Oceanological and Hydrobiological Studies

The breaking wave phenomenon signi cantly takes part in the mechanisms of mass, heat and gas exchange at the air-water boundary and depends on the wind velocity. Some of the energy dissipated during this process is converted into underwater sound emitted by oscillating gas bubbles and bubble plumes. However, the underwater noise accompanying the lowest wind speed conditions has received only little attention. This report describes a study aimed at advancing the knowledge of underwater noise emission from air bubbles injected during small-scale breaking events occurring on the water surface. Results of model experiments performed in a small tank are presented. The object of the research is the relationship between the generated noise and the dissipated potential energy of water poured into a tank lled with water of varying physical water properties. Additionally, the impact of various water properties such as salinity, surface tension or microscale gas bubbles was examined. The experiment revealed that noise spectra are a ected by di erent water properties and most likely re ect the varying e ciency of bubble formation and bubble size spectra.