In our most recent episode, we answered questions about really big animals: whales!
We covered a lot when it comes to these huge aquatic mammals but there was one big topic we didn't get to: and that's how whales communicate. We'll learn more about the sounds whales make: singing, whistles, and echolocation clicks with Amy Van Cise, a biologist at NOAA Northwest Fisheries Science Center in Seattle, Washington.
"The way whales produce sound is similar to the way that we produce sound. They have a larynx with vocal folds and push air through it and that produces sound. That's what sound is: vibrations pushing sound through the air!" Amy explained. Most of the biggest whales, baleen whales, communicate that way. That is pretty easy to understand and imagine. It's kind of like how we make and use sound!
But in addition to having a larynx, toothed whales also have another way to make sound:
"Smaller whales: dolphins, killer whales, short-finned pilot whales have larynx, but they also have echolocation," she said.
Those are clicks and whistles produced in a different system in their bodies. And they use those high frequency sounds in two different ways, to communicate, but also to "see" what's around them, without using their eyes! That's what echolocation is.
This is a little harder for us to wrap our minds around, because it's so different from how most of us know what's around us, but they send the sound out, and the way the sound travels through the water, like bouncing off a fish or another animal nearby, can give the whale a really clear picture of its surroundings.
Amy says there's another big difference in the way whales produce sound from how we humans do:
"I'd say the biggest difference between whales and humans is where they produce that sound. We produce sounds out of our mouth. But they breathe through their blow holes, so they're producing sound out of the back of their head, where we're producing sound at the front," she said.
Try to picture your voice coming out of the back of your head!
Another difference is that we humans live above water! So when we produce sound, our voices carry through the air. But whale noises are being carried through the water.
"Sound travels much faster through the water than through the air. And the other big difference is acoustic impedance; or just the fact that sound tends to dissipate quickly in the water. So it either gets absorbed in the water or it bounces off different objects in the water," Amy said.
That means that for some sounds, like the ones you and I might be able to hear, they don't always travel very far in the water. So whales use different frequencies-very high sounds or very low sounds to help the sound move better through the water. Those low frequencies can help the larger whales move sound all the way across an ocean basin!
Whale audio recordings in this episode come from the Whale Acoustics Laboratory at Scripps Institution of Oceanography and NOAA Fisheries.