close

Вход

Забыли?

вход по аккаунту

JP2005236636

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2005236636
An object of the present invention is to realize generation of a plane wave whose spread is
suppressed by the size of an acoustic output element array. In an acoustic output element array
in which a plurality of acoustic output elements are disposed in space, an acoustic signal is
applied to each acoustic output element through an independent filter, and a plurality of controls
in which the filters are disposed in the same space The observation signal at the point becomes a
desired plane wave in the sound reproduction direction set in advance, and is set to a filter
coefficient such that the observation signal becomes zero in the sound cut-off area set in
advance. By arranging a plurality of control points in a direction perpendicular to each other, a
means for confirming that the plane wave is a plane wave is provided. [Selected figure] Figure 8
Sound output element array
[0001]
The present invention relates to an audio device that reproduces an audio signal and a
communication device, and relates to an audio output element array that provides sound only to
people in a specific direction.
[0002]
In recent years, communication conferences connecting remote places using ISDN lines, ADSL
lines, optical networks and the like have come to be held frequently.
09-05-2019
1
Such communication meetings are generally conducted in a conference room or the like that is
acoustically closed, but communication meetings may be held easily in one corner of an open
office (large room with disks lined up). It is desired. In a teleconference in such a place, since
people who are not in the conference do not want to hear loud voices, a technology that can
reproduce sound only in a specific area or in a specific direction is desired. . A directional
speaker is known as an acoustic output element that emits a sound only in a specific direction to
realize this. As directional speakers, horn speakers, parametric speakers, analog speaker arrays,
digital filter type speaker arrays and the like are conventionally known.
[0003]
The horn speaker (Non-Patent Document 1) realizes directivity by the geometric shape of the
horn, and is usually limited to the high frequency band, and in order to obtain sharp directivity in
a wide frequency range, It requires a horn of a large size exceeding 1 m and can not be used for
general applications. A parametric speaker (Patent Document 1) is a system that attempts to
obtain sharp directivity for an audible sound by making ultrasonic waves with sharp directivity
into a carrier (carrier wave) of the audible sound, and is an audio signal. This is a scheme in
which the original speech signal is demodulated by the non-linearity in air of the modulated
ultrasonic waves. This method is known to obtain sharp directivity, but has problems such as the
need for a special amplifier for emitting ultrasonic waves and the suppression of the influence of
ultrasonic waves on the human body.
[0004]
On the other hand, the method of using a speaker array as an acoustic output element achieves
directivity by using an acoustic output element (i.e., a speaker) of ordinary audible sound, which
is smaller in size than a horn speaker, and not ultrasonic waves. It is intended to be a method that
does not have size problems and problems with ultrasound listening. As a system using a speaker
array, there are an analog speaker array and a digital speaker array in which speakers are simply
arranged in parallel. Hereinafter, these two methods will be described in detail as prior art. FIG. 1
is an explanatory view showing a configuration of an acoustic output element array in which a
plurality of acoustic output elements (speakers) are linearly arranged. In this figure, 10 is an
acoustic signal input terminal for inputting an acoustic signal to be reproduced to the acoustic
output element array, 11 is a weighting circuit for adjusting the volume to be reproduced to each
acoustic output element, 12 is a sound emission to space An acoustic output element array is
shown, 13 is a listener, and 14 is a speaker amplifier. In the following example, the case where
17 acoustic output elements are arranged on a straight line at an interval of 12 cm will be
09-05-2019
2
described. Assuming that a linear acoustic output element array arranged in a straight line under
a TV monitor or the like is installed at a teleconference etc., the overall horizontal size is 1.92 m
(12 cm × (17-1) = 192 cm ). At this time, it is assumed that the listener 13 is in a direction
perpendicular to the axial direction of the acoustic output element array.
[0005]
First, as a simple example, the case where all the weightings of the weighting circuit 11 of FIG. 1
are set to 1 will be described (Non-Patent Document 1). This case corresponds to the input of
acoustic signals of the same phase and volume to the acoustic output elements of the linear
acoustic output element array of FIG. A state in which both the reproduced sound pressure in the
sound field and the spatial impulse response distribution showing how the impulse response is
spatially changed is superimposed and displayed is shown in FIG. In FIG. 2, the linear acoustic
output element array is disposed in the longitudinal direction at a position of 0 m along the
horizontal axis. The gentle curve in FIG. 2 represents the equal sound pressure distribution in the
case where the sound source signal is a sine wave of 500 Hz, and the display shading is changed
at intervals of 5 dB. Also, in FIG. 2, for example, it is a space impulse response that is displayed in
the vertical direction at a position of 0.9 m and 1.6 m on the horizontal axis in a vertical
direction, and impulses as the sound source signal (here, band limited to 2 kHz) When impulse
(impulse) is applied to the acoustic signal input terminal, the waveform sound pressure observed
in space every 2.5 ms is shown in dB. By looking at the spatial impulse response, it is possible to
know how a wavefront that is unknown only by the sound pressure distribution is a plane wave.
