ON THE DIPOLE ACOUSTIC SOURCE LEVEL OF BREAKING WAVES

Wave breaking is believed to be the primary physical mechanism for generation of ambient noise. Yet previous measurements of ambient noise have been based on averaged results of noise sources randomly distributed in space and related primarily to wind speed. Recent progress in direct measurement of breaking waves has made it possible to examine the sound radiated from individual sources and relate it to breaking wave parameters. Here we present field observations of dipole acoustic source levels of breaking waves obtained during the surface wave processes program. The acoustic source level is related to measured breaking wave speed, which is believed to be an important parameter relevant to wave energy dissipation. It is found that the source level has a much better correlation with the breaking wave speed than with the wind speed. The data also indicate that the acoustic source level can be modeled as an exponential distribution. These results are explained using laboratory observations of acoustic radiation and wave energy dissipation due to breaking.