CN110657880B - A new type of hydrophone based on resonant air cavity - Google Patents

Abstract

The invention discloses a novel hydrophone based on a resonant air cavity, which comprises a sealed spherical shell (1) in a spherical shape; the interior of the spherical shell (1) is provided with a hollow air cavity (3); a microphone (2) is arranged at the spherical center of the spherical shell (1); the spherical shell (1) is placed in a water area and used for isolating external water from the air cavity (3); a microphone (2) for measuring sound projected from the external body of water. The invention discloses a novel hydrophone based on a resonant air cavity, which utilizes the air cavity resonance inside a spherical shell, adopts a microphone to sense the sound pressure transmitted into the air cavity from a water area outside the sphere, has high sensitivity and high signal-to-noise ratio near the resonance frequency, and has great production practice significance.

Description

A new type of hydrophone based on resonant air cavity

technical field

The invention relates to the technical field of hydrophones, in particular to a novel hydrophone based on a resonant air cavity.

Background technique

The hydrophone can effectively convert the acoustic signal into an electrical signal under water, and realize the application of the acoustic signal by processing the electrical signal, so as to achieve the purpose of underwater target detection or underwater information extraction. Most hydrophones operate in the frequency band of the principle resonant frequency, and the frequency response is flat, which can receive broadband signals or be used for standard hydroacoustic metering. And some hydrophones for detection and communication work at the resonant frequency, so as to have the highest possible sensitivity at certain frequencies, and relatively low sensitivity at other frequencies to suppress the interference of environmental noise.

It has been experimentally demonstrated that the sensitivity of the hydrophone in the non-resonant range is much lower than the sensitivity around the resonant frequency and is slightly frequency dependent. Scholars at home and abroad have carried out a lot of researches on using the resonance phenomenon to improve the sensitivity of hydrophones. Some scholars use hydrophones near the resonance frequency to study the nonlinear emission of gas-filled bubbles; some scholars use piezoelectric ceramics for ultrasound imaging at its resonance frequency, which has higher sensitivity and clearer imaging than other frequencies; Some scholars have studied the magnetoelectric composite PZT ring with two resonance frequencies, which improves the sensitivity and the resolution of resonance displacement; some scholars have developed a new 1-3 composite piezoelectric hydrophone, and studied the piezoelectric hydrophone. The dynamic model and frequency response of the device use the resonance frequency to improve the sensitivity to weak signals; some scholars use the Helmholtz resonance principle to place the liquid cavity structure outside the cylindrical piezoelectric ceramics, which can selectively improve the liquid cavity. The sensitivity near the resonant frequency of the structure is more suitable for narrow-band applications; some scholars spliced two hemispherical shell piezoelectric ceramics into a spherical shape, and used their first-order resonance mode to transmit and receive ultrasonic waves for underwater communication. Thickness is directly related.

The above resonance type hydrophones all use the resonance of the piezoelectric ceramic sensitive element itself, and its resonance frequency is closely related to the size and material properties of the shell. In addition, there are some resonant hydrophones that use the resonance of the liquid cavity inside the shell, such as the Helmholtz resonant cavity hydrophone that works at medium and low frequencies. The resonance frequency is related to the shape and size of the internal liquid cavity. Traditional hydrophones The device is placed in the liquid chamber.

However, the existing conventional hydrophones have complex structures and poor sensitivity, which cannot fully meet the needs of users.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a novel hydrophone based on a resonant air cavity in view of the technical defects existing in the prior art.

To this end, the present invention provides a novel hydrophone based on a resonant air cavity, including a sealed spherical shell;

The interior of the spherical shell has a hollow air cavity;

A microphone is installed at the center of the spherical shell;

The spherical shell is placed in the water to isolate the external water from the air cavity;

Microphone to measure sound projected from outside waters.

Among them, the radius R1 of the air cavity is 8mm, and the thickness T of the spherical shell is 0.8mm.

Wherein, a ball cover mounting through hole is penetrated through the spherical shell;

A ball cover is inserted into the mounting through hole of the ball cover;

The center of the dome cover has a vertical wire lead-out hole;

The microphone is soldered with wires for signal transmission and power supply;

The wires extend out of the spherical shell through the wire lead-out holes.

