Functions of diffraction correction and analytical solutions in   nonlinear acoustic measurement
  This paper presents an analytical formulation for correcting the diffraction associated to the second harmonic of an acoustic wave, more compact than that usually used. This new formulation, resulting from an approximation of the correction applied to fundamental, makes it possible to obtain simple solutions for the second harmonic of the average acoustic pressure, but sufficiently precise for measuring the parameter of nonlinearity B/A in a finite amplitude method. Comparison with other expressions requiring numerical integration, show the solutions are precise in the nearfield. 
Laurent Alli\`es (LIEN), D. Kourtiche (LIEN), M. Nadi (LIEN)