Thin sidewall interlayer standing wave tube and transducer structure

Abstract

The invention provides a thin side wall interlayer standing wave tube and transducer structure, which comprises a standing wave tube and a transducer, and is characterized in that the standing wave tube comprises an outer tube wall and an inner tube wall, an interlayer with two open ends is formed between the outer tube wall and the inner tube wall, and the inner tube wall and the interlayer are filled with water; a transducer serving as a sound source is arranged at the bottom of the standing wave tube, when the transducer acts on the center of the standing wave tube, sound field distribution of the interlayer is affected by deformation of the two layers of side walls, the position of a node and a node of a sound field in the center of the standing wave tube are staggered, the influence of a tube wall breathing phenomenon on the sound field is restrained, and the sound field in the center of the standing wave tube is kept in a plane wave state. The low-frequency sound tube has the beneficial effects that the thickness of the side wall of the sound tube is reduced, the weight of the sound tube is greatly reduced and the construction difficulty of the low-frequency sound tube is reduced while a plane wave sound field is ensured by utilizing the respiration effect of the double-layer thin-walled tube.

Description

Technical Field

[0001] The present invention relates to the field of metrology and testing, specifically belonging to the field of acoustics (underwater acoustics), and mainly relates to a structure of a thin-sidewall sandwich standing wave tube and a transducer. Background Art

[0002] The standing wave tube is the most commonly used acoustic container in underwater acoustic research and has a large number of applications in fields such as hydrophone calibration and acoustic material measurement. The ideal acoustic field inside the standing wave tube is a plane wave acoustic field, which is used to simulate the acoustic phenomenon of sound waves from a point source at an infinite distance reaching the water-air interface. Its acoustic characteristics are mainly that the sound pressure at the water-air interface is 0 Pa, and the sound pressure is equal everywhere on the cross-section perpendicular to the central axis in the sound tube, which requires the inner wall of the standing wave tube to be an absolute hard boundary.

[0003] The absolute hard boundary of the sound tube does not exist in reality, and only a suitable sound tube wall can be designed to approximately obtain a rigid inner wall. According to the regulations in the national standard GB5266-85 "Attenuation and Measurement of Longitudinal Sound Velocity of Underwater Acoustic Materials - Pulse Tube Method", the wall of the underwater sound tube should be made of stainless steel, and the wall thickness should be 1 / 2 of the inner diameter of the sound tube. This regulation is mainly for two reasons: First, the acoustic characteristic impedance of water and ordinary solids only differs by an order of magnitude, and it is necessary to consider the influence of the sound field when sound waves enter the tube wall from water and are scattered back into the water multiple times. When the calculated wall thickness is 1 / 2 of the inner diameter of the sound tube, the acoustic admittance of the acoustic field formed in the tube wall at the inner wall can be ignored, meeting the hard boundary condition; second, when the tube wall is too thin, the breathing effect of the sound tube caused by the non-uniform acoustic field in the vertical direction of the sound tube is more obvious, and the deformation of the sound tube caused by the breathing effect will have a strong coupling effect with the acoustic field, making it impossible to form a plane wave in the acoustic field of the sound tube.

[0004] However, as the research direction of underwater acoustics gradually expands towards low frequencies, in order to cooperate with the design of the sound source, the inner diameter of the sound tube has gradually increased. If the requirement that the wall thickness should be 1 / 2 of the inner diameter of the sound tube still needs to be met at this time, the weight of the sound tube will greatly increase the processing and installation costs of the sound tube. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies existing in the prior art and provide a structure of a thin-sidewall sandwich standing wave tube and a transducer.

[0006] The object of the present invention is achieved by the following technical solutions. A thin sidewall sandwich standing wave tube and transducer structure includes a standing wave tube and a transducer. The standing wave tube includes an outer tube wall and an inner tube wall. A two-end open sandwich is formed between the outer tube wall and the inner tube wall, and the inner tube wall and the sandwich are filled with water. A transducer serving as a sound source is arranged at the bottom of the standing wave tube. When the transducer acts on the center of the standing wave tube, the sound field distribution in the sandwich is affected by the deformation of the two sidewalls, and the position of the node is misaligned with the node in the sound field at the center of the standing wave tube, suppressing the influence of the tube wall breathing phenomenon on the sound field and maintaining the sound field at the center of the standing wave tube in a plane wave state.

