ELI5 Yawning - why does it muffle your hearing?

It's a myth that we yawn to intake more oxygen - so why do we yawn? Why is hearing reduced when you yawn? Why does yawning pop your ears on a plane? Why are yawns contagious?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community as always and in particular the following users whose questions and comments formed the basis of this discussion: provin1327, torsionfree, rob3110, rhapsodysparkles, wingfoot6, fendrbud, xucker, halikan & duzzeno To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]