Calculations are presented of the unsteady flow and noise radiation of high speed circular and rectangular jets. The computations are performed on parallel computers. The simulations use both a traditional LES approach as well as the nonlinear disturbance equations. The formulation and numerical approach are described and the use of a PC cluster for the computations is discussed. The effect on the simultations of several parameters in the numerical method and turbulence model are discussed. Calculations of the jet flow field including the instantaneous and mean velocities are given. Predictions of the radiated noise are based on both a direct calculation and the Kirchhoff method. Comparisons are made with experimental measurements. For the rectangular jets considered the azimuthal asymmetry in the radiated noise field is described.