Other than the clicks made by dolphins and other toothed whales, whale noises remain mysterious. Various baleen whales moan, but only the males of a few species really sing well: humpback, minke, some blue and fin whales, and the more distantly related bowhead whales. These creatures are often huge and protected, so they aren’t the easiest animals to observe (or dissect). Nevertheless, very recent discoveries have been made.
Dissection of the first four species has revealed folds – vocal cords – in their voice boxes. Like us, the cords probably vibrate as air moves over them, producing sound.
Human vocal cords simply restrict the airflow like sliding doors, while those of a whale are more complex structures that join onto special sacs that line its throat. It has been suggested that, when underwater, air can be moved between these sacs and the lungs, allowing whales to sing without losing air.