A study investigated numerically the case when an incident shock wave propagated in a duct. The computational domain was two-dimensional, and computations were performed using a compressible inviscid flow model, solving the Euler equations. Computations were conducted for compressible flows inside the two-dimensional duct. In all computations, the duct was filled with air, while different gases filled the cavity. The same initial pressure prevailed in the duct and in the cavity.