system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I lose my hearing when I yawn?
gpt
The reply above is mostly nonsense. 

When you yawn, a reflex that often accompanies is the flexing of the tensor tympani muscle. This tightens the tympanic membrane (ear drum) and as a result dampens sound/vibrations being conducted through the mechanical parts of your ear. This creates the muffled and quietened sound that you might associate with a 'loss of hearing.' 

The flexing of the tensor veli palatini often occurs during yawning also, however this does not have any effect on your hearing under normal circumstances. In the case of significant pressure differences between your middle ear and the external environment, this contraction can facilitate the  opening of the pharyngotympanic/eustachian tubes, and as a result, equalisation of pressure and restoration of normal hearing.