Which of the following sounds is typically associated with obstruction or irritation of the upper airway?

Stridor is a high-pitched, wheezing sound that occurs when there is an obstruction or narrowing of the upper airway, particularly in the larynx or trachea. This sound is often audible without a stethoscope and is mainly associated with conditions such as croup, epiglottitis, or anaphylaxis, where the airway is compromised.

In contrast, rales (or crackles) are typically heard when there is fluid in the lungs, indicating alveolar or bronchial issues rather than upper airway obstruction. Rhonchi are lower-pitched sounds that can indicate mucus in the larger airways, suggesting bronchial irritation or obstruction in the lower airways rather than the upper airway. Wheezing is a musical or whistling sound associated primarily with lower airway constriction typically seen in conditions like asthma or bronchospasm.

Therefore, stridor stands out as the sound specifically linked to upper airway obstruction, making it the correct choice in this context.