the details of the first delay processing.
[0011]
Assuming that the n first delayed audio signals obtained by the first delay processing are
temporarily supplied to the m speaker line SP (i, j) (i = 1 to m, j = 1 to n), as shown in FIG. It is
considered that an acoustic beam is formed which converges on a vertical line segment L passing
through the focal point P as illustrated in FIG. This is because each speaker line SP (k, j) (j = 1 to
n) forms an acoustic beam that converges to the projection point of the focal point P in the
horizontal plane including each.
[0012]
Next, in the present embodiment, a second delay process is performed on each of the n first delay
audio signals in order to give the acoustic beam a predetermined directivity in the second axial
direction. The second delay processing will be described below.
[0013]
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The speaker array 10 can be understood as a speaker unit row consisting of m speaker units
arranged in the second axial direction, arranged in n rows in the first axial direction. Here, if it is
assumed that a common first delayed audio signal is supplied to each speaker unit constituting
one speaker unit row, a band-like acoustic beam directed to the vertical line segment L along the
vertical plane including the speaker unit row Is formed.
[0014]
The second delay process is a delay process for providing directivity in a second axial direction
such as to converge on the band-like acoustic beam, for example, to a point P illustrated in FIG. 2.
In this embodiment, a plurality of types of means for performing the second delay processing
with different directivity in the second axial direction are prepared in advance. When the position
of the focal point P in the second axial direction (the height if the second axis is a vertical axis) or
the like is specified, in this embodiment, the acoustic beam is directed in the direction of such a
position. The second delay process that is most suitable to cause is selected. Then, according to
the selected second delay processing, each of the n first delay audio signals associated with each
of the n speaker unit rows is selected to each of m speaker lines in the second axial direction.
Each of m associated second delayed audio signals is generated, and each of the generated n ×
m second delayed audio signals is supplied to a speaker unit associated with each of the speaker
arrays.
[0015]
Then, in the present embodiment, the control means (not shown) such as a CPU or the like
determines each of the input audio signal and the n first audio signals in the first delay
processing based on the information specifying the directivity of the acoustic beam. And the
second delay processing to be performed is selected.
[0016]
FIG. 4 is a block diagram showing a specific configuration example of a speaker array system that
generates an acoustic beam according to the principle described above.
The CPU 101 is control means for receiving information for specifying the directivity of an
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acoustic beam from a host device (not shown) and controlling each part for forming an acoustic
beam having such directivity on the speaker array 10. Parameters necessary for this control are
stored in advance in the memory 102. As information for specifying the directivity of the
acoustic beam, for example, in the case of forming an acoustic beam focused on the focal point in
front of the speaker array 10, the three-dimensional coordinate value of the focal point is
included in this.
[0017]
The DSP 103 is a device that performs first delay processing for performing directivity control in
the first axial direction under control of the CPU 101. The DSP 103 applies n types of digital
filter processing DF-j (j = 1 to n) to the common input audio signal IN to generate n first delayed
audio signals. Each digital filter processing DF-j convolutes the filter coefficient sequence
associated with the delay time instructed by the CPU 101 with the sample sequence of the input
audio signal IN generated within a predetermined time in the past, and has the indicated delay
time Generate a delayed audio signal. The purpose of generating the delayed audio signal by such
a convolution operation is to control the delay time of the delayed audio signal with a resolution
finer than the sampling period of the input audio signal IN. The n delayed audio signals output
from the DSP 103 are converted into analog signals by a D / A converter (not shown) and then
supplied to n analog delay line units 104-j (j = 1 to n). Be done.
[0018]
The n analog delay line units 104-j (j = 1 to n) are devices that perform second delay processing
for performing directivity control in the second axial direction under control of the CPU 101.
Each analog delay line unit 104-j has a plurality of analog delay lines ADL for performing a
plurality of types of second delay processing. 5 and 6 respectively show analog delay lines ADL1
and ADL2 which are examples of these analog delay lines. In these figures, D1, D2,... Are analog
delay lines each having a certain length (delay amount). In these figures, an example in which the
number m of the speaker units aligned in the second axial direction is 13 is shown.
