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JP2003023687

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2003023687
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
underwater wave transmitter capable of realizing a wide band and high output.
[0002]
2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional
Langevin type transducer, and FIG. 5 is an explanatory view of its operation. In the figure, 10 is
an outer casing of a Langevin type transducer, 11 is a rear mass, 12 is a drive element, and 13 is
a front mass (prior art 1). In this prior art 1, as shown in FIG. 5, the single vibration (piston
vibration) of the drive element 12 inside is simply transmitted to the front mass 13 and sound is
emitted from the front mass 13 into water. The characteristic is a sound pressure that maximizes
the vicinity of the resonance frequency between the elasticity of the drive element 12 and the
front mass 13 and the water load mass, and the sound pressure decreases in a band away from
the resonance frequency.
[0003]
In recent years, in various analyzes of water (ocean), development of a transmitter with a wide
frequency characteristic so that complex signal waveforms can be reproduced in order to
improve the SN ratio and analysis accuracy of analysis signals, etc. It is in progress. However,
04-05-2019
1
since a low sound pressure level is unavoidable, a general transmitter attempts to raise the sound
pressure level even by using a band centered on the resonance frequency. However, when the
resonance frequency is at the center, the sound pressure decreases at frequencies before and
after that, so it is difficult to achieve a wide band. In addition, if priority is given to wide band, the
sound pressure level is lowered, so it has been considered difficult to simultaneously achieve
high output and wide band.
[0004]
FIG. 6 shows a Langevin transducer having a flexural diaphragm on its acoustic emission surface
(Asahi, Yamamoto, described on pages 37 to 40 of the Proceedings of the Meeting of the Society
of Ocean Acoustics by the Beach, June 1999). FIG. 7 is an explanatory view of its operation. This
transducer has a gap 14 inside the surface of the front mass 13 in order to broaden the
bandwidth of the prior art 1 so that the mechanical properties of the combined water load can be
made relative to the fundamental resonance frequency of the prior art 1. Bending resonance
occurs at a somewhat high frequency (prior art 2).
[0005]
That is, at frequencies lower than the flexural resonance frequency, as shown in FIG. 7A, the front
mass 13 acts only as a rigid body as a rigid body, and the same fundamental resonance as in the
prior art 1 occurs. Then, when the sound pressure starts to decrease after passing the
fundamental resonance frequency, it approaches the bending resonance frequency, and as shown
in FIG. 7B, the displacement of the central portion of the front mass 13 increases again, and the
sound pressure level Will rise. As a result, as compared with the prior art 1, the phenomenon that
the sound pressure is lowered even in the frequency band higher than the fundamental
resonance frequency is suppressed, so the band is broadened.
[0006]
SUMMARY OF THE INVENTION In the prior art 1 configured as described above, as described
above, since it is a single resonance transmitter, it is difficult to achieve a wide band. In the prior
art 2, although a wider band is achieved than in the prior art 1, strictly speaking, the
displacement portion of the center portion of the front mass at fundamental resonance and the
displacement portion of the front mass at bending resonance are the drive elements 12. It is in
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2
the opposite phase when taking the vibration of. That is, the level of the sound pressure
reduction band seems to be compensated for by the fundamental resonance and the bending
resonance, and in fact, the levels at the time of resonance with each other are crushed, and as a
result, they are only broadband. For this reason, although the wide band is achieved, it is
disadvantageous to increase the sound pressure level. In addition, since the radiation surface of
the Langevin transducer itself is limited by the area of the front mass 13, it is not suitable for
high output.
[0007]
The present invention was made in order to solve the above-mentioned problems related to the
high output and wide band of the Langevin transducer and the high power output due to the
wide band of the Langevin type sound source of the literature. A bending portion having a
curvature in advance is provided between two wave devices, and the fundamental resonance of
the piston type transmitter itself and the bending resonance where the bending portion is bent
are brought close to wide band, and the displacement of the piston type transmitter is It is an
object of the present invention to provide a new underwater transmitter having a new
transmitter structure in which displacement can be increased in phase by enabling displacement
of a bent portion to be in phase and increase in transmission area.
[0008]
[Means for Solving the Problems] (1) The underwater wave transmitter according to the present
invention comprises a shell having a bending portion coupled between opposed piston type
transmitters, and a driving element and The fundamental resonance frequency of the piston type
transmitter and the bending resonance frequency at which the bending portion of the shell
resonates in the bending mode is brought close to an appropriate distance, and the bandwidth is
broadened to a band between both frequencies.
In this way, in the underwater wave transmission device, wide band and high output are realized.
[0009]
(2) In the underwater wave transmitter as described in (1) above, a shell is used in which the
bent portion is bent outward from the center.
[0010]
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3
BEST MODE FOR CARRYING OUT THE INVENTION [Embodiment] An underwater wave
transmitter according to the present invention has two piston type wave transmitters having a
curvature on the outside as viewed from the center of the wave transmitter. It connects by the
shell which has a bent part.
