This paper presents shielding effectiveness measurements of board level shielding materials using the dual vibrating intrinsic reverberation chamber. Various sized board level shielding materials mounted on specifically designed printed circuit boards are examined in order to evaluate the shielding performance in each case. Experiments presented in this paper aim to investigate the effect of appropriate mounting of the test samples before performing a shielding effectiveness measurement, as well as to compare the shielding mechanisms of these kinds of materials. Additionally, based on the obtained measurement data, a discussion on the definition of shielding effectiveness and the effect of the aperture on the coupling of the two cavities of the dual VIRC is briefly conducted.