At critical incidence, the critically refracted longitudinal (L_CR) wave propagating in the subsurface domain of a solid specimen can be used in numerous non-destructive testing (NDT) applications, such as characterization of surface geometric aspects or structural subsurface properties of materials, like residual stress measurement. Generally speaking, L_CR wave has bigger penetration depth, which may change with driven frequency and incident angle. This communication paper deals with the study of L_CR beam profile using numerical tools based on Finite Element (FE) method. The simulations are performed in time and frequency domain in the case of elastic, homogenous and isotropic material. For the frequency simulations, Fourier transform is applied to separate the different spectrum components. The FE results are compared to the experimental results for different frequency and incidence angle configurations.