A small-sized dynamic ultra-low frequency underwater acoustic transducer

Abstract

The present invention provides a small-sized dynamic coil ultra-low frequency underwater acoustic transducer, which includes a radially arranged magnetic circuit system structure and a corresponding radiation system structure installed in a watertight shell. When current flows through the coil, a driving force is generated in the air gap of the magnetic circuit under the action of the magnetic field, driving the radiation system to vibrate according to a certain rule, and radiating sound waves outward from the radiation plate. The present invention has the advantages of small size, light weight, and easy use. It has good adaptability and can achieve ultra-low frequency broadband acoustic emission of 40Hz to 1kHz. It can be used as an acoustic load and equipped on sonar equipment and acoustic countermeasure devices, especially for small-caliber navigation bodies, and has good adaptability; it can also be used as a general ultra-low frequency sound source for laboratory and lake and sea experiments.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater acoustic transducers, and in particular relates to a small-sized moving coil type ultra-low frequency underwater acoustic transducer. Background Art

[0002] So far, sound waves are considered to be the only information carrier that can be transmitted over long distances in the ocean. The use of underwater acoustic transducers can realize the transmission or reception of sound wave information. The lower the frequency of the sound wave, the smaller the propagation loss in the water, and the more suitable it is for long-distance transmission. With the development of acoustic stealth technology, the mid- and high-frequency parts of the radiation noise of underwater vehicles such as submarines have been suppressed to a level below the ocean background noise, and the mid- and low-frequency and ultra-low-frequency parts of the radiation noise have become the key factors in detecting underwater vehicles. As one of the key components of underwater acoustic technology, ultra-low frequency underwater acoustic transducers can be used in military technical fields such as submarine detection and anti-submarine, noise simulation, and underwater acoustic deception and interference, and have important research value and military significance.

[0003] Generally, the lower the working frequency of the transducer, the larger its volume and the heavier its mass. The ultra-low frequency transmitting transducer designed with piezoelectric ceramic elements and working frequency below 100Hz usually weighs hundreds of kilograms or more. The ultra-low frequency transmitting transducer HX-554 with a resonant frequency of 75Hz designed by bending vibration has a diameter of 0.94m and a total length of 2.05m, and its weight in the air is as high as 2300kg. The ultra-low frequency transmitting transducer with a resonant frequency of 65Hz designed by Helmholtz resonator structure also weighs as high as 1900kg in the air. The UW350 transducer produced by GW Company in the UK has an operating frequency band of 20Hz-20kHz, an average sound source level of 165dB, a length of 935mm, and a weight of 100kg; the weight of the UW600 dynamic ultra-low frequency transmitting transducer is also as high as 1070kg, the transducer diameter reaches 880mm, and the operating frequency band of this transducer is 4Hz~1kHz.

[0004] The above-mentioned underwater acoustic transducers can all achieve ultra-low frequency acoustic emission, but obviously, the above-mentioned transducers all have the disadvantages of large size, heavy weight, and inconvenient use. In particular, due to the limitations of underwater acoustic countermeasure equipment platforms, the size and weight of ultra-low frequency underwater acoustic transducers as acoustic loads should not be too large. The above-mentioned transducers obviously cannot be directly applied to conventional underwater acoustic countermeasure platforms. It is technically difficult to achieve ultra-low frequency acoustic emission below 100Hz using traditional piezoelectric transducers.

[0005] Therefore, how to design an ultra-low frequency underwater acoustic transducer with the advantages of small size, light weight, simple structure, high electroacoustic conversion efficiency and easy use has become an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0006] In view of the above-mentioned deficiencies of the prior art, the present invention provides a small-sized dynamic ultra-low frequency underwater acoustic transducer, which has the advantages of small size, light weight, and convenient use, and has good adaptability, and can achieve ultra-low frequency broadband acoustic emission of 40Hz to 1kHz. It can be used as an acoustic load and equipped on sonar equipment and acoustic countermeasure devices, especially for small-caliber navigation bodies, and has good adaptability; it can also be used as a general ultra-low frequency sound source for laboratory and lake and sea experiments.

