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JP2004056261

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DESCRIPTION JP2004056261
The present invention provides an acoustic system capable of setting an appropriate sound field
by arranging a center speaker so as not to disturb a video displayed on a screen. SOLUTION: Left
and right speakers 2, 3 are arranged on both sides of a screen 1, and a center speaker 4 having a
sharp directivity characteristic is arranged on the front side of the screen 1. Then, the sound
output from the center speaker 4 is reflected on the front side of the screen 1 to reach the sound
receiving point. [Selected figure] Figure 1
Sound system
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic system suitable for a projector that displays an image using, for example, a screen. 2.
Description of the Related Art In recent years, a projector that displays a large screen image
using a screen has been widely spread in general homes and the like. In such a projector, a multichannel audio system using a plurality of speakers such as a 5.1 channel surround system is
provided as an audio system. [0003] FIG. 8 is a view showing an arrangement example of a
fluorocarbon speaker in a conventional acoustic system. The sound system shown in FIG. 8 is
provided with a left speaker 101, a right speaker 102, and a center speaker 103 as front
speakers. In this case, the left speaker 101 is disposed on the front left side of the screen 100,
and the right speaker 102 is disposed on the front right side. Further, a center speaker 103 is
disposed substantially at the center of the screen 100. By the way, in the case where the front
speakers are arranged as described above, when the center speaker 103 is arranged on the front
side of the screen 100, ie, on the front side of the screen 100, the user can When looking at the
screen 100, the center speaker 103 gets in the way. For this reason, usually, the center speaker
103 is disposed below or above the screen 100. However, if the center speaker 103 is disposed
at the lower side or the upper side of the screen 100, the sound image localization position by
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the center speaker 103 is absolutely deviated from the proper arrangement position, so an
optimal sound field is set according to the user's viewing position. Can not do it. Therefore, for
example, it is conceivable to dispose the center speaker 103 on the back side of the screen 100
so that the center speaker 103 can not be seen from the front side of the screen 100. However,
in this case, the high-frequency component of the sound output from the center speaker 103 is
attenuated due to the transmission acoustic characteristic of the screen 100, and as a result, the
optimum sound field setting according to the user's viewing position is performed. I could not In
order to prevent the attenuation of high frequency components due to the screen 100 as
described above, there are screens in which fine holes are made in the screen 100 to improve the
acoustic characteristics. From the relationship, it is difficult to improve the acoustic
characteristics by enlarging the shape of the holes formed in the screen, and therefore it was not
possible to sufficiently prevent the attenuation of the high frequency component.
Therefore, the present invention has been made in view of such a point, and it is possible to set
an appropriate sound field after arranging a center speaker so as not to disturb the image
displayed on the screen. It aims at providing an acoustic system. In order to achieve the above
object, according to the sound system of the present invention, the sound radiated to the sound
reflection surface disposed in the listening space is reflected by the sound reflection surface. It is
arranged to reach a predetermined listening position and is provided with a sharp pointing
speaker having a sharp pointing characteristic as a pointing characteristic. According to the
present invention, a sharp pointing speaker having a sharp pointing characteristic is disposed on
the front side of the acoustic reflection surface. Then, the sound output from the sharp
directional speaker is reflected on the front side of the acoustic reflection surface to reach a
predetermined sound receiving point. BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below. In the present embodiment, an
audio system provided in an AV system such as a projector using a screen will be described as an
example. FIG. 1 is a view showing an arrangement example of front speakers in the acoustic
system of the present embodiment. In addition, this FIG. 1 is the figure which looked at the sound
system of this Embodiment from the upper surface side. As shown in FIG. 1, in the sound system
of the present embodiment, a screen 1 for displaying an image projected from a projector main
body 6, a left speaker 2, a right speaker 3, and a center speaker 4 3. Consisting of two speakers.
The left speaker 2 is disposed on the left side of the screen 1. The sound emission surface is
directed to the sound receiving position (listening position) L. The sound of the left channel (Lch)
is output from such a left speaker 2. In this case, the direct sound of the left speaker 2 reaches
the user at the sound reception position L. The right speaker 3 is disposed on the right side of
the screen 1. The sound emitting surface of the right speaker 3 is also directed to the sound
receiving position L as described above. The sound of the right channel (Rch) is output from such
a right speaker 3. In this case, the direct sound of the right speaker 3 reaches the user at the
sound reception position L. The center speaker 4 is disposed on the front side of the screen 1. In
addition, the center speaker 4 is structured to have sharp directivity so as to emit a sound wave
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only in a specific direction (for example, an axial direction orthogonal to the sound emission
surface).