[0019]
The analog delay line ADL1 shown in FIG. 5 is, as shown in FIG. 7, when the focal point P is
positioned at the center height of 13 speaker unit rows arranged in the second axial direction
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(vertical direction). It is selected. In this analog delay line ADL1, the phase of the second delayed
audio signal output to the speaker units SP (1, j) and SP (13, j) at the upper and lower ends is the
most advanced, and the center speaker unit SP (7, j) In order to delay the second delayed audio
signal output to the most, the delay process for generating the thirteen second delayed audio
signals is performed. More precisely, the delay time between the 13 second delayed audio signals
and the original first delayed audio signal is determined as follows. First, it is assumed that an arc
having the focal point P as a center and passing through the speaker units SP (1, j) and SP (13, j)
at the upper and lower ends. Then, for each speaker unit, a straight line passing through the focal
point P and the position of the speaker unit is assumed, an intersection point of the straight line
with the arc of the straight line is determined, and the sound wave propagates from the
intersection point to the position of the speaker unit Determine the time required for. The
extraction position of each of the 13 second delay audio signals is determined so that the analog
delay line ADL1 is delayed and output by a time corresponding to the required time determined
for each speaker unit in this manner.
[0020]
The analog delay line ADL2 shown in FIG. 6 is selected when the focal point P is located above
the center of the speaker unit row, as shown in FIG. In this analog delay line ADL2, the phase of
the second delayed audio signal output to the lowermost speaker unit SP (13, j) is the most
advanced, and the second delayed audio signal output to each speaker unit as it gets further
apart In order to be delayed, a delay process is performed to generate 13 second delay audio
signals. The calculation direction of the delay time of the 13 second delay audio signals is the
same as the method described for the analog delay line ADL1.
[0021]
The CPU 101 in FIG. 4 is an analog capable of obtaining the directivity in the second axial
direction closest to the designated directivity among the plurality of analog delay lines as
described above based on the information specifying the directivity. A delay line is selected, and
second delay processing by the selected analog delay line is instructed to n analog delay line
units 104-j (j = 1 to n). The n analog delay line units 104-j (j = 1 to n) perform second delay
processing by the analog delay line selected by the CPU 101 according to this command, and the
first delay audio signal supplied to each of them is generated. generating m second delayed audio
signals; The n × m second delayed audio signals generated in this manner are amplified by the
amplifier A in FIG. 4, and each speaker unit SP (i, j) (i = 1 to m, j = 1 to n) Supplied to
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[0022]
In this embodiment, with the above configuration, directivity control using the high-accuracy
delay processing by the DSP 103 is performed in the first axis direction in which the requirement
on directivity control is severe, and the requirement on directivity control is not severe. Simple
directivity control using an analog delay line is performed in the axial direction of 2. Therefore,
directivity control meeting requirements can be realized at low cost.
[0023]
As mentioned above, although one Embodiment of this invention was described, other
embodiment besides this can be considered to this invention. (1) In the above embodiment, the
analog delay line is used as the means for performing the second delay processing, but the
second delay processing may be performed using a RAM or a shift register. When the second
delay processing is performed using the RAM, the CPU 101 bears a burden of managing the
delay time from the writing of the first delay audio signal to the RAM to the reading as the
second delay audio signal. However, even in such a case, the CPU 101 does not have to perform
an operation for obtaining the delay time between the first delay audio signal and the second
delay audio signal, and a request is made from among the delay times obtained in advance. The
burden on the CPU 101 is significantly reduced because it is only necessary to select one that
matches the directivity in the second axial direction.
[0024]
(2) Depending on the distance from the speaker array 10 of the focal point P, the aspect of the
second delay processing may be changed. That is, n analog delay line units 104-j (j = 1 to n) are
used when the focal point P is near the speaker array 10 and when the focal point P is far from
the speaker array 10 Two systems of things are prepared, and an appropriate one is selected
according to the distance from the speaker array 10 of the focal point P and used for the second
delay processing. When the focal point P is near, the delay time difference between the m second
delay audio signals increases, whereas when the focal point P is far, the delay time between the
m second delay audio signals The difference between the two must be small and delicate control
of the delay time. If the means for the second delay processing are prepared separately for the
short distance and the long distance, it is possible to meet such a demand. Switching of the
analog delay line portion according to the distance from the speaker array 10 to the focal point is
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not limited to switching in two steps as described above, and may be appropriately determined
according to the necessary focal range .
[0025]
(3) The first delay means for directivity control in the first axial direction may be configured by a
ring buffer instead of the digital filter group. FIG. 9 is a block diagram showing an example of the
configuration. The first delay means shown in this figure is composed of an A / D converter
1031, a ring buffer 1032 composed of a dual port RAM or the like, a write control unit 1033,
and a read control unit 1034. In this aspect, the input audio signal IN to be processed is an
analog signal. The A / D converter 1031 samples this input audio signal with a sufficiently fast
sampling clock φ and converts it into samples of a digital signal. The write control unit 1033
counts the sampling clock φ, supplies the count result as the write address WA to the ring buffer
1032, and writes the sample output from the A / D converter 1031 to the ring buffer 1032. Read
control unit 1034 receives information designating delay time td (j) (j = 1 to n) between the input
audio signal and the n first delayed audio signals from CPU 101 in FIG. Control for reading the
first delayed audio signal from the ring buffer 1032 is performed.