Wherein, the ball cover is in the shape of a boss, and the convex part of the ball cover is inserted into the installation through hole of the ball cover.

The protruding part is an interference fit with the mounting through hole of the ball cover.

Among them, UV glue is used for bonding and sealing between the convex part and the mounting through hole of the ball cover.

Among them, the gap between the wire and the wire lead-out hole is filled with UV glue.

It can be seen from the above technical solutions provided by the present invention that, compared with the prior art, the present invention provides a new type of hydrophone based on a resonant air cavity, which utilizes the resonance of the air cavity inside the spherical shell, and uses a microphone to sense The sound pressure transmitted from the water outside the sphere into the air cavity. The hydrophone utilizes the resonance effect, and has high sensitivity and high signal-to-noise ratio near the resonance frequency. Compared with other traditional hydrophones, the cost is low and the production is simple. It can be used for underwater communication, underwater acoustic fuze, underwater ranging, etc., and has great practical significance in production.

Description of drawings

1 is a model diagram of a novel hydrophone based on a resonant air cavity provided by the present invention;

Fig. 2a and Fig. 2b are respectively the overall model and the simulation model diagram of the hydrophone part established by using multi-physics finite element simulation software to carry out two-dimensional axisymmetric frequency domain simulation;

3 is a schematic diagram of a frequency response curve of a hydrophone of a specific size;

Figure 4 is a two-dimensional axisymmetric simulation characteristic peak sound field distribution diagram (the characteristic peak frequencies of Figure 4a, Figure 4b, Figure 4c are 14200Hz, 22800Hz, 30800Hz, respectively);

Fig. 5 is the eigenfrequency mode of the air cavity simulation (the resonant frequencies of the air cavity in Fig. 5a, Fig. 5b, Fig. 5c are 14163Hz, 22810Hz, 31176Hz, respectively);

Figure 6 is a schematic diagram of the simulation results of eigenfrequency under different spherical shell thicknesses;

Fig. 7 is a schematic diagram of the relationship between characteristic frequency and air cavity radius;

8 is a cross-sectional view of a novel hydrophone based on a resonant air cavity provided by the present invention;

Fig. 9 is the experimental apparatus diagram of frequency response test;

Fig. 10 is a kind of novel hydrophone based on resonant air cavity provided by the present invention, the frequency response curve schematic diagram of experimental measurement;

11 is a partial schematic diagram of the experimentally measured frequency response of a novel hydrophone based on a resonant air cavity provided by the present invention;

12 is a schematic diagram of a signal-to-noise ratio curve of a new type of hydrophone based on a resonant air cavity (ie, a self-made hydrophone) provided by the present invention.

In the figure: 1: spherical shell; 2: microphone; 3: air cavity; 4: spherical cover; 40: convex part; 5: lead-out hole.

Detailed ways

In order to make those skilled in the art better understand the solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

1 to 12, the present invention provides a novel hydrophone based on a resonant air cavity, including a sealed spherical shell 1;

Inside the spherical shell 1, there is a hollow air cavity 3;

A microphone 2 is installed at the center of the spherical shell 1;

The spherical shell 1 is placed in the water to isolate the external water from the air cavity 3;

Microphone 2, for measuring sound projected from outside waters.

It should be noted that, for the present invention, the designed hydrophone structure is a spherical hollow inside, the spherical shell can be used to isolate water and provide an air cavity, and a microphone is placed inside the spherical shell 1 to measure the sound projected from the external water. . The overall hydrophone model is shown in Figure 1. The rectangle at the center of the sphere represents the microphone, the radius of the hollow part of the sphere (ie, the air cavity 3) is R1, and the thickness of the spherical shell is T.

In terms of specific implementation, multi-physics finite element simulation software is used to perform two-dimensional axisymmetric frequency domain simulation. The established overall model is shown in Figure 2a, and the model established by the hydrophone part is shown in Figure 2b. Figure 2b shows that the water area on the outside of the spherical shell 1. The inside of the box in Figure 2a represents water, and the perfectly matched layer means that the acoustic impedance on both sides is the same, and sound is not reflected here. The plane wave is incident from one side of the hydrophone, and the frequency is swept in the sound-structure coupling physics field. Now select a point in the air cavity close to the microphone to draw the frequency response curve. Figure 3 shows the frequency response curve obtained by the hydrophone simulation when R1 is 8mm and T is 0.8mm. It can be seen from Figure 3 that the hydrophone has characteristic peaks at 14200Hz, 22800Hz and 30800Hz.

