JPH11164385A - Underwater sound wave receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noises in an acoustic sensor and to perform satisfactory sound wave detection by providing a rigid body tube of axial symmetry in a rubber elastic vessel, and arranging the acoustic sensor on a symmetry axis in the rigid body tube. SOLUTION: An acoustic sensor 1 is supported by an elastic material such as sponge on a central axis of a rigid cylindrical body tube with axial symmetry 4 which is inserted in a rubber hose 2. When this underwater sound wave receiver is towed by a boat, turbulent flow is generated outside the hose 2, and pressure is applied to the surface of the hose 2 to generate vibrations of a complicated mode. In the tube 4, a vibration vertical to the center axis becomes a primary vibration mode (translation vibration) because of its rigidity and the vibration mode of the hose 2 of a part where the tube 4 is inserted is also controlled according to the vibration of the tube 4. Then, in the vibration of the hose 2 of the part where the tube 4 is inserted, the primary vibration mode becomes predominant. An output of the sensor 1 is canceled by a pressure distribution that undergoes positive and negative inversion, thus noises are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater receiver for performing acoustic measurement by towing underwater or the like, and more particularly, to an underwater receiver for reducing noise generated by towing or the like. Things.

[0002]

2. Description of the Related Art As an underwater receiver for performing acoustic measurement, for example, an electroacoustic transducer provided in a rubber elastic container is disposed inside a hollow hollow shell made of a rigid body having an acoustic entrance. There is a rubber elastic container in which a fluid is filled.
When the underwater receiver is towed, the rubber elastic container vibrates due to turbulence generated on the surface of the rubber elastic container and the fluid filled inside vibrates, but the vibrating fluid first collides with the shell, The shell acts as a shield to reduce noise without directly colliding with the electro-acoustic transducer.

[0003]

However, in the prior art configured as described above, the rubber elastic container vibrates due to the turbulent pressure, and the internal fluid vibrates, causing a pressure difference in the flow direction. Then, a complicated mode of vibration is generated, and the pressure distribution inside the rubber elastic container becomes complicated.
In the prior art, the oscillating fluid is prevented from colliding with the acoustic sensor by covering the acoustic sensor with a shell.However, the pressure distributed to the oscillating fluid propagates from the acoustic entrance to the inside of the shell, and the acoustic sensor has an acoustic sensor. There was a problem of output, that is, noise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an underwater receiver capable of performing good sound wave detection by reducing noise generated in an acoustic sensor. .

[0005]

SUMMARY OF THE INVENTION The present invention relates to an underwater receiver in which an acoustic sensor is provided in a rubber elastic container and a fluid is filled in the rubber elastic container to perform acoustic measurement in water.
An axially symmetric rigid pipe is provided in a rubber elastic container so as to be inscribed therein, and an acoustic sensor is arranged on a symmetric axis in the rigid pipe.

[0006] Thus, the sound wave reaches the acoustic sensor from both end openings of the rigid tube, is converted into an electric signal by the acoustic sensor, and is detected through the signal cable. In addition, in the translational movement of the rigid pipe, a positive / negative pressure is generated from the inner walls of the rigid pipe on both sides in the vibration direction, and the pressure distribution inside the rigid pipe becomes a positive / negative reverse distribution with the central axis as a symmetric axis. The output of the sensor cancels out and noise is reduced.

[0007] The acoustic sensor is covered with a shell having an acoustic entrance, and the acoustic entrance is arranged on the axis of symmetry in the rigid tube. Thus, the sound waves reach the acoustic sensor having the characteristics of a Helmholtz resonator, are converted into electric signals by the acoustic sensor, and are detected through the signal cable.

Further, since the acoustic sensor is covered with the shell, the vibrating fluid does not collide with the acoustic sensor.
Furthermore, in the translational movement of the rigid pipe, positive and negative reversed pressures are generated from the inner walls of the rigid pipe on both sides in the vibration direction, and the pressure distribution inside the rigid pipe becomes a positive and negative reversed pressure distribution with the central axis as a symmetric axis, The output of the acoustic sensor cancels out, reducing noise.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a configuration diagram of a first embodiment of the present invention. Reference numeral 1 denotes an acoustic sensor, which is made of a piezoelectric ceramic such as lead titanate / lead zirconate or a polymer piezoelectric material such as PVDF, but may be any element that responds to pressure as the acoustic sensor.

