PASSIVE ACOUSTIC DETECTION OF WAVE BREAKING EVENTS IN THE BALTIC SEA Agata Dragan a , Barbara Swerpel b , Zygmunt Klusek a a Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81-712 Sopot, Poland b Institute of Hydroengineering, Polish Academy of Sciences, Koscierska 7, 80-328 Gdansk, Poland Agata Dragan, Powstancow Warszawy 55, 81-712 Sopot, Poland, adragan@iopan.gda.pl, phone: +48 58 7311805, fax.: 058 551 21 30 Abstract: The quantity of wave energy lost during breaking is an important component in the wind wave energy budget. Nevertheless, there is still not enough information about statistics of breaking waves  how many waves are breaking and how much energy do they lose. An attempt to investigate this process with passive acoustic methods was made in the shallow water of the Baltic Sea. Underwater noise was recorded by the Autonomous Hydroacoustic Buoy equipped with four omnidirectional hydrophones. By processing the noise and using the time-delay estimation technique, the detection, localization and parameterization of individual breaking wave events were accomplished. Wave field parameters were registered concurrently by a Waverider buoy, anchored in a close distance to the hydroacoustic system. Once per hour, water elevation was converted to frequency-directional wave spectrum. In a five-day long experiment over 16 000 individual events of the wave-breaking were found and about 2500 parameterized. For each of them, the speed and direction of propagation, time of duration and amount of acoustic energy were obtained. This allowed for finding associations between individual events and wind wave spectrum. Majority of detected breaking events were located in a most energetic part of a wave spectrum. This confirmed the hypothesis that individual breaking waves were observed. In consequence, spectral distribution of the acoustic energy in a wave spectrum was obtained. Keywords: breaking wave, passive acoustics, acoustic energy, Baltic Sea 1st International Conference and Exhibition on Underwater Acoustics 1187