RESUMEN
Underwater ambient sound has been recently re-addressed in regard to the impact of anthropogenic sound from commercial shipping on marine life. Passive acoustic monitoring provides the overall ambient sound levels at a given location and is often used to calibrate the sound propagation modeling for assessing ambient sound levels in larger marine areas. To quantify the pressure on the environment, the proportion of the anthropogenic component in the total measured levels of the monitored sound should be properly assessed. The present paper addresses the methodology for categorisation of the measured sound into its wind-driven natural and anthropogenic components.
RESUMEN
During last decades, anthropogenic underwater sound and its chronic impact on marine species have been recognised as an environmental protection challenge. At the same time, studies on the spatial and temporal variability of ambient sound, and how it is affected by biotic, abiotic and anthropogenic factors are lacking. This paper presents analysis of a large-scale and long-term underwater sound monitoring in the Baltic Sea. Throughout the year 2014, sound was monitored in 36 Baltic Sea locations. Selected locations covered different natural conditions and ship traffic intensities. The 63 Hz, 125 Hz and 2 kHz one-third octave band sound pressure levels were calculated and analysed. The levels varied significantly from one monitoring location to another. The annual median sound pressure level of the quietest and the loudest location differed almost 50 dB in the 63 Hz one-third octave band. Largest difference in the monthly medians was 15 dB in 63 Hz one-third octave band. The same monitoring locations annual estimated probability density functions for two yearly periods show strong similarity. The data variability grows as the averaging time period is reduced. Maritime traffic elevates the ambient sound levels in many areas of the Baltic Sea during extensive time periods.