Rales cannot be heard in the lungs of normal people. The rales that can be heard in the lungs include dry rales and wet rales. Dry rales are mainly caused by narrowing of the airways, including bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, and airway narrowing caused by tumors. If it is wet rales, also called alveolar sounds, is the air passing through the local exudative lesions produced by the air over water sound, air over water sound of the alveolar sound is called wet rales. Wet rales are divided into large alveolar sounds, medium alveolar sounds, small alveolar sounds, also called large wet rales, coarse wet rales and fine wet rales. The presence of a variety of wet rales indicates a localized infectious lesion and requires chest CT and fiberoptic bronchoscopy to understand the specifics of the infection. Dry rales are mainly due to airway narrowing disease and can disappear quickly with anti-inflammatory, wheezing and cough suppressant treatments. In conclusion, dry rales that disappear easily and wet rales that do not disappear easily are indicative of airway narrowing or infectious lesions in the lungs.