Ear Clearing refers to equalizing pressure between the middle and outer ear.
Ear Clearing in Water Training
The most frequent problem in pool training and during the first few diving sessions is ear damage (barotrauma) as a result of inability to equalize pressure between the middle and outer ear. Equalizing this pressure is also called clearing the ears, and the process is incredibly simple to master. It is possible to burst the eardrum if equalization is not done. A burst eardrum will not only damage hearing, but cold water in the middle ear will cause vertigo by chilling the inner ear. Vertigo could induce extreme nausea and vomiting. There are many ways to clear the ears; it makes the pressure in the middle ear become the same as the outside pressure, by letting air enter along the Eustachian tubes, as this does not always happen automatically when the pressure in the middle ear is lower.
Methods of Ear Clearing
The Valsalva Maneuver is the most commonly taught technique. It was created by a 17th Century physician named Antonio Maria Valsalva; it is done by pinching the nose shut and GENTLY blowing as though attempting to blow air out the nostrils. Blowing too hard can cause inner ear damage.
The Frenzel Procedure was created by a German physician named Herman Frenzel, and was used by German Stuka bomber pilots in WWII because they needed a method of hands-free equalization. It is done by placing the tongue on the roof of the mouth, as far forward as possible. While the tongue is held in place, the back of the tongue is gently moved upward. Often a "click" sound is heard internally as the tongue is moved. This action does not constrict the Eustachian tubes or over-pressurize the middle or inner ear, and it allow for use of the hands. It is the safest, most effective way for divers to equalize the pressure in he middle ear. It does, however, take practice to master.
The Toynbee method was discovered by an English physician named Joseph Toynbee. It is done by pinching the nostrils and swallowing.