Underwater Acoustic Detection Research Articles

The error analysis of an underwater acoustic short baseline array detection and location system

This paper briefly introduces the composition, working principle and the common installation method of the shipborne underwater acoustic short baseline array detection and positioning system. Based on the underwater acoustic direction measurement and location algorithm and the underwater acoustic short baseline array detection and positioning system, the error sources affecting the accuracy of the underwater acoustic direction and positioning are analysed in great detail, and the influence of each error source is quantitatively analysed. In this paper, through theoretical calculation and analysis, the influence factors and the influence degree of the error sources on the direction and location measurement are obtained, the technical indexes of direction measurement accuracy and positioning accuracy of the system are estimated. The results of the error analysis of short baseline array system in this paper provide a theoretical basis for the operation of related underwater acoustic location systems at sea, and has important guiding and practical significance for the underwater target detection and positioning system design.

A Design of The Underwater Acoustic Beacon Detection and Location Method

Aiming at the search of the underwater acoustic beacons used in aircraft or ship parameter recorders, this paper mainly introduces the underwater acoustic beacon detection and location method of the short baseline array system. According to the signal form of underwater acoustic beacon, this paper discusses the basic algorithm and the engineering algorithm applied in this system. In theory, the basic algorithm is a necessary algorithm for short baseline array to calculate target azimuth, which including the two-element linear array direction measurement algorithm, two-direction cross-location algorithm and the virtual direction discrimination algorithm. In addition, according to the experience of offshore operations, this paper introduces the engineering practice methods such as the angle measurement, the data extraction, the location ray screening and the location ray starting point coordinate calculation. The combination of engineering algorithm and basic algorithm can effectively reduce the impact of the test equipment and environment, and improve the accuracy of underwater acoustic beacon detection and position, which has been tested in actual operation at sea.

Analysis on an improved resistance tuning type multi-frequency piezoelectric spherical transducer

The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.

Simulation research of underwater passive direction finding technology

As one of the indispensable technologies for underwater target detecting, underwater acoustic passive detection technology has always been a hot spot in marine system research. A vector sensor can detect underwater targets by combination with the pressure and vibration velocity information; vector sensor array can obtain higher gain than pressure array with the same number hydrophones. Vector sensor can reduce the length of the underwater sensor array and can detect underwater targets in the case of low signal to noise ratio. This is the goal that many researchers strive to solve for many years; therefore, vector sensor passive detection technology has far-reaching scientific research value.Through the verification of the simulation experiment, the azimuth estimation technique and the adaptive frequency estimation technique are feasible. By estimating the azimuth sequence and frequency sequence of the target radiation signal, the relevant information of the target can be obtained, and so it is of great significance in the research of underwater acoustic detection technology.

A Steganographic Approach to Sonar Tracking

Steganographic transmission waveforms are desirable for many applications, such as underwater acoustic communications, surveillance, detection, and tracking. In the context of active sonar tracking, an overall approach is presented that covers several topics including background sound modeling, steganographic security assessment of transmission waveforms, target motion modeling, and batch track detection. In shallow water, environment background sound dominated by snapping shrimp, the presented approach shows feasibility of steganographic sonar for target track detection. A background sound modeling approach is presented that utilizes symbolic time-series analysis with phase space representation and clustering of time-series segments. The time-evolving characteristics are captured with a hidden Markov model. Steganographic security of the transmission waveform can be assessed by measuring the Kullback-Leibler divergence between the cover model and the stego model. Conventional tracking approaches fail to perform reliably and existing track-before-detect approaches also fail due to overwhelming search computation when they use simplistic short timescale motion models. A long timescale target motion model with considerations for plausibility is presented and utilized in a batch track detection approach. A Monte-Carlo-based simulation is performed to find the scenarios that demonstrate the feasibility of steganographic sonar in a shallow water environment with snapping shrimp sound.

Discussion on the sensitivity of optical cables based on distributed acoustic sensing

Distributed acoustic sensing (DAS) technology plays an increasingly important role in the field of underwater acoustic detection because of its own advantages. To measure acoustic pressure sensitivity of seven kinds of optical cables in the same condition synchronously, the experimental setup based on DAS is proposed. Seven kinds of optical cables are connected in series to the DAS system, and the acoustic pressure sensitivity at different locations (different optical cables) is detected simultaneously via the DAS system. The highest acoustic pressure sensitivity of the sensitized optical cable is 69.9 mrad/Pa. The experimental results provide experimental data support for the selection of optical cables.

