Near field noise is of interest when you want to get a feeling for the maximum sound levels occurring directly adjacent to your device, or when designing devices that take advantage of acoustic-flow couplings. For example, maximizing acoustic resonance at a given frequency in some combustor designs is used to enhance combustion efficiency (pulse combustors are a common example). Using a time accurate solution of the compressible Navier-Stokes equations, CFX can directly analyze near field noise and its effects upon the flow field. The CFX expression language can easily be used to calculate the near field sound pressure levels using both Equation 15–1 and Equation 15–2 and algebraic Additional Variables.