Abstract: Superfluid ⁴He is a special fluid, it shows the features of quantum fluid, The study of propagation of sound in superfluid ⁴He is a important aspect of development of quantum hydrodynamics. This study provides a simple and powerful approach to research the variaty of complex problems in condensed state physics, e.g. phonon, roton and other elemental excitations. This is also a evidence of the ability of acoustical waves as a important method for studying the properties of materials.
This paper is a review of researches about sound in superfluid ⁴He at recent years.