A Factor-Graph Clustering Approach for Detection of Underwater Acoustic Signals

We address the challenge of detecting an arbitrary-shaped underwater acoustic signal. Instead of setting a detection threshold, which due to noise transients may result in a high false alarm rate (FAR), our method classifies each measured sample as either “noise” or “signal.” Utilizing a priori knowledge of only the minimal duration of the signal, the decision is made using loopy belief propagation over a factor graph. Numerical simulations and sea experimental results show that our scheme achieves a favorable tradeoff between the Recall and FAR, and noise robustness, which far exceeds that of benchmark schemes.

Theoretical and experimental study on multibeam synthetic aperture sonar.

High-resolution imaging method is one of the researching focuses of underwater acoustic detection. Underwater small-target detection also requires detailed imaging technology. Multibeam echo sounders (MBESs) and synthetic aperture sonar (SAS) are the effective instruments widely researched to obtain underwater acoustic images. Constrained by the theory, the along-track resolution of MBES decreases with distance and the gaps problem of SAS always exists and both inevitably limit the quality of acoustic imaging. In this paper, a two dimensional multibeam synthetic aperture sonar (MBSAS) model is designed to overcome the shortcomings of conventional underwater imaging instruments. MBSAS can provide a three dimensional (3D) high-resolution acoustic image without a gap problem. An echo model and transducer array manifold are designed to meet the requirements of engineering applications. Imaging theory and target simulations prove the feasibility of the MBSAS model. The performance of the proposed model is demonstrated with a tank experiment. A detailed image is obtained through an experiment that can indicate the shapes of targets and has the ability to separate adjacent targets. The simulations and experimental results indicate that MBSAS can obtain a more detailed 3D full-scan image than conventional MBES and SAS system with a better energy focusing ability.

The research of passive detection parameter measurement based on vector sensor

As one of the indispensable technologies for underwater target detecting, underwater acoustic passive detection technology has always been a hot spot in marine system research. A vector sensor can detect underwater targets by combination with the pressure and vibration velocity information; vector sensor array can obtain higher gain than pressure array with the same number hydrophones. Vector sensor can reduce the length of the underwater sensor array and can detect underwater targets in the case of low signal to noise ratio. This is the goal that many researchers strive to solve for many years; therefore, vector sensor passive detection technology has far-reaching scientific research value. Through the verification of the simulation experiment, the azimuth estimation technique and the adaptive frequency estimation technique are feasible. By estimating the azimuth sequence and frequency sequence of the target radiation signal, the relevant information of the target can be obtained, so it is of great significance in the research of underwater acoustic detection technology.

Underwater Acoustic Detection: Current Status and Future Trends

Underwater Acoustic Detection: Current Status and Future Trends

Acoustic Transmission Characteristics Based on H-Type Metamaterials

To achieve the artificial manipulation of the acoustic wave front, and to produce high-efficiency acoustic focusing effect, this paper designed an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -type locally resonant metamaterial structure based on a two-dimensional three-component local resonance unit. The transmission characteristics of acoustic waves in this model were analyzed by using COMSOL, which is a finite element simulation software. We found that the incident acoustic energy was absorbed by the model, and the transmission path was consistent with the model structure. We also found that in different frequencies, the transmission characteristics of acoustic waves were different. The acoustic transmission characteristics improved as the waves approached the resonant frequency. Because of the flexibility and controllability of metamaterials, the structure can be designed according to specific conditions in practical applications to meet the resonant frequency required for transmitting acoustic signals, thus, improving the acoustic transmission efficiency. In addition, if the point excitation source of spherical waves was replaced by the line excitation source of plane waves, a plane acoustic wave focusing phenomenon would occur, which further proved that the local resonance acoustic metamaterial has good focusing characteristics and manipulation characteristics. The result of our research provides a new direction for underwater acoustic imaging, acoustic communication, and acoustic detection.