[0007] Specifically, the present invention is achieved as follows:

[0008] A small-sized dynamic coil ultra-low frequency underwater acoustic transducer is provided, wherein a radially arranged magnetic circuit system structure and a corresponding radiation system structure are installed in a watertight shell, wherein the magnetic circuit system structure comprises: an outer soft iron arranged inside the watertight shell, a radial permanent magnet arranged inside the outer soft iron, and an inner soft iron arranged inside the radial permanent magnet; the radiation system structure comprises: a centering spring sheet exposed and installed on the top of the watertight shell; a radiation plate installed below the centering spring sheet and rigidly connected thereto; a coil inserted in the magnetic circuit air gap between the inner soft iron and the radial permanent magnet is installed below the radiation plate; the outer edge of the radiation plate is installed on the watertight shell through a rubber folding ring to realize reciprocating motion; the area below the radiation plate constitutes a watertight area, and the coil outlet of the coil is connected from a channel in the middle of the inner soft iron to a connector on the outside of the bottom of the watertight shell.

[0009] Furthermore, at least one side of the rubber fold ring is processed to have a semicircular protrusion structure upward in the middle, and has sufficient compliance and certain damping, which can improve the frequency response characteristics of the ultra-low frequency underwater acoustic transducer and facilitate impedance matching and response balancing.

[0010] Furthermore, it also includes an annular conical support plate, which is installed on the watertight shell. The outer wall of the conical support plate is circumferentially provided with an O-ring sealing groove and is in close contact with the watertight shell through a first O-ring to achieve radial sealing.

[0011] Furthermore, the upper end of the inner soft iron is in the shape of a concave cone, which can effectively reduce the cavity volume of the transducer cavity.

[0012] Furthermore, the radiation plate is provided with a rubber fold ring sealing groove for installing the rubber fold ring on its end face, and a radiation plate pressure ring is also installed above it, and the lower end face of the radiation plate pressure ring is also provided with a rubber fold ring sealing groove for installing the rubber fold ring; a rubber fold ring sealing groove for installing the rubber fold ring is provided on the upper end face of the conical support plate, and a sealing pressure ring is installed above it, and the lower end face of the sealing pressure ring is provided with a rubber fold ring sealing groove; the four rubber fold ring sealing grooves are respectively clamped and fixed in pairs to the rubber fold ring.

[0013] Furthermore, the radiation plate pressure ring and the sealing pressure ring are both squeezed and fixed by fastening screws to ensure watertightness.

[0014] Furthermore, the centering spring is rigidly connected to the stud at the front end of the radiation plate through a nut and a gasket, so that the centering spring moves synchronously with the radiation plate.

[0015] Furthermore, the coil is wound on a bracket below the radiation plate, and a high-temperature epoxy resin glue is coated on the surface of the coil to ensure that the coil is securely fastened after winding.

[0016] Furthermore, it also includes a plug placed at the bottom end of the watertight shell, and a second O-ring is installed circumferentially on the outer wall of the plug to maintain a seal with the watertight shell. The coil outlet is connected to an external connector through the plug, and the connector is used to transmit the audio control signal to the coil to realize the sound wave radiation of the transducer.

[0017] Furthermore, the bottom tail end of the watertight shell is reserved with air inlet and outlet holes connected to the interior, and the small-sized dynamic ultra-low frequency underwater acoustic transducer also includes an external pressure compensation system, which is connected to the air inlet and outlet holes to solve the problem that the acoustic performance of the dynamic underwater acoustic transducer changes with depth.

[0018] Furthermore, both ends of the top and / or one end of the bottom of the watertight shell are installed with lifting rings, and the inner surface of the watertight shell is treated, and the surface quality meets the roughness design requirements of the sealing surface; the rubber folding ring is potted with butyl rubber or silicone rubber material with a certain hardness and low water permeability.