[0007] Further, the outer tube wall and the inner tube wall are made of stainless steel, forming a stainless steel - water - stainless steel structure on the sidewall of the standing wave tube.

[0008] Further, the transducer adopts a planar piston transducer, and the shape and size of the planar piston transducer are the same as the inner diameter of the inner tube wall.

[0009] The beneficial effect of the present invention is as follows: In order to reduce the wall thickness of the low - frequency sound tube, the present invention proposes a thin sidewall sandwich standing wave tube and transducer structure. By utilizing the breathing effect of the double - layer thin - walled tube, while ensuring a plane wave sound field, the thickness of the sidewall of the sound tube is reduced, greatly reducing the weight of the sound tube and the construction difficulty of the low - frequency sound tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art or ordinary technicians, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 FIG. is a schematic structural diagram of a standing wave tube with a traditional structure.

[0012] Figure 2 FIG. is a schematic structural diagram of the standing wave tube of the present invention.

[0013] Figure 3 FIG. is a schematic diagram of the finite - element simulation result of a standing wave tube with a traditional structure.

[0014] Figure 4 FIG. is a schematic diagram of the finite - element simulation result of the standing wave tube of the present invention.

[0015] Figure 5 FIG. is a schematic diagram comparing the sound field distributions at the central axes of a standing wave tube with a traditional structure and the standing wave tube of the present invention.

[0016] Explanation of reference numerals: Standing wave tube 1, outer tube wall 1 - 1, inner tube wall 1 - 2, sandwich 1 - 3, transducer 2. Detailed implementation manners

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] As Figure 1 shown, for a standing wave tube with a traditional structure, the height h is 1500 mm, the inner diameter a is 208 mm, and the wall thickness b is 104 mm. The sound source is a planar piston transducer, which is located at the bottom of the sound tube, and the size and shape of the sound source are the same as the inner diameter of the sound tube.

[0019] Calculating the dispersion equation of the breathing effect of the sound tube is very complicated. In order to more intuitively show the influence of the sound tube wall on the sound field, finite element simulation of the standing wave tube was carried out, as Figure 3 shown. Figure 3 The finite element simulation results of the standing wave tube are as follows: (a) the sound field distribution of the standing wave tube; (b) the stress distribution of the tube wall. It can be seen from the simulation that the wall of the sound tube will undergo wavy deformation under the influence of the standing wave field, that is, the breathing phenomenon of the sound tube. This deformation will inversely affect the sound field and make it a non-plane wave.

[0020] As Figure 2 shown, a thin sidewall sandwich standing wave tube and transducer structure proposed by the present invention includes a standing wave tube 1 and a transducer 2. The standing wave tube 1 includes an outer tube wall 1-1 and an inner tube wall 1-2. The outer tube wall 1-1 and the inner tube wall 1-2 are made of stainless steel. A two-end open sandwich 1-3 is formed between the outer tube wall 1-1 and the inner tube wall 1-2. The openings of the two layers of the thin sidewall sandwich standing wave tube cannot be connected, which will affect the vibration mode of the tube wall. The inner tube wall 1-2 and the sandwich 1-3 are filled with water. Compared with the integral structure of the sidewall of the traditional standing wave tube, the sidewall of the thin sidewall sandwich standing wave tube adopts a stainless steel-water-stainless steel structure, and a plane wave sound field is obtained by mutually suppressing the breathing effects of the double-layer tube walls. A transducer 2 serving as a sound source is arranged at the bottom of the standing wave tube 1, and the transducer 2 adopts a planar piston transducer.

