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JPH03195293

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DESCRIPTION JPH03195293
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
underwater acoustic wave receiver used to measure the sound pressure level and the like of
underwater acoustic waves. (Prior Art) Conventionally, as a technology in such a field, [J.
??????????????????? city of America (Journal of Acute Societies of America)
J 80 [6] (1986-12) (US) P, 1803-1.809. The configuration will be described below with reference
to the drawings. FIG. 2 is a perspective view showing a configuration example of a conventional
underwater acoustic wave receiver. The underwater acoustic wave receiver is, for example,
housed in a casing of a ship or the like, and has a sound absorbing plate for absorbing the
interfering sound wave S1. This sound absorbing plate 1. In the inside of the apparatus, the
compose tube 2 is provided, and on the outer surface of the sound absorbing plate]-, the flat
plate-like receiving part 3 is directly attached to receive the signal sound wave S2. FIG. 3 is a
cross-sectional view of the Conbian I tube 2 in FIG. As shown in FIG. 3, the compliant agent tube
2 has, for example, a laminated structure of two layers. In the underwater acoustic wave receiver
configured as described above, when the signal sound wave S2 comes from the direction in
which the wave receiver 3 is mounted, and the interfering sound wave S] ? comes from the
direction in which the wave receiver 3 is not mounted A sound field is generated by the signal
sound wave S2 and the interference sound wave S1. In the sound field, as shown in FIG. 4 <a,> to
(h) showing the bending vibration of the conjugate tube 2, the bending tube 2 causes bending
vibration. This vibration causes the interfering sound wave S1 to interfere and dissipate. As a
result, the interfering sound wave S1 traveling to the wave receiver 3 is blocked. In the case of a
conventional underwater acoustic wave receiver which does not take the above-mentioned
measures against sound absorption, the signal acoustic wave S2 is combined with the signal
acoustic wave S2 (this interference acoustic wave Sco is In the receiver, since the interference
sound wave S1 is blocked and only the signal sound wave S2 is received, good acoustic
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characteristics can not be obtained. (Problems to be Solved by the Invention) However, the
underwater acoustic wave receiver using the connectors 1 to 2 as described above has the
following problems. FIG. 5 is a sound absorption characteristic diagram in the case of using a
two-layer displacement compliant I tube having a predetermined shape and dimension and
material constant, and waveform 1) shows the measured value waveform, and waveform Q1
shows the calculated value waveform. It is shown. As shown in this figure, in the vicinity of the
respective resonance frequencies f and f (where f 2 ? ?) ? and 1 of 725 of the combined tube
determined by the predetermined shape dimension and material constant, good sound
absorption characteristics are exhibited. .
However, in the frequency range out of this resonance point, the sound absorption loss decreases
(that is, the amount of sound wave transmission increases). Therefore, a diagram showing a
three-layer structure of a composite tube shown in FIG. 6 and a sound absorption characteristic
diagram when using a seven-layer three-layer consist tube (waveform P2 is a measured value
waveform, and waveform Q1 is a waveform). As shown in the calculated value waveform), the
method of obtaining the sound absorption characteristics with a wide band frequency
characteristic is also included by increasing the layering of the Conbrian 1 heave with different
geometric dimensions. Then, the frequency range where the sound absorption loss is large is
certainly expanded. However, the following problems occur when multiple tubes are stacked in
order to achieve a wide band. When the sound absorption characteristics are increased in the low
frequency region, the bending resonance frequency of the coupled tube must be lowered in the
low frequency region, and as a result, the cross-sectional length of the conduit 1 to tube
increases. The volume of the entire wave increases. (2) The increase in the number of stacks of
the compliant tubes results in thickening of the sound absorbing plate 1, and the overall weight
of the receiver increases. That is, the equivalent stiffness in the thickness direction of the sound
absorbing plate 1 is lowered, and the pressure resistance is deteriorated. (3) Since the wave
receiving portion 3 is directly attached to the outer surface of the sound absorbing plate 1-1,
when mounted on a vibrating housing etc., the vibration from the housing is transmitted to the
wave receiving portion 3 through the sound absorbing plate 1. Therefore, noxious vibration noise
such as acceleration noise is induced in the wave receiver 3, and the delivery characteristic of the
signal sound wave S2 is deteriorated. An object of the present invention is to provide an
underwater acoustic wave receiver which solves the problems such as increase in volume and
weight, deterioration of signal sound wave reception performance, and the like as problems of
the prior art. (Means for Solving the Problems) In the first invention, in order to solve the abovementioned problems, in an underwater acoustic wave receiver having a flat plate-like wave
receiving portion for converting an input signal sound wave into an electric signal, Means of A
frame portion attached to the wave receiving portion and formed by a rigid frame substantially
parallel to the wave receiving portion, an elastic body with low volume elastic modulus mounted
on the inner wall surface of the frame portion, and the elastic body A plurality of ducts 1 located
within the body-worn framed part and filled with a liquid having an acoustic impedance
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substantially equivalent to water in the framed part, having a 1514 + 1 impedance equivalent to
the acoustic impedance, The receiver, the frame, the elastic body, and the mold for integrally
molding the duct are provided.
