Sound waves (normally longitudinal) demonstrated transverse with spin-orbit interactions coupling between two types of angular momentum

https://www.cityu.edu.hk/research/stories/2021/12/09/cityu-physicists-discovered-special-transverse-sound-wave

"carries both spin and orbital angular momentum like light does...shattering scientists’ previous beliefs about the sound wave, opening an avenue to the development of novel applications in acoustic communications, acoustic sensing and imaging... requires shear force... synthetic shear force may arise if the air is discretised into “meta-atoms”, i.e. volumetric air confined in small resonators with size much smaller than the wavelength"