[0019] The working principle of the present invention is introduced as follows: a magnetic circuit system composed of outer soft iron, radial permanent magnet and inner soft iron, the permanent magnet is radially polarized, the materials of the outer soft iron and the inner soft iron can be selected from but not limited to soft magnetic materials such as electrical pure iron DT4 or 10 steel; the material of the radial permanent magnet can be selected from but not limited to permanent magnetic materials such as neodymium iron boron rare earth material or ferrite; the coil can be wound by copper core wire, aluminum core wire or copper clad aluminum wire, the rubber folding ring is potted by materials such as butyl rubber or silicone rubber with a certain hardness and low water permeability, the outer surface of the raised part is flat and smooth, the rubber folding ring has sufficient compliance and a certain damping, which can improve the frequency response characteristics of the ultra-low frequency underwater acoustic transducer and facilitate impedance matching and response balancing. The material of the centering reed can be anti-corrosion elastic materials such as beryllium bronze. The centering reed and the radiation plate move synchronously. The centering reed not only plays a centering role for the radiation system, but also provides a certain restoring force and damping for the radiation system. The audio control signal of the ultra-low frequency underwater acoustic transducer can be transmitted to the coil via the connector to realize the sound wave radiation of the transducer; when current flows through the coil, in the magnetic circuit air gap of the magnetic circuit system, a driving force is generated by the magnetic field, driving the radiation system to vibrate according to a certain rule, and radiating sound waves outward from the radiation plate. The upper end of the inner soft iron of the present invention is in the shape of an inwardly concave cone, and the magnetic circuit system adopts a radial magnetic circuit design, so that the uniformity of the magnetic lines of force in the magnetic circuit air gap is greatly improved, which is beneficial to improve the linearity of the sound wave radiation of the transducer.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] 1. When the transducer is equipped with a pressure compensation device, the maximum size does not exceed Φ150mm×300mm, and the weight does not exceed 6kg. When it is not equipped with a pressure compensation device, the maximum size does not exceed Φ150mm×100mm, and the weight does not exceed 3kg. It has the outstanding advantages of small size and light weight, and can be directly used as an acoustic load for sonar equipment and acoustic countermeasure devices. In particular, it has good adaptability for small-caliber navigation bodies. The transducer can also be directly used as a general sound source for laboratory and lake and sea tests;

[0022] 2. The overall design scheme of external centering reed is innovatively proposed, which cleverly solves the problems of excessive internal cavity volume and inconvenient assembly caused by the internal centering reed of traditional dynamic transducers. Especially for dynamic hydroacoustic transducers used in deep water, the excessive internal cavity volume of the transducer will lead to an overly large pressure compensation system;

[0023] 3. The design scheme of using rubber folding ring and centering spring to form the transducer spring-damping system can make the resonance frequency of the radiation system in water lower than 100Hz under the maximum diameter limit of Φ150mm, so as to realize the ultra-low frequency sound wave radiation of the transducer. In addition, the rubber folding ring has sufficient compliance and certain damping, and the centering spring can ensure the reciprocating motion of the radiation system to avoid friction between the radiation system and the magnetic circuit system.

[0024] 4. The radial magnetic circuit design greatly improves the uniformity of the magnetic force lines in the magnetic circuit air gap, which is beneficial to improve the linearity of the transducer's acoustic radiation;

[0025] 5. It can achieve broadband acoustic emission of 40Hz to 1kHz, and the average sound source level in the working frequency band is not less than 145dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the overall structure of a small-sized moving coil ultra-low frequency underwater acoustic transducer provided in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of the appearance and structure of a small-sized dynamic ultra-low frequency underwater acoustic transducer provided in an embodiment of the present invention.

[0028] Among them: 1-centering spring, 2-nut, 3-gasket, 4-radiation plate, 5-fastening screw, 6-radiation plate pressure ring, 7-flange ring, 8-right angle lifting ring, 9-sealing pressure ring, 10-rubber folding ring, 11-watertight shell, 12-first O-ring, 13-conical support plate, 14-external soft iron, 15-radial permanent magnet, 16-coil, 17-inner soft iron, 18-lifting ring, 19-coil outlet, 20-second O-ring, 21-plug, 22-connector, 23-pressure compensation system, 24-long screw, 25-mounting screw. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0030] See attached Figure 1 and attached Figure 2The present embodiment provides a small-sized dynamic ultra-low frequency underwater acoustic transducer, which includes: a centering spring 1, a nut 2, a gasket 3, a radiation plate 4, a fastening screw 5, a radiation plate pressure ring 6, a flange ring 7, a right-angle lifting ring 8, a sealing pressure ring 9, a rubber folding ring 10, a watertight shell 111, a first O-ring 12, a conical support plate 13, an outer soft iron 14, a radial permanent magnet 15, a coil 16, an inner soft iron 17, a lifting ring 18, a coil outlet 19, a second O-ring 20, a plug 21, a connector 22, a pressure compensation system 23, a long screw 24 and a mounting screw 25. The centering spring 1, radiation plate 4, rubber folding ring 10, coil 16 and related fastening screws 5, nuts 2 and gaskets 3 together constitute the radiation system of the ultra-low frequency underwater acoustic transducer; the outer soft iron 14, radial permanent magnet 15, and inner soft iron 17 together constitute the magnetic circuit system of the ultra-low frequency underwater acoustic transducer. When current flows through the coil 16, a driving force is generated in the magnetic circuit air gap of the magnetic circuit system under the action of the magnetic field. Under the action of the driving force, the radiation system vibrates according to a certain rule, and the radiation plate 4 radiates sound waves to the outside.