In the second aspect of the invention, the wave receiving section is provided with vibration
proofing means for attenuating vibration displacement from the outside, and the thickness of the
skeleton is set within the non-scattering range of the signal sound wave. (Operation) According to
the first aspect, since the underwater acoustic wave receiver is configured as described above,
the frame portion formed by the rigid frame is within the target frequency range with respect to
the vibration displacement from the outside. Work to avoid resonance. The elastic body and the
duct work to absorb sound waves such as interfering sound waves, and the molding material for
integrally molding the wave receiving portion, the frame portion, the elastic body and the duct 1
protects the entire wave receiver. To work. According to the second aspect of the invention, the
vibration-damping means attenuates the external displacement of vibration that has propagated
the molding material, and the frame whose thickness is set within the non-scattering range of the
signal sound wave is the entire receiver. Work to reduce weight. Therefore, the problem can be
solved. FIG. 1 (a> (b) is a block diagram of an underwater acoustic wave receiver showing an
embodiment of the present invention, and FIG. 1 (a) is a cross sectional view and FIG. 1 (b) It is
sectional drawing of the AA line of the figure (a,). The underwater acoustic wave receiver
includes a wave receiving unit 10 and a sound absorbing unit 20. The wave receiving unit 10 has
a transformer user -1 for converting the sound pressure of the signal sound wave StO into an
electric signal, and the)) transducer 1) via a signal line for deriving the electric signal. As well as
being connected to the output terminals 11a and 11b, the output terminals 11a and 11b are
encapsulated in the anti-vibration means 12 made of a soft visco-elastic molding material using
urethane rubber or the like. The sound absorbing unit 20 is attached to the wave receiving unit
10, and includes a skeleton 22 formed in a lattice shape by a skeleton 21 made of a rigid body
such as metal and substantially parallel to the wave receiving unit] 0. The thickness d of the
framework 2] is set to be thin in a range where the signal sound wave 310 is not scattered 6
Furthermore, the inner wall surface of the framework part 22 (This is a low volume elastic
modulus such as Kirk rubber containing air The elastic body 23 is attached. In the frame portion
22 on which the elastic body 23 is mounted, a plurality of ducts 24 are formed, which are filled
with a liquid such as oil having an acoustic impedance substantially equal to water. The duct 24
has a rectangular parallelepiped axis set in a predetermined -.1 method (this is set in the
direction of orthogonal coordinate axes x,) ', z' as shown in FIG. 1). In the seventh part, the wave
receiving part 10, the framework part 22, the elastic body 23, and the duct 24 are integrally
molded with a hard visco-elastic molding material 30 using urethane rubber or the like.