Robust passive underwater acoustic detection method for propeller

Characteristic amplitude modulated radiated noise signals are generated as the propeller operates underwater. Generally, passive underwater acoustic detection is accomplished by processing the radiated noise of a marine’s propeller. This study proposes a robust passive underwater acoustic detection method of a propeller by combining cyclostationary mechanism and principal component analysis (PCA). The proposed method can extract the characteristic frequency information of a propeller accurately. The effectiveness of the proposed method is verified according to simulated signals and real application cases. Both monocomponent and multicomponent modulated simulated signals are used to test the performance of the proposed method. The proposed method is then applied to the acoustic signals of propeller experiments and merchant ship propeller. Finally, the superiority of the proposed method is demonstrated by comparing the application results with the kurtogram and cyclostationary analysis method, during the extraction of the characteristic frequency of the propeller under low signal-to-noise ratio (SNR). The innovation of the proposed method not only realizes marine propeller detection from propeller acoustic signals but also has remarkable performance under low SNR.

Modeling and Experiment of a Small Size Dual Mode Transducer for Underwater Acoustic Communication and Detection

Modeling and Experiment of a Small Size Dual Mode Transducer for Underwater Acoustic Communication and Detection

Viscoelastic and acoustic characterization of polyurethane‐based acoustic absorber panels for underwater applications

ABSTRACTAcoustic absorbers that can have applications in a desired frequency band are a challenge often encountered in underwater acoustic absorber panel design. Polyurethane‐based sound absorbing composite panels were designed with the help of finite element method (FEM) modeling using COMSOL for material formulations that can give optimum performance of echo reduction (ER) with minimum thickness. Polyurethanes of different compositions were evaluated for their acoustic performance using FEM modeling and experimental validation of the modeling results was done. The frequency‐dependent modulus and damping properties were generated using dynamic mechanical analyzer and time–temperature superposition were performed to generate the material properties in the high frequency range (up to 25 kHz), which are significant for underwater acoustic detection applications and these data were used as inputs for modeling studies. Acoustic properties of the samples were experimentally evaluated using a water‐filled pulse tube in 2–15 kHz frequency range as well as in an acoustic tank test facility for bigger dimension panels. These are nonresonant type absorbers capable to overcome limitations arising from environmental factors such as high hydrostatic pressures and also they are effective over a broad range of frequency (500 Hz–15 kHz) with ER &gt; 15 dB. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47165.

Underwater acoustics array spatial reversal convolution and beamforming

A novel underwater acoustic array signal processing method based on spatial reversal and convolution, aiming at improving detection performance, is proposed to meet the engineering application demand of the underwater acoustic array detection system. The theoretical and mathematical model of the proposed method is deduced and presented in detail. Based on the extended covariance matrix of the physical array, the array sensitivity equalization and the noise suppression technique of the underwater acoustic array are studied. The additional gain provided by sensitivity equalization and noise suppression techniques is analyzed and exploited. Computer modelling and various numerical simulations are applied to demonstrate the proposed method’s effectiveness. At-sea experimental data are processed to test the performance in real underwater acoustic environment. These results indicate that the proposed array processing method can effectively improve the detection ability. The proposed techniques in this paper provide an insightful way to improve the detection performance of the underwater acoustic array.

Passive detection parameter measurement of azimuth and frequency based on single vector sensor

This paper mainly studies the measurement technology of passive detection parameters based on single vector sensor. Ship radiated noise contains a lot of target information, so the extraction of the line noise of the ship's radiated noise is of great significance in the measurement of passive detection parameters. The radiation noise of the ship is a broadband spectrum modulated by the spectral signal envelope. In this paper, the mathematical model of the radiation noise of the ship is simulated and the demodulation of the ship's radiated noise is carried out by using the square demodulation and the absolute value demodulation. The average azimuth and complex intensifier are used to estimate and analyze the target azimuth, and the estimated angle is statistically processed by histogram and weighted histogram. For the frequency estimation technique, the adaptive frequency estimator based on the adaptive notch filter and the adaptive LMS (least mean square) algorithm is chosen to study the target signal frequency.Through the verification of the simulation experiment, the azimuth estimation technique and the adaptive frequency estimation technique are feasible. By estimating the azimuth sequence and frequency sequence of the target radiation signal, the relevant information of the target can be obtained, so it is of great significance in the research of underwater acoustic detection technology.

