It’s something unusual that you don’t hear your surroundings when you yawn or stretch to the breaking point. Ever wondered, why we turn a deaf ear during these stretches?
A little about the human ear
How it works?
Human ear works by amplifying the sound waves that reaches the eardrum through the ear canal. The eardrum then mechanically vibrates the three tiny bones of the ears, Malleus, Incus and Stapes. The Stapes then finally transfers this mechanical energy into the Cochlea, which is filled with a fluid called Endolymph, which when comes in contacts with the hair cells, produce the impulses that are interpreted by the brain as sound.
Eustachian tube is more like a pressure regulator that prevents your ears from popping out. One end of this tube is found between the eardrum and the cochlea, and the other end behind the nasal cavity (Nasopharynx), the uppermost part of the pharynx. Whenever, the pressure changes in your ears, this tube opens and balances the pressure. This tube is normally closed all the time and opens when you chew something, yawn, stretch or when there is a necessity to balance the pressure (when you travel in an airplane).
Why no sounds?
The reason why we don’t hear any external sound while yawning is that, when the Eustachian tube is opened, the source of the sound is now actually two – The ear canal and the Eustachian tube. The sound through the Eustachian tube fills the middle ear, which thereby also reduces the ability to amplify the sound from the ear canal. This is the reason, why we hear our internal sounds more, when we yawn or stretch. This opening of the tube is just temporary while yawning, stretching, and a few people develop the ability to open it voluntarily.
The next time you click your ear to hear your own voice, you should understand that you are actually opening you Eustachian tubes.