In noisy environments, the acoustic wave is complicated and consists of the radiated wave, the incident wave, as well as its scattering wave. Double-layered pressure measurement is introduced to the boundary element method based near field acoustic holography to recover the free field quantities. First, the incoming and outgoing propagation waves are separated by exploring the propagation property of the two waves from their source to the field with the boundary integral equation. Subsequently, the scattering wave is filtered out by considering the boundary condition of the vibrating structure. Further, a measurement on an enclosing hologram is adopted to accurately reconstruct the distribution of normal velocity on the boundary. Two sets of the system of linear equations are built on the double-layered measurements. The Schur complement equation is then applied in conjunction with the Tikhonov regularization method to obtain an optimized reconstruction. Numerical examples are set up for two representative radiators impinged by incident waves. It is demonstrated that the free field normal velocity can be correctly reconstructed even if the signal-to-noise ratio is negative. An experiment is conducted for the cubic radiator to verify the accuracy and potential for the practical reconstruction in a noisy environment.

中文翻译：

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噪声环境中基于边界元方法的近场声全息技术。

在嘈杂的环境中，声波很复杂，由辐射波，入射波及其散射波组成。将双层压力测量引入基于近场声全息的边界元方法中，以恢复自由场量。首先，通过使用边界积分方程探索两个波从其源到场的传播特性，来分离传入和传出的传播波。随后，通过考虑振动结构的边界条件将散射波滤除。此外，采用围绕全息图的测量以精确地重建边界上法向速度的分布。在双层测量中建立了两组线性方程组。然后，将Schur补码方程与Tikhonov正则化方法结合使用，以获得优化的重构。针对两个受入射波撞击的辐射器建立了数值示例。结果表明，即使信噪比为负，也可以正确地重建自由场法向速度。对立方散热器进行了一项实验，以验证在嘈杂环境中进行实际重建的准确性和潜力。