Wheezing is a whistling sound that happens when you breathe because of narrowed airways. It is more audible when exhaling compared to inhaling. Wheezing can be a common symptom during a cough, codl or viral infection in the respiratory tract. It can also be caused by asthma, bronchitis and Chronic Obstructive Pulmonary Disease like emphysema. When wheezing is experienced it is best to see a doctor to determine its cause. Wheezing can only be treated based on its cause.