Sound amplitude of discrete bubbles entrained by a breaking wave.

Abstract

The exchange of gases between the ocean and the atmosphere plays a major role in regulating global climate, influencing processes like carbon sequestration and the balance of atmospheric gases. This paper investigates the acoustic emissions generated from the bubbles produced by breaking waves and analyzes the relationship between bubble diameter and sound intensity. This relationship is important for estimating bubble size distributions and thus achieving a better understanding of the gas exchange between ocean and atmosphere. Experiments were conducted in a controlled laboratory setting, generating linear focused breaking waves. High-speed cameras and four hydrophones captured synchronised audio and video data from bubble formation and acoustic emission events. Results are characterized by a polynomial relationship between bubble size and acoustic emission, showing that larger bubbles produced louder sounds. This behaviour is consistent with underwater bubbles generated from other, more fundamental mechanisms, such as underwater nozzles and plunging water streams and jets.