Bubble noise and wavelet spills recorded 1 m below the ocean surface

A remote instrument has been used to record the sound and environment of small surface spills in light winds from a depth of approximately 1 m in the open ocean. Recordings from the instrument indicate that these small breaks have no correlation with the amplitude or phase of long-period swells moving faster than prevailing winds. The sound from the spills, which is composed of a number of distinct resonant bubble oscillations, is very similar to that described by Medwin and Beaky [J. Acoust. Soc. Am. 86, 1124–1130 (1989)] for windless artificial wave breaks. Peak oscillation source pressures range up to 1.2 Pa. The average of several acoustic spectra from a single energetic spill has shown a slope of −5 dB per octave over the frequency range of the instrument, roughly 500–8000 Hz. The unique frequency for each oscillating bubble within a spill indicates that bubbles are “rung” as they are formed during entrainment, die out exponentially within milliseconds, and then no longer contribute actively to the a...