Equalizing ear pressure gradient when diving is very important in order to avoid pain and sometimes lasting damage to the ear. The key to safe equalizing is opening the normally closed eustachian tubes, allowing higher-pressure air from the throat to enter the middle ears. The most known method to equalize the ears is by pinching the nose and blowing gently. This method is called the Valsalva Maneuver, it essentially forces the tubes open with air pressure.
But the Valsalva maneuver has three problems:
Divers who experience difficulty equalizing may find it helpful to master some alternative techniques.
Toynbee Maneuver. With nostrils pinched or blocked against the mask skirt, swallow. Swallowing pulls open the eustachian tubes while the movement of the tongue, compresses air against them.
Lowry Technique. A combination of Valsalva and Toynbee: while closing nostrils, blow and swallow at the same time.
Edmonds Technique. Do a Valsalva Maneuver, while tensing the soft palate and throat muscles and pushing the jaw forward.
Frenzel Maneuver. Close nostrils, back of the throat as if straining to lift a weight. Then make the sound of the letter «K.» This forces the back the tongue upwards, compressing air against the openings of the eustachian tubes.
Voluntary Tubal Opening. This requires a lot of practice to master. Tense the muscles of the soft palate and the throat while pushing the jaw forward and down as if starting to yawn. These muscles pull the eustachian tubes open and some divers can learn to control those muscles and hold their tubes open for continuous equalization.