The mold material 30 has an acoustic impedance equivalent to the acoustic impedance. The outer
surface of the mold l ? 30 on the sound absorbing unit 20 side is attached to a housing 40 such
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as a ship. FIG. 8 is a view showing a unit lattice in the sound absorbing unit 20 in FIG. 1; one unit
lattice of the sound absorbing unit 20 (a frame 21, an elastic body 23 and a duct I и 24 as
described above) Each is configured as a series. The underwater acoustic wave receiver
configured as described above operates as follows. In the underwater acoustic wave receiver, as
shown in FIG. 1, ?one side I3 ?: a pond from which the signal sound wave SIO arrives at the
wave receiving portion 10 from the desired direction, an interference that has propagated in the
case 40 7. When the vibration displacement due to the sound wave S20 or the vibration of the
casing 40 arrives at the sound absorbing portion 20 When the vibration displacement
propagates the skeleton portion 22, the skeleton portion 22 works as resonance without
resonating within the target frequency range. Therefore, the vibration displacement is directly
transmitted to the wave receiver 10 through the framework 22. Thereafter, it is attenuated in the
process of passing through the molding material 30 and the vibration isolation means 12 and is
transmitted to 1 to 1). On the other hand, the interfering sound wave S20 is absorbed by the
sound absorbing unit 20 as follows. First, the sound absorption principle will be described. Each
of the ducts 1 to 2 has a rectangular parallelepiped shape in which the periphery is wound with
an elastic body 23 made of a soft material such as Kirk rubber. The sound pressure in the tough
[и 24 can be obtained by solving the wave equation in the duct 24 that satisfies the boundary
condition between the elastic body 23 and the tough 1 to 24. When stress-0 is approximated
around the cross section of the duct 24 in consideration of the fact that the bulk elastic modulus
of the elastic body 23 is sufficiently small compared to the volume of the liquid which is the
medium in the duct I 24, the duct I ~ The sound pressure P in 24 is expressed by the following
equation. Where: a; length in the Z-axis direction of the doug l-24 UT surface; length o in the Yaxis direction of the duct 24 cross section; to the angular frequency of the interfering sound
wave S20: with the speed of sound C of the medium in the duct 24 Determined wave number ? /
CB mn; Undetermined constant determined by incoming sound wave Next, the phenomenon that
the sound pressure P of the above equation (1) attenuates within the duct I-24 will be described
with reference to FIG. FIG. 9 is an operation explanatory view of FIG. Assuming that the
orthogonal coordinate axes x, y, z are set as shown in the figure, for example, the interference
sound wave s2o in water, the coordinate axis Z, the Z axis and the angle ? in the X plane. The
sound pressure Pi of the interference sound wave S20 at this time is 1Aej (.omega. Is 10 k sin
?OX I is k CO 3 ? oz) at the duct 24 aperture plane coordinates (?1, Y, Z) when it arrives at
the duct 24 aperture as a plane wave from the direction of (2) where A: the amplitude of the
sound pressure of the interference sound wave s20 (here, 1).
For example, assuming that the cross-sectional areas of the elastic body 23 and the frame portion
22 in the Z and Y axes are sufficiently smaller than the cross-sectional areas of the Z and Y axes
of the duct 24, the coordinate axis X-X1 by the elastic body 23 and the frame portion 22
Ignoring the reflection in the above equation (1) and equation (2) etc. i! Then, the undetermined
constant Bmn is determined. The sound pressure P in the duct 24 is obtained as follows.
(EjkcO3?0 (1> ? ? 1),). jks group ? o X Go "210 m ? Z Sin n 7 ry. j?t (3) where m = 1.2. и и и и
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и и и и и Oo, n = 1. . 2. As is clear from the equation (3), the sound pressure P is a duct 24 if the
phase term is 2- (m? / a,) 2- (r + ? / 'b) 2 is negative. The attenuation distribution is shown
toward the direction in which the wave receiver 10 is located. That is, the values of m? / a and
n? / b in the equation (3) are made larger than the values of the sound number determined by
the sound speed of the medium in the duct I-24 such as ailel and the upper limit frequency of the
target frequency range. If the cross-sectional dimensions a and b of the duct I и 24 are small and
not selected, the phase term in the equation (3) is 2- (m? / a> 2- (n?, / b) The value of can
always be negative. That is, the distribution of the sound pressure P in the duct 24 can be
attenuated. By the way, if attention is paid only to the purpose of blocking the interfering sound
wave S20, it can be realized by filling the inside of the duct 24 with gas. That is, the acoustic
impedance of the gas is small, and the interference sound wave S20 is reflected on the surface of
the gas. In addition, the weight also becomes lighter. However, in the case of gas filling, the signal
sound wave SIO coming directly to the wave receiving part 10 is reflected by the outer surface of
the duct 24 filled with gas or gas after passing through the wave receiving part, and the reflected
wave is Further, the wave is received by the wave receiver 1-0. That is, since the reflected sound
waves are added to the signal sound waves S 1] and O, the wave receiving characteristics of the
wave receiving unit 10 are degraded. FIG. 10 is a characteristic diagram of the sound pressure
attenuation amount Q5 with respect to the length ?1 of the duct 24 standardized by the
wavelength of the medium in the duct 24. Specific numerical calculations for confirming the
effects of the present invention will be described with reference to this figure. The sound
pressure attenuation amount Q can be expressed by the following equation. P?1 / PO (4) where
PX3 is the value PO at the center of the incident surface of the interfering sound wave S20 to the
duct 1; PO is the value at the end face of the receiving portion 10 of the duct I as apparent from
this figure It can be seen that the sound pressure attenuation amount Q represented by the
equation (4) significantly increases as the cross-sectional area of the duct 24 decreases.
