The mechanism of wet rales is the sound produced by the rupture of blisters formed by gas passing through secretions in the respiratory tract such as exudate, sputum, blood, mucus, and pus during inspiration, so it is also called the blister sound. The sound produced by the rupture of blisters formed by gas passing through secretions such as exudate, sputum, blood, mucus and pus in the respiratory tract during inspiration is also known as the blister sound. Wet rales are additional sounds outside the respiratory sounds, intermittent and brief, often more than once in a row, more obvious during inspiration or at the end of inspiration, sometimes also in early expiration, the location is more constant, the nature is not easy to change, medium and small wet rales can exist at the same time, can be reduced or disappear after coughing. 1, coarse wet rales (coarsecrackles): also known as large blistering sounds, occurring in the trachea, the main bronchus or cavity site, mostly in the early inspiration. See in bronchiectasis, pulmonary edema, tuberculosis or lung abscess cavity. In patients who are unconscious or dying, coarse wet rales can be heard at the trachea due to the inability to expel respiratory secretions, which is called sputum sound. 2, medium wet rales (mediumcrackles): also known as medium vesicular sounds, occurring in medium-sized bronchi, mostly in the middle of inspiration, seen in bronchitis, bronchopneumonia, etc. 3, fine wet rales (finecrackles): also known as small vesicular sounds, occurring in small bronchi, mostly in the late inspiration. It is commonly seen in fine bronchitis, bronchopneumonia, pulmonary stasis and pulmonary infarction. In patients with diffuse interstitial pulmonary fibrosis, fine wet rales appear in the late inspiratory period, with a high pitch, and near the ear is rather like the sound made when tearing the nylon buckle belt, called Velcro sound. 4.Twisting sound (crepitus): It is a very fine and uniform wet rales. Mostly heard at the end of inhalation, rather like the sound made when twisting a bunch of hair with the fingers in the ear. This is due to the presence of secretions in the bronchi and alveolar walls and the mutual adhesion of closed, when inspiration by the airflow to re-inflate, issued by the high-pitched, high frequency of small burst sound. It is common in fine bronchial and alveolar inflammation or congestion, such as pulmonary bruising, early pneumonia and alveolitis. However, in normal elderly or bedridden patients, twang sounds can be heard at the base of the lungs, which may disappear after several deep breaths or coughs and are generally not clinically significant.