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JP2009296153

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DESCRIPTION JP2009296153
The present invention provides a directional speaker that achieves a desired narrow directivity
by forming a uniform sound field around an acoustic tube. And in the directional speaker
provided with an acoustic pipe for emitting the sound generated by the speaker from the
plurality of sound emission holes provided on the outer periphery, the plurality of sound
emission holes are predetermined along the center line of the acoustic pipe on the outer
periphery At least two or more sound emission holes are provided on the outer circumference
centering on one point of the center line of the sound pipe provided with the sound emission
holes at intervals, and a uniform sound field is formed around the sound pipe. Radiate sound with
a narrower directivity. [Selected figure] Figure 1
Directional speaker
[0001]
The present invention relates to a directional speaker having an acoustic pipe whose sound
emission hole is opened on the side and forming a narrow directional sound field.
[0002]
Conventionally, there is a method for realizing narrow directivity (hereinafter referred to as
narrow directivity) using a normal speaker unit.
The methods for realizing narrow directivity speakers are roughly classified into passive methods
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and active methods. The passive system is a system for realizing narrow directivity by using one
or a plurality of conventional speakers and devising the speaker peripheral shape and the spatial
arrangement (geometrical arrangement). The active method is a method in which a plurality of
conventional speakers are arranged (arrayed), and the signal processing circuit controls the level
and phase of the drive signal of each speaker to form a narrow beam and change the sound
radiation direction. . The passive method can be configured relatively inexpensively, while the
active method can precisely change the sound radiation direction and the width of directivity by
implementing precise signal processing, but the design and manufacturing cost increase, Product
prices tend to be expensive. As a passive type directional speaker, for example, there is one as
disclosed in Patent Document 1. This directional speaker is an acoustic pipe provided with small
holes (sound emission holes) at regular intervals in the longitudinal direction of the side face, and
a speaker attached to one end of the directional pipe. It is a directional speaker which can obtain
narrow directivity in the tube extension direction.
[0003]
Unexamined-Japanese-Patent No. 11-234784 gazette
[0004]
The conventional directional speaker has an uneven sound pressure distribution around the
periphery of the sound pipe perpendicular to the axis of the sound pipe because the sound
emission holes are opened in a straight line on the ridgeline of the side surface of the sound pipe.
For example, the sound pressure in the opposite direction to the sound emission hole is lower
than that on the side with the sound emission hole, and the tendency is particularly strong when
the frequency is high. Therefore, the main lobe, which is the largest radiation beam in the target
direction, is formed in a direction inclined from the extension of the central axis of the acoustic
tube, and there is a problem that a desired directivity can not be obtained.
[0005]
The present invention has been made to solve the above-described problems, and provides a
directional speaker that achieves desired narrow directivity by forming a uniform sound field
around an acoustic tube. The purpose is
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[0006]
The directional speaker according to the present invention is a directional speaker comprising a
speaker for generating sound, and an acoustic pipe which is connected to the speaker at one end
and which radiates a sound generated by the speaker from a plurality of sound emitting holes
provided on the outer periphery. The plurality of sound emission holes are provided at
predetermined intervals on the outer periphery along the center line of the acoustic tube, and at
least two or more on the outer periphery centering on one point of the center line of the sound
tube provided with the sound emission holes. A sound emission hole is arranged.
[0007]
According to the directional speaker of the present invention, the sound emission holes are
provided at predetermined intervals along the center line of the acoustic tube and at least two or
more on the outer periphery centering on one point of the center line of the acoustic tube Since it
is provided, it is possible to form a uniform sound field, and it is possible to form a narrow
directional sound field.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to explain the present
invention in more detail, the best mode for carrying out the present invention will be described
according to the attached drawings.
Embodiment 1
FIG. 1 is an overall perspective view showing the concept of a directional speaker 1 according to
Embodiment 1 of the present invention, and as shown in FIG. 1, the directional speaker 1
includes a speaker 10, a cabinet 11 and an acoustic tube 20. ing.
[0009]
The speaker 10 has a well-known speaker structure, includes a diaphragm, a coil, a magnet, and
the like, and is configured to convert a drive signal into an audio vibration to emit a sound.
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The speaker 10 is housed in the cylindrical portion of the cabinet 11 and connected to the
acoustic tube 20 via the tapered connection portion of the cabinet 11.