It should be noted that, for a hydrophone, its resonance may occur in two parts: the resonance of the spherical shell and the resonance of the air cavity inside the spherical shell. Therefore, in order to reasonably design the working frequency and structure size of the hydrophone, the resonance frequency of the hydrophone is determined by finite element simulation to determine whether the resonance frequency of the hydrophone comes from the spherical shell or the air cavity in the spherical. The eigenfrequency simulation of the spherical shell with a thickness of 0.8mm is carried out in the solid mechanics physics field, and the eigenfrequency simulation of the air cavity with an internal radius R1 of 8mm is carried out in the pressure acoustics physics field using the model shown in Figure 1. The characteristic frequencies obtained by the two simulations are compared with the characteristic peaks of the frequency response curves, as shown in Table 1. See Table 1 below.

Table 1: Comparison of eigenfrequency (unit: Hz).

Frequency response characteristic peak Spherical Shell Eigenfrequencies air cavity resonant frequency 14200 17909 14163 22800 22057 22810 30800 35357 31176

It can be seen from Table 1 that the frequency response characteristic peak is very close to the characteristic frequency of the air cavity, and has a large deviation from the characteristic frequency of the spherical shell. The corresponding sound field distribution under the above-mentioned several frequency response characteristic peaks is shown in Figure 4, and the corresponding sound field distribution under the characteristic frequency of the air cavity close to the characteristic peak frequency is shown in Figure 5. By comparison, it can be seen that the distributions of the two are almost identical. From this, it can be judged that the resonance frequency of the hydrophone is only related to the air cavity and has nothing to do with the vibration of the spherical shell.

In order to further verify that the resonant frequency of the hydrophone has no relationship with the spherical shell, the thickness of the spherical shell was changed without changing the radius of the air cavity of the hydrophone, and the frequency response curves of the air cavity in the spherical shell under different thicknesses were obtained, as shown in shown in Figure 6. In Figure 6, the abscissa is the frequency, and the ordinate is the sound pressure. If the thickness of the spherical shell changes, the resonant frequency of the spherical shell will inevitably change due to the change of stiffness, but the resonant frequency of the air cavity in the sphere does not change. Therefore, the working frequency of the hydrophone is only related to the size of the air cavity in the sphere, which further confirms the above conclusion.

After it has been concluded that the resonance frequency of the hydrophone is only related to the air cavity, keep the thickness T of the spherical shell unchanged, and use the simulated parametric scanning function to change the radius R1 of the air cavity to explore the first-order resonance of the air cavity inside the sphere and the hydrophone. Frequency relationship, the results are shown in Figure 7. The finite element simulation shows that as the radius R1 of the air cavity inside the spherical shell increases, the first-order resonance frequency of the spherical hydrophone of the present invention decreases significantly, and the two are reciprocal of each other.

After a series of simulations and actual tests, it can be seen that when the air cavity with R1 of 8mm and T of 0.8mm receives sound of about 30kHz, the sound pressure field at the center position is stronger, and the received signal is better, which is conducive to the reception of sound signals. . However, when R1 and T are quite different from the above-mentioned values, the effect of the received signal decreases significantly.

In the present invention, in terms of specific implementation, the radius R1 of the air cavity 3 is preferably 8 mm, and the thickness T of the spherical shell 1 is preferably 0.8 mm.

For the present invention, in terms of specific implementation, a spherical cover mounting through hole is formed through the spherical shell 1;

A ball cover 4 is inserted into the ball cover installation through hole;

The center of the ball cover 4 has a wire lead-out hole 5 that penetrates vertically;

The microphone 2 (specifically, the microphone chip) is welded with wires for transmitting signals and supplying power;

The wires protrude to the outside of the spherical shell 1 through the wire lead-out holes 5 .

In specific implementation, the ball cover 4 is in the shape of a boss, and the convex part 40 of the ball cover 4 is inserted into the mounting through hole of the ball cover.

In specific implementation, the protruding portion 40 is an interference fit with the mounting through hole of the ball cover, so as to ensure a good sealing effect.

