What sound is characterized by a whistling noise during expiration?

The sound characterized by a whistling noise during expiration is wheezing. Wheezing occurs when air moves through narrowed airways, which can happen due to inflammation, bronchospasm, or increased secretions in conditions like asthma or bronchitis. The whistling or musical quality of the sound is typically more pronounced during expiration because the airways are often more constricted during this phase of breathing.

Rales, also known as crackles, are a different type of sound that suggests fluid in the lungs and are usually heard during inspiration. Ronchi are often described as low-pitched, snoring sounds that indicate obstruction or secretions, but they do not have the high-pitched whistling quality of wheezing. Stridor, on the other hand, is a high-pitched sound typically heard during inspiration and is associated with upper airway obstruction. Hence, wheezing is the correct answer as it specifically relates to the described whistling noise during expiration.