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1. Acoustic Pressure

   Linked via "wave impedance"

   where $\rho_0$ is the equilibrium density, $u$ is the particle velocity, and $x$ is the spatial coordinate.
   In the context of wave impedance, acoustic pressure is intimately related to the particle velocity ($u$) through the specific acoustic impedance ($Z_{\text{ac}}$) of the medium. For plane waves propagating in an ideal fluid:
   $$ Z_{\text{ac}} = \frac{p}{u} = \rho c $$
   where $\rho$ is the [ambient dens…