[0011]
According to the underwater wave transmitter configured as described above, the mechanical
impedance of the bending portion is large in the resonance band of the piston wave transmitter,
and the two piston wave transmitters are close to the one-end fixed condition. It vibrates in a
state and is acoustically output from the front mass of the piston type transmitter.
Then, as the bending resonance is approached including the bending portion, the mechanical
impedance of the bending portion decreases, and the bending portion coupling side vibrates in
the piston type transmitter portion, and the one-end fixing condition is not satisfied.
Then, in the vicinity of the bending resonance, the energy is divided by the displacement of the
front mass of the piston type transmitter and the bending portion, and sound is output from
both. Here, from the low frequency to the bending resonance band, since the front mass of the
piston type transmitter and the displacement of the central portion of the bending portion are in
phase, a wide band can be obtained by setting the basic resonance of the piston type transmitter
and the bending resonance. At the same time, it becomes a high-power transmitter with low
acoustic loss.
[0012]
FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, reference
numeral 1 denotes a pair of opposed piston type transmitters, which comprises a drive element
2, a front mass 3, a rear mass 4 and a housing 5 in which these are housed. A shell 6 is
interposed between the two piston type transmitters 1 and comprises a bending part 7 curved
outward from the center part of the transmitter and fixing parts 8 provided at both ends of the
bending part 7 The rear mass 4 of the piston type transmitter 1 is integrally fixed to the fixed
portion 8.
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4
[0013]
Here, the fundamental resonance frequency generated between the spring constant of the full
length of the drive element 2 and the load mass of water outside the front mass 3 and the front
mass 3 is f 1, of the water outside the shell 6 and the shell 6 The load mass and the frequency at
which the entire piston type transmitter 1 resonates with the spring constant in the bending
mode of the shell 6 is set to f2, and f1 <f2.
[0014]
In the present invention configured as described above, assuming that the frequency of sound
pressure is f, if f <f1, as shown in FIG. 2 (a), the mechanical impedance of the shell 6 is large.
Only the mass 3 vibrates and is acoustically output from the front mass 3 (displacement of the
acoustic radiation surface is indicated by oblique lines.
same as below). At f = f1, as shown in FIG. 2 (b), the mechanical impedance of the shell 6
gradually decreases, but the mechanical impedance of the drive element 2 and the front mass
portion (piston type transmitter portion) resonates due to resonance. Since it becomes minimum,
a large acoustic output can be obtained from the front mass 3 as well. At this time, the shell 6
also vibrates, but the vibration is also in the same phase as the front mass 3 at the bending
portion 7 and there is no acoustic loss.
[0015]
When f1 <f <f2, as shown in FIG. 2C, the mechanical impedance of the piston type transmitter
increases and the mechanical impedance of the shell 6 further decreases. The displacement of
the joint surface with 6 gradually increases, and the flexural vibration mode of the shell 6
becomes remarkable. However, even in this region, the front mass 3 side vibrates, and the piston
type transmitter vibrates in a mode of displacement on both sides. In this case, since the
displacement of the bending portion 7 due to the bending vibration of the shell 6 and the
displacement of the front mass 3 are in phase from the transmitter to the outside, the loss in
acoustic radiation is small.
[0016]
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5
At f = f2, as shown in FIG. 2 (d), the bending mode of the shell 6 is maximized, and an in-phase
acoustic output is obtained from both the front mass 3 and the bending portion 6. At f> f2, the
bending mode of the shell 6 changes to the higher mode, the piston type transmitter also moves
to the higher resonance, and the sound pressure level decreases. The relationship between the
sound pressure level and the frequency f is shown in FIG. In the figure, the horizontal axis
indicates the frequency f of sound pressure, and the vertical axis indicates the sound pressure
level.
[0017]
As apparent from the above description, according to the present invention, the sound output can
be obtained by appropriately setting the resonance of the piston type transmitter unit and the
resonance of the bending mode including the shell. In this band, the acoustic emission planes are
independent of each other and oscillate in phase, so that the emission plane can be large and the
acoustic loss does not occur. It becomes possible.
[0018]
Brief description of the drawings
[0019]
1 is a block diagram of an embodiment of the present invention.
[0020]
2 is an operation explanatory view of FIG.
[0021]
3 is a diagram showing the relationship between the frequency and the sound pressure level.
[0022]
4 is a block diagram showing an example of a conventional Langevin type transducer.
[0023]
5 is an operation explanatory view of FIG.
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6
[0024]
6 is a configuration diagram showing another example of a Langevin type transducer having a
conventional bending diaphragm provided on the acoustic radiation surface.
[0025]
7 is an operation explanatory view of FIG.
[0026]
Explanation of sign
[0027]
1 piston type transmitter 2 drive element 6 shell 7 bending part
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