GAIA Marine supported an offshore vessel acoustic signature assessment in Western Australia, measuring underwater radiated noise under controlled operating conditions to support vessel noise management, environmental assessment and alignment with international acoustic standards.
The assessment was designed to characterise the vessel’s underwater acoustic footprint in accordance with ISO 17208-1:2016 and ISO 17208-2:2019, with consideration of AMSA, IMO and NOPSEMA guidance. Testing was conducted offshore in the Pilbara region in low-traffic conditions to minimise interference from other anthropogenic sound sources, with stable sea state, wind and environmental conditions supporting high-quality data acquisition. The vessel was assessed under multiple operational conditions, including 4-knot transit, 6-knot transit, 6-knot transit with sub-bottom profiler active, and static dynamic positioning.
The field methodology used three calibrated Ocean Instruments ST500 acoustic recording units deployed at defined depths in a bottom-anchored array, supported by sound-velocity profiling and controlled vessel transects at a 100 m closest point of approach. Data processing translated the acoustic recordings into standardised outputs including RMS sound pressure level, power spectral density, 1/3-octave bands, underwater radiated noise and sound exposure metrics. This allowed the vessel’s acoustic signature to be assessed across frequency bands and compared between operational modes.
The results established a defensible acoustic baseline for the vessel, with underwater radiated noise increasing with vessel speed and the highest values concentrated below 125 Hz. The 6-knot condition produced the highest mean underwater radiated noise, while static dynamic positioning showed lower overall noise but different thruster-related characteristics. Additional analysis indicated that the tested sub-bottom profiler did not significantly affect received levels in the hydrophone configuration used, and that no temporary or permanent hearing damage to low-frequency cetaceans was predicted at 100 m based on the available frequency range, although short-term behavioural disturbance remained possible.
This project demonstrates GAIA Marine’s acoustic monitoring capability beyond simple deployment and retrieval of recorders. The value is in controlled test design, ISO-aware methodology, environmental noise screening, acoustic data processing, interpretation of vessel operating modes and translation of complex acoustic metrics into practical management information. It positions GAIA to support vessel operators, offshore contractors and project proponents requiring defensible underwater noise assessments, vessel comparison, acoustic impact screening and noise management planning.