laryngeal sac

an inflatable “pouch”, or often a pair of pouches, that are generally located ventral to the larynx in many mammals, particularly in primates (but not in humans), hooved mammals (e.g., reindeer, horses, antelopes), and cetaceans. The functions of laryngeal sacs are not completely understood. Like the vocal sacs of frogs, laryngeal sacs may amplify calls but in some species, they may assist extended, rapid vocalizations by acting as air reservoirs.