WO2024113493A1 - Low-noise vector hydrophone - Google Patents

Abstract

A low-noise vector hydrophone, comprising a vector hydrophone body (100), wherein the vector hydrophone body (100) is specifically configured to comprises a piezoelectric accelerometer (110), a sound pressure sensor (120), a preamplifier circuit (130), and an aluminum alloy housing (140), wherein an annular limiting rib (150) is fixed below an inner wall surface of the aluminum alloy housing (140), the piezoelectric accelerometer (110) is mounted on the inner wall surface of the aluminum alloy housing (140) above the annular limiting rib (150) by means of epoxy adhesive (160), and a piezoelectric disc (121) is bonded to the bottom of an inner side of the aluminum alloy housing (140) to directly form the sound pressure sensor (120); and the preamplifier circuit (130) is fixedly mounted on a top surface of the piezoelectric accelerometer (110) by means of four copper struts (170) and can be used for measuring ocean environment noise and detecting an underwater target in an ocean.

Description

A low noise vector hydrophone Technical Field

The invention relates to the technical field of hydrophones, in particular to a low-noise vector hydrophone.

Background technique

Marine environmental noise has its own unique characteristics. There are many types of noise sources, and the sound generation mechanisms are also different, including wind noise, industrial noise, ship noise, sea wave noise, rain noise, biological noise, ocean turbulence noise and seawater thermal noise, etc. The study of marine environmental noise is an important process for understanding the ocean and the basis for the effective use of all acoustic equipment. The study of underwater environmental noise is of great significance to marine research, underwater acoustic detection and ship engineering.

At present, the measurement and research of marine environmental noise basically only uses the physical quantity of sound pressure. The vector hydrophone can synchronously pick up the three components of the sound field, namely, sound pressure and particle velocity, at the same point in space, and can directly measure and obtain noise intensity information, providing a more comprehensive research method from the perspective of acoustic energy, which is of great research significance for the research and analysis of noise sources. In addition, the vector hydrophone can obtain the performance equivalent to that of a four-element sound pressure array sonar system, and has many advantages such as cosine directivity that is independent of frequency and strong ability to suppress isotropic noise, which can meet the needs of low-noise target detection.

Marine environmental noise measurement requires that the vector hydrophone has the ability to detect weak sound signals, that is, a low self-noise level (generally required to be lower than the marine environmental noise value under zero-level sea conditions). The self-noise of the vector hydrophone is related to the sensitive components and structural parameters. At present, most of the vector hydrophones are designed for high sensitivity, and few are designed for self-noise.

Patent No. CN200710072328.4 proposes a composite co-resonance high-frequency three-axis vector hydrophone, which is mainly composed of a three-axis vibration sensor and a low-density composite material. The characteristic is that the upper limit operating frequency can reach 12.5kHz.

Patent No. CN201110301913.3 proposes a synchronous vector receiver that can be used in deep water underwater. It adopts the working mode of longitudinal vibration of piezoelectric film and is characterized by deep water and low frequency underwater acoustic measurement.

Patent No. CN202011189207.X proposes a vector hydrophone with a composite cymbal-type piezoelectric ceramic transducer. It adopts a structure of four groups of cymbal-type piezoelectric ceramic transducers and a central inertial body, and is characterized by low frequency and high sensitivity.

None of them are designed for self-noise.

technical problem

In view of the shortcomings of the above-mentioned existing production technology, the applicant provides a low-noise vector hydrophone, which can conveniently complete the low-noise underwater target detection in the ocean.

Technical Solutions

The technical solution adopted by the present invention is as follows:

A low-noise vector hydrophone comprises a vector hydrophone, wherein the specific structure of the vector hydrophone is as follows: it comprises a piezoelectric accelerometer, a sound pressure sensor, a preamplifier circuit and an aluminum alloy shell, an annular limiting rib is fixed below the inner wall surface of the aluminum alloy shell, the piezoelectric accelerometer is mounted on the inner wall surface of the aluminum alloy shell above the annular limiting rib by epoxy resin glue, a piezoelectric disc is bonded to the bottom position of the inner side of the aluminum alloy shell, directly constituting the sound pressure sensor; the preamplifier circuit is fixed on the top surface of the piezoelectric accelerometer by four copper pillars.