[0031] See attached Figure 1 The magnetic circuit system provided in this embodiment is composed of an outer soft iron 14, a radial permanent magnet 15 and an inner soft iron 17. The permanent magnet is radially polarized, the outer dimensions are Φ115mm×50mm, and the magnetic circuit air gap width is 3.8mm. Among them, the materials of the outer soft iron 14 and the inner soft iron 17 can be selected but not limited to soft magnetic materials such as electrical pure iron DT4 or 10 steel; the material of the radial permanent magnet 15 can be selected but not limited to permanent magnetic materials such as neodymium iron boron rare earth materials or ferrite. The magnetic circuit system is fixedly connected to the bottom of the watertight shell 11 through a long screw 24 passing through the conical support plate 13. The coil 16 on the radiation plate 4 can be wound by copper core wire, aluminum core wire or copper clad aluminum wire.

[0032] See attached Figure 1The conical support plate 13 has an O-ring sealing groove in its circumference and a rubber folding ring sealing groove on its end face; the inner surface of the watertight shell 11 is processed, and the surface quality reaches the roughness design requirement of the sealing surface; the radiation plate 4 has a rubber folding ring sealing groove on its end face; the sealing pressure ring 9 has a rubber folding ring sealing groove on its end face; the radiation plate pressure ring 6 has a rubber folding ring sealing groove on its end face. The materials of the conical support plate 13, the watertight shell 11, the radiation plate 4 and the radiation plate pressure ring 6 can all be made of aluminum alloy or titanium alloy, and the sealing pressure ring 9 needs to be made of hard materials such as stainless steel or titanium alloy; the rubber folding ring 10 has an upper convex structure, and both the inner and outer sides are processed with semicircular convex structures. The rubber folding ring 10 is potted with butyl rubber or silicone rubber with a certain hardness and low water permeability. The outer surface of the convex part is flat and smooth. The rubber folding ring 10 has sufficient compliance and certain damping, which can improve the frequency response characteristics of the ultra-low frequency underwater acoustic transducer and facilitate impedance matching and response balancing.

[0033] The conical support plate 13 cooperates with the watertight shell 11 through the first O-ring 12 to achieve radial sealing; the semicircular raised portion on the outer side of the rubber folding ring 10 is placed between the rubber folding ring sealing groove of the sealing pressure ring 9 and the rubber folding ring sealing groove of the conical support plate 13, and the sealing ring 9 is squeezed by the fastening screw 5 to ensure watertightness; the semicircular raised portion on the inner side of the rubber folding ring 10 is placed between the rubber folding ring sealing groove of the radiation plate pressure ring 6 and the rubber folding ring sealing groove of the radiation plate 3, and the radiation plate pressure ring 6 is pressed by the fastening screw 5 to ensure watertightness.

[0034] The material of the centering spring 1 can be selected from anti-corrosion elastic materials such as beryllium bronze. The centering spring 1 is rigidly connected to the stud at the front end of the radiation plate 4 through the nut 2 and the gasket 3 to achieve synchronous movement of the centering spring and the radiation plate. The centering spring 1 not only plays a centering role in the radiation system, but also provides a certain restoring force and damping for the radiation system; the centering spring 1 is connected to the flange ring 7 by the fastening screw 5, and the flange ring 7 and the watertight shell 111 are tightened by the mounting screw 25 to achieve fixation; after the ultra-low frequency transducer is installed and adjusted, the mounting screw 25 can be coated with thread glue to achieve reliable connection; due to the wall thickness of the watertight shell 11 and the conformal installation design requirements, the mounting screw 25 can be selected from a countersunk screw or a set screw.