[0006]
As can be seen from the example of FIG. 2, when the acoustic output element array is driven at
the same phase and volume, a clean plane wave is produced, but the directional characteristics
are not so good from the sound pressure distribution, and sound around You can see how it
leaks. The cosine weighting method is known as a method for reducing the sound leakage to the
surroundings. In this method, assuming that the weight of the weighting circuit 11 in FIG. 1 is M,
and the number of the sound output element to be the center of the sound output element array
is cnt (cnt = M / 2), ai = cos (π) This is a method of setting / 2 <*> (i-cnt) / M) (Non-Patent
Document 1). This is to prevent the sound leakage to the surroundings due to the sound
reproduction of the end sound output element by setting the weight of the center sound output
element to 1 and reducing the weight coefficient toward the end. FIG. 3 shows a superimposed
display of the reproduced sound pressure distribution and the spatial impulse response
distribution of the acoustic output element array driven by this method. As compared with FIG. 2,
09-05-2019
3
it can be seen that the reproduced sound pressure distribution falls within the range of the
original acoustic output element array, and substantially good directivity characteristics are
obtained.
[0007]
At this time, when the size of the sound output element is reduced, the directivity tends to be
deteriorated. This can also be understood from the fact that when the lowest one speaker is
sounded, it becomes an omnidirectional speaker. In other words, in order to realize a directional
speaker, it can be said that the number and size of acoustic output elements are required to some
extent. The above characteristic evaluation ideally assumes that the sound output element is a
non-directional speaker, and it is considered that the directivity characteristic actually produced
is wider than that shown here in general. Therefore, even if the size of the acoustic output
element array is the same, a method for reducing the sound leakage to the surroundings is
desired, and in recent years, a speaker control method using a digital signal processing circuit
has been developed.
[0008]
In this method, more detailed processing can be performed by controlling the phase and the
amplitude for each frequency by connecting a digital filter to the acoustic output element array.
FIG. 4 shows a configuration diagram of an acoustic output element array using this digital signal
processing method. Reference numeral 41 denotes a digital filter, which is usually constituted by
an FIR filter. Further, Bi (z) represents the characteristic of the filter, and is connected to the FIR
filter coefficient bi (n) by the following relationship. Here, L represents the number of filter taps,
and z represents z conversion. Reference numeral 42 denotes a receiver (microphone) for
observing the sound emitted into space when determining the filter coefficient, and its position is
called a control point. The other components are the same as in FIG. Reference numeral 46
denotes an A / D converter, and 47 denotes a D / A converter.
[0009]
As a method of determining the filter coefficient by digital signal processing, there is known a
method of applying feedback to the filter coefficient so that the signal observed by the receiver
42 disposed at the control position of the sound field has a desired directional characteristic. It is
09-05-2019
4
done. The conventionally known sound field control method is a method of controlling the sound
pressure at each control point (Patent Document 2), but by arranging the control points
continuously, directivity characteristic control and the like are also possible. It is also known to
be. Reference numeral 50 denotes a controller that controls the filter coefficients of the digital
filter 41 in accordance with the detection signal of the receiver 42.
[0010]
According to Patent Document 2, arbitrary sound pressure control can be accurately performed
if the number of control points is one or more than the number of control sound sources.
Therefore, here, as an example of directivity control using the method of sound field control,
consider the design of directivity characteristics as shown in FIG. 5 with 17 sound output
elements and 12 control points. Here, a cross mark 43 indicates a control point, and the sound
pressure of the point is observed by placing the sound receiver 42. Further, a hatched area 44
indicates a sound reproduction area as a target of directivity characteristics, and 45 indicates a
main sound source speaker. Further, in FIG. 5, the amplifier, the A / D converter and the D / A
converter are omitted. In order to obtain desired directivity characteristics under such conditions,
one of the acoustic output element arrays is used as the main sound source speaker 45, and the
filter characteristic of the main sound source speaker 45 is through (the filter is eliminated). The
filter coefficients of the digital filter that applies an acoustic signal to the remaining acoustic
output elements so that sound is first emitted into space and the sound pressure at the control
point 43 indicated by x in the drawing is zero. By setting, the desired directivity characteristic
can be obtained as a whole. 44 shows a sound reproduction area.