Reference numeral 2 denotes a hermetically sealed rubber hose which forms a rubber elastic container, has a sound-transmitting property, and has an acoustic sensor 1 disposed therein. A signal cable 3 also serves as a towing cable, and is connected to an output terminal of the acoustic sensor 1 by a lead wire.

Reference numeral 4 denotes an axially symmetric, for example, cylindrical rigid tube inscribed in the rubber hose 2, which is formed of a light hard material such as a light metal such as aluminum or a hard resin such as a glass epoxy resin, and has an axisymmetric positive and negative. An inverted pressure distribution is generated. The length of the rigid tube 4 is limited due to the acoustic characteristics of the acoustic tube and the operability of winding and storage, etc., but the length of the rigid tube 4 is to keep noise entering from the openings at both ends and to restrict the vibration mode of the rubber hose 2. It is better to form it long so as to make it wider. The acoustic sensor 1 is supported on a central axis of the rigid tube 4 by an elastic material (not shown) such as a sponge. Numeral 5 is a fluid having sound permeability in water filled in the rubber hose 2.

The operation of the first embodiment configured as described above will be described. First, an operation for detecting a sound wave (signal) will be described. The sound wave passes through a portion of the rubber hose 2 where the rigid tube 4 is not provided, reaches the acoustic sensor 1 from both ends of the rigid tube 4, is converted into an electric signal by the acoustic sensor 1, and Detected through cable 3.

Next, an operation related to noise reduction will be described. When the underwater receiver is towed, turbulence is generated outside the rubber hose 2, and pressure is applied to the surface of the rubber hose 2. Since the rubber hose 2 has flexibility, vibration in a complicated mode is generated. Due to the rigidity of the rigid pipe 4, the vibration in the direction perpendicular to the central axis becomes the primary vibration mode (translational vibration), and the vibration mode of the rubber hose 2 in the part in which the rigid pipe 4 is inscribed is also the rigid pipe 4. It is suppressed according to the vibration. Therefore, even if pressure due to turbulence is applied to the outside of the rubber hose 2, the portion of the rubber hose 2 in which the rigid pipe 4 is inscribed
Is dominated by the primary vibration mode.

In the translational movement of the rigid pipe 4, if the influence of the opening at both ends is ignored, a pressure is generated from the inner wall of the rigid pipe 4 on both sides in the vibration direction. Due to the axial symmetry, the pressure distribution has a positive / negative inversion with the central axis as the symmetry axis. Since the acoustic sensor 1 is installed on the central axis of the rigid pipe 4, the output of the acoustic sensor 1 is canceled by the positive / negative pressure distribution, and noise is reduced.

As in the prior art, when the rubber hose 2 alone is used, the vibration is in a complicated mode due to its flexibility. However, in the first embodiment, since the rigid tube 4 is inscribed in the rubber hose 2, the vibration mode is limited. Suppressed, the primary vibration mode becomes dominant. Since the acoustic sensor 1 is disposed on the central axis, the output of the acoustic sensor 1 is cancelled to zero due to the positive and negative reversed pressures with the central axis as the axis of symmetry.

In the above description, the case where the rigid pipe 4 is cylindrical is shown. However, in order to generate an axially symmetric positive / negative pressure distribution, the rigid pipe 4 does not need to be cylindrical but has an axially symmetric shape. I just need. In addition, the underwater receiver used in towing is described, but the invention can also be applied to an underwater receiver used for suspension in order to reduce noise due to tidal current and vertical movement of waves.

Embodiment 2 FIG. 2 is a configuration diagram of Embodiment 2 of the present invention. The same or corresponding parts as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 6 denotes a shell covering the acoustic sensor 1, and the rigid tube 4
Similarly, a lightweight hard material made of a light metal such as aluminum or a hard resin such as a glass epoxy resin is used.

