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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.
Because the glottis is closed, air cannot return to the lungs. The tongue creates an airtight seal against the upper teeth or in the rear of the mouth, preventing air from escaping. Because there is nowhere else for the air to go, it enters the eustachian tubes and the middle ear, equalizing the pressure. [4]
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 first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term Fletcher–Munson used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
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.
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 ...
Under normal circumstances, the human Eustachian tube is closed, but it can open to let a small amount of air through to prevent damage by equalizing pressure between the middle ear and the atmosphere. Pressure differences cause temporary conductive hearing loss by decreased motion of the tympanic membrane and ossicles of the ear. [13]
The acoustic reflex (also known as the stapedius reflex, [1] stapedial reflex, [2] auditory reflex, [3] middle-ear-muscle reflex (MEM reflex, MEMR), [4] attenuation reflex, [5] cochleostapedial reflex [6] or intra-aural reflex [6]) is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.