Baleen whales and toothed whales each have a unique way of vocalizing. Only baleen whales produce long sequences of deep sounds known as whale songs. They have a larynx, an organ at the top of the trachea, which may be involved in sound production. Researchers are unclear about the organ’s role in the songs as whale larynxes are unlike those of humans, which have vocal chords. Toothed whales, on the other hand, rely on sequences of high-pitched clicks and whistles for both echo location and communication with their mates. Their phonic lips, a structure analogous to human nasal passages, press together when air is forced through them, vibrating the surrounding tissue. The sound waves then penetrate an oily organ in the whale’s head, called the “melon”, where they are focused into a beam of sound. When this beam strikes a fish, the seabed, or another object, the sound is reflected back to the whale as an echo. Toothed whales can thus locate prey and navigate in total darkness. However, during their long, deep dives, toothed whales cannot inhale air every time they want to produce a sound. So they collect it in a sac at the back of their head and reuse it.