A Deeper Analogy between Electromagnetism and Acoustics

Based on an assumption of that the cosmological constant term in Einstein field equation can be modeled as a material medium, we propose the concept of cosmological acoustic wave (CAW). In the process, we will see: 1) By the dual framework of electromagnetic theory, it is possible to consider some implications of CAW, such as, the acoustic charge quantization, the unit spin of phonon, the mechanical meaning of acoustic current and the acoustic radiation. It shows that, besides the transverse and longitudinal waves, there should be a sort of adjoint waves without contribution to energy flows. 2) The electromagnetic-acoustic equations are applied in homogeneous and isotropic material media, which can help us to describe uniformly the electromagnetic-acoustic phenomena. 3) It will be verified that, the acoustic interaction is identical to the gravitational one in classical physics. This decision suggests the so-called gravitational wave could be indeed understood as an acoustic radiation in cosmological space.