[0010]
The acoustic tubes 20 have a cylindrical shape with a circular cross section perpendicular to the
central axis, and are provided at regular intervals d in the axial direction of the outer periphery
along the center line of the acoustic tubes 20. Four sound emitting holes 21 are provided on the
outer periphery centering on one point, and the four sound emitting holes 21 are arranged so
that the cross section of the acoustic tube 20 is equally spaced at 90 ° from the central axis. In
addition, a sound absorbing portion 22 using a porous material such as soft urethane foam or
glass wool is provided at the other end of the acoustic tube 20 opposite to one end to which the
speaker 10 is connected.
[0011]
As described above, in the acoustic tube 20 of the directional speaker 1 according to the first
embodiment, four sound emitting holes 21 face each other at an opening angle of 90 ° from the
central axis at regular intervals d in the axial direction of the outer periphery. It was configured
to be arranged.
[0012]
Next, formation of a sound field by the directional speaker 1 of this configuration will be
described.
When a drive signal is applied to the speaker 10, the sound generated from the speaker 10
enters the acoustic pipe 20 through the connection part of the cabinet 11 and propagates in the
direction of the other end of the acoustic pipe 20 to absorb the sound It reaches 22. In this
process, a sound field is generated which is sequentially radiated to the outside from the sound
release hole 21 close to the speaker 10 and a sound having a delay in the propagation direction
is generated, so the directivity area 30 is formed in the extension direction of the acoustic tube.
Be done. Since the sound release holes 21 open at equal intervals from the central axis of the
acoustic tube 20 toward the outer periphery at an angle of 90 °, a substantially concentric
sound field in a plane perpendicular to the central axis of the acoustic tube 20 is created. As a
result, a directional region 30 as desired is formed on the extension of the central axis of the
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acoustic tube 20.
[0013]
Here, a simulation example of the directional speaker 1 according to the present invention is
shown. As a simulation model of the directional speaker 1, the acoustic tube 20 has an inner
diameter of 10 cm, an outer diameter of 14 cm (thickness 2 cm), a length of 140 cm, and a sound
emitting hole interval d = 3 cm (four on the same circumference).
[0014]
Inside the acoustic tube 20 of the simulation model, a sound wave propagating in the acoustic
tube 20 whose diameter is smaller than the wavelength does not cause reflection on the tube
wall of the acoustic tube 20, and its plane wave propagates only in the direction of the tube axis
It is a method that applies the point management theory formula that applies the sound
management theory formula that was made and the sound emission hole 21 opened on the side
surface of the sound pipe 20 to the point sound source is applied to the outside of the sound pipe
20. Is shown in FIG.
[0015]
FIG. 2 is a directional polar pattern diagram for each of the frequencies 500 Hz, 1000 Hz, 2000
Hz and 3000 Hz.
The 0 ° direction (upper side in FIG. 2) is the sound radiation direction, which is a direction in
which the central axis of the acoustic tube 20 is extended. In FIG. 2, the scale in the radial
direction from the center to the outer periphery is a sound pressure dB value (normalized by the
sound pressure level in the 0 ° direction).
[0016]
The half full angle of the 0 ° direction main lobe (total angle at which the sound pressure level
is half) at each frequency is a result of about 90 degrees, about 70 degrees, about 40 degrees,
and about 30 degrees. As described above, although there is frequency dependency, the sound
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pressure level of the side lobes indicating sound radiation other than the target direction in the
frequency is 10 dB or less with respect to the 0 ° direction, and the sound toward 90 ° The
pressure level drops. Furthermore, above 1000 Hz, the sound pressure level of sound radiation
(back lobe) behind 90 degrees with respect to the direction of interest indicates approximately
20 dB or less with respect to the 0 ° direction. From the above, in the directional speaker
according to the present invention, the sound pressure level of the main lobe is larger than the
sound pressure levels of the side lobes in the lateral direction and the back lobe in the backward
direction, and a narrow directivity can be realized accurately in the sound radiation direction.
Know that
[0017]
As described above, in the directional speaker 1 according to the first embodiment, the sound
emission holes 21 are provided on the outer periphery of the acoustic tube 20 that divides the
acoustic tube 20 cross section into 90 °, and are arranged at every interval d in the axial
direction. Thus, it is possible to form a uniform sound field, radiate sound with desired directivity,
and improve the design accuracy of a speaker that forms the desired directivity sound field. .
[0018]
In the first embodiment, an example in which four sound release holes 21 exist in the vertical
plane at one point for every interval d of the central axis of the acoustic tube 20 has been
described, but two sound release holes 21 ( The opening angle may be 180 °), three (opening
angle 120 °), or five or more. The greater the number, the more uniform the sound field.