The sound emission surface of the center speaker 4 is directed to the required position of the
screen 1 such that the reflected sound reflected by the screen 1 reaches a predetermined sound
receiving position L when the sound is emitted from the center speaker 4. There is. The sound of
the center channel (Cch) (hereinafter, referred to as “center sound”) is output from such a
center speaker 4. In this case, the sound output from the center speaker 4 is reflected by the
screen 1 because the center speaker 4 has sharp directional characteristics and the sound
emission surface of the center speaker 4 is directed to the screen 1. And the sound receiving
position L is reached. The installation positions of the left speaker 2 and the right speaker 3 in
the sound system of the present embodiment are determined, for example, by setting the sound
field based on the viewing position of the user. If the center speaker 4 is at a position where the
sound of the center speaker 4 is reflected by the screen 1 and reaches the predetermined sound
receiving position L, for example, the vicinity of the projector main body 6 or this embodiment It
is possible to install in the ceiling etc. of the room in which the acoustic system of a form is set.
Further, for example, when the sound field is set so that the user's viewing position is located
substantially at the center of the screen 1, the arrangement position of the center speaker 4 is
approximately the center position of the screen 1. In this case, the arrangement position of the
center speaker 4 substantially coincides with the projector main body 6. In this case, the path of
the center sound output from the center speaker 4 and the optical axis of the image output from
the projector main body 6 also substantially match. Therefore, in this case, since the center
speaker 4 can be integrated with the projector main body 6, there is an advantage that the user
does not have to install the center speaker 4 in this case. FIG. 2 is a diagram showing the path of
the sound output from the center speaker. As shown in FIG. 2, the sound wave P1 output from
the center speaker 4 is reflected by the screen 1 and the reflected sound wave P1 reaches the
user at the sound receiving position L. Thus, at the sound receiving position L, an appropriate
center sound can be obtained from the center speaker 4. Further, in this case, although not
shown in this figure, since there is a distance from the center speaker 4 to the screen 1
compared to the left and right speakers 2 and 3, the center sound of the center speaker 4 and
the left and right speakers When the two or more sounds are output at the same timing, the
center sound of the center speaker 4 can be heard delayed at the sound receiving position L.
Therefore, in the present embodiment, the sound output from the left and right speakers 2 and 3
and the center speaker 4 is delayed according to the distance from the center speaker 4 to the
screen 1 as described later. The timings of the center sound of the center speaker 4 and the
sounds of the left and right speakers 2 and 3 are made to coincide with each other. In this case,
as described above, since the center speaker 4 has a sharp directivity such that it emits a sound
wave only in the direction of the screen 1, it is shown in FIG. Thus, for example, even if the center
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speaker 4 is disposed behind the user at the sound receiving position L, the direct sound of the
center speaker 4 hardly reaches the user. FIG. 3 is a block diagram showing the internal
configuration of the acoustic system shown in FIG. As shown in FIG. 3, the audio signal of the
center channel (Cch) to be input is input to the adders 16 and 19 through a low pass filter (LPF)
11 that extracts low frequency components. Further, the audio signal of the center channel (Cch)
is input to an amplifier 13 via a high pass filter (HPF) 12 for extracting high frequency
components, amplified by the amplifier 13 and input to a center speaker 4. Then, this center
speaker 4 outputs an audible sound. The HPF 12 extracts a predetermined high frequency
component from the sound signal of the center channel (Cch). In this case, the signal band
extracted by the HPF 12 is determined according to the frequency band in which the center
speaker 4 exhibits sharp directivity. Also, the audio signal of the right channel (Rch) that is input
is input to the adder 16 via the delay circuit 15, and the low-pass component of the audio signal
of the center channel input via the LPF 11 in the adder 16. Are added and amplified by the
amplifier 17 and input to the right speaker 3. Then, the right speaker 3 outputs an audible
sound. The voice signal of the left channel (Lch), which is similarly input, is input to the adder 19
via the delay circuit 18, and after the low-frequency component of the audio signal of the center
channel is added in the adder 19, The signal is amplified by the amplifier 20 and input to the left
speaker 2. Then, the left speaker 2 outputs an audible sound. The delay circuits 15 and 18 are
provided to delay audio signals input from the left and right speakers 2 and 3 in accordance with
the distance from the center speaker 4 to the screen 1 as described above.