Its further technical solution is:

The structure of the piezoelectric accelerometer is as follows: it includes a piezoelectric triad, a brass mass block, an ejector pin, and an aluminum alloy base. Two piezoelectric discs with holes are respectively bonded to the two sides of the brass backing by conductive glue to form a piezoelectric triad. A groove is arranged on the inner side of the brass backing. The brass mass block is a cylindrical structure as a whole. Four conical ejectors are evenly processed at the midline position of the side surface to support the brass mass block in the air. The aluminum alloy base is a cylindrical structure as a whole. Four circular grooves with internal threads are evenly distributed at the midline position of the side surface. The axial direction is a through hole, in which the brass mass block is located. The gland is a cup-shaped structure as a whole, and the outer surface is an external thread. A hexagonal through hole is set at the bottom, and four piezoelectric tripartite sheets are fixed in four circular grooves on the side of the aluminum alloy base by four pressure covers. At the same time, the brass mass block and the piezoelectric tripartite sheets are fixed by a ejector pin. The groove of the brass backing matches the shape of the ejector pin head, and the gap between the brass mass block and the aluminum alloy base is filled with polyurethane rubber.

The sound pressure sensor adopts a piezoelectric double-laminate structure.

The specific installation structure of the sound pressure sensor is as follows: a plane structure is processed on both the inner and outer sides of the bottom of the aluminum alloy shell, a circular groove is set on the inner outer edge of the plane structure, the piezoelectric disc is bonded in the groove, the outer side of the plane structure is filled with polyurethane rubber, the piezoelectric disc leads out a wire, and the sound pressure signal is transmitted to the preamplifier circuit.

A hole is opened in the center of the piezoelectric disc.

The structure of the preamplifier circuit is as follows: it includes a voltage amplifier, four charge amplifiers, two differential amplifiers and three low-pass filters. One sound pressure signal first enters the voltage amplifier to complete amplification, and then the high-frequency signal is filtered out by the low-pass filter; the four sound particle vibration signals first enter the charge amplifier to complete charge or voltage conversion and first-level amplification, and then enter the differential amplifier to realize second-level differential amplification, and finally the high-frequency noise signal is filtered out by the low-pass filter.

A watertight connector is installed in the middle of the top surface of the aluminum alloy shell for connecting the vector hydrophone cable.

The aluminum alloy shell adopts a split structure.

The aluminum alloy shell is divided into two parts, an upper part and an lower part, which are sealed with each other by epoxy resin glue.

The cross-sections of the upper and lower end surfaces of the aluminum alloy shell are in an elliptical structure.

Beneficial Effects

The beneficial effects of the present invention are as follows:

(1) The vector hydrophone proposed in the present invention can detect very weak acoustic signals, including acoustic wave pressure signals and acoustic vector signals, in ocean hydroacoustic measurement and detection, so that a more refined ocean noise field structure can be obtained, and underwater targets with lower noise can be discovered;

(2) The piezoelectric accelerometer inside the vector hydrophone adopts a differential structure, which helps to improve the axial sensitivity, reduce the lateral sensitivity, and suppress the impact of the rotation of the vector hydrophone;

(3) In a piezoelectric accelerometer, the parameters of the accelerometer can be easily adjusted by adjusting the size of the mass block;

(4) In the sound pressure sensor, the piezoelectric ceramic sheet is directly bonded to the inner surface of the aluminum alloy shell, avoiding the underwater sealing problem caused by the signal line cabin;

(5) The vector hydrophone uses an aluminum alloy shell, which can effectively shield external electromagnetic interference and improve measurement accuracy;

(6) The aluminum alloy shell of the vector hydrophone is in the shape of a cylinder with ellipsoidal caps at both ends, which can reduce the impact of flow noise.

(7) The present invention is a low-noise vector hydrophone based on a piezoelectric triplex structure, which can be applied to ocean environmental noise measurement and ocean underwater low-noise target detection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a structural cross-sectional view of a vector hydrophone according to the present invention.

FIG. 2 is a cross-sectional view of the structure of the piezoelectric accelerometer of the present invention.

FIG. 3 is a schematic structural diagram of the sound pressure sensor of the present invention.

