Stridor
Stridor is a high-pitched sound caused by disrupted airflow. This disruption is however at the level of the larynx (voice box) or trachea (windpipe). In contrast to crackles, stridor can be heard by the patient himself without a stethoscope on inspiration (inspiratory stridor) or expiration (expiratory stridor). Also called musical breathing or extrathoracic airway obstruction, stridor is an uncommon sign of acute or chronic bronchitis that usually develops in less than 50% cases. It usually resolves when the disease regress.