In general, since the sound image localization position of the low frequency range audio signal is
not clear, there is no particular problem even if the low frequency component of the center
channel audio signal is reproduced by the left speaker and / or the right speaker. Also, by
inputting substantially the same level to the left and right speakers and reproducing, it is possible
to localize the sound image substantially at the center of the screen. As described above, in the
sound system of the present embodiment, only the high frequency component of the input center
channel signal is input to the center speaker 4. Then, the low frequency component of the center
channel audio signal is added to the audio signals of the left and right channels. Thereby, at the
sound receiving position L, an appropriate sound is obtained. Then, in this case, only the high
frequency sound of the center channel is output from the center speaker 4, and the low
frequency sound of the center channel is output from the left and right speakers 2 and 3. In this
way, the high frequency component of the center channel signal output from the center speaker
4 and the low frequency component of the center channel signal output from the left and right
speakers 2 and 3 are users of the sound receiving position L at the same timing. And the proper
center voice can be obtained. The internal configuration of the sound system shown in FIG. 3 is
merely an example, and it is of course possible to realize it by other configurations. For example,
in the example shown in FIG. 3, the audio signal input to the center speaker 4 is the high
frequency component of the center channel signal extracted by the HPF 12, and the low
frequency component of the center channel signal is output from the left and right speakers 2
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and 3. However, the HPF 12 may be deleted and the band limitation of the center channel signal
input to the center speaker 4 may be deleted. That is, a center voice whose band is not limited
may be output from the center speaker 4, and the LPF 11 and the adders 16 and 19 may be
deleted. Here, FIG. 4 shows a structural example of a sharp directional speaker used as a center
speaker as described above. FIG. 4A is a view showing a structural example of a horn speaker
having a sharp directivity. When constructing the horn speaker 21 having a sharp directional
characteristic as shown in FIG. 4A, for example, the length of the flange 22 portion is larger than
that of a normal horn speaker having a wide directional characteristic having a shape as shown
by a broken line. shorten.
Further, the spread of the flange 22 is reduced to reduce the opening area of the opening surface
23. As a result, a compact and superdirective horn speaker can be configured. Further, FIG. 4B
shows an array speaker constituted by a plurality of speaker units SP as another structural
example of the sharp directional speaker. Such an array speaker 31 changes the amplitude and
phase of the audio signal input to each speaker unit SP, SP according to a certain function after
forming each speaker unit SP, SP. Thus, it is possible to configure a speaker having any
directivity. Therefore, in the present embodiment, the center speaker 4 may be configured by the
horn speaker 21 or the array speaker 31 described above, and the directivity characteristic of the
center speaker 4 may be a characteristic as shown in FIG. That is, almost no output sound
pressure can be obtained in the sound receiving direction in which the user is located, for
example, in the left-right direction (90 °, -90 °) with respect to the axial direction (0 °). It may
be a sharp directional speaker having a The center speaker 4 can also be configured by an
ultrasonic speaker having directivity. Although illustration and detailed description of the
ultrasonic speaker is omitted, the ultrasonic speaker is also called a so-called parametric speaker,
and emits two types of ultrasonic waves having different frequencies, so that the non-linearity of
air as a propagation medium causes these. An audible sound is output on the screen surface
(acoustic reflection surface) on which the ultrasonic waves are reflected. In the sound system of
the present embodiment, the center speaker 4 is disposed on the front side of the screen 1 so
that the sound emitting surface is directed to the screen 1, and the center sound is output from
the center speaker 4. I have to. Thereby, even when the center speaker 4 is disposed on the front
side of the screen 1, an appropriate center sound can be obtained at the sound receiving position
L. Further, according to the sound system of the present embodiment, since the center speaker 4
can be disposed at a position other than the lower side or the upper side of the screen 1, the
degree of freedom of the installation position of the center speaker 4 can be expanded. FIG. 6 is a
view showing an example of the arrangement of speakers in an acoustic system according to
another embodiment. In addition, this FIG. 6 is the figure which looked at the arrangement
position of the speaker from the upper surface side.