[0011]
Specifically, in order to control the sound pressure to 0 at the control point 43 marked by x, the
sum of the sound reached from the main sound source speaker 45 and the sound reached from
the other sound output elements is 0 Just do it. Now, for example, when an impulse signal is
applied to the input terminal 10, the sound pressure Pj (z) observed at the j-th control point can
be described as follows. Pj (z) = G0j (z) + B1 (z) G1j (z) + B2 (z) G2j (z) +... + BM (z) GMj (z) where
G0j is a control point j from the main sound source speaker The transfer function up to Gij is a
transfer characteristic from the acoustic output element i = 1 to M of the acoustic output element
array to each control point j = 1 to N. In this example, M is 16 because the number of main sound
source speakers has been removed, and N is 12 because N is the number of control points.
09-05-2019
5
[0012]
Now, since the sound pressure of the j-th control point can be set to 0 by this equation becoming
0, the following equation is established if Pj (z) = 0. B1 (z) G1 j (z) + B2 (z) G2 j (z) + ... + B M (z)
GM j (z) =-G 0 j (z) If this is expanded for all j and expressed in matrix, It can be written as
However, z is omitted because it is common. Now, assuming that the determinant is G · B = R, B is
obtained by B = G <T> · (G · G <T>) <− 1> · R. This content is the same processing as that of the
second embodiment described in Patent Document 2.
[0013]
FIG. 6 is a diagram in which the sound pressure distribution and the space impulse response
distribution obtained by the processing of the prior art are superimposed on each other. The
view of the figure is the same as in FIGS. 2 and 3. From FIG. 6, in order to narrow down the
directional characteristics, by narrowing the arrangement of the control points 43, the directional
characteristics are narrowed in the vicinity of the narrowed portion formed by the control points
43. You can see how it has spread. Here, if it is attempted to increase the number of control
points 43 and narrow the diaphragm as shown in FIG. 7 to suppress the spread, the result is that
no sound is emitted from the acoustic output element array, and it was found that control was
impossible. . Patent Document 1: Japanese Patent Application Laid-Open No. 2003-153369
Patent: Japanese Patent No. 2558445 Acoustic Engineering, written by Mitsuida Toshiro p. 101
(Seishodo: 1993) Acoustic Engineering, written by Mitsuida Toshiro p.
[0014]
As mentioned above, in the acoustic output element array of the analog system which is the prior
art, the beam width can not be reduced depending on the size of the array, and also in the digital
system, the vicinity of the diaphragm portion formed by the control point 43 It was found that
although the beam width can be narrowed at this point, there is a problem that the beam width
widens when it goes out of the aperture part. Further, when the number of control points is
increased to narrow the beam width, there is a problem that no sound is emitted from the
acoustic output element array. The present invention has been made in view of such
conventional problems, and it is an object of the present invention to realize an acoustic output
element array in which directivity smaller than the size of the acoustic output element array can
be obtained.
09-05-2019
6
[0015]
According to claim 1 of the present invention, in an acoustic output element array in which a
plurality of acoustic output elements are disposed in space, acoustic signals are applied to the
respective acoustic output elements through independent filters, and the filters are disposed in
the same space The observation signal at a plurality of control points becomes a desired plane
wave in the sound reproduction direction set in advance, and is set to a filter coefficient in which
the observation signal becomes zero in the sound cut-off area set in advance. A means for
confirming that the plane wave is a plane wave is provided by arranging a plurality of control
point rows arranged by arranging a plurality of control points in a direction orthogonal to the
direction of movement in the direction of movement of the plane wave. We propose an acoustic
output element array.
[0016]
According to a second aspect of the present invention, in the acoustic output element array
according to the first aspect, the plurality of control points arranged in the direction orthogonal
to the traveling direction of the plane wave is a sound emphasis control point. The columns
receive the sound emitted from the acoustic output element array at almost the same sound
pressure at all the sound emphasis control points, and the second column has the first and
second columns at all the sound emphasis control points We propose an acoustic output element
array characterized in that the characteristics of the filter are controlled to receive the sound
pressure taking into consideration the phase delay by the time difference obtained by dividing
the eye distance difference by the sound velocity.
According to a third aspect of the present invention, in the acoustic output element array
according to the first or second aspect, the sound blocking area sets a plurality of control points
on the boundary with the sound reproduction direction area, and the plurality of control points A
sound output element array is proposed, which is characterized in that the setting of the sound
blocking area is confirmed by controlling the filter coefficient of the filter so as to make the
sound pressure zero.
[0017]
According to the present invention, even if the number of control points is increased and the
beam width is narrowed, sound can be generated from the acoustic output element array by
09-05-2019
7
providing the sound emphasis control points. That is, a plane wave whose spread is suppressed
more than the size of the acoustic output element array can be realized, and a plane wave with
high directivity can be obtained.