[0035] The coil 16 is wound on the bracket below the radiation plate, and the surface of the coil 16 is coated with high-temperature epoxy resin glue to ensure that the coil is reliably fastened after winding. The plug 21 is located at the tail end of the ultra-low frequency underwater acoustic transducer, and is sealed with the watertight shell 11 through the second O-ring 20. The coil outlet 19 of the coil 16 passes through the plug 21 and is connected to the external connector 22; the audio control signal of the ultra-low frequency underwater acoustic transducer can be transmitted to the coil via the connector 22 to realize the sound wave radiation of the transducer. The plug 21 is reserved with inlet and outlet holes. When the working depth of the transducer exceeds a certain pressure threshold (the threshold value of the ultra-low frequency underwater acoustic transducer shown in the embodiment is around 10 meters deep), a pressure compensation system 23 can be installed to solve the problem that the acoustic performance of the dynamic coil underwater acoustic transducer changes with depth. Among them, the pressure compensation system includes but is not limited to an active compressed air pressure compensation system, an airbag passive pressure compensation system, and a passive combined pressure compensation system.

[0036] The right-angle lifting ring 8 and the lifting ring 18 can form a lifting device to facilitate rope lifting; if vertical (i.e. upward) lifting is required, only a pair of right-angle lifting rings 8 need to be installed; if horizontal lifting is required, only one right-angle lifting ring 8 and one lifting ring 18 need to be installed.

[0037] The assembly process of the small-sized ultra-low frequency underwater acoustic transducer provided in this embodiment is as follows:

[0038] Before starting the assembly process, all parts need to be cleaned, especially the sealing surface, O-ring and rubber folding ring. Use anhydrous ethanol to wipe and remove surface dust and stains.

[0039] The first step is to place the magnetic circuit system assembly composed of the outer soft iron 14, the radial permanent magnet 15 and the inner soft iron 17 into the watertight shell 11, and with the help of the positioning pin, preliminarily align the threaded hole at the bottom of the watertight shell 11 and the circular hole of the outer soft iron 14;

[0040] Step 2: Place the first O-ring 12 in the radial sealing groove of the conical support plate 13, align the circular hole of the conical support plate 13 with the circular hole of the outer soft iron 14, and then slowly press the conical support plate 13 into the watertight housing 11, and then tighten the long screw 24 to achieve a rigid connection;

[0041] The third step is to place the radiation plate 4 with the coil 16 wound on it into the air gap of the magnetic circuit system, and pass the coil outlet 19 through the center holes of the inner soft iron 17 and the outer soft body 14, then place the semicircular raised parts inside and outside the rubber folding ring 10 into the rubber folding ring sealing grooves of the conical support plate 13 and the radiation plate 4, and then install the radiation plate pressure ring 6 and the sealing pressure ring 9 on the sealing folding ring 10 in turn, and screw the fastening screw 5 into the radiation plate 4. At this time, attention should be paid to the assembly strength so that the radiation plate pressure ring 6 lightly presses the sealing folding ring to achieve the purpose of preliminary positioning;

[0042] Step 4: Place the flange ring 7 on top of the sealing ring 9. Figure 2 The mounting screw 25 shown is passed through the watertight shell 11 and screwed into the flange ring 7 to achieve a rigid connection between the flange ring 7 and the watertight shell 11. The centering spring 1 is then placed above the flange ring 7. After the fastening screw 5 is passed through the flange ring 7, it is tightened in a symmetrical and step-by-step manner to compress the sealing pressure ring 9. At the same time, all the fastening screws on the radiation plate pressure ring 6 are also tightened in a symmetrical and step-by-step manner, so that the rubber folding ring 10 is pressed by the metal part at the sealing position to ensure watertightness. Subsequently, the nut 2, the gasket 3 and the stud of the radiation plate 4 are rigidly connected;

[0043] Step 5: Install the plug 21, seal it with the bottom of the watertight housing 11 through the second O-ring 20, connect the coil outlet 19 to the watertight cable connector 22 on the plug, and the plug 21 is designed with necessary interfaces such as the air inlet and outlet holes required by the pressure compensation system 23 and the pressure sensor installation hole;

[0044] Step 6. Install the right-angle lifting ring 8 or the lifting ring 18 according to the needs of use. If vertical (i.e. upward) lifting is required, only a pair of right-angle lifting rings 8 need to be installed; if horizontal lifting is required, only one right-angle lifting ring 8 and one lifting ring 18 need to be installed.