Directional acoustic transmission based on metamaterials

To explore the simple low-loss operation of directional acoustic transmission technology, the propagation of acoustic waves in resonant phononic crystals was studied, and a transmission model based on acoustic metamaterials was constructed. Using the local resonance characteristics between acoustic waves and original cells, the multi-directional transmission of acoustic waves was modeled in the COMSOL software. It was found that acoustic waves generated by a point source are refocused into another point source after passing through the transmission model, and that the transmission loss is small. Under the control of this model, the effect of point-source propagation in various directions was achieved. The acoustic field characteristics of the model samples were also tested to verify the feasibility of the model structure, providing a new direction for applications such as underwater acoustic communication and detection.

Modeling and analysis of multilayer piezoelectric-elastic spherical transducers

An exact analytical model of multilayer piezoelectric-elastic spherical transducers is established in this article, and their dynamic characteristics are studied. Based on the linear theory of piezoelasticity, the dynamic analytical solution is derived in terms of Bessel functions, Lommel functions, Gamma functions, and Generalized Hypergeometric functions, and the electric impedance is obtained to determine the resonance frequencies. By proper selection of the layer number and geometric dimensions, the proposed model can approximately degrade into some special cases in the previous works, including single-layer piezoelectric spherical transducer, two-layer piezoelectric-elastic spherical transducer, and three-layer sandwiched piezoelectric-elastic-piezoelectric spherical transducer. Comparisons between the results of the proposed model and the ones of these special cases are also given and good agreements are found. Furthermore, parametric studies are conducted to discuss the effects of the key parameters on the dynamic characteristics of these special cases and a multilayer case, such as the first resonance and anti-resonance frequencies as well as the corresponding electromechanical coupling factor. This work contributes to an overall understanding of the dynamic characteristics of miniature piezoelectric hollow sphere transducers (BBs) and stacked piezoelectric spherical transducers. The developed model can be used to guide the design of the multilayer piezoelectric-elastic spherical transducers for promising applications in underwater acoustic detection, ultrasonic imaging, hydrophones, and nondestructive testing.

Acoustic Propagation Characteristics of Metamaterials With Tubular Structures

To generate acoustic waves with abnormal transmission characteristics different from those of traditional natural acoustic materials, we studied the propagation of acoustic waves in resonant phononic crystals. We identified the vibration mechanism of 2D three-component locally resonant phononic crystals. Using the finite element software COMSOL, an acoustic propagation model of a tubular structure based on acoustic metamaterials was constructed, and the local resonance characteristics of the acoustic waves and the original cells were used to simulate the propagation characteristics of the acoustic waves. We found that after low-loss wavefront propagation, most of the incident acoustic waves were absorbed by the model and reconverged with the outgoing acoustic waves on the other side of the model. Acoustic metamaterials with different layers emit acoustic waves at different locations, and thus, the propagation distance can be controlled by the design of the acoustic metamaterials. In addition, the propagation characteristics of the acoustic waves tend to be better at frequencies close to the resonance frequency. Because of the flexibility and the controllability of the acoustic metamaterials, the structure can be designed according to the actual situation to achieve the resonance frequency needed to propagate acoustic signals. This can improve the efficiency of acoustic propagation and provide new ideas for actual underwater acoustic source detection and acoustic communication.

An improved target detection and azimuth angle estimation method using a single acoustic vector sensor

In this paper, an improved underwater acoustic target detection and azimuth angle estimation method using a single acoustic vector sensor (AVS) is proposed based on time-reversal and convolution theory. The proposed method can be applied in the active and the passive sonar detection system. According to the conventional detection and estimation method based on complex acoustic intensity measurement, the mathematical and physical model of this proposed method is described in detail. Computer modelling and simulation is applied to demonstrate the proposed method’s effectiveness. In order to further verify the practical application performance of the proposed method, the research group carried out the open lake experiments. The computer simulation and open lake experiments results indicate that this method can realize the azimuth angle estimation with high precision by using only a single AVS. Compared with these conventional methods, the proposed method achieves better detection and estimation performance.