[0026]
More specifically, the period of the sampling clock φ is TS, and the delay time between the input
audio signal and the first delayed audio signal S (j) (j = 1 to n) is td (j) (j = 1 to n). When the
sampling clock φ is supplied, the read control unit 1034 performs the following processing. That
is, the read address RA (j) (j = 1 to n) given by the following equation is sequentially supplied to
the ring buffer 1032 during one sampling period, and the first delayed audio signal S (j) (j = 1 to
n) are sequentially read out from the ring buffer 1032. RA(j)=WA−td(j)/TS
……(1)
[0027]
The n first delayed audio signals S (j) (j = 1 to n) read out in this manner are simultaneously
transmitted by the D / A converter (not shown) when the next sample clock φ is generated. It is
converted to an analog signal. The n analog signals are respectively supplied to n analog delay
line units 104-j (j = 1 to n) in FIG. 4. According to this aspect, the delay time of the first delayed
audio signal S (j) (j = 1 to n) can be adjusted with high accuracy by sufficiently shortening the
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cycle TS of the sample link clock φ.
[0028]
(4) In each embodiment described above, an input audio signal of one channel was handled.
However, by improving the first delay means in these embodiments, it is possible to
independently control the directivity in the first axial direction for audio signals of a plurality of
channels. FIG. 10 shows an example of the configuration of the first delay means modified to be
able to control the directivity in the first axial direction independently for a plurality of channels.
The first delay means includes a plurality of delay processing units that respectively execute the
first delay processing for each of the input audio signals of a plurality of channels (p channel in
the example shown in FIG. 10), and a subsequent stage of these delay processing units. And n
mixing units MX. The first delay processing in this case may be configured by digital filter
processing as shown in FIG. 4 or processing using a ring buffer as shown in FIG. The n analog
delay line units 104-j (j = 1 to n) in FIG. 4 are connected to the output terminals of the n mixing
units MX.
[0029]
The CPU 101 in FIG. 4 calculates the delay time of n delayed audio signals to be generated in the
first delay processing corresponding to each channel based on the information specifying the
directivity of the acoustic beam given to each channel. , Which of the plurality of analog delay
lines ADL is selected in the n analog delay line units 104-j (j = 1 to n), that is, a second delay
process to be commonly applied to all channels Decide. The delay processing unit corresponding
to each channel receives, from the CPU 101, information specifying a delay time between the
input audio signal of that channel and the n first delayed audio signals, and generates n delayed
audio signals from the input audio signal. Execute a first delay process to generate. The n mixing
units MX mix the delayed audio signals output from the plurality of delay processing units
corresponding to the same speaker unit string with each other to obtain n first delayed audio
signals as n analog delay lines It outputs to each part 104-j (j = 1 to n). The mixing performed by
the mixing unit may simply add the delayed audio signals of the respective channels, or may be
performed by multiplying and adding different weighting factors for each channel. In the latter
case, the user may set the weighting factor to be applied to each channel by the operation of the
operation element. According to this aspect, the directivity in the first axial direction can be
controlled independently for a plurality of channels, and acoustic reproduction with rich
presence can be realized.
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[0030]
It is a front view showing composition of a speaker array in a speaker array system which is one
embodiment of this invention. It is a figure explaining the principle of operation of the speaker
array system. It is a figure explaining the principle of operation of the speaker array system. It is
a block diagram which shows the specific structural example of the same speaker array system. It
is a block diagram which shows an example of the analog delay line in the same speaker array
system. It is a block diagram which shows an example of the analog delay line in the same
speaker array system. It is a figure which shows the example of directivity control of the 2nd
axial direction performed by the analog delay line in the same speaker array system. It is a figure
which shows the example of directivity control of the 2nd axial direction performed by the
analog delay line in the same speaker array system. It is a figure which shows the other
structural example of the 1st delay means in the embodiment. It is a figure which shows the
other structural example of the 1st delay means in the embodiment.
Explanation of sign
[0031]
101 ... CPU, 103 ... DSP, 104-j (j = 1 to n) ... Analog delay line section, SP (i, j) (i = 1 to m, j = 1 to
n) ... Speaker unit, 10 ... Speaker array.
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