Abstract: The analysis of acoustic fields is usually based on the well-known mathematics of second order partial differential equations called wave equations. The author explores the duality and symmetry of linear fluid mechanics and develops two distinct equations of acoustics on the basis of a causal approach to local small-scale phenomena. Wavefields that are solutions of these equations have different composition, the spherical pressure wave being only a specific components of one of them. A new perspective on the phenomena, presented in this paper, endeavours to establish the right equilibrium between mathematical formalism and physical phenomenology in the perception of acoustic wavefields.