What happens in the ear when we yawn?
Have you noticed, if it happens that you yawn while people are talking to you, it seems like momentarily you can’t hear them. But why does this happen?
Sound is vibration of air molecules. When a sound is picked up by ear, the air in the ear canal causes the eardrum to vibrate. This vibration is conveyed further into the ear and the nerve signals send it to the brain.
The eardrum can vibrate freely only if the pressure on both sides of it is similar. The pressure outside the eardrum, at the entrance of the ear, is the atmospheric pressure, but in middle ear the pressure drops over time because the air molecules are gradually absorbed by blood flowing through the tissue.
The Eustachian tube that connects the throat with the middle ear is normally closed. But when we yawn or swallow, the tube opens in a second, so that the pressure in the middle ear is equal. One of the muscles that helps to open the Eustachian tube is the tensor tympani. When this little muscle is stretched, the eardrum and the other parts of the hearing apparatus do not vibrate as normally, thus the hearing is weakened as long as the yawning lasts.
Source: Illustrated Science