Measurements have been made on the critical pressurepcrequired to cause gas flow from a capillary into liquid in the presence of sound. It is found thatpcincreases as the square of the sonic amplitude. Results are explained in terms of acoustic radiation pressure exerted on the meniscus. Specifically, it is deduced that radial vibration of an emerging hemispherical meniscus with average (peak) displacement amplitude ξ0causes it to be subjected to the excess time‐averaged pressure(ρ0ω2ξ02/4); here, ω is the angular frequency and ρ0the liquid density.