What is the cause of a whisitling noise with bronchitis?

Tight airway: In children with bronchitis the whistling may be wheezing or it may be for mucous in the upper airway and the air moving by is making a whistling noise because the airway is tighter.

Wheezing: Many patients who have bronchitis will experience "wheezing", which is caused by bronchospasm. Bronchospasms are spasms of the airways that can cause a whistling sound, particularly heard when someone is breathing out. Oftentimes, a medication called "albuterol" is prescribed to alleviate the wheezing caused by the bronchospasms so as to make breathing easier.