Ocean Acoustic Inversion

海洋对电磁波是不透明的，但对声音是透明的；因此，声学被用于许多水下应用，如海底*属性/过程的遥感或声源(例如，潜艇、海洋哺乳动物)的位置，以及地质、岩土、环境和声纳/防御应用。然而，声学遥感*需要非线性反演，需要定量模型选择和不确定性估计，才能进行有意义的解释。建议的研究建立在我们的海洋声遥感贝叶斯(概率)反演长期研究计划的基础上，共六个项目。*(1)海底声散射参数和过程的反演。我们的初步工作表明，反向散射数据的反演可以解决海底粗糙度和沉积物非均质谱的问题。我们建议开发定量的模型选择*方法来确定各种物理散射机制的相对重要性，并估计不同海底类型的相关*散射参数，以更好地理解海底*散射的物理。*(2)为海军数据库或电缆铺设等岩土工程应用估算横向变化的海底散射参数。这项研究基于对使用移动系统收集的新声学数据集的顺序贝叶斯反演，该移动系统包括由自动水下机器人在*海底附近拖曳的声源和接收器阵列。*(3)通过考虑横波、散射和倾斜层的影响，扩展了我们现有的高分辨率海底地声参数反演的反射率，并应用于解决海洋沉积物中的色散(声速和衰减频率相关性)。*(4)使用固定*接收器阵列记录的全场声波数据进行海底地声特性的层析(2D)反演。二维定量非线性反演的一个主要组成部分是开发新的自适应稀疏/不规则网格，以与数据的分辨率一致的方式对环境进行参数化，以实现严格的不确定性估计。*(5)声源定位和不确定性估计，包括海洋*环境属性的不确定性影响。我们最初的工作是在海军(被动声纳)应用方面，但我们正在与加拿大领先的海洋技术公司JASCO Research Ltd合作，进入海洋哺乳动物*研究领域。建议的方法包括一种新的方法，用于非同步阵列系统/子系统的匹配场定位，*以及在单个接收器处通过模式色散(时频分析)进行源测距。*(6)使用长期的声学监测数据跟踪数量未知的发声海洋哺乳动物，以提供一个概率解决方案，从中可以提取有关种群和行为的信息。**

Oceans are opaque to electromagnetic waves but transparent to sound; hence, acoustics is used for many underwater applications such as the remote sensing of seabed*properties/processes or the locations of sound sources (e.g., submarines, marine mammals), with geological, geotechnical, environmental and sonar/defence applications. However, acoustic remote sensing*requires nonlinear inversion, with quantitative model selection and uncertainty estimation required for meaningful interpretations. The proposed research builds on our long-term program in Bayesian (probabilistic) inversion for ocean acoustic remote sensing with six projects.***(1) Inversion for seabed acoustic scattering parameters and processes. Our initial work shows that inversion of backscatter data can resolve seafloor roughness and sediment heterogeneity spectra. We propose to develop quantitative model-selection*approaches to determine the relative importance of various physical scattering mechanisms and to estimate relevant*scattering parameters for different seabed types, to better understand the physics of seabed*scattering. ***(2) Estimation of laterally-variant seabed scattering parameters for naval databases or geotechnical*applications such as cable laying. This  is based on sequential Bayesian inversion of novel acoustic data sets collected using a mobile system comprising an acoustic source and receiver array towed near the*seabed by an autonomous underwater vehicle. ***(3) Extending our existing high-resolution reflectivity inversions for seabed geoacoustic parameters by including effects of shear waves, scattering, and dipping layers, with application to resolving dispersion (sound speed and attenuation frequency dependence) in marine sediments. ***(4) Tomographic (2D) inversion for seabed geoacoustic properties using full-field acoustic data recorded at a fixed*receiver array. A major component of quantitative nonlinear inversion in 2D involves developing new self-adaptive*sparse/irregular grids to parameterize the environment in a manner consistent with the resolving power of*the data to allow rigorous uncertainty estimation. ***(5) Acoustic source localization and uncertainty estimation, including the effects of uncertainty in ocean*environmental properties. Our initial work was in naval (passive sonar) applications, but we are moving into marine mammal*studies in collaboration with JASCO Research Ltd, a leading Canadian marine-technology company. Proposed*methods include a novel approach to matched-field localization with non-synchronized array systems/sub-systems,*and source ranging via modal dispersion (time-frequency analysis) at a single receiver. ***(6) Tracking an unknown number of vocalizing marine mammals using long-term acoustic monitoring data to provide a probabilistic solution from which information on*population and behaviour can be extracted. **