Comparisons show good agreement between empirical and theoretical relations describing finite amplitude distortion for both plane and spherical waves. Magnitudes of the harmonic components of pressure in an originally sinusoidal spherical wave can be described in terms of a parametre called distortion factor which is a simple function of wavelength distance from the source and the source intensity. Evidence for the existence of a limiting acoustic pressure both for plane and spherical waves will be reviewed and useful interpretations of this limiting pressure will be offered.