Supraglottic web

Laryngomalacia (literally, "soft larynx") is the most common cause of chronic stridor in infancy, in which the soft, immature cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction. It can also be seen in older patients, especially those with neuromuscular conditions resulting in weakness of the muscles of the throat. [Source: Wikipedia ]