| Summary: | The rising underwater noise levels generated by human activities has prompted the international community of marine scientists to assess its potential impact on marine ecosystems and establish indicators for monitoring ‘‘noise pollution'' in submarine environments. The underwater Noise Level (NL) is a crucial acoustic parameter in determining the detection threshold of sound signals and acoustically characterizing the marine environment. However, NL measurements are not evenly distributed throughout the Earth's oceans, neither in space nor in time. They are scarce in the South Atlantic Ocean and particularly in waters off the Argentinian coast. To accurately estimate ambient NL and its long-term evolution, controlled at-sea measurements were conducted in San Jorge Gulf located in the south-eastern coast of Argentina during two consecutive fall seasons as part of a national interministerial programme. The data were collected using a custom-built, portable system consisting of calibrated omnidirectional broadband hydrophones, a two-channel charge amplifier, an acquisition board, and computational codes for measurement, visualization, and signal processing. The results, based on the analysis of acoustic time series taken at CTD stations, are presented. Different signal processing techniques were employed to spectrally characterize the underwater noise in the 10 Hz to 10 kHz frequency range. Additionally, the noise radiated by the measurement platform was characterized in order to attempt separating it from the ambient noise.
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