The Earth is surrounded by an atmosphere that gets thinner and thinner with increasing altitude from the ground, and the pressure gets lower and lower. At sea level, one atmosphere is equivalent to 101.32 kPa (760 mmHg) of pressure. Generally speaking, at an altitude of 5,500 meters above sea level, the air pressure is reduced by about half; at an altitude of 11,000 meters above sea level, it is only 1/4 of an atmosphere. When we rise to 36-59 meters above sea level, the outside air pressure decreases by 0.4–00.7 kPa (3–5 mmHg), at which time we start to feel a sense of fullness in our ears, because the pressure inside the tympanic chamber is still 1 atmosphere, which is larger than that outside, and due to this pressure difference, the tympanic membrane is slightly convex. When the plane rises to 150 meters above sea level, the air pressure decreases by 2.0 kPa (15 mmHg). At this point, we will suddenly feel a “ta” sound in our ears, and the feeling of fullness in our ears will disappear at once. This is because the gas in the tympanic chamber breaks open the nasopharyngeal opening of the eustachian tube and escapes into the nasopharynx. If the aircraft continues to rise and the air pressure continues to fall, the above situation will occur periodically. However, the pressure difference required each time will no longer be 2.0 kPa (15 mmHg), but lower, because the outside air becomes progressively thinner and the air inside the drum chamber is more easily expelled. Until the air pressure inside the drum chamber is only 0.48 kPa (3.6 mmHg), there is no more force to flush the pharyngeal tube. When the aircraft is descending, the situation is the opposite. At this time, the external air pressure gradually rises, and the tympanic chamber is at a relatively low pressure. However, due to the one-way valve of the eustachian tube, the outside air is not easy to enter the drum chamber, so the only way to obtain the balance of air pressure inside and outside the drum chamber is to rely on the opening action of the pharyngeal opening of the eustachian tube when swallowing. When the aircraft descends slowly, the natural swallowing action is sufficient to balance the pressure inside and outside the tympanic chamber. However, during rapid descent or dive, the situation is different, when the external air pressure rises sharply. If the air pressure in the tympanic chamber is 8 kPa (60 mmHg) lower than the air pressure, the patient will feel ear pain, tinnitus and even vertigo; if the air pressure is 13.3 – 20.0 kPa (100 – 150 mmHg) lower, the tympanic membrane will rupture, and then suddenly hear a “boom” sound, like thunder in the ear. The pain is unbearable. This is followed by severe vertigo, tinnitus, bleeding from the ear canal, and even fainting, when not only the tympanic membrane ruptures, but also the mucous membrane of the tympanic chamber is damaged, resulting in “aviation otitis media”. Even if you are not in an airplane, the atmospheric pressure on the ground does not remain constant permanently and can fluctuate. However, the fluctuation range is generally no more than 2.7 – 4.0 kPa (20 – 30 mmHg), and this change is slow. In normal people, the eustachian tube opens regularly enough to produce a regulating effect, so there is no discomfort. In the case of diseases such as the flu, the eustachian tube becomes momentarily impaired in regulating air pressure, and a small negative pressure may appear in the tympanic chamber. At this time, the tympanic membrane becomes mildly invaginated, and the patient feels symptoms such as stuffy ears and tinnitus. Once the cold is cured, the tinnitus symptoms will disappear.