Furthermore, the characteristic substantially irrelevant to the incident direction ? 0 (??, 45 ░,
90 ░) of the interference sound wave S 20 is shown. Next, the dimensions of the duct 24 will be
described. Here, as an example, as shown in the symmetrical frequency unit 0 ░ 1 f to f (where f
o ? = I K Hz>, desired 0) -6 sound absorption level 32 (j, B, and FIG. 8) The average sound
absorption coefficient hole per 1-unit lattice of the sound absorption unit 20 is 0.8. Here, the
average sound absorption coefficient hole is given by the ratio of the cross sectional area of the
duct 24 to the cross sectional area of the 1-unit cell. However, the framework 21. The sound
absorption coefficient of the elastic body 23 is set to zero, the sound absorption coefficient of the
duct 24 is set to 1, and the wall thickness of the framework 21 is taken into consideration in
pressure resistance, and the wall thickness of the one shell and the elastic body 23 is 1. Set as
mm. In FIG. 10, the upper limit frequency f. The desired sound absorption level 34 dB is satisfied,
assuming that the duct dimensions at are a = b-.lambda.150, .zeta.1 = 0.02.lambda. On the other
hand, the actual size of the duct I-24 is a = b = 3 an, x when the ? is calculated from the sound
speed of the medium inside the duct 1 (to be 1500 m / s as equivalent to the aile) and the double
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frequency fO. It is determined that 1 = 3 am. According to this dimension, the average sound
absorption coefficient X is 0.82 according to the calculation based on the definition of the sound
absorption coefficient, and the set 1 1 1 L average sound absorption coefficient is also satisfied.
On the other hand, when the duct dimension is a-b = ? / 100, the length of the duct 24 is a
dimension ?1 = o, which is shorter than ?1 = 0.02?. Although it is satisfied at ?, the average
sound absorption coefficient is 0.7, and the set average sound absorption coefficient is not
satisfied. Therefore, the duct dimensions are now set to a = b = 3 cyn, mark ? 1-3. FIG. 11 is a
diagram showing sound pressure attenuation 1 frequency characteristics in the duct size. The
same figure also shows the results when the duct size is set to {square root over (a)}, ? = b? =
1.5 m, ?1 = 3 CM, and a = b = 1-5 cm, and ?1 = 3 am for comparison. . As is apparent from this
figure, a, = 1): 3 (1), ? 1 ? ? ? ? 3 (in the case of m, the sound pressure ratio was
substantially constant at 34 dB at a symmetric frequency unit of 0.1 f0 to fo) It can be seen that
the value is shown. As described above, in the symmetrical frequency range, a sound absorbing
effect that is omnidirectional and has no frequency dependency is obtained. Further, FIGS. 12 (a)
and 12 (b) are sound pressure distribution maps in the duct 24 when the interfering sound wave
520 (plane wave) is incident on the duct 24; FIG. The figure which shows the case where it is
parallel to an axial plane, and the figure (b) is a figure which shows the case where an incident
nop direction is parallel to X and Z axial plane.
As shown in FIG. 1-2 (a> (b), it can be seen that the sound pressure is almost attenuated at the
end of the receiving portion 10 of the duct I и 24. The present embodiment has the following
advantages. (1) Based on the sound absorption principle, in the symmetrical frequency range, the
cross-sectional dimension in the Y and Z axial directions of the duct 24 is selected small in a
range that satisfies the desired interference sound absorption level, Since the depth is set to be
short and the thickness of the framework 21 is set to be thin within a range in which the signal
sound wave S10 does not scatter, it is possible to reduce heavy paper and volume of the entire
receiver. (2) The pressure resistance is improved because the frame portion 22 is formed in a
lattice shape. (3) Wave receiving section]-. Since the vibration isolation means 12 made of a soft
visco-elastic molding material is provided inside, double molding by the vibration damping
means 12 and the hard visco-elastic molding material 30 that wraps around it Structure is
composed. As a result, the vibration displacement transmitted through the hard molding material
30 of the outside can be damped by the spring effect of the soft anti-vibration means 12 inside.
