  A number of qualitative comparisons of experimental results on unidirectional
freak wave generation in a hydrodynamic laboratory are presented in this paper.
A nonlinear dispersive type of wave equation, the nonlinear Schr\"{o}dinger
equation, is chosen as the theoretical model. A family of exact solutions of
this equation the so-called Soliton on Finite Background describing
modulational instability phenomenon is implemented in the experiments. It is
observed that all experimental results show an amplitude increase according to
the phenomenon. Both the carrier wave frequency and the modulation period are
preserved during the wave propagation. As predicted by the theoretical model, a
phase singularity is also observed in the experiments. Due to frequency
downshift phenomenon, the experimental signal and spectrum lose their symmetric
property. Another qualitative comparison indicates that the Wessel curves for
the experimental results are the perturbed version of the theoretical ones.