[0019]
Second Embodiment
FIG. 3 is a side view showing an acoustic tube 20 of the directional speaker 1 of the second
embodiment.
The sound tube 20 of the directional speaker 1 of the first embodiment is arranged such that
four sound emitting holes 21 face each other at an opening angle of 90 ° from the central axis
at constant intervals d in the axial direction of the outer periphery. In the second embodiment, as
shown in FIG. 3, the sound emission holes 21 at regular intervals d are arranged at positions
alternately rotated by 45 °.
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[0020]
Further, by rotating the position of the sound release hole 21 little by little, as shown in FIG. 4A,
the arrangement of the plurality of sound release holes 21 continuous in the axial direction of
the outer periphery of the acoustic tube 20 is helical. Become. Further, FIG. 4 (b) shows an
acoustic tube 20 in which the sound emission holes 21 of this spiral array are arranged in two
rows, and may be a multi-helix having three rows, four rows, etc. It is preferable to shorten the
distance between the sound release holes 21 in the direction for more uniform sound field.
[0021]
As described above, according to the directional speaker 1 of the second embodiment, the sound
emission holes 21 are provided on the outer periphery of the acoustic tube 20 which divides the
acoustic tube 20 cross section into 90 °, and for every interval d in the axial direction Since the
positions of the continuous sound emission holes 21 are arranged to be offset from the straight
line, it becomes possible to form a uniform sound field, and it is possible to radiate sound with a
narrower directivity and to narrow the directivity Speakers can be designed to form a sound field.
[0022]
Third Embodiment
FIG. 5 is a side view showing an acoustic tube 20 of the directional speaker 1 of the third
embodiment. In the first and second embodiments, the arrangement of the sound emission holes
21 of the acoustic tube 20 is changed. However, in the third embodiment, the depth of the sound
emission holes 21 is changed. is there.
[0023]
In the directional speaker 1, the sound generated by the speaker 10 propagates in the acoustic
tube 20 and is radiated to the outside from the sound emission hole 21, and the directivity of this
radiated sound is the inside of the acoustic tube 20. It depends on the size and the size and shape
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of the sound emission hole 21. For example, when the internal dimensions (inside diameter,
length) of the acoustic tube 20 are fixed, the sound emission hole 21 becomes a regularly
distributed acoustic load when viewed from inside the acoustic tube 20. When the shape is
changed, the intensity of the sound radiated from the sound emission hole 21 changes in the
length direction of the sound emission hole 21 and the directivity formed as a result is affected.
Therefore, the directional speaker 1 of the third embodiment is configured to be provided with
an adapter 25 for changing the length in the depth direction of the sound output hole 21 (the
thickness of the acoustic tube 20).
[0024]
The adapter 25 has a ring (annular) shape in which holes are arranged in the same arrangement
as the sound emission holes 21 of the sound tube 20 as shown in FIG. 5, and the sound tube 20
is inserted to emit sound from the holes. It is attached according to the position of the opening of
the hole 21 to extend the length of the sound emission hole 21 in the depth direction. When the
length in the depth direction of the sound output hole 21 is thus extended, the directivity formed
in the directivity region 30 becomes narrow.
[0025]
As described above, according to the directional speaker of the third embodiment, the adapter 25
for extending the length in the depth direction of the sound emission hole 21 is provided on the
outer periphery of the acoustic tube 20. A uniform sound field can be formed, sound can be
emitted with a narrower directivity, and a speaker can be designed to form a narrow directivity
sound field.
[0026]
The length in the depth direction of the hole of the adapter 25 is designed in accordance with the
desired directivity.
[0027]
Fourth Embodiment
In the third embodiment, the configuration in which the length of the sound output hole 21 of
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the acoustic tube 20 is increased by the adapter 25 has been described, but in the fourth
embodiment, the cross-sectional shape of the sound output hole 21 is changed.
6 is a partial cross-sectional view of the acoustic tube 20 showing the cross-sectional shape of
the sound output hole 21, FIG. 6 (a) shows the sound output hole 21 in a straight horn shape,
and FIG. 6 (c) shows the sound emission hole 21 of a curved cross-section, which spreads on the
inner and outer peripheries of the acoustic tube 20 and the cross-sectional area changes
continuously.
