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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic apparatus used in water and to a hydrophone array capable of obtaining low noise due
to unidirectionality to a relatively deep degree.
2. Description of the Related Art A conventional hydrophone, as shown in FIG. 10, has a cork
plate 21 for producing a free reflection surface of sound waves, and a dimension between the
transducer 23 and the reflection surface in the propagation path of sound waves. 11 is composed
of a support rubber plate 22 for keeping the wavelength at 1/4 wavelength, and one composed
of a reflection rubber plate 24 including an air chamber 25 and a vibrator 26 as shown in FIG. It
was getting unidirectional as shown in 6.
However, the conventional hydrophone has a drawback that the air chamber is crushed by the
external water pressure of several atmospheric pressure, and the function of the free reflecting
surface is lost.
An object of the present invention is to provide a hydrophone array having improved water
pressure resistance characteristics, which operates only in the direction in which it needs to
function as a free reflecting surface.
SUMMARY OF THE INVENTION According to the present invention, a plurality of vibrators
arranged in a cylindrical shape and a support cylinder which embeds these vibrators and
supports the sound receiving surface in the radial direction and supports them A grid having an
outer peripheral surface in a cylindrical shape and having a grid shape, the outer peripheral
surface being in close contact with the inner peripheral surface of the support cylinder to form a
small air chamber between the grids; A hydrophone array is obtained, which comprises a box
supporting a grid, and an outer cover body closely covering the vibrator and the outer peripheral
surface of the support cylinder.
Embodiments of the present invention will be described in detail below with reference to the
According to an embodiment of the present invention, as shown in FIGS. 1 to 3, a plurality of
vibrators 2 arranged in a cylindrical shape, a support cylinder 3 in which these vibrators 2 are
embedded, and a large number of air chambers A box 5 supporting a large number of grids 1 for
forming 13 side walls is stacked in close proximity and concentrically in sequence, and covers
the outer peripheral surface of each transducer 2 and the support cylinder 3 on the outermost
layer thereof. , And the cover body 6 is closely laminated, and both ends thereof are fixed by a
band 7.
Further, as shown in FIG. 2, a shock absorbing material 4 is provided between each grid 1 and
the box 5 of this embodiment for damping the vibration transmitted from the box 5 during
operation. Being
As shown in FIG. 4, the vibrator 2 in this embodiment directly receives the sound wave Pi coming
from the outside, passes through the vibrator 2 and the periphery thereof, and the boundary
between the support cylinder 3 and the grid 1 The sound wave Pr freely reflected at the entrance
of the air chamber 13 in the surface is also received, and these sound waves Pi and Pr are both
converted into an electric signal.
Here, on the free reflection surface A, the reflected wave is inverted in phase with respect to the
incident wave, so that the synthetic sound pressure at the interface between the support cylinder
3 and the grid 1 is always "0".
Therefore, the sound wave vertically incident on the vibrator 2 and the free reflection surface A
is the sound that is largest to the vibrator 2 at a frequency at which the dimensions of the
vibrator 2 and the free reflection surface A are equal to 1/4 wavelength. Pressure is applied to
cause the transducer 2 to output the largest electrical signal.
On the other hand, as shown in FIG. 5, the reflection path length of the sound wave having the
incident angle from the perpendicular to the angle 短 く is shorter in proportion to cos 比 べ as
compared with the reflection path length in the case of normal incidence. The input sound
pressure to the vibrator 2 by the sound wave, that is, the output voltage of the vibrator 2
As a result, as shown in FIG. 6, a unidirectional signal having the characteristic of cos Θ is
transmitted from the cable 10 through the cable penetrating portion 9 provided on the lid 8 as
shown in FIG. Out
Here, as shown in FIG. 1, the lid 8 is fixed to the top of the housing 5 by a bolt 12 through an Oring 11 for maintaining water tightness.
Further, the frequency characteristic of the receiving voltage sensitivity represented by the ratio
of the input voltage to the vibrator 2 to the output voltage from the cable 10 is, as shown in FIG.
Shows a characteristic that the half wavelength, that is, the dimension d between the transducer
2 and the free reflection surface A becomes maximum at the frequency f1 where it is a quarter
By the way, in the hydrophone array according to the present invention configured as described
above, when external water pressure is added thereto, the support cylinders 3 bite into the air
chambers 13 of the grids 1 as shown in FIG. The interface strength is maintained by the material
strength of the support cylinder 3 at the biting portion.
Therefore, the hydrophone array can withstand a high water pressure as the material of high
strength is used for each grid 1 and the supporting cylinder can support the free reflecting
surface A of the interface. It is necessary to be a material with low elasticity and a large
elongation which is easy to displace the biting portion 3.
Under these conditions, a rubber-based material is suitable as the material of the support
cylinder 3 of the hydrophone array.
Further, as the grid 1 of this hydrophone array, a high strength elastic body, for example, a metal,
a high strength resin or the like is used to enhance its water pressure resistance and to prevent
the side walls of the air chambers 13 from being crushed. Do.
That is, as a structure of the grid 1 in the present embodiment, as shown in FIG. 8, a structure in
which a large number of through holes 1b are formed in a cylindrical elastic body 1a, or as
shown in FIG. For example, a cylindrical structure in which a large number of doughnut-shaped
disks 1c and a large number of longitudinally long flat plates 1d are combined in a grid shape
can be considered.
Here, the structure of these grids 1 is selected according to the design requirements for its water
pressure resistance.
According to the present invention, since the free reflection surface of the hydrophone array can
be made to have a high strength structure, it is possible to maintain single directivity with less
directional noise even under high water pressure. It is possible to provide a hydrophone array
having the
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