Lung auscultation sounds commonly include normal respiratory sounds as well as abnormal respiratory sounds such as dry rales, wet rales, pleural friction sounds, etc. 1. Normal and abnormal breath sounds: These include normal or abnormal tracheal breath sounds, bronchial breath sounds, alveolar breath sounds, bronchoalveolar breath sounds and so on. Abnormal breath sounds are mostly caused by restricted thoracic movement, tracheal and bronchial obstruction. 2. Dry rales: Dry rales are the sounds produced by inhalation or exhalation when the trachea, bronchus, or fine bronchus is narrowed or partially obstructed, which are mostly seen in bronchial asthma, chronic bronchitis and other diseases. 3. Wet rales: also known as blistering sounds, including large blisters, medium blisters, small blisters. They usually appear in acute pulmonary edema, pneumonia, bronchiectasis and other diseases. Large vesicular sounds usually appear in the early stage of inspiration, and medium and small vesicular sounds usually appear in the middle and late stages of respiration. 4. Pleural friction: When the pleural surface becomes rough due to inflammation and cellulose exudation, pleural friction will appear with breathing. It is common in fibrinous pleurisy, pulmonary infarction, pleural tumor and other diseases.