[0021] Keeping the height and outer diameter of the standing wave tube unchanged, the tube wall is designed as a sandwich structure. The sandwich is a double-layer structure, the thickness of both layers of the tube wall is 20 mm, and the thickness of the sandwich is 16 mm. At this time, the inner diameter of the standing wave tube becomes 314 mm. Without changing the size of the transducer (the optimal solution is: the shape and size of the planar piston transducer are the same as the inner diameter of the inner tube wall 1-2. In the experiment, the size of the transducer is not changed in order to have basically the same experimental conditions), the sound field distribution of the tube wall and the stress distribution of the tube wall obtained by simulation under the same boundary conditions are as Figure 4As shown, the simulation results of the sandwich layer: (a) Sound field distribution in the standing wave tube; (b) Wall stress distribution.

[0022] When transducer 2 acts on the center of the standing wave tube, it can be seen that the sound fields in both the standing wave tube sandwich layer and the standing wave tube are standing waves. However, the sound field distribution in the sandwich layer is affected by the deformation of the two side walls, and the position of the wave node is misaligned with that of the wave node in the sound field at the center of the standing wave tube, suppressing the influence of the wall breathing phenomenon on the sound field and maintaining the sound field at the center of the standing wave tube in a plane wave state.

[0023] To better compare the influence of the two standing wave tubes on the sound field, the sound field distribution along the central axis of the standing wave tube is as Figure 5 shown Figure 5 for the influence of the two standing wave tubes on the sound field. (a) is the sound pressure distribution perpendicular to the central axis of the traditional standing wave tube; (b) is the sound pressure distribution perpendicular to the central axis of the standing wave tube with a thin side wall sandwich layer.

[0024] It can be seen that there are obvious differences in the envelopes of the spatial distributions of the sound fields along the central axes of different standing wave tubes. The envelope of the spatial distribution of the sound field perpendicular to the central axis of the traditional standing wave tube, Figure 5 the red line in (a), shrinks as the water level in the horizontal plane rises; while the envelope of the spatial distribution of the sound field perpendicular to the central axis of the standing wave tube with a thin side wall sandwich layer can remain unchanged, Figure 5 the red line in (b). This shows that the sound field in the standing wave tube with a thin side wall sandwich layer is more uniform and more approximate to the characteristics of a plane wave.

[0025] In addition, through the sandwich layer design, while ensuring a plane sound field inside the sound tube, the thickness of the sound tube wall is reduced, the weight of the sound tube is reduced, and the installation difficulty is reduced, indicating that the design of the standing wave tube with a thin side wall sandwich layer is effective.

[0026] During specific implementation:

[0027] 1. Before using the standing wave tube with a thin side wall sandwich layer for experiments, water must be injected into both the middle of the standing wave tube and the sandwich layer until the water level reaches near the mouth of the sound tube;

[0028] 2. Drive out the air bubbles in the middle of the standing wave tube and the sandwich layer;

[0029] 3. Use a sine signal to excite the transducer, and a stable plane standing wave field can be obtained when the sound field in the standing wave tube is stable.

[0030] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A thin-side-wall sandwich standing wave tube and transducer structure, characterized in that: The invention comprises a standing wave tube (1) and a transducer (2), wherein the standing wave tube (1) comprises an outer tube wall (1-1) and an inner tube wall (1-2), a sandwich layer (1-3) with two ends opened is formed between the outer tube wall (1-1) and the inner tube wall (1-2), and the inner tube wall (1-2) and the sandwich layer (1-3) are filled with water; a transducer (2) as a sound source is arranged at the bottom of the standing wave tube (1), and when the transducer (2) acts on the center of the standing wave tube, the sound field distribution of the sandwich layer (1-3) is affected by the deformation of the two side walls, and the position of the wave node is misaligned with the wave node of the sound field at the center of the standing wave tube, thereby suppressing the influence of the tube wall breathing phenomenon on the sound field, so that the sound field at the center of the standing wave tube maintains a plane wave state.

2. The thin-side-wall sandwich standing wave tube and transducer structure according to claim 1, characterized in that: The outer tube wall (1-1) and the inner tube wall (1-2) are made of stainless steel, forming a stainless steel-water-stainless steel structure on the side wall of the standing wave tube.

3. The thin-side-wall sandwich standing wave tube and transducer structure according to claim 2, characterized in that: The transducer (2) is a planar piston transducer, and the shape and size of the planar piston transducer are the same as the inner diameter of the inner tube wall (1-2).

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