Time-domain modelling of underwater transient noise for environmental risk assessment

Abstract

Underwater transient noise has the potential to cause auditory damage in marine mammals, fish, and invertebrates. The risk of auditory damage is closely linked to the temporal structure of transient signals (e.g., rise time, peak pressure), which is modulated through propagation in the environment. Current models used in environmental risk assessment of underwater noise are based on pulse energy and do not predict the change in temporal structure as the transient propagates away from the source. To address this, the current work presents a time-domain model of transient propagation, based on Fourier synthesis of frequency domain solutions computed using a parabolic equation method. The model outputs are benchmarked first against standard analytical models, then validated against measurements of seismic survey and pile driving noise at various ranges from the source. The results will be discussed in the context of recent regulatory guidelines on the extent of transient acoustic fields and the associated risk of auditory damage to marine mammals.