[0028]
As described above, according to the directional speaker 1 of the fourth embodiment, the crosssectional shape of the sound output hole 21 is changed to expand in a tapered shape in the
external direction emitting the sound, and the cross section in the depth direction of the sound
output hole 21 is cut. The area is formed such that the opening on the outer wall side of the
acoustic tube 20 is enlarged, so that the sound waves radiated in the direction perpendicular to
the axis of the acoustic tube 20 are spread and the sound in the depth direction of each sound
emission hole is mixed Since the sound waves radiated in the direction of the center line of the
acoustic tube 20 strengthen each other while being canceled, a uniform sound field can be
formed around the acoustic tube, and sound can be emitted with a narrower directivity.
[0029]
The same effect can be obtained as long as the opening on the outer wall side of the acoustic
pipe is larger in cross section than the opening on the inner wall side other than the shape of the
sound release hole shown in the fourth embodiment.
In addition, in the case where the internal dimensions (inner diameter and length) of the acoustic
tube 20 are not fixed, the same effect can be obtained by configuring the inner diameter to be
successively smaller or larger in the longitudinal direction of the acoustic tube 20. Can.
[0030]
Embodiment 5 In the first to fourth embodiments, the directional speaker 1 which radiates the
sound generated from one of the speakers 10 has been described, but in the fifth embodiment,
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the sound on the rear face of the speaker 10 is also positively used. The
[0031]
FIG. 7 is an overall perspective view showing the configuration of the directional speaker 1
according to the fifth embodiment. The directional speaker 1 is a configuration in which two
acoustic tubes 20 as shown in FIG. 1 are combined. The acoustic tube 20 supports the speaker
10 so as to cover the diaphragm 10 from both sides facing the diaphragm with a tapered
connection, and is combined such that the central axes of the acoustic tube 20 on both sides of
the speaker 10 are on a straight line. ing.
[0032]
The sounds generated from the front and back sides of the diaphragm of one speaker 10 are
emitted at the same sound pressure level in opposite phase (phase difference of 180 degrees),
and are the same due to the sound emitted from the sound emission hole 21 of the acoustic tube
20. Directional regions 30 are formed in two directions.
[0033]
As described above, according to the fifth embodiment of the directional speaker 1, the acoustic
tube 20 is provided on both sides so as to face the surface of the diaphragm of the speaker 10.
Therefore, the uniform sound field is provided around the acoustic tube. And a narrow directivity
area can be formed in two directions by one speaker.
[0034]
Loudspeaker 10 of directional speaker 1 of the fifth embodiment is configured to emit sound at
the same sound pressure level from both sides, for example, a diaphragm in which a meandershaped conductor coil is formed on the surface of a thin resin film, A Gamuzon-type
electromagnetic transducer made of a permanent magnet may be used.
[0035]
Further, in the fifth embodiment, the configuration has been described in which the central axes
of the acoustic tubes 20 on both sides are in a straight line, but the central axis of one acoustic
tube 20 is inclined with respect to the other. The direction of the directivity area 30 can also be
changed.
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[0036]
As described above, in the directional speaker of the present invention, the acoustic pipe
provided in the direction facing the diaphragm of the speaker has at least two sound emission
holes on the outer periphery centering on one point of the center line, Since the sound emission
holes are arranged at regular intervals along the center line of the acoustic tube, a uniform sound
field can be formed around the acoustic tube, and narrower directional sound can be emitted.
[0037]
In the directional speaker 1 according to the first to fifth embodiments, the acoustic tube 20 has
a circular cylindrical central axis direction cross section, but the present invention is not limited
to this, and the cross section has a polygonal shape. Even the same effect can be obtained.
Moreover, the speaker which has desired directivity can be designed by combining the said
Embodiment 1-5.
[0038]
It is a whole perspective view which shows the external appearance of the directional speaker by
Embodiment 1 of this invention.
It is a directional polar pattern figure of the directional speaker by Embodiment 1 of this
invention.
It is a partial side view which shows arrangement | positioning of the sound emission hole of the
directional speaker by Embodiment 2 of this invention.
It is a partial side view which shows the other arrangement | positioning of the sound emission
hole of the directional speaker by Embodiment 2 of this invention.
It is a partial side view which shows the external appearance of the directional speaker by
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Embodiment 3 of this invention. It is a fragmentary sectional view which shows the shape of the
sound emission hole by Embodiment 4 of this invention. It is a whole perspective view which
shows the external appearance of the directional speaker by Embodiment 4 of this invention.
Explanation of sign
[0039]
1 Directional speaker, 10 speakers, 11 cabinets, 20 acoustic tubes, 21 sound output holes, 22
sound absorbers, 25 adapters, 30 directivity areas.
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