In terms of specific implementation, UV glue (shadowless glue, also known as photosensitive glue, UV curing glue) is used for bonding and sealing between the protruding portion 40 and the mounting through hole of the ball cover.

In terms of specific implementation, the gap between the wire and the wire lead-out hole 5 is filled with UV glue (shadowless glue, also known as photosensitive glue, ultraviolet curing glue), and is bonded and sealed by UV glue.

It should be noted that the hydrophone used in the design of the present invention is a miniature hydrophone, which encapsulates the microphone (specifically, the microphone chip circuit) in a hollow spherical shell. The cross-sectional view is shown in FIG. 8 . The hollow spherical shell and spherical cover are processed by 3D printing, which is convenient, fast, and low in cost. The printing material is photosensitive resin with good sound permeability.

Among them, spherical shell 1 is a hollow sphere with holes perforated on the surface (that is, the spherical cover installation through hole). The spherical shell has a radius of R1 and a thickness of T. The specific values have been determined by the above conclusions; There is no special requirement, as long as the spherical cover can be fixed on the spherical shell.

Among them, the ball cover 4 is a boss-shaped, with small through holes (ie, wire lead-out holes 5) on the surface, which are used to lead out the wires for power supply and signal transmission.

Wherein, the convex part 40 of the spherical cover 4 can be inserted into a hole on the surface of the spherical cover (ie, the mounting through hole of the spherical cover), and the height of the convex part is the same as the thickness of the spherical shell, so as to seal the whole sphere.

It should also be noted that the microphone 2 is specifically a microphone chip, which is located in the center of the spherical shell 1 . The microphone chip is welded with long wires, and the signal pins protrude from the holes of the ball cover through the long wires. The long wire is fixed on the ball cover with insulating and waterproof UV glue, and the ball cover and the ball shell are glued with UV glue (shadowless glue, also known as photosensitive glue, UV curing glue) to achieve the purpose of fixing the microphone and waterproofing.

For the present invention, it can be found during simulation that the sound field in the ball is not uniform, so when making a small ball, the microphone should be accurately fixed at the center of the spherical shell 1 .

For the present invention, it should be noted that for the microphone 2, a wire is welded on it, and the end of the wire passes through the ball cover and is fixed on the ball cover. Since the wire between the microphone and the ball cover is short and rigid, so The microphone can be fixed at the center of the spherical shell 1 .

In terms of specific implementation, there is no specific requirement for the model of the microphone chip used in the design of the present invention, and the range of the acceptable frequency only needs to cover the resonant frequency of the designed hydrophone. There is no special requirement for power supply, and the size needs to be smaller than the resonance frequency. The radius of the cavity can be, for example, a microphone chip model ADMP401-1ACEZ-RL7 or WM7120AIMS/RV.

Compared with the prior art, the novel hydrophone based on the resonance air cavity provided by the present invention has the following beneficial effects:

1. The actual measured frequency response curve of the novel hydrophone based on the resonant air cavity of the present invention is consistent with the theoretical value. The test device is shown in Figure 9, the hydrophone is placed in the water of the water tank, the NI acquisition card (data acquisition card) and the power supply board in Figure 9 are connected with the wires in the hydrophone of the present invention, and the power amplifier is used for Amplify the excitation signal of 5kHz to 40kHz generated by the host computer, and then transmit the signal into the water through the transducer.

The hydrophone is placed in the center of the water tank, powered by the power supply board, and used to receive the signal sent by the transducer, and then collect the signal through the NI acquisition card, transmit it to the computer for software processing, and obtain the frequency response curve. Since the frequency response of the transducer used for sound source emission and the microphone receiving the signal in the ball is not flat, normalization is required to eliminate the influence of the transducer and microphone on the frequency response of the hydrophone. frequency response curve. Figure 10 is the result of dividing the measured frequency response curve of the hydrophone by the product of the frequency response curve of the microphone and the transducer. The measured characteristic peaks are 14300 Hz, 22600 Hz and 30800 Hz, which are very close to the simulation results in Table 1.

