The occlusion effect refers to the altered perception of one's own voice when the ear canal is fully or partially obstructed. While the loudness increase due to body conducted sounds requires an assessment by psychoacoustic methods, the ratio of sound pressure inside the ear canal with occluded versus open ear canal for the same internally generated signal can be measured physically. This paper aims at better understanding the occlusion effect from a physical viewpoint and at determining the influence of different physical factors on the own voice perception, introducing a simple and intuitively understandable model for this phenomenon. Based on this model, the dependency of the occlusion effect on (i) the geometries of the individual ear canal and the vent, (ii) the insertion depth of the occluding object and (iii) vocalization are discussed.