(4) The size and shape of the ducts 1 to 24 can be set so as to rapidly attenuate within the duct I
even if the interfering sound S20 or the signal sound SIO arrives on the duct I. As in the case of
filling the gas instead of the liquid, the signal sound wave S 10 arriving at the wave receiving
portion 10 passes through the duct 24 and is reflected on the outer surface of the ducts 1 to 24,
and the reflected sound wave is further There is no occurrence of a phenomenon in which the
wave is received by the wave receiving unit 10. Thereby, deterioration of the delivery
characteristic of the wave receiver ? 0 can be prevented, and a good delivery characteristic can
be realized. (5) When receiving the interfering sound wave S20 at the sound absorbing unit 20,
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the aperture size of the duct I 24 can be set sufficiently smaller than the wavelength of the
interfering sound wave 320 in the target frequency range. Sound absorption characteristics can
be provided. That is, an omnidirectional sound absorption function is possible. In addition, flat
sound absorption characteristics substantially independent of frequency can be obtained in the
target frequency range. The present invention is not limited to the illustrated embodiment, but
various modifications are possible. For example, there is the following as a modification. (I) In the
above embodiment, although the shape of the framework 22 is formed in a lattice shape, it is not
limited to this, and any modification is possible as long as it is in accordance with the subject
matter of the present invention. (II> Although the urethane rubber of the soft viscoelastic mold
material was used as the vibration isolation means 12, it is not limited to this, and other means
may be used.
(III) As the elastic body 23 having a low volume elastic modulus, a Kirk rubber containing air is
used, but the invention is not limited thereto. (IV) In the above embodiment, although the duct 24
is a rectangular solid, deformation corresponding to the shape of the skeleton 22 is possible. (V)
Although the urethane rubber of the hard visco-elastic molding material was used as the molding
material 30, it is not limited to this. (Vl) As the liquid to be filled in the framework portion 22, no.
0 IL was used, but any other liquid may be used as long as it has a substantially equivalent
acoustic impedance to water. (Effects of the Invention) As described in detail in the following,
according to the first invention, a plurality of ducts surrounded by an elastic body of low volume
elastic modulus are formed in the framework, and further, each duct h Is filled with a liquid
having an acoustic impedance approximately equal to that of water, and blocking sound waves
etc. by the sound absorption function of each duct, so even if the length of each duct is short, it is
possible to block sound waves etc. The volume and weight of the entire receiver is significantly
reduced, as compared to conventionally using the Conbian 1 heave as a disturbing sound
absorbing structure. According to the second aspect of the invention, since the vibration
receiving means is provided in the wave receiving portion to damp the vibration displacement
from the outside, harmful vibration and interfering sound waves are blocked by the vibration
absorbing function of the wave receiving portion and the soundproof function of the duct. As
compared with the first aspect of the invention, the reception performance of the signal sound
wave of the reception wave is further improved. Moreover, the wall thickness of the framework is
set within the non-scattering range of the signal sound wave, so the weight of the whole receiver
is reduced further.
[0002]
Brief description of the drawings
[0003]
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1- (a) and (b) are block diagrams of the underwater acoustic wave receiver showing an
embodiment of the present invention, and FIG. 1- (a) is a cross-sectional view thereof and FIG. 1
(b) is a diagram (a) 2 is a perspective view of a conventional underwater acoustic wave receiver,
FIG. 3 is a cross-sectional view of a connective tube in FIG. 2, and FIGS. Fig. 5 shows the flexural
vibration of the Conbrian I tube in h), Fig. 5 shows the sound absorption characteristics when
using a two-layer structure conjoint tube, Fig. 6 shows a three-layer structure conjoint tube, Fig.
6 Fig. 7 shows the sound absorption characteristics when using a three-layer structure of the
Conbian I tube, Fig. 8 shows the unit cell in the sound absorbing section in Fig. 1, and Fig. 9 is an
operation explanatory diagram of Fig. 1 10 is a characteristic diagram of sound pressure
attenuation with respect to the duct length, and FIG. 11 is a sound pressure attenuation
frequency characteristic in the duct size. Figure 12 is a sound pressure distribution map in the
duct at the time of incident disturbance sound wave, (a> is a figure showing a case parallel to the
X, Y axis plane, the figure (b) is X, Z It is a figure which shows three cases parallel to an axial
plane.
10 иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии parts, 23 ...... elastic body
24 ...... duct 30 ..... mold Temple, 51-0 ...... signal waves, S20 ..... interference waves .
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