Often Occlusion is also referred to as Occlusion Effect. It is the phenomenon resulting from wearing solid earplugs, hearing aids or some IEMs that makes the wearer’s voice sound hollow and boomy to themselves, i.e., a voice-in-a-barrel effect. The earplugs block the ear canal resulting in a sound similar to sticking a finger in each ear and talking. This closure effect also produces louder sounds to the wearer since the ear canal blockage allows additional sound pressure to build up (rather than escape out the open ear canal) and be conducted to the inner ear. This is easily demonstrated by pronouncing and sustaining the word “fee,” then sticking your fingers in your ears and notice how much louder it sounds (oh go ahead, no one is looking).