[Toutouxc]

But why would there be elevated pressure? Headphones can't pump air into your ear, they can only make it wiggle back and forth. ANC headphones use the same speaker that normally plays your music and just mix the noise-cancelling sound into your music, nothing else. When you aren't playing any music, outside noise makes the air wiggle back and forth and the membrane of the speaker makes the air wiggle back and forth in the opposite phase. These movements destructively interfere, resulting in the air staying still.

BTW where in the video do they mention elevated pressure?