Rales are additional sounds to respiratory sounds, due to lesions such as tracheobronchial or luminal partial obstruction; depending on the nature of the sound, they can be divided into dry rales and wet rales, and dry rales are generally divided into snoring sounds and whistling sounds; wet rales have coarse, medium and fine sounds, and twisted sounds and fine wet rales are similar in nature, which are sometimes difficult to distinguish. Dry rales are seen in inflammation, spasm and luminal narrowing of tracheobronchial tubes; bilateral extensive dry rales are seen in bronchial asthma, chronic bronchitis, cardiogenic asthma, hay fever, cotton dust lung, etc. Pathogenesis Dry rales are a long-lasting respiratory sound that is produced by turbulent airflow during inhalation or exhalation due to narrowing or incomplete obstruction of the trachea, bronchi or fine bronchi. The pathological basis is inflammation causing mucosal congestion and edema, increased secretion, spasm of bronchial smooth muscle, obstruction by intraluminal foreign bodies, tumors, and compression of airways by enlarged lymphatic or mediastinal objects. The pathological basis for its occurrence is inflammation of the trachea and bronchial walls, increased mucosal congestion and swelling of secretions, and spasm of bronchial smooth muscle; intraluminal tumor invasion, partial obstruction by foreign bodies or secretions; or narrowing of the walls by compression of enlarged lymph nodes, etc. Characteristics: High tone, musical, long duration, can be heard in both inspiration and expiration, but is obvious in expiration, the emphasis, nature and location of the rales are variable, and the number can increase or decrease significantly within an instant. Dry rales occurring in the airway can sometimes be heard without a stethoscope and are called stridor.