[0018]
Each of the acoustic output elements constituting the acoustic output element array is connected
to an independent digital filter. The characteristics of this digital filter are that the observation
signals at a plurality of control points arranged in the same space become desired plane waves in
the sound reproduction direction set in advance, and the observation signals in the sound
interruption region set in advance simultaneously. It is set to satisfy zero. Furthermore, by
arranging a plurality of control points in a plurality of lines in a direction orthogonal to the
desired plane wave traveling direction in the sound reproduction direction area, a means for
confirming that it is a plane wave is configured in the sound reproduction area. Adjust the filter
characteristics so that the sound of the sound becomes a plane wave, and set the control point on
the boundary line with the sound reproduction direction area, and the sound pressure at the
control point on the boundary line becomes zero. By including means for confirming the setting
in the sound blocking area, the filter characteristic is adjusted to be an acoustic output element
array having directional characteristics.
[0019]
FIG. 8 shows a diagram for explaining a detailed embodiment of the present invention. In FIG. 8,
81 indicates a first row of sound enhancement control points, 82 indicates a second row of
sound enhancement control points, 83 indicates a digital filter used in the present invention, and
Hi (z) indicates each filter characteristic. Other symbols are the same as described above.
Compared with FIG. 7 showing the prior art, it is characterized in that all the sound output
elements 12 are equipped with digital filters 83 and that sound emphasis control points 81 and
82 are increased. Therefore, the controller 50 receives the detection signal from each control
point 43 and the detection signals from the sound emphasis control points 81 and 82, and the
following control is performed.
[0020]
In this embodiment, in order to confirm that it is a plane wave, a sound emphasis control point
09-05-2019
8
81 is disposed perpendicularly to the sound traveling direction, and in order to ensure that the
sound wave which has further advanced maintains the plane wave, A second sound emphasis
control point 82 is arranged. Here, at the sound emphasis control points indicated by ○, the
sound emitted from the acoustic output element array is 1 for all sound emphasis control points
81 in the first column, and all sound emphasis control points for the second column. At 82, the
sound pressure is controlled to a value that reproduces the sound pressure considering the phase
delay by the time difference obtained by dividing the distance difference between the first row
and the second row by the sound velocity. Further, at the control point indicated by x, the sound
pressure is controlled to be 0 as in the prior art. The filter characteristics that satisfy such
conditions can be described as follows. Here, Gij is a transfer characteristic from the i-th speaker
to the j-th control point. In this equation, the control points are control points at which the sound
pressure is made zero from 1 to j-1, j to k-1 are the sound enhancement control points of the first
row, and k to N are the sound of the second row It represents emphasis control points. Also, Δ is
a delay time obtained by dividing the difference in distance between the front row (control points
j to k-1) and the rear row (control points k to N) by the speed of sound, and ω is a frequency.
[0021]
Now, assuming that the above equation is GH = R, the characteristics of the digital filter
connected to the acoustic output element array can be obtained by H = G <T> · (G · G <T>) <− 1>
· R . In addition, H may be determined by using the following equation, where δ is a positive
constant smaller than the maximum eigenvalue of G · G <T> so that the inverse matrix does not
become unstable. H = G <T>. (G.G <T> +. Delta.I) <-1> .R However, I is a unit matrix.
[0022]
FIG. 9 shows the sound pressure distribution and the spatial impulse response distribution of the
acoustic output element array according to the present invention. The view of the figure is the
same as in FIGS. 2 and 3. It can be understood from this figure that a plane wave whose spread is
suppressed more than the size of the acoustic output element array can be realized as compared
with the prior art.
[0023]
The present invention can be applied to a communication conference apparatus installed in an
open office as an application example.
09-05-2019
9
[0024]
The block diagram for demonstrating the structure of the conventional acoustic output element
array of an analog system.
The figure which shows the sound pressure distribution and space impulse response distribution
example of the acoustic output element array of the conventional analog system. The figure
which shows the sound pressure distribution at the time of adding a cosine load, and the example
of space impulse response distribution in the acoustic output element array of the conventional
analog system. The block diagram for demonstrating the structure of the conventional sound
output element array of a digital system. FIG. 8 is a layout diagram showing an example of
desired directivity characteristics in a conventional digital sound output element array and
control point layout for realizing the same. The figure which shows the example of sound
pressure distribution and space impulse response distribution of the conventional acoustic
output element array of a digital system. FIG. 8 is a layout diagram showing an example of
desired directivity characteristics with a reduced spread and control point layout for realizing the
same in a conventional digital sound output element array. FIG. 8 is a layout diagram for
explaining an example of desired directivity characteristics of a plane wave with a reduced
spread, and control points and sound emphasis control point arrangement for realizing the
desired spread in the acoustic output array of the present invention. The figure which shows the
sound pressure distribution of the acoustic output array of this invention, and the example of
space impulse response distribution.
Explanation of sign
[0025]
DESCRIPTION OF SYMBOLS 10 input terminal 50 controller 12 sound output element array 81,
82 sound emphasis control point 43 control point 83 digital filter 44 sound reproduction area
09-05-2019
10
1/--страниц
Пожаловаться на содержимое документа