Shallow-Water Geoacoustic Parameter Inversion with Stokes Parameters and a Multi-Task Attention U-Net
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摘要: 浅海地声参数对水声传播特性的分析具有重要作用,然而,传统的反演方法在实际应用中面临计算复杂度和成本较高以及对模型准确性依赖性较强等问题。为此,本文提出一种基于矢量声场Stokes极化参数与注意力增强多任务U-Net的地声参数反演方法。针对单矢量水听器各通道所接收的信号实施warping变换处理,把将提取到的各阶简正波信号经计算和归一化后所得的Stokes参数作为网络输入特征;构建多任务U-Net神经网络模型,采用共享编码器与多分支独立预测纵波声速等地声参数,同时引入通道和空间注意力机制,增强关键特征提取能力并抑制无关特征;此外,采用多任务不确定性加权损失函数实现各地声参数反演任务的自适应平衡,使得反演结果更准确。200组测试集数据的仿真结果表明,引入注意力机制后模型预测波动范围降低,整体反演精度与稳定性均有所提升,该反演方法受模型参数失配影响较小,展现出较强的鲁棒性。进一步的海事实验数据验证表明,该方法在实际浅海环境下的地声参数反演中具有高效性和可靠性。Abstract:
Objective Geoacoustic parameters in shallow water are crucial for analyzing the characteristics of underwater acoustic propagation. However, traditional inversion methods face challenges such as high computational complexity, significant cost, and strong dependence on the accuracy of environmental models. To address these issues, this study proposes an efficient and robust inversion approach designed to overcome the limitations of conventional methods. The proposed method aims to provide more reliable and stable estimation of shallow-water geoacoustic parameters, enabling improved performance in practical applications while maintaining computational efficiency and robustness. Methods This study is based on the Stokes polarization parameters of the vector acoustic field. Signals received by a single vector hydrophone are processed using a warping transformation to separate and extract normal modes propagating in a shallow-water waveguide. The extracted signals are subsequently used to compute the Stokes parameters, which are normalized and employed as input features for the inversion model. An attention-enhanced multi-task U-Net neural network is constructed, adopting a shared encoder and multiple decoder branches to predict key geoacoustic parameters, including compressional wave velocity, shear wave velocity, density, and attenuation coefficients. In addition, channel and spatial attention mechanisms, together with a multi-task loss function incorporating uncertainty weighting, are applied to optimize feature extraction and achieve adaptive balancing among the different parameter inversion tasks. Results and Discussions The introduced attention mechanism proves effective in suppressing fluctuations in model predictions, thereby significantly boosting the accuracy and stability of geoacoustic parameter inversion.The mean absolute percentage errors for both compressional and shear wave velocities were consistently below 5 %( Table 2 ) upon evaluation on a dataset comprising 200 test cases. With the incorporation of attention mechanisms, the errors in shear wave velocity and seabed density were further reduced to less than 3 %(Table 3 ), demonstrating enhanced precision in predicting these key parameters. The proposed method is not only insensitive to parameters mismatch but also exhibits strong robustness against environmental variations. Furthermore, the approach was validated using real measurement data from a shallow-water region in the northern South China Sea(Fig.16 ), confirming both the effectiveness and reliability of the method in practical scenarios(Table 4 andFig.18 ). These results collectively demonstrate that the attention-enhanced multi-task U-Net framework can effectively capture critical features from Stokes polarization parameters, leading to more stable and accurate geoacoustic parameter estimation in shallow-water environments.Conclusions The inversion method based on Stokes parameters and an attention-enhanced multi-task U-Net can effectively improve the accuracy and stability of shallow-water geoacoustic parameter estimation, showing particularly strong performance in predicting compressional wave velocity, shear wave velocity, and density. However, it still has limitations in the inversion of seabed attenuation coefficients. Future research should further improve feature extraction methods and network architecture, and explore the applicability of this approach under more complex marine conditions. -
表 1 待反演的5个地声参数
待反演参数 参考值 搜索范围 步长 海底纵波声速($ {\mathrm{c}}_{\mathrm{b}} $)(m/s) 1800 [ 1600 ,1800 ]1 海底横波声速($ {\mathrm{c}}_{\mathrm{s}} $)(m/s) 400 [200,600] 1 海底密度($ {\rho }_{\mathrm{b}} $)(g/cm3) 1.7 [1.6,1.8] 0.1 海底纵波衰减($ {\alpha }_{\mathrm{p}} $)(dB/λ) 0.15 [0.1,0.2] 0.01 海底横波衰减($ {\alpha }_{\mathrm{s}} $)(dB/λ) 0.5 [0.3,0.7] 0.01 表 2 测试集的模型评估结果
参数 单位 MAE MAPE(%) 海底纵波声速($ {\mathrm{c}}_{\mathrm{b}} $) m/s 60.931 3.521 海底横波声速($ {\mathrm{c}}_{\mathrm{s}} $) m/s 27.415 7.825 海底密度($ {\rho }_{\mathrm{b}} $) g/cm3 0.051 3.023 海底纵波衰减($ {\alpha }_{\mathrm{p}} $) dB/λ 0.024 17.337 海底横波衰减($ {\alpha }_{\mathrm{s}} $) dB/λ 0.098 21.323 表 3 CBAM-U-Net与U-Net, TCN模型测试集结果对比
参数 MAE MAE_CBAM MAE_TCN MAPE(%) MAPE_CBAM(%) MAPE_TCN(%) $ {\mathrm{c}}_{\mathrm{b}} $(m/s) 60.931 9.828 79.696 3.521 0.570 4.615 $ {\mathrm{c}}_{\mathrm{s}} $(m/s) 27.415 19.205 168.026 7.825 5.347 49.772 $ {\rho }_{\mathrm{b}} $(g/cm3) 0.051 0.050 0.052 3.023 2.945 3.009 $ {\alpha }_{\mathrm{p}} $(dB/λ) 0.024 0.024 0.025 17.337 17.407 17.450 $ {\alpha }_{\mathrm{s}} $(dB/λ) 0.098 0.099 0.099 21.323 21.409 21.412 表 4 实验数据上的反演结果
距离 参数 $ {\mathrm{c}}_{\mathrm{b}} $(m/s) $ {\mathrm{c}}_{\mathrm{s}} $(m/s) $ {\rho }_{\mathrm{b}} $(g/cm3) $ {\alpha }_{\mathrm{p}} $(dB/λ) $ {\alpha }_{\mathrm{s}} $(dB/λ) 方法 误差% 误差% 9.7 km U-Net 1652.72 3.10 442.57 1.67 1.76 0.15 0.5 CBAM 1622.80 1.23 430.63 1.71 0.59 0.14 0.46 17.4 km U-Net 1660.81 3.60 448.65 1.74 2.35 0.16 0.54 CBAM 1630.56 1.71 440.01 1.69 0.59 0.15 0.49 匹配场 1603.1 / 1.7 / / -
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