FIG. 4 is a functional schematic diagram of a preamplifier circuit of the present invention.

Among them: 100, vector hydrophone; 110, piezoelectric accelerometer; 120, sound pressure sensor; 130, preamplifier circuit; 140, aluminum alloy shell; 150, annular limit rib; 160, epoxy resin glue; 170, copper column; 180, watertight connector; 111, piezoelectric triplet; 112, piezoelectric disc with hole; 113, conductive glue; 114, brass backing; 115, ejector pin; 116, gland; 117, brass mass block; 118, polyurethane rubber; 119, aluminum alloy base;

121. piezoelectric disc; 122. circular groove; 123. wire;

131. Sound pressure signal; 132. Sound particle vibration signal; 133. Voltage amplifier; 134. Charge amplifier; 135. Differential amplifier; 136. Low-pass filter.

Embodiments of the present invention

The specific implementation of the present invention is described below in conjunction with the accompanying drawings.

As shown in FIGS. 1 to 4 , the low-noise vector hydrophone of the present embodiment includes a vector hydrophone 100. The specific structure of the vector hydrophone 100 is as follows: it includes a piezoelectric accelerometer 110, a sound pressure sensor 120, a preamplifier circuit 130 and an aluminum alloy shell 140. An annular limiting rib 150 is fixed below the inner wall of the aluminum alloy shell 140. The piezoelectric accelerometer 110 is installed on the inner wall of the aluminum alloy shell 140 above the annular limiting rib 150 through an epoxy resin glue 160. A piezoelectric disc 121 is bonded to the bottom of the inner side of the aluminum alloy shell 140 to directly constitute the sound pressure sensor 120. The preamplifier circuit 130 is fixed on the top surface of the piezoelectric accelerometer 110 through four copper pillars 170.

The structure of the piezoelectric accelerometer 110 is as follows: it includes a piezoelectric triad 111, a brass mass block 117, a pin 115, and an aluminum alloy base 119. Two piezoelectric discs 112 with holes are respectively bonded to the two sides of a brass backing 114 by using a conductive adhesive 113 to form a piezoelectric triad 111. A groove is arranged on the inner side of the brass backing 114. The brass mass block 117 is a cylindrical structure as a whole. Four conical pins 115 are evenly processed at the midline position of the side to support the brass mass block 117 in the air. The aluminum alloy base 119 is a cylindrical structure as a whole. Four conical pins 115 are evenly distributed at the midline position of the side. A circular groove with internal threads, a through hole in the axial direction, a brass mass block 117 is located therein, a gland 116 is a cup-shaped structure as a whole, an external thread on the outer surface, and a hexagonal through hole is set at the bottom, and four piezoelectric triplet sheets 111 are fixed to the four circular grooves on the side of the aluminum alloy base 119 by four glands 116, and the brass mass block 117 and the piezoelectric triplet sheets 111 are fixed by ejector pins 115 at the same time, the groove of the brass backing 114 matches the shape of the head of the ejector pin 115, and the gap between the brass mass block 117 and the aluminum alloy base 119 is filled with polyurethane rubber 118. The design of the hexagonal through hole of the present invention is mainly to facilitate the use of an inner hexagonal wrench to tighten the gland 116.

The sound pressure sensor 120 adopts a piezoelectric double-laminate structure.

The specific installation structure of the sound pressure sensor 120 is as follows: a plane structure is processed at the bottom of the aluminum alloy housing 140, a circular groove 122 is set at the inner outer edge of the plane structure, a piezoelectric disc 121 is bonded in the circular groove 122, the outer side of the plane structure is filled with polyurethane rubber 118, a wire 123 is led out of the piezoelectric disc 121, and the sound pressure signal 131 is transmitted to the preamplifier circuit 130. A hole is opened in the center of the piezoelectric disc 121.

The structure of the preamplifier circuit 130 is: it includes a voltage amplifier 133, four charge amplifiers 134, two differential amplifiers 135 and three low-pass filters 136. One sound pressure signal 131 first enters the voltage amplifier 133 to complete amplification, and then passes through the low-pass filter 136 to filter out the high-frequency signal; the four sound particle vibration signals 132 first enter the charge amplifier 134 to complete charge or voltage conversion and first-level amplification, and then enter the differential amplifier 135 to realize second-level differential amplification, and finally pass through the low-pass filter 136 to filter out the high-frequency noise signal.

