What is the sound produced during wheezing caused by?

Wheezing is a high-pitched sound that occurs when airflow is obstructed, particularly during exhalation. This sound is primarily produced when there is narrowing of the air passages in the lower airway, which includes the bronchi and bronchioles. Conditions such as asthma, chronic obstructive pulmonary disease (COPD), or allergic reactions can cause inflammation and bronchoconstriction, leading to this narrowing. As the air struggles to pass through these constricted spaces, it creates the characteristic wheezing noise.

While narrowing in the upper airway can produce different types of sounds, such as stridor, it does not lead to wheezing specifically. Similarly, increased lung capacity and fluid accumulation in the pleural cavity are not associated with the wheezing sound. Thus, the underlying cause of wheezing is indeed the narrowing of structures within the lower airways.