Analysis and prediction of underwater sound radiation from a cylindrical pile driven by an impact hammer.

Abstract

A vibroacoustic model for sound radiation from a submerged pile was developed to predict sound pressure levels generated during offshore construction activities. It was implemented in MATLAB and verified with measured data reported in the literature. The modal response of a cylindrical pile to hammer impact is first determined. Contributions from all dominant modes are then summed at various ranges to produce a two‐dimensional spatial mapping of sound pressure level. The analysis was used to investigate the effects of pile material, size, and geometry on radiated sound pressure levels. Results indicate that smaller diameter piles of the same material do not necessarily produce lower sound pressure levels, but rather shift the peak sound pressure levels to higher frequencies. Because these basic parameters affect bandwidth as well as sound levels, there is no simple way to classify source level and frequency. Peak sound pressure levels generated underwater by driving steel piles with impact hammers into the sea bottom can easily exceed 200 dB re 1 μPa at a range of 10 m, so accurate prediction of the sound field is needed to assess potential risks to the environment.