Sputum

Generally, the sputum sound is generated by the vibration of the thicker secretions in the main trachea. It is a special wet rales that can be heard during inhalation and exhalation, but is mainly inspiratory and can be transmitted to both lungs. Therefore, it can be heard in both lungs (not really produced by the lungs). Once the secretions are eliminated or sucked out, the sputum sounds weaken or disappear.