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Sound propagation in shallow water is significantly influenced by geoacoustic properties. Estimating these geoacoustic parameters is essential for sound field analysis and sonar performance assessment. As a common practice, the seafloor is often treated as a single-layer or two-layer range-independent geoacoustic model to reduce the number of involved parameters. However, acoustic parameters inverted through these two geoacoustic models are typically limited in their applicability to a specific frequency range, thus posing challenges when applied across a broader frequency range. A range-dependent multi-layer geoacoustic model based on experimental measurements obtained with a sub-bottom profiler is proposed in this study. The inversion scheme combines three inversion methods to estimate geoacoustic parameters, considering the different sensitivities of geoacoustic parameters to different physical parameters within the acoustic field. Firstly, modal dispersion is used to invert the geoacoustic parameters of each layer, with the dispersion curve obtained through warping transform and the Wigner-Ville distribution. After that, both the localization using matched field processing and the dispersion curve fitting demonstrate the effectiveness of the inversion results for each layer, although the peak of the probability distribution of sound speed in the first layer is broader than in others. Secondly, matched field processing is employed to invert the geoacoustic parameters of the first layer. This method is based on the theory that as frequency increases, the depth of sound rays penetrating the seabed decreases, revealing changes in the first layer's sound speed with the seabed depth. Lastly, bottom attenuation coefficients at different frequencies are inverted by the transmission loss (TL), and a fitting relationship between the attenuation coefficient and the frequency is derived. The inversion results obtained by using the range-dependent multi-layer geoacoustic model are compared with results estimated by the single-layer geoacoustic model. The findings indicate that the transmission loss (TL) error from the range-dependent multi-layer geoacoustic model in this study is smaller than that from the single-layer geoacoustic model, especially in the lower frequency band. The range-dependent multi-layer geoacoustic model proves to be suitable for a broader frequency range, providing better precision in explaining various acoustic phenomena.
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Keywords:
- broadband geoacoustic inversion/
- range-dependent multi-layer geoacoustic model/
- modal dispersion/
- transmission loss
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] -
反演参数 符号 单位 样本1 样本2 样本3 样本4 样本5 收发距离 $r$ ${\mathrm{ km}} $ 5.3 5.8 6 7.8 9.3 第一层海底声速 ${c_{{\text{b}}1}}$ ${\mathrm{m/s}}$ 1640 1614 1631 1613 1600 第二层海底声速 ${c_{{\text{b}}2}}$ ${\mathrm{m/s}}$ 1566 1576 1576 1570 1578 第三层海底声速 ${c_{{\text{b}}3}}$ ${\mathrm{m/s}}$ 1610 1624 1636 1613 1603 第一层海底平均厚度 ${h_1}$ $ {\mathrm{m}} $ 8.82 8.68 8.71 8.55 8.29 第一层海底密度 ${\rho _1}$ ${\text{g}}/{\mathrm{c}}{{\mathrm{m}}^3}$ 1.79 1.73 1.76 1.73 1.69 第二层平均海底厚度 ${h_2}$ $ {\mathrm{m}} $ 9.07 9.13 8.92 8.78 8.83 第二层海底密度 ${\rho _2}$ ${\text{g}}/{\mathrm{c}}{{\mathrm{m}}^3}$ 1.60 1.63 1.62 1.61 1.63 第三层海底平均厚度 ${h_3}$ $ {\mathrm{m}} $ 32.46 32.78 32.22 30.97 29.77 第三层海底密度 ${\rho _3}$ ${\text{g}}/{\mathrm{c}}{{\mathrm{m}}^3}$ 1.72 1.75 1.78 1.72 1.70 
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频率/${\text{Hz}}$ 50 100 150 200 250 300 350 400 450 500 声速/(m·s–1) 1725 1625 1605 1595 1590 1585 1585 1585 1580 1585 代价函数 0.36 0.57 0.54 0.30 0.31 0.21 0.14 0.10 0.12 0.15 DownLoad:
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距离/km $ {c_{{\text{b}}11}} $/(m·s–1) $ {c_{{\text{b}}12}} $/(m·s–1) $ {c_{{\text{ba}}}} $/(m·s–1) $ {h_{11}} $/m $ {c_{{\text{b}}13}} $/(m·s–1) $ {h_{12}} $/m 3.7 1540 1585 1562.5 4.18 1665 4.55 4.1 1535 1599 1567 4.24 1665 4.49 4.3 1566 1604 1585 4.28 1672 4.51 4.8 1568 1598 1583 4.31 1670 4.45 5.5 1568 1597 1582.5 4.33 1669 4.37 6 1565 1592 1578.5 4.32 1657 4.35 DownLoad:
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土样编号 层位 温度 水深 声速 密度(湿) 名称 D/cm T/℃ Z/m c/(m·s–1) ρ/(g·cm–3) S63511-1 0—40 20.5 83 1542.93 1.66 粘土质粉砂 S63512-1 40—80 20.5 83 1558.55 1.66 粘土质粉砂 S63513-1 80—120 20.5 83 1528.57 1.69 粘土质粉砂 S63514-1 120—150 20.5 83 1539.44 1.75 砂质粉砂 S63521-1 150—190 21.0 83 1564.67 1.82 粘土质粉砂 S63522-1 190—230 21.0 83 1517.44 1.77 粘土质粉砂 S63523-1 230—270 21.0 83 1588.24 1.77 粘土质粉砂 S63524-1 230—300 21.0 83 1564.69 1.77 粘土质粉砂 S63531-1 300—330 21.0 83 1565.55 1.90 砂质粉砂 S63532-1 330—360 21.0 83 1616.20 1.92 粉砂质砂 S63533-1 360—400 21.0 83 1568.53 1.98 粉砂质砂 平均 1560 DownLoad:
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频率/Hz 100 150 200 225 300 325 375 400 450 475 $ \alpha /({\mathrm{dB}} {\cdot} {{\mathrm{m}}^{ - 1}}) $ 0.001 0.007 0.015 0.022 0.033 0.04 0.045 0.061 0.078 0.094 误差$ /{\mathrm{dB}} $ 2.91 1.70 1.68 1.42 1.61 1.78 2.27 2.23 2.37 2.60 DownLoad:
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频率/Hz 100 150 200 225 300 ${c_{\text{e}}}/({\text{m}} {\cdot }{{\text{s}}^{{{ - }}1}})$ 1615 1615 1615 1613 1600 $ \alpha /({\mathrm{dB}}{ \cdot} {{\mathrm{m}}^{ - 1}}) $ 0.0001 0.011 0.022 0.032 0.04 误差$ /{\mathrm{dB}} $ 3.98 1.81 1.71 1.53 1.68 DownLoad:
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[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27]
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