Low-frequency sound transmission through a gas-liquid interface

Area of Science:

• Acoustics
• Fluid Dynamics
• Wave Propagation

Background:

• Gas-liquid interfaces exhibit strong acoustic impedance contrasts, typically hindering sound transmission.
• Weak sound transmission is expected across boundaries with significant differences in acoustic properties.

Purpose of the Study:

• To investigate acoustic power output and flux through a plane gas-liquid interface.
• To explore the phenomenon of anomalous transparency for low-frequency sound.
• To analyze the influence of liquid stratification and guided sound propagation.

Main Methods:

• Analysis of acoustic power output from localized sources.
• Calculation of acoustic power fluxes across a gas-liquid interface.
• Examination of plane-wave decomposition including inhomogeneous (evanescent) waves.

Main Results:

• Anomalous transparency allows significant acoustic power radiation from liquid to gas half-spaces at low frequencies.
• Evanescent waves are identified as the primary mechanism for this acoustic power transfer.
• Liquid stratification and guided sound propagation affect the degree of anomalous transparency.

Conclusions:

• The study demonstrates a counter-intuitive acoustic phenomenon at gas-liquid interfaces.
• Anomalous transparency has potential implications for understanding infrasound propagation in natural environments.
• The findings contribute to the physics of wave propagation across strongly contrasting media.