On the origin and nature of acoustic emissions from bubbles departing an underwater nozzle

Bubble acoustics provides deeper insights into bubble dynamics beyond visualization. This study experimentally, numerically, and analytically investigates the origin and nature of sound from bubbles departing an underwater nozzle. Numerical modeling, incorporating air compressibility, closely matches experiments, underscoring its critical role in bubble acoustics. Findings reveal that liquid jet inrush during necking fracture excites the bubble, following a Maxwell–Boltzmann distribution. A novel analytical model extends Minnaert's framework, treating the pulsating bubble as a forced oscillator. These insights not only explain the mysterious attenuation of acoustic signals in continuous bubble streams but also clarify many of the longstanding confusions in the literature, paving the way for futuristic applications and controlled underwater acoustic emissions.