Fig. 4From: Far-field approximations to the derivatives of Green’s function for the Ffowcs Williams and Hawkings equationSound pressures correspond to (a) the second term and (b) the third term at different observer distances S. The sound pressures corresponding to the second term are computed by using the Eqs. (27) and (30), respectively. The sound pressures corresponding to the third term are computed by using the Eqs. (28) and (31), respectively. The sound pressures at the non-time dimensional time t=120 are plotted. The convecting Mach number of the vortex is Ma=0.2 and the observers are distributed along the line with θ=0∘Back to article page