Laboratory Measurements of the Sound Generated by Breaking Waves

摘要

The primary motivation for this research was to determine whether measurements ofthe sound generated by breaking waves could be used to quantitatively study the dynamics of the breaking process. The sound beneath two and three-dimensional breaking waves was measured. It was determined that the mean square acoustic pressure correlates with the wave slope and dissipation for waves of moderate slope and that the amount of acoustic energy radiated by an individual breaking event scales with the amount of mechanical energy dissipated by breaking. Sound at frequencies as low as 10 Hz was observed and the mean square acoustic pressure, in the frequency bands below 1 kHz correlate strongly with the wave slope and dissipation. The correlations of the mean square acoustic pressure and the wave amplitude were found to be similar for the two and three-dimensional breakers. The spectra of the sound generated by the large scale three-dimensional breaking waves sloped at -5 to -6 dB per octave at frequencies greater than 1KHz. Evidence is presented which supports the hypothesis that the low frequency signals observed beneath both the two and three-dimensional breaking waves were caused by the collective oscillation of bubble clouds. A model of the sound produced by breaking waves which uses the sound radiated by a single bubble oscillating at its linear resonant frequency and the bubble size distribution to estimate the sound spectrum is presented. Sound, Breaking, Waves.