Autonomous diving platforms for high-quality sound measurements in space and throughout the water column

With the continuous increase of human activities at sea, predicting noise propagation from a given source is paramount to understanding the potential extent of its effects on the marine environment. Sound propagation models serve this purpose. These are complex modeling frameworks which account for both the physics of sound traveling in water as well as some environmental parameters which may affect it. However, in-situ sound measurements are required for validating such models, particularly at large distances from the source, where predictions can deviate largely from reality. Traditionally, such measurements are obtained from hydrophones placed on installations (buoys, landers) at fixed depths which do not allow verification of the vertical propagation of sound. In this study, a hydrophone was mounted on a mobile uncrewed platform (Slocum glider from Teledyne) which was moving up and down the water column as well as at different distances from the sound source during a full scale industrial seismic survey. The dBSea sound propagation model was used to predict sound levels from the seismic source and the measurements were used for validation. An array of simulations was performed to test which model settings best aligned with the data, with particular focus on the vertical propagation properties. This exercise gave insight on which areas of the model tend to either over- or underestimate sound levels and showed how autonomous diving platforms can help gather large amounts of high-quality sound measurements both in space and throughout the water column.