By: Nina He

If you’re a fan of sea animals, you have probably heard of mermaids. These mythical creatures are known for their human body and a fishtail replacing their legs. And they are also known for their beautiful singing voices. But how does a mermaid share her songs with a friend underwater?

There are lots of theories, and one of them is that mermaids had developed ears like sea creatures. But we have to start on how we hear out of the water first.

For humans, when an object makes a sound, it vibrates, causing sound waves. When the sound waves reach someone’s ears, it goes into the brain, which defines the sound. Above the water, you can hear where a sound is coming from. For example, if a sound comes from your left, your left ear will pick up the sound waves first before it reaches your right ear. Under the sea, however, it’s a whole different story.

Since water enters your ears, sound waves have to vibrate against the skull for you to hear. But humans are more attuned to hearing things on land than in the water, so the sound isn’t as clear as it would be if it were above the water. It’s also hard to detect where a sound is coming from since sound waves move faster in the water than in air, so the sound hits both of your ears at the same time.

Colleen Reichmuth, a biologist who studies marine life at the University of California, Santa Cruz, said that whales, dolphins, and seals have very similar hearing to humans. But theirs are more…updated on underwater hearing and “talking.”

Some underwater animals have special lower jaws with fat that gives sound to the ear. The fat has a “special chemical composition that makes it really suitable for transmitting acoustic waves,” says Laela Sayigh, a marine biologist at Hampshire College in Amherst, Mass. and Woods Hole Oceanographic Institution in Massachusetts.

Maybe mermaids have that special jaw that just doesn’t look as obvious on them.

Mermaids might’ve also developed a special skill that helped them sing lengthy songs without going up to the surface for air. Like mermaids, whales, seals, and dolphins have several pitches, which can make a “song.” But instead of blowing out air when you let out a noise, like humans do, these sea creatures can make noises without letting out any air.

Joy Reidenburg, who studies animal anatomy at the Icahn School of Medicine at Mount Sinai in New York City, said, “Underwater, air is a precious commodity.”

Whenever mermaids have updated ears on underwater hearing or don’t let out air when they sing, they obviously have their secret “mermaid” ways.