2020, Seiche, Triton Knoll, Analysis of Underwater Noise and Source Level Estimation series https://portal.medin.org.uk/portal/start.php?tpc=015_86db5fea-371f-4ca4-9bc1-d13fbf05aff9 An underwater acoustic survey was carried out during the installation of the first four foundations V11, V12, U10, and T09 between 17th January 2020 and 26th February 2020. This survey was performed to record the noise levels emitted during installation. The levels were measured at different distances from the piles and results were compared to the outputs of a prior modelling outcome. The report in this series presents the results and subsequent analysis of the underwater noise data recorded in this survey. The data was analysed using signal processing and acoustic propagation modelling for the survey region and Source Levels based on recorded data were reported. The underwater noise levels were recorded using two calibrated Acoustic Recording Units (ARUs) deployed at 500 m and 750 m from the foundations along pre-defined transects. In addition to ARUs, a Vertical Sound Profiling (VSP) system with a hydrophone was deployed from the starboard side of the noise monitoring vessel at distances between 4 km and 12 km. The recorded data was processed using peak detection algorithms to identify individual strike data and these are matched with relevant hammer strikes. The matched strikes were post-processed into different frequency bands and their Received noise Levels (RL) were calculated. 20250813T11:46:05