Ear bulbs are the scientific instruments used by doctors to clear the ear canal from possible infections. When we catch cold, the mucous membranes in the nose and throat swell up and generate much more fluid than usual. Often the mucous membranes in the tubes will produce fluid too, but they usually swell up also. The swelling blocks the tubes and allows fluid to accumulate in the middle ear.
This fluid blocks high-pitched sounds by absorbing the sound energy. Even worse, since bacteria can and it usually does enter the middle ear through the tubes, if the fluid can't be kept out bacteria will start growing in it, and this inflames the eardrum and increases the pressure inside the ear even more. The pain comes both from the pressure increase pushing on the drum and from the inflamed drum itself.
When children are examined to see if they have a middle ear infection it is always looked to see if the eardrum is moving, using a rubber bulb attached to our otoscope. The doctor can see the eardrum move as he blows air into the ear with the ear bulb.