Reference numeral 7 denotes an acoustic entrance provided in the shell 6 and the rigid tube 4
Are arranged on the central axis of In this way, the acoustic sensor 1 is covered with the shell 6 and the small acoustic entrance 7 is provided in the shell 6, so that the acoustic sensor 1 exhibits characteristics as a Helmholtz resonator. The volume of the shell 6 and the size of the sound entrance 7 are set so that the resonance frequency is higher than the operating frequency.

The operation of the second embodiment configured as described above will be described. The detection of sound waves (signals) is substantially the same as the case described in the first embodiment. In this case, the acoustic sensor 1 is covered with a shell 6, and the shell 6 has a small acoustic entrance 7
, The characteristics as a Helmholtz resonator are exhibited.

Next, the operation related to noise reduction will be described. Since the acoustic sensor 1 is covered with the shell 6, the vibrating fluid 5 does not collide with the acoustic sensor 1. Further, since the rigid tube 4 is provided in contact with the rubber hose 2, the rigid tube 4 works in the same manner as in the first embodiment. Therefore, even if pressure due to turbulent flow is applied to the outside of the rubber hose 2, the vibration of the rubber hose 2 at the portion where the rigid pipe 4 is inscribed is dominated by the primary vibration mode. Regarding the translational vibration of the rigid pipe 4, if the influence of the opening at both ends is ignored, a pressure in the positive and negative directions is generated from the inner wall of the rigid pipe 4 in the vibration direction.
Has an axially symmetric pressure distribution inverted in the positive and negative directions. Therefore, the pressure becomes zero on the central axis. Since the sound entrance 7 is provided on the center axis of the rigid tube 4, the sound entrance 7
The pressure (noise) incident on is zero.

According to the second embodiment, the operation of the rigid pipe 4 is the same as that of the first embodiment. Also, since the acoustic sensor 1 is covered with the shell 6 having the acoustic entrance 7, the acoustic sensor 1
Since the sound inlet 7 is placed on the central axis where the pressure becomes zero without the fluid 5 oscillating at the same time, the pressure incident on the sound inlet 7 becomes zero.

At low frequencies where the wavelength of the sound wave is at least twice the inner diameter of the rigid tube 4, the absolute value of the pressure increases from the axial center toward the inner wall of the rigid tube 4. Actually, in the first embodiment, the influence of an object placed in the rigid tube 4 such as the acoustic sensor 1 and the shell 6 in the present embodiment, and the effect of the openings at both ends of the rigid tube 4. That is, the inside of the rigid tube 4 is not completely axially symmetric and does not have a pressure distribution in which the sign is reversed. However, since the sound entrance 7 is located on the central axis where the absolute value of the pressure is the smallest, the influence of the noise portion which is not canceled out is minimized.

Third Embodiment FIG. 3 is a configuration diagram of a third embodiment of the present invention. The same or corresponding parts as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 9 denotes a hard rubber tube generally called an acoustic rubber, which has an acoustic impedance substantially equal to that of water, that is, is made of a rubber material having sound permeability. The hard rubber tube 9 is formed in a cylindrical shape inscribed in the rubber hose 2 as in the first embodiment, and generates an axially symmetric positive / negative pressure distribution. The length of the hard rubber tube 9 is limited due to the operability of winding and storing, etc., but is long so as to keep noise entering from the openings at both ends and to widen the range for regulating the vibration mode of the rubber hose 2. It is better to form. The acoustic sensor 1 is supported on the central axis of the hard rubber tube 9 by an elastic material (not shown) such as a sponge.

