Dear MARMAM community, On behalf of my co-authors, I am pleased to inform you on the publication of our open-access article: Pereira, A.; Romagosa, M.; Corela, C.; Silva, M.A.; Matias, L. "Source Levels of 20 Hz Fin Whale Notes Measured as Sound Pressure and Particle Velocity from Ocean-Bottom Seismometers in the North Atlantic" J. Mar. Sci. Eng. 2021, 9, 646. ABSTRACT: Source level is one factor that determines the effectiveness of animal signal transmissions and their acoustic communication active space. Ocean-bottom seismometers (OBS) are platforms of opportunity to monitor marine species because they record data as pressure fluctuations in the water using a hydrophone and/or as particle velocity of the seabed using a seismometer. This study estimates source levels of 20 Hz fin whale notes recorded simultaneously in these two OBS channels and in two areas of the North Atlantic (Azores and southwest Portugal). It also discusses factors contributing to the variability of the estimates, namely geographical (deployment areas), instrumental (recording channels and sample size), and temporal factors (month of detected notes, inter-note interval, and diving duration). The average source level was 196.9 dB re 1 µPa m for the seismometer (derived from particle velocity measurements) and 186.7 dB re 1 µPa m for the hydrophone. Variability was associated with sample size, instrumental characteristics, acoustic propagation, and month of recordings. Source level estimates were very consistent throughout sequences, and there was no indication of geographical differences. Understanding what causes variation in animal sound source levels provides insights into the function of sounds and helps to assess the potential effects of increasing anthropogenic noise. The full article is available here: https://doi.org/10.3390/jmse9060646 The article was published in a special issue of the Journal of Marine Science and Engineering titled "Ocean Noise: From Science to Management<https://www.mdpi.com/journal/jmse/special_issues/ocean_noise>". Kind regards, Andreia Pereira -- Andreia Pereira Research Fellow IDL - Instituto Dom Luiz Faculty of Sciences of the University of Lisbon Edifício C8 - Room 8.3.20 | Campo Grande | 1749-016 Lisboa | Portugal | +351966321466 ECCO Ocean https://ecco-ocean.com/ Associação para as Ciências do Mar https://cienciasmar.wixsite.com/associacao