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JPH04105799

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DESCRIPTION JPH04105799
[0001]
[Industrial application field]
[0002]
The present invention relates to a portable megaphone used when talking to a relatively large
number of people in places without broadcasting facilities such as outdoors.
[0003]
BACKGROUND OF THE INVENTION A device for adjusting the length of a horn in order to change
the sound reachability of a portable megaphone is attached to the Japanese Patent Application
No. 1-116314 filed by the same applicant. It is described in the specification etc.
That is, according to the specification, etc., as shown in FIG. 8, the conventional portable
megaphone 11 is provided with the first horn 12 and the second horn 13 whose length can be
adjusted. By configuring in this manner, the directivity of the sound becomes narrower as the
horn 13 is lengthened, and the reach of the sound can be extended.
[0004]
[0003] However, in order to change the reach of the sound, it is necessary to operate to extend
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and retract the horn, and because it is composed of two horns, the outer shape tends to be large,
and it is heavy It was easy to become.
[0005]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present
invention relates to a portable megaphone, a first speaker for reproducing middle-to-high range
audio signals, and a low-range audio signal. A second speaker, a switch for turning on and off the
second speaker, and a horn for guiding the sound output from the first and second speakers.
[0006]
[Operation] In addition to the first speaker for reproducing the middle-to-high-range audio signal,
the directivity of the sound can be broadened by turning on the second speaker for reproducing
the low-range audio signal. it can.
Conversely, the directivity of the sound can be narrowed by turning off the second speaker.
[0007]
Embodiments of the present invention will be described below with reference to the attached
drawings.
FIG. 1 is a cross-sectional view showing an example of a portable megaphone according to the
present invention, FIG. 2 is a front view of the portable megaphone, and FIG. 3 is an external
perspective view of the portable megaphone. In FIG. 1, a portable megaphone 1 comprises a
bottomed cylindrical holder 2, a supporter 3 provided at the open end of the holder 2, and an
audio signal of a medium to high range facing the holder 3 and provided on the holder 2 side. A
first speaker 4 for reproduction, a second speaker 5 for reproducing an audio signal of a low
frequency band facing the first speaker and provided on the holder 2 side, and the second
speaker 5 provided on the holder 2 It is comprised by the switch 6 which turns on and off a
speaker.
[0008]
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Further, a vent horn 7 for guiding the medium to high frequency range audio signal outputted
from the first speaker 4 through the supporter 3 is fixed to the supporter 3, and the vent horn 7
is surrounded to surround the vent horn 7. The slide horn 8 is formed on the extension of the
holder 2. In FIG. 2, a plurality of holes 3 a are formed on the outer periphery of the flat portion of
the supporter 3, and an audio signal output from the second speaker 5 is mainly passed forward
through the holes 3 a. In the present embodiment, the holder 2 is formed in a double bottom
shape, and the switch 6 is disposed between the bottom and the bottom. However, the switch 6
can be disposed at any position, for example, as shown in FIG. It may be arranged in part of the
handshake. The wiring of the speakers 4 and 5, the switch 6 and the like is not directly related to
the description of the present invention, so the illustration is omitted.
[0009]
As shown in the external perspective view of FIG. 3, the slide horn 8 of the portable megaphone
1 according to the present invention is constituted by one piece, but a switch for turning on and
off the low range speaker on the holder 3 It has six.
[0010]
Next, the operation will be described.
When the switch 6 is turned off, the second speaker 5 is turned off, and the frequency band has
less bass components as shown in the frequency characteristic diagram of FIG. 4 and the band is
relatively narrowed. That is, only the first speaker 4 is driven, and the sound output from the
speaker 4 is emitted through the vent horn 7 and the slide horn 8.
[0011]
FIG. 5 is a correlation diagram of directivity and frequency band. That is, curves a and b show the
sound pressure characteristics at a position of 1.5 m from the portable megaphone 1 in the
direction of 30 degrees from the front and right to the front when a signal of 1 mV is input. It
can be seen from this figure that the directivity is narrow. That is, in the curve b, the low range
component is reduced, and the voice of only the middle and high range is emitted in a relatively
narrow range, so that the voice can be clearly transmitted to a relatively far place.
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[0012]
On the other hand, when the switch 6 is turned on at a relatively close place, the second speaker
5 is turned on, and the voice of the low range is added to the voice of the middle to high range of
the first speaker. Be As shown in FIG. 6, in the frequency characteristic of the audio signal at this
time, not only the middle-high range component but also the low-range component is output.
[0013]
The sound in the middle to high range output from the speaker 4 is emitted as in the case where
the switch 6 is off, but the sound in the low range output from the speaker 5 is the hole of the
supporter 3 It passes 3 a and is emitted from the vent horn 7. The characteristics as a
predetermined low pass filter can be obtained by appropriately setting the size and position of
the hole 3a. FIG. 7 is a correlation diagram of directivity and frequency band when the speaker 5
is on. Curves a and b in the figure are the same as in FIG. 5, and curve c shows sound pressure
characteristics at a distance of 1.5 m from the portable megaphone 1 in the direction of 60
degrees from the front to the right. . Thus, as shown in FIG. 7, the curves b and c are also output
to the relatively near place of the wide angular range together with the midrange component,
with the bass range component hardly decreasing compared to the curve a. .
[0014]
As described above, according to the present invention, the directivity of the voice is changed by
turning on and off the low range speaker with a switch, so the structure of the portable
megaphone can be simplified. Thus, downsizing and weight reduction are facilitated, and
operability can be improved.
[0015]
As the speaker for the middle to high range is provided and the speaker for the low range that
can be turned on and off by the switch is provided, the directivity can be broadened when the
speaker for the low range is turned on, When the low frequency range speaker is turned off, the
directivity can be narrowed.
[0016]
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Brief description of the drawings
[0017]
Cross-sectional view showing an example of a portable megaphone according to the present
invention
[0018]
Figure 2 Front view of the same portable megaphone
[0019]
Fig. 3 Appearance perspective view of the same portable megaphone
[0020]
Fig. 4 Frequency characteristics when the low range speaker is off
[0021]
Fig. 5 Correlation between directivity and frequency characteristics
[0022]
Fig. 6 Frequency characteristics when the low range speaker is on
[0023]
Fig. 7 Correlation diagram of directivity and frequency characteristics
[0024]
Fig. 8 is an external perspective view showing an example of a conventional portable megaphone
[0025]
Explanation of sign
[0026]
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DESCRIPTION OF SYMBOLS 1 ... Portable megaphone, 3 ... Supporter, 3a ... hole, 4 ... 1st speaker,
5 ... 2nd speaker, 6 ... Switch, 7 ... Bent horn, 8 ... Slide horn.
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