Underwater Noise Simulation of Impact Pile Driving for Offshore Wind Farm in Taiwan

Abstract

The radiated acoustic waves from impact pile driving produce high noise level into the water which may cause damage to marine mammals living close to the offshore construction location. In this paper, a linear, axisymmetric finite element (FE) model is applied to predict pile driving noise in the water. Measurement from bottom-mounted hydrophone deployed at a site 230 m from the source is used to validate the model results. The comparisons between model results and measurement, such as structure modal analysis, sound exposure level at different pile penetration and unweighted one-third octave band level, are presented and show useful predictions of noise level from the model. Furthermore, a time domain case is demonstrated to show Mach wave associated with the radial deformation of the pile and supersonic speed. Finally, analysis of variance (ANOVA) and linear regression are made after verifying the model prediction. The ANOVA results identifies some significant parameters on pile driving noise and the empirical equation from linear regression represents the noise level from pile driving impact at close range. These are possible metrics on offshore wind farm environment assessment in Taiwan.