A watertight connector 180 is installed in the middle of the top surface of the aluminum alloy shell 140 for connecting the cable of the vector hydrophone 100 .

The aluminum alloy housing 140 adopts a split structure.

The aluminum alloy housing 140 is divided into two parts, an upper part and an lower part, which are sealed with each other by epoxy resin glue 160 .

The cross-sections of the upper and lower end surfaces of the aluminum alloy shell 140 are elliptical structures.

The preamplifier circuit 130 of the present invention is composed of a charge amplifier 134, a differential amplifier 135, and a low-pass filter 136, and is used for amplifying and filtering the signals of the piezoelectric accelerometer 110 and the sound pressure sensor 120 to improve the signal-to-noise ratio level of the signal.

The aluminum alloy housing 140 of the present invention is used to seal the piezoelectric accelerometer 110, the sound pressure sensor 120 and the preamplifier circuit 130 as a whole, and to make the average density of the vector hydrophone 100 consistent with that of seawater.

The vector hydrophone 100 of the present invention is in the shape of a cylinder with slight negative buoyancy, and the upper and lower ends use semi-ellipsoidal shells as end covers, which can play a good role in guiding flow.

The preamplifier circuit 130 of the present invention is provided with a magnetic sensor for measuring the orientation of the vector hydrophone 100 itself.

The vector hydrophone 100 of the present invention may also have a data acquisition circuit inside to convert the signal into a digital signal and output it.

The vector hydrophone 100 of the present invention can effectively monitor low-frequency noise signals below 1 kHz in the ocean, and can achieve accurate measurement even for infrasonic signals in the range of 5-20 Hz.

As shown in FIG1 , the vector hydrophone 100 includes a piezoelectric accelerometer 110, a sound pressure sensor 120, a front The vector hydrophone 100 is generally cylindrical in shape. The piezoelectric accelerometer 110 is located at the center of the vector hydrophone 100 and is rigidly fixed inside the aluminum alloy shell 140 by means of annular limiting ribs 150 and epoxy resin glue 160. The sound pressure sensor 120 is located on the inner side of the bottom of the aluminum alloy shell 140. The preamplifier circuit 130 is fixed to the upper end face of the piezoelectric accelerometer 110 by means of four copper pillars 170. The aluminum alloy shell 140 is divided into two parts, the upper and lower parts, which are sealed with each other by epoxy resin glue 160. The watertight connector 180 is located at the uppermost part of the aluminum alloy shell 140 and is used for the cable to pass through the cabin to realize the output of various signals of the vector hydrophone 100. The watertight connector 180 and the aluminum alloy shell 140 are sealed with epoxy resin glue 160.

As shown in FIG2 , the piezoelectric accelerometer 110 is used to measure the vibration signal 132 of the sound particle of the environmental noise. The specific structure is as follows: it is composed of a piezoelectric triad 111, a pin 115, a brass mass block 117, an aluminum alloy base 119 and a pressure cap 116. The two piezoelectric discs 112 with holes are respectively bonded to the two sides of the brass backing 114 by means of a conductive adhesive 113 to form the piezoelectric triad 111. A groove is arranged on the inner side of the brass backing 114. The brass mass block 117 is a cylindrical structure as a whole. Four conical pins 115 are evenly processed at the midline position of the side surface to support the brass mass block 117 in the air. The aluminum alloy base 119 is a cylindrical structure as a whole. Four circular grooves with internal threads are evenly distributed at the midline position of the side surface. The axial direction is a through hole, and the brass mass block 117 is located therein. The pressure cap 116 is a cup-shaped structure as a whole. The outer surface is an external thread, and a hexagonal through hole is arranged at the bottom. Four piezoelectric triplet sheets 111 are fixed to four circular grooves on the side of the aluminum alloy base 119 by four glands 116, and the brass mass block 117 and the piezoelectric triplet sheets 111 are fixed by ejector pins 115. The groove of the brass backing 114 matches the shape of the head of the ejector pin 115. The gap between the brass mass block 117 and the aluminum alloy base 119 is filled with polyurethane rubber 118 to play a damping role.

