A dolphin hunting in murky river water, or navigating total darkness at depth, doesn’t rely on its eyes. It relies on an organ that works less like a camera and more like a sonar — built entirely around sound.

Dolphins don’t produce their echolocation clicks the way most animals make sound. Their vocal cords are essentially non-functional. Instead, the clicks originate in the nasal passages, at a pair of structures known as phonic lips. By forcing air recycled from internal nasal sacs past these lips, a dolphin sets tissue vibrating and produces a sharp click — without ever releasing that air into the water.

Each click isn’t simply radiated outward. It’s shaped by the melon, a fatty organ in the dolphin’s forehead that works as an acoustic lens, focusing sound into a narrow, directional beam aimed exactly where the animal is looking.

Echolocation clicks sit in a range far above what the human ear can register — researchers have recorded them anywhere from the tens of kilohertz up past a hundred, with each click lasting only tens to a couple of hundred microseconds. Higher frequencies mean shorter wavelengths, and shorter wavelengths mean finer resolution: a dolphin can pick out small, precise details most sonar can’t.

The returning echo doesn’t reach the dolphin through anything resembling a human ear. It’s picked up largely through the lower jaw, filled with specialized fatty tissue that channels the vibration to the inner ear. From the tiny delay between the outgoing click and the returning echo, the dolphin’s brain reconstructs distance, size, shape — and, researchers believe, even something about what an object is made of.