[0045] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0046] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A small-sized dynamic ultra-low frequency underwater acoustic transducer, characterized in that: A radially arranged magnetic circuit system structure and a corresponding radiation system structure are installed in the watertight housing (11). The magnetic circuit system structure comprises: an outer soft iron (14) disposed inside a watertight housing (11), a radial permanent magnet (15) disposed inside the outer soft iron (14), and an inner soft iron (17) disposed inside the radial permanent magnet (15); The radiation system structure comprises: a centering spring (1) exposed and mounted on the top of a watertight shell (11); a radiation plate (4) mounted below the centering spring (1) and rigidly connected thereto, the centering spring (1) and the radiation plate moving synchronously; a coil (16) placed in the air gap of the magnetic circuit between the inner soft iron (17) and the radial permanent magnet (15) is mounted below the radiation plate (4); the outer edge of the radiation plate (4) is mounted on the watertight shell (11) via a rubber folding ring (10) to achieve reciprocating motion; the centering spring (1) is rigidly connected to a stud located at the front end of the radiation plate (4) via a nut and a gasket; The area below the radiation plate (4) constitutes a watertight area, and the coil outlet (19) of the coil (16) is connected from the channel in the middle of the inner soft iron (17) to the connector (22) on the outside of the bottom of the watertight housing (11); An annular conical support plate (13), the conical support plate (13) being mounted on the watertight housing (11), an O-ring sealing groove being circumferentially opened on the outer wall of the conical support plate (13) and being in close contact with the watertight housing (11) through a first O-ring sealing ring (12) to achieve radial sealing; At least one side of the rubber folding ring (10) is processed to have a semicircular convex structure in the middle portion and upward, and has sufficient compliance and a certain damping, which can improve the frequency response characteristics of the ultra-low frequency underwater acoustic transducer and facilitate impedance matching and response balancing.

2. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 1 is characterized in that: The radiation plate (4) has a rubber fold ring sealing groove for mounting a rubber fold ring (10) on its end surface, a radiation plate pressure ring (6) is mounted above the radiation plate, and a rubber fold ring sealing groove for mounting the rubber fold ring (10) is also formed on the lower end surface of the radiation plate pressure ring (6); A rubber fold ring sealing groove for mounting the rubber fold ring (10) is formed on the upper end surface of the conical support plate (13), and a sealing pressure ring (9) is mounted above the conical support plate (13). A rubber fold ring sealing groove is formed on the lower end surface of the sealing pressure ring (9); The four rubber fold ring sealing grooves are respectively clamped and fixed in pairs on the rubber fold rings (10).

3. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 2 is characterized in that: The upper end of the inner soft iron (17) is in the shape of a concave cone, which can effectively reduce the cavity volume of the inner cavity of the transducer.

4. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 1 is characterized in that: The coil (16) is wound on a bracket below the radiation plate (4), and a high-temperature epoxy resin glue is coated on the surface of the coil (16) to ensure that the coil (16) is securely fastened after winding.

5. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 1 is characterized in that: It also includes a plug (21) disposed at the bottom end of the watertight housing (11); a second O-ring (20) is circumferentially mounted on the outer wall of the plug (21) to maintain a seal with the watertight housing (11); a coil outlet (19) passes through the plug (21) and is connected to an external connector (22); the connector (22) is used to transmit an audio control signal to the coil (16) to achieve sound wave radiation of the transducer.

6. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 1 is characterized in that: The bottom tail end of the watertight shell (11) is reserved with air inlet and outlet holes connected to the interior. The small-sized dynamic ultra-low frequency underwater acoustic transducer also includes an external pressure compensation system (23). The pressure compensation system (23) is connected to the air inlet and outlet holes to solve the problem that the acoustic performance of the dynamic underwater acoustic transducer changes with depth.

7. The small-sized dynamic ultra-low frequency underwater acoustic transducer according to claim 1 is characterized in that: Both ends of the top and / or one end of the bottom of the watertight shell (11) are provided with lifting rings (18) or right-angle lifting rings (8); the inner surface of the watertight shell (11) is treated, and the surface quality meets the roughness design requirements of the sealing surface; the rubber folding ring (10) is potted with butyl rubber or silicone rubber material with a certain hardness and low water permeability.

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