Visualization of the wave train development in 2D and 3D supersonic boundary layer at Mach number M=2.0 via hot-wire measurements is presented. The model of a smooth swept wing and the model of a flat plate with roughness elements were used. Artificial disturbances in the boundary layer were excited by periodical glow discharge. The spatial amplitude-phase disturbance distributions are presented. In the case of a swept wing the linear development of disturbances at frequencies 10 and 20 kHz is shown. In the case of a flat plate with stickers it was found out that both types of nonlinear interaction (subharmonic resonance and oblique breakdown) in the physical space are not distinguish at Mach 2.