As shown in FIG3 , the sound pressure sensor 120 is located on the inner side of the bottom of the aluminum alloy housing 140 and is composed of a piezoelectric disc 121 with a through hole in the center, which helps to further improve the acoustic sensitivity. Part of the bottom area of the aluminum alloy housing 140 is processed into a plane structure inside and outside, and a circular groove 122 is set on the inner outer edge of the plane to reduce the rigidity of the bending movement of the structure. The piezoelectric disc 121 is bonded into the circular groove 122, and the outer side is filled with polyurethane rubber 118 to play a damping role. The wire 123 is led out from the electrode surface of the piezoelectric disc 121 to transmit the sound pressure signal 131 to the preamplifier circuit 130.

As shown in FIG4 , the preamplifier circuit 130 is used to pre-process the sound pressure signal 131 and the sound particle vibration signal 132 of the vector hydrophone 100, and includes a voltage amplifier 133, four charge amplifiers 134, two differential amplifiers 135, and three low-pass filters 136. The sound pressure signal 131 first enters the voltage amplifier 133 to complete amplification, and then passes through the low-pass filter 136 to filter out high-frequency signals. The four sound particle vibration signals 132 first enter the charge amplifier 134 to complete charge/voltage conversion and first-stage amplification, and then enter the differential amplifier 135 to achieve second-stage differential amplification, and finally pass through the low-pass filter 136 to filter out high-frequency noise signals.

In actual operation, when the vector hydrophone 100 is placed in an underwater sound field, it will oscillate synchronously with the sound particles in the sound field. The brass mass block 117 inside the vector hydrophone 100 is subjected to inertial force and is relatively displaced with the aluminum alloy base 119. The inertial force acts on the piezoelectric triplet 111 through four conical ejector pins 115 to deform it. At this time, the perforated piezoelectric discs 112 on both sides of the brass backing generate charge signals under the action of the forward piezoelectric effect. The charge signals are proportional to the amplitude of the acceleration of the vibration of the sound particles and have the same phase. The piezoelectric triplet 111 is configured in parallel connection mode, and the piezoelectric triplet 111 on the other side is configured in differential mode to increase the charge value to increase sensitivity. The other axial working mode is the same. A wire is welded on the surface of the piezoelectric triplet 111, and the generated signal is sent to the preamplifier 130 for further signal acquisition and processing. On the other hand, due to the pressure of the sound wave, the bottom shell of the vector hydrophone 100 is compressed and deformed, and at the same time, the inner piezoelectric disc 121 is deformed at the same time. Due to the forward piezoelectric effect, the piezoelectric disc 121 will generate a voltage signal proportional to the sound pressure signal. A wire 123 is welded on the surface of the piezoelectric disc 121, and the generated signal is sent to the preamplifier circuit 130 for further signal collection and processing.

The theoretical basis of the present invention's design is:

When a low-noise amplifier circuit is used, the self-noise of the vector hydrophone mainly comes from the background noise of the internal accelerometer.

The background noise of the accelerometer is composed of mechanical thermal equilibrium noise and Johnson electrical thermal noise, which can be expressed as:

In the formula,

Boltzmann constant K = 1.381e-23 J/K,

T is the absolute temperature,

ωn is the natural frequency,

m is the inertial mass,

Qm is the mechanical quality factor,

tanδ is the dielectric loss tangent,

ω is the angular frequency,

Ma is the accelerometer voltage sensitivity,

C0 is the static capacitance.

It can be seen from the formula that once the structure of the piezoelectric accelerometer is determined, the self-noise can be reduced by increasing the inertial mass, sensitivity, and static capacitance in the structure.

Therefore, in the present invention, an independent mass block is arranged outside the triple stack to increase the inertial mass, adjust the sensitivity and the resonant frequency, and change the prestress of the triple stack by adjusting the ejector pin length to optimize the sensitivity of the accelerometer.