Further, in FIG. 6, the same parts as those in FIG. In the sound system shown in FIG. 6, the left
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and right speakers 2 and 3 disposed on both sides of the screen 1 in FIG. 1 are disposed on the
front side of the screen 1. That is, in this case, in addition to the center sound output from the
center speaker 4, the left and right sounds output from the left and right speakers 2 and 3 are
also emitted from the front surface of the screen 1. In this case, the left and right speakers 41
and 42 have a sharp directivity such that sound waves are emitted only in a specific direction
(axial direction orthogonal to the sound emitting surface), similarly to the center speaker 4. The
sound emitting surfaces of the left and right speakers 41 and 42 are directed from the left and
right speakers 41 and 42 to the position of the screen 1 where the reflected sound reflected by
the screen 1 reaches the sound receiving position L. Accordingly, the left and right speakers 41
and 42 have sharp directional characteristics, and the sound emitting surfaces of the left and
right speakers 41 and 42 are directed to the screen 1. Since the left and right sounds output
from the left and right speakers 41 and 42 are also reflected by the screen 1 and reach the user
at the sound receiving position L. As a result, at the sound receiving position L, appropriate
sound can be obtained from the center speaker 4 and the left and right speakers 41 and 42. FIG.
7 is a block diagram showing an internal configuration of the acoustic system shown in FIG. Also
in this case, the same parts as those in FIG. In this case, as shown in FIG. 7, an audio signal of the
right channel (Rch) is amplified by the amplifier 11 and input to the right speaker 42, and an
audio signal of the left channel (Lch) is input to the left speaker 41. It may be amplified by the
amplifier 20 and input. Further, an audio signal of the center channel (Cch) may be amplified by
the amplifier 13 and input to the center speaker 4. Even when the sound system is configured as
described above, it is possible to obtain an appropriate sound at the sound receiving position L. If
such an acoustic system is applied to, for example, a projector using a large screen where the left
and right speakers 2, 3 can not be arranged on the side of the screen 1, the degree of freedom of
the arrangement position of the left and right speakers 2, 3 is increased. It has the advantage of
In FIG. 6, since the path length from the left and right speakers 2 and 3 to the sound receiving
position L is longer than the path length from the center speaker 4 to the sound receiving
position L, the delay for making their propagation delay time uniform In the circuit shown in FIG.
6, for example, a delay circuit may be inserted to the center channel signal. In the present
embodiment, the sound system provided in an AV system such as a projector using a screen has
been described as an example, but this is merely an example, and the sound system of the
present invention is It is applicable if it is a projector apparatus using the screen surface which
can reflect the center sound of the center speaker 4. In addition to the screens described above,
the acoustic reflection surface may be, for example, a wall surface as long as it has a reflection
surface that is disposed in the listening space and reflects sound. Furthermore, the present
invention is applicable to a projector device or the like using the screen as a screen, and the
acoustic system does not necessarily have to be provided together with the projector device.
Furthermore, in the present embodiment, the case where the left and right speakers and the
center speaker are provided as the front speakers has been described as an example, but the
sound system of the present invention includes at least the center speaker as the front speakers.
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Can be realized. As described above, according to the sound system of the present invention, a
sharp pointing speaker having a sharp pointing characteristic is disposed on the front side of the
screen surface which is a sound reflecting surface. By reflecting the sound from the front side of
the screen surface to the screen surface, it is possible to obtain an appropriate sound output at a
predetermined sound receiving point. For example, if a sharp pointing speaker having a sharp
pointing characteristic on the front side of the screen is disposed as a center speaker, an
appropriate voice output can be obtained at a predetermined sound receiving point by the
reflected sound reflected on the screen surface. In this way, the degree of freedom of the
installation position of the speaker can be expanded, and an acoustic system in which the sound
field is set so as to be an appropriate sound field can be easily realized. BRIEF DESCRIPTION OF
THE DRAWINGS FIG. 1 is a view showing an arrangement example of speakers in an acoustic
system as an embodiment of the present invention. FIG. 2 is a diagram showing a sound wave
path of sound output from a center speaker. 3 is a block diagram showing an internal
configuration of the acoustic system shown in FIG.
FIG. 4 is a view showing an example of the structure of a sharp directional speaker. FIG. 5 is a
view showing directivity characteristics of a sharp directional speaker. FIG. 6 is a view showing
an arrangement example of speakers in an acoustic system of another embodiment. 7 is a block
diagram showing an internal configuration of the acoustic system shown in FIG. FIG. 8 is a view
showing an example of arrangement of speakers in a conventional sound system. [Description of
code] 1 screen, 2 41 left speaker, 3 42 right speaker, 4 center speaker, 6 projector body, 11 LPF,
12 HPF, 13 1720 amplifier, 15 18 delay circuit, 16 19 adder, 21 horn speaker, 31 array
speakers
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