ON THE DIPOLE ACOUSTIC SOURCE LEVEL OF BREAKING WAVES

Wave breaking is believed to be the primary physical mechanism for gen eration of ambient noise. Yet previous measurements of ambient noise h ave been based on averaged results of noise sources randomly distribut ed in space and related primarily to wind speed. Recent progress in di rect 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 sou rce levels of breaking waves obtained during the surface wave processe s program. The acoustic source level is related to measured breaking w ave 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 spe ed. The data also indicate that the acoustic source level can be model ed as an exponential distribution. These results are explained using l aboratory observations of acoustic radiation and wave energy dissipati on due to breaking.