2. The sensitivity of the novel hydrophone based on the resonant air cavity of the present invention is about 30 times that of the standard hydrophone, and the sensitivity is greater when the signal is small, which is beneficial to the measurement of small signals. In the experiment, the frequency when the hydrophone received the maximum signal, 30.8kHz, was selected. The standard hydrophone and the designed hydrophone were put together to test the sensitivity of different sound pressures. The former was used as a reference to calculate the resonant cavity hydrophone. the sensitivity of the device. Among them, the standard hydrophone TC4013 has a sensitivity of 0.84mV/Pa (obtained through its data sheet) at a pre-amplification of 30dB. Under different excitation voltages of sound sources in the laboratory (10-400Vpp), the sensitivity of the resonant cavity hydrophone is between 8.03mV/Pa-8.62mV/Pa, which is relatively stable.

3. The novel hydrophone based on the resonant air cavity of the present invention has a small difference in signal-to-noise ratio with the standard hydrophone, and the signal-to-noise ratio of the resonant cavity hydrophone is even higher. During the experiment, the standard hydrophone and the resonant cavity hydrophone were put together to receive signals at the same time to compare the signal-to-noise ratio of the two. The signal-to-noise ratio curves of the two are shown in Figure 12, where the solid line is the signal-to-noise ratio curve of the self-made hydrophone (that is, the novel hydrophone based on the resonant air cavity of the present invention), and the dashed line is the signal-to-noise ratio of the standard hydrophone. Noise ratio curve. It can be seen that as the excitation voltage of the transducer becomes larger, the transmitted signal becomes larger and the signal-to-noise ratio increases; when the signal is small, the signal-to-noise ratio of the self-made hydrophone and the standard hydrophone is relatively small. In addition, the signal-to-noise ratio of the resonant cavity hydrophone is 5dB higher than that of the standard hydrophone, and the signal-to-noise ratio is higher.

To sum up, compared with the prior art, the present invention provides a new type of hydrophone based on a resonant air cavity, which utilizes the resonance of the air cavity inside the spherical shell, and uses a microphone to sense the transmission from the water outside the sphere. the sound pressure into the air cavity. The hydrophone utilizes the resonance effect, and has high sensitivity and high signal-to-noise ratio near the resonance frequency. Compared with other traditional hydrophones, the cost is low and the production is simple. It can be used for underwater communication, underwater acoustic fuze, underwater ranging, etc., and has great practical significance in production.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (7)

1. A novel hydrophone based on a resonant air cavity, characterized by comprising a sealed, spheroid-shaped spherical shell (1);

the interior of the spherical shell (1) is provided with a hollow air cavity (3);

a microphone (2) is arranged at the spherical center of the spherical shell (1);

the spherical shell (1) is placed in a water area and used for isolating external water from the air cavity (3);

a microphone (2) for measuring sound projected from the outside water area and sensing sound pressure transmitted from the outside water area into the air chamber (3);

wherein the radius of the air cavity (3) and the first-order resonance frequency of the hydrophone are reciprocal;

the resonance frequency of the hydrophone is irrelevant to the spherical shell;

the air chamber 3 is a spherical chamber with an operating frequency of 30kHz and a radius of 8 mm.

2. The resonant air cavity-based hydrophone according to claim 1, characterized by the fact that the radius R1 of the air cavity (3) is 8mm and the thickness T of the spherical shell (1) is 0.8 mm.

3. The hydrophone based on the resonant air cavity of claim 1 or 2, wherein the spherical shell (1) is provided with a spherical cover mounting through hole;

a ball cover (4) is inserted in the ball cover mounting through hole;

the center of the ball cover (4) is provided with a lead wire leading-out hole (5) which is vertically penetrated;

a wire for transmitting signals and supplying power is welded on the microphone (2);

the lead extends out of the spherical shell (1) through the lead leading-out hole (5).

4. The hydrophone based on the resonant air cavity of claim 3, wherein the spherical cap (4) is boss-shaped, and the spherical cap (4) has a protruding portion (40) inserted into the spherical cap mounting through hole.

5. A novel hydrophone based on a resonant air cavity as claimed in claim 3 where the raised portions (40) are an interference fit with the ball cap mounting through holes.

6. The resonant air cavity-based hydrophone of claim 3 wherein the raised portions (40) are adhesively sealed to the ball cap mounting through holes using UV glue.

7. The resonant air cavity-based hydrophone according to claim 3, wherein the gap between the leads and the lead exit holes (5) is filled with UV glue.

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