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Diver clearing ears Section of the human ear, the Eustachian tube is shown in colour. Ear clearing, clearing the ears or equalization is any of various maneuvers to equalize the pressure in the middle ear with 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 than the outside pressure.
The Frenzel Maneuver is named after Hermann Frenzel (German ear, nose and throat physician and Luftwaffe commander). The maneuver was developed in 1938 and originally was taught to dive bomber pilots during World War II. The maneuver is used to equalize pressure in the middle ear.
Variations of the maneuver can be used either in medical examination as a test of cardiac function and autonomic nervous control of the heart (because the maneuver raises the pressure in the lungs), or to clear the ears and sinuses (that is, to equalize pressure between them) when ambient pressure changes, as in scuba diving, hyperbaric oxygen ...
The Valsalva maneuver can also help to temporarily unblock or equalize the pressure in the middle ear. To do this, simply pinch your nostrils closed with one hand and blow air through your nose.
Middle ear barotrauma (MEBT), also known to underwater divers as ear squeeze and reverse ear squeeze, is an injury caused by a difference in pressure between the external ear canal and the middle ear. It is common in underwater divers and usually occurs when the diver does not equalise sufficiently during descent or, less commonly, on ascent.
The pressure in the middle ear not equalizing with external (ambient) pressure, usually due to failure to clear the Eustachian tube. [31] Ears can be equalized early and often during the descent, before the stretching is painful. The diver can check if the ears will clear on the surface as a precondition for diving. [31]
Normally, the air pressure in the ear canal is the same as ambient pressure. Also, under normal conditions, the air pressure in the middle ear is approximately the same as ambient pressure since the eustachian tube opens periodically to ventilate the middle ear and equalize pressure. In a healthy individual, the maximum sound is transmitted ...
Free field reciprocity calibration (to give the free-field response, as opposed to the pressure response of the microphone) follows the same principles and roughly the same method as pressure reciprocity calibration, but in practice is much more difficult to implement. As such it is more usual to perform reciprocity calibration in an acoustical ...