The operation of the third embodiment configured as described above will be described. The detection of sound waves (signals) is substantially the same as the case described in the first embodiment. However, in the third embodiment, since the rigid rubber tube 9 having sound permeability is used instead of the rigid tube, the sound waves first pass through the rubber hose 2 and are further transmitted through the hard rubber tube 9 or the rigid rubber tube 9.
, Reaches the acoustic sensor 1, is converted into an electric signal by the acoustic sensor 1, and is detected through the signal cable 3. When the underwater receiver is towed, rubber hose 2
Generates a turbulent flow outside the rubber hose 2, and a random local pressure is applied to the surface of the rubber hose 2. Since the elastic modulus (rigidity) of the hard rubber tube 9 is high, when compared with the rubber hose 2,
It can be considered a rigid body. Therefore, as in the first embodiment, the vibration mode of the rubber hose 2 at the portion where the hard rubber tube 9 is inscribed is also suppressed according to the vibration of the hard rubber tube 9,
The deformation of the rubber hose 2 is reduced. For this reason, even if pressure due to turbulence is applied to the outside of the rubber hose 2, the primary vibration mode of the vibration of the rubber hose 2 where the hard rubber tube 9 is inscribed is dominant.

According to the third embodiment, a rigid rubber tube 9 having sound permeability is used instead of the rigid tube 4 in the first embodiment.
The length of the tube, which is limited by the resonance characteristics of the acoustic tube, can be increased. Thus, even when the length of the tube is long, the frequency characteristics of the reception sensitivity do not change even in a high frequency range, so that a high frequency can be detected. In addition, the ability to lengthen the tube
Because the end of the tube is relatively small relative to the length of the tube,
It is possible to keep noise entering from the opening at the end part away, and to prevent a decrease in accuracy due to the noise. Further, the vibration of the fluid inside the hard rubber tube becomes closer to the translational motion, and the effect of noise reduction is increased.

Fourth Embodiment FIG. 4 is a configuration diagram of a fourth embodiment of the present invention. The same or corresponding parts as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Numeral 8 is made of a soft rubber elastic material having an acoustic impedance substantially equal to that of water, fills the inside of the rigid tube 4 and supports the acoustic sensor 1. The rubber elastic material 8 is obtained by mixing a two-component curable rubber material such as urethane rubber without bubbles, filling the rigid tube 4, and then curing.

The operation of the fourth embodiment configured as described above will be described. The detection of sound waves (signals) is substantially the same as the case described in the first embodiment. However, in the fourth embodiment, since the rubber elastic material 8 is used in place of an elastic material such as a sponge (not shown), the sound wave passes through the rubber hose 2 and the opening at both ends of the rigid pipe 4, and the sound is transmitted through the rubber elastic material 8. The light propagates and reaches the acoustic sensor 1. The sound wave is converted into an electric signal by the acoustic sensor 1 and detected through the signal cable 3.

According to the fourth embodiment, since the rubber elastic material 8 is used in place of the elastic material (not shown) such as the sponge in the first embodiment, even if bubbles are generated in the fluid 5, the acoustic sensor 1 Can't get close to For this reason, the receiving characteristics of the acoustic sensor 1 are not affected, and a more reliable underwater receiver can be provided. When rubber having continuous cells such as sponge is used, it is necessary to perform vacuum defoaming when filling the rubber hose 2 with the fluid 5, but it takes time to defoam because the surface area is large,
Also, complete degassing is difficult. By using the rubber elastic material 8, defoaming can be performed in a short time, and complete defoaming becomes possible.
Although the rigid pipe 4 is a rigid body, it is not a perfect rigid body, so that some vibrations occur. By using the rubber elastic material 8, the influence on the acoustic sensor 1 due to the vibration of the rigid tube 4 can be reduced, and the underwater receiver with further reduced noise can be obtained. Although the two-component curable rubber material has been described as an example of the rubber elastic material, other rubber materials can be used. When a two-component curable rubber material is used, there is an advantage that the filling operation into the rigid pipe becomes easy.

Fifth Embodiment FIG. 5 is a block diagram of a fifth embodiment of the present invention. Note that the same or corresponding portions as in Embodiment 4 are denoted by the same reference numerals, and description thereof is omitted. 1-1 is an acoustic sensor existing in the rubber elastic material 8 in the rigid tube 4-2, and 1-2 is an acoustic sensor existing in the rubber elastic material 8 in the rigid tube 4. Reference numeral 3 denotes a signal cable connected to the acoustic sensor 1-1 and the acoustic sensor 1-2. Reference numeral 10 denotes a cylindrical thick portion of the rigid pipe 4-2, which is a hole penetrating both ends of the pipe. The signal cable 3 passes through the hole 10 of the rigid tube 4-2.

