JPH05227586

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DESCRIPTION JPH05227586
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
directional loudspeaker device.
[0002]
2. Description of the Related Art When different explanations are given at adjacent booths in
exhibition halls or when different announcements are made at homes next to a station,
directional loudspeakers that can obtain strong sound pressure only at specific locations are
effective. It is.
[0003]
As a means for achieving narrow directivity, there is known a method of placing the speaker unit
on the concave surface of the reflector at the focal point of the parabolic or elliptical reflector, or
a method of arranging a plurality of speaker units in a straight line. ing.
Hereinafter, the configuration will be described with reference to (FIG. 7), (FIG. 9) and (FIG. 11).
[0004]
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(FIG. 7) arrange ¦ positions the speaker unit 2 facing the concave surface of a reflector at the
focus of the reflector 1 of a paraboloid. The sound wave emitted from the speaker unit 2 is
reflected by the reflector 1 and exhibits a sound pressure distribution having a strong directivity
as shown in FIG. (FIG. 8) is the result of calculating the in-plane sound pressure distribution when
the parabolic reflector with an aperture diameter of 1.5 m and a depth of 0.5 m is installed at 3.5
m above the floor. The frequency is 1 kHz, and reflections from the floor, walls, etc. are not
considered.
[0005]
(FIG. 9) arrange ¦ positions the speaker unit 4 to the concave surface of a reflector at the focus of
the reflector 3 of an elliptical surface. The sound wave emitted from the speaker unit 4 is
reflected by the reflector 3 and converges at the other focal point of the ellipse. FIG. 10 shows
the sound pressure distribution when an ellipsoidal reflector with an aperture diameter of 1.5 m
and a depth of 0.8 m is installed 3.2 m above the floor. The frequency is 1 kHz and reflection is
not considered.
[0006]
(FIG. 11) arranges the speaker unit 5 in linear form. As a result, the phases of the sounds from
the speaker units at symmetrical positions on the central axis become equal, and the directivity in
the direction parallel to the straight line becomes sharp. (FIG. 12) shows the sound pressure
distribution when eight speaker units with a diameter of 9.4 cm are arranged at intervals of 15
cm.
[0007]
However, as shown in FIG. 13, when there is a reflecting surface such as a floor surface or a wall
surface around the directional speaker, the sound wave is diffused by the reflecting surface
depending on the frequency. There is a problem that the inherent narrow directivity can not be
obtained, for example, high side lobes occur in the service area of the adjacent channel speaker.
[0008]
SUMMARY OF THE INVENTION In view of the above problems, the present invention aims to
prevent the diffusion of sound waves by a reflective surface and to obtain the narrow directivity
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of the directional speaker.
[0009]
SUMMARY OF THE INVENTION The directional speaker device of the present invention
comprises a directional speaker and a concave or convex reflecting surface disposed opposite to
the directional speaker.
[0010]
According to the present invention, narrow directivity can be obtained by preventing the
diffusion of sound waves by the reflecting surface by the above-mentioned construction.
[0011]
The first embodiment of the present invention will be described below with reference to FIG.
6 is a speaker unit having an aperture of 8 cm, and eight pieces are arranged in an arc shape of
1.5 m in diameter.
The figure shows the case where there are five speaker units.
A spherical shell-like reflective surface 8 having a diameter of 1.5 m and sharing the center 7 is
disposed opposite to the speaker array on the floor, and the concave surface of the reflective
surface 8 is filled with a sound absorbing material 9. It is possible for people to walk on the
street.
Of the sound waves emitted from the speaker unit 6, the high-pitched part is mainly absorbed by
the sound absorbing material 9, and the low-pitched part is mainly reflected by the reflecting
surface 8, but the reflected wave converges at the center 7 and the diffusion of the sound wave
can be prevented. . The sound pressure distribution for the case of 250 Hz is shown in (FIG. 5).
Compared with the sound pressure distribution (FIG. 6) in the case where the floor surface is a
horizontal reflection surface using the same speaker array 6, in the present embodiment, the
sound wave converges at the center of the spherical shell and the diffusion of the sound wave is
prevented. Know that
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[0012]
Although the speaker units are arranged in an arc shape in the present embodiment, they may be
spherical, may be arranged linearly, and generally, even when arranged in a planar or curved
shape, the reflected waves are adjacent channels. There is no major impact on the service area of
In addition, although the reflecting surface is spherical, the same effect can be obtained as a
cylindrical surface.
[0013]
Next, a second embodiment of the present invention will be described along with FIG. The same
speaker units 10 as those used in the first embodiment are arranged in a straight line. The
directions are set such that the normals of the respective speaker units intersect at the center 7.
The reflecting surface 8 and the sound absorbing material 9 are the same as those of the first
embodiment, and in this embodiment as well, the reflected wave converges at the center 7 to
prevent the diffusion of the sound wave.
[0014]
Next, a third embodiment of the present invention will be described with reference to FIG. A
parabolic reflector 12 has a speaker unit 11 disposed at the focal point so as to face the concave
surface of the reflector 12 and attached to the ceiling. The parabolic reflecting surface 13 is
disposed on the floor facing the reflector 12 with a concave surface on the upper side, and the
concave surface of the reflective surface 13 is filled with a sound absorbing material 14, and a
person overlies the sound absorbing material 14. It is possible to walk. As in the first
embodiment, among the sound waves emitted from the speaker unit 11, the high-pitched portion
is mainly absorbed by the sound absorbing material 14 and the low-pitched portion is mainly
reflected by the reflecting surface 13. Can be focused at the focal point 15 of the lens to prevent
the diffusion of sound waves.
[0015]
It is to be noted that the same effect can be obtained also in the case where the reflector is an
ellipsoid and the reflecting surface of the ellipsoid sharing the focal point with the reflector is
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provided on the floor surface.
[0016]
Finally, the fourth embodiment of the present invention will be described with reference to FIG.
10 consists of a speaker unit arranged linearly, and is attached to the ceiling. 10, the reflecting
surface 16 of the spherical shell is arranged with the convex surface facing up, and the sound
absorbing material 17 is filled around the reflecting surface 16 so that a person can walk on the
sound absorbing material 17 There is. When the floor's reflective surface is concave, a strong
reflected wave from the floor arrives at the service area, so complex sound pressure distribution
is shown, whereas when it is convex, the reflected wave goes upward The ratio is reduced, and
there is an effect that the directivity characteristic of the speaker can be obtained without
disturbing the sound field in the service area.
[0017]
In the embodiment, the directional speaker is installed on the ceiling and the reflecting surface is
installed on the floor, but the same effect can be obtained when the reflecting surface is installed
on the wall facing the directional speaker. It is natural. Moreover, in the embodiment, the sound
absorbing material is filled in the inside of the concave surface and the periphery of the convex
surface formed on the floor reflecting surface, but as shown in the sound pressure distribution
chart, it is effective even without the sound absorbing material. is there. By filling the sound
absorbing material, the component of the reflected wave from the floor decreases in inverse
proportion to the sound absorption coefficient, and sharper directivity can be realized.
[0018]
As described above, according to the present invention, the directional speaker and the concave
or convex reflecting surface disposed opposite thereto are narrowed by preventing the diffusion
of sound waves by the reflecting surface. A directional sound field can be obtained.
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