Sound radiation from impact-driven raked piles

Sound emissions from impact pile driving of raked piles present a significant azimuthal dependence in the radiated sound field due to the non-axisymmetric orientation of the pile. In this work the sound radiation from raked piles is modeled using a finite element method (FEM) model of the pile and near-field region. The near-field model of the sound field is then used as input into a normal mode model to predict the sound radiation in the far-field. The azimuthal dependence of the radiated sound field is shown to be accurately predicted using an equivalent axisymmetric FEM model of the pile configuration, thus negating the need to construct a fully three-dimensional model (3D) of the raked pile. This is achieved by matching the radiated field from the equivalent axisymmetric pile model to a vertical array of phased point sources, and then horizontally offsetting the source locations to match the incline of the raked pile. The resulting sound field closely matches the numerical predictions from a fully 3D FEM model of the raked pile. The results of numerical modeling are compared to corresponding acoustic measurements taken on the North West shelf of Western Australia. (C) 2017 Acoustical Society of America.