The sound we hear is a traveling oscillation of the pressure of air, but it can also occur in liquids like water. An article from Claudiu Stan, Assistant Professor in the Department of Physics, in the journal Physical Review Fluids, describes an exotic method to make very loud sounds in water, by inducing with an X-ray laser a shock wave in a microjet of water thinner than a strand of hair. This shock wave then bounced repeatedly off the jet surface, generating a travelling pattern of wave reflections. This pattern is of the loudest sounds ever produced in liquid water. Its loudness is comparable to the one made at the launch of the largest orbital rockets despite the vast difference in sizes, and the wave pattern inside liquid microjets has similar properties to the ones inside rocket jets.
This exotic phenomenon can help us study how materials and biological molecules are affected and damaged by very loud sound.
Generation of high-intensity ultrasound through shock propagation in liquid jets
G. Blaj, M. Liang, A. L. Aquila, P. R. Willmott, J. E. Koglin, R. G. Sierra, J. S. Robinson, S. Boutet and C. A. Stan., Phys. Rev. Fluids 4, 043401, 2019.