The operation of the fifth embodiment configured as described above will be described. The detection of sound waves (signals) is substantially the same as the case described in the fourth embodiment. However, in the fifth embodiment, each of the acoustic sensor 1-1 and the acoustic sensor 1-2 detects a sound wave and outputs the sound wave to the outside through the signal cable 3.

According to the fifth embodiment, since a plurality of acoustic sensors are provided, sound waves at each point can be detected. Therefore, the detection accuracy can be improved by the directivity of the plurality of acoustic sensors. Since the signal cable 3 passes through the hole 10 of the rigid tube 4-2, the signal cable 3
Does not directly affect the rubber elastic material filled in the rigid tube 4-2. Therefore, the influence on the acoustic sensor in the rubber elastic material can be reduced, so that a more reliable underwater receiver can be obtained.
When filling the rubber hose 2 with the fluid 5, it is necessary to perform vacuum defoaming. However, the presence of the hole 10 in the rigid pipe 4-2 makes it possible to replace the air in the rubber hose 2 with the fluid 5 to be filled. It will be easier.

Sixth Embodiment FIG. 6 is a configuration diagram of a sixth embodiment of the present invention. Note that the same or corresponding portions as in Embodiment 5 are denoted by the same reference numerals, and description thereof is omitted. Reference numeral 11 denotes an outer side surface of the rigid pipe 4-3, which is a groove penetrating both ends of the pipe. The signal cable 3 passes through the groove 11 of the rigid pipe 4-3 and is connected to the signal cable 3.

The operation of the sixth embodiment configured as described above will be described. The detection of sound waves (signals) is substantially the same as the case described in the fourth embodiment.

According to the sixth embodiment, since a plurality of acoustic sensors are provided, sound waves at each point can be detected. Therefore, the detection accuracy can be improved by the directivity of the plurality of acoustic sensors. Since the signal cable 3 passes through the groove 11 of the rigid pipe 4-3, the signal cable 3
Does not directly affect the rubber elastic material filled in the rigid pipe. Therefore, the influence on the acoustic sensor in the rubber elastic material can be reduced, so that the underwater receiver can further reduce noise. Also,
When filling the rubber hose 2 with the fluid 5, it is necessary to perform vacuum defoaming. However, the presence of the groove 11 of the rigid pipe 4-3 facilitates replacement of the air 5 in the rubber hose 2 with the fluid 5 to be filled. Become. Further, by providing the groove 11 on the outer side surface of the rigid tube 4-3, the acoustic sensor and the rubber elastic material can be reduced by one.
As a single unit, the unit can be replaced without cutting the signal cable 3.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram according to a sixth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 acoustic sensor 2 rubber hose 3 signal cable 4 rigid pipe 5 fluid

Claims (6)

[Claims] 1. A rubber elastic container, a rigid tube inscribed in the rubber elastic container, an acoustic sensor located on an axis of symmetry of the rigid tube, and a support filled in the rigid tube for supporting the acoustic sensor And a signal cable for outputting a signal detected by the acoustic sensor to the outside. 2. The underwater receiver according to claim 1, wherein the acoustic sensor is covered with a shell having an acoustic entrance located on an axis of symmetry of the rigid tube. 3. The underwater receiver according to claim 1, wherein the rigid pipe is made of hard rubber. 4. The underwater receiver according to claim 1, wherein the support is made of a rubber elastic material. 5. The rigid pipe according to claim 1, wherein the rigid pipe has a hole in a thick portion of the rigid pipe, and the signal cable passes through the hole. Underwater receiver. 6. The rigid pipe according to claim 1, wherein the rigid pipe has a groove on an outer side surface of the rigid pipe, and the signal cable passes through the groove. Underwater receiver.