The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims (10)

1. A low-noise vector hydrophone, characterized in that it comprises a vector hydrophone (100), wherein the specific structure of the vector hydrophone (100) comprises a piezoelectric accelerometer (110), a sound pressure sensor (120), a preamplifier circuit (130) and an aluminum alloy shell (140), wherein an annular limiting rib (150) is fixed below the inner wall surface of the aluminum alloy shell (140), the piezoelectric accelerometer (110) is mounted on the inner wall surface of the aluminum alloy shell (140) above the annular limiting rib (150) via epoxy resin glue (160), a piezoelectric disc (121) is bonded to the inner bottom of the aluminum alloy shell (140), and the sound pressure sensor (120) is directly formed; and the preamplifier circuit (130) is fixedly mounted on the top surface of the piezoelectric accelerometer (110) via four copper pillars (170).
2. A low-noise vector hydrophone as described in claim 1, characterized in that: the structure of the piezoelectric accelerometer (110) is: including a piezoelectric triad (111), a brass mass block (117), a pin (115), and an aluminum alloy base (119); two piezoelectric discs (112) with holes are respectively bonded to the two sides of the brass backing (114) by conductive glue (113) to form a piezoelectric triad (111); a groove is arranged on the inner side of the brass backing (114); the brass mass block (117) is a cylindrical structure as a whole, and four conical pins (115) are evenly processed at the midline position of the side surface to suspend and support the brass mass block (117); the aluminum alloy base (119) is a cylindrical structure as a whole. The invention discloses a piezoelectric triplet (111) having a shaped structure, four circular grooves with internal threads are evenly distributed at the midline of the side, and the axial direction is a through hole, in which the brass mass block (117) is located. The pressure cover (116) is a cup-shaped structure as a whole, with an external thread on the outer surface and a hexagonal through hole arranged at the bottom. The four pressure covers (116) are used to fix the four piezoelectric triplet sheets (111) in the four circular grooves on the side of the aluminum alloy base (119), respectively. At the same time, the brass mass block (117) and the piezoelectric triplet sheets (111) are fixed by an ejector pin (115). The groove of the brass backing (114) matches the shape of the head of the ejector pin (115), and the gap between the brass mass block (117) and the aluminum alloy base (119) is filled with polyurethane rubber (118).
3. The low-noise vector hydrophone according to claim 1, characterized in that the sound pressure sensor (120) adopts a piezoelectric double-laminate structure.
4. A low-noise vector hydrophone as described in claim 1, characterized in that: the specific installation structure of the sound pressure sensor (120) is: a plane structure is processed at the inner and outer sides of the bottom of the aluminum alloy shell (140), a circular groove (122) is arranged on the inner outer edge of the plane structure, the piezoelectric disc (121) is bonded into the circular groove (122), the outer side of the plane structure is filled with polyurethane rubber (118), the piezoelectric disc (121) leads out a wire (123), and the sound pressure signal is transmitted to the preamplifier circuit (130).
5. A low-noise vector hydrophone as claimed in claim 4, characterized in that a hole is opened in the center of the piezoelectric disc (121).
6. A low-noise vector hydrophone as claimed in claim 1, characterized in that: the structure of the preamplifier circuit (130) is: including a voltage amplifier (133), four charge amplifiers (134), two differential amplifiers (135) and three low-pass filters (136), one sound pressure signal (131) first enters the voltage amplifier (133) to complete amplification, and then passes through the low-pass filter (136) to filter out high-frequency signals; four sound particle vibration signals (132) first enter the charge amplifier (134) to complete charge or voltage conversion and first-level amplification, and then enter the differential amplifier (135) to achieve second-level differential amplification, and finally pass through the low-pass filter (136) to filter out high-frequency noise signals.
7. A low-noise vector hydrophone according to claim 1, characterized in that a watertight connector (180) is installed in the middle of the top surface of the aluminum alloy shell (140) for connecting the vector hydrophone (100) cable.
8. The low-noise vector hydrophone according to claim 1, characterized in that the aluminum alloy shell (140) adopts a split structure.
9. The low-noise vector hydrophone according to claim 1 is characterized in that the aluminum alloy shell (140) is divided into two upper and lower parts, which are sealed with epoxy resin glue (160).
10. The low-noise vector hydrophone according to claim 1, characterized in that the upper and lower end surfaces of the aluminum alloy shell (140) have an elliptical cross-section structure.