Now the melon is kind of a large sac-like pouch made up of fat tissue.And this fat tissue has some rather fascinating acoustical properties.Most of the fat that you find in an animal's body is used for storing energy, but this fat that you find in dolphins, and only in the melon and around the lower jaw this fat is very different, very rich in oil and it turns out it has a very different purpose as well. So, how do the dolphin's clicks get transmitted from its air-filled nasal sacs into the ocean water?Because given the difference in density between the air in the nasal cavity and the seawater, we'd expect those sounds to just kinda go bouncing around inside the dolphin's head!Which would do it no good at all if it's going to navigate, it needs those sounds to be broadcast and bounce back from objects in its path.Well, turns out dolphins have a structure in their foreheads, just in front of their nasal sacs, called a melon. What's gonna happen then?Well, some of the energy is gonna be reflected back, and some of it's gonna be transmitted into the second medium.An-an-and if the two media have really different densities-like air and water- then most of the energy is gonna be reflected back very little of it will keep going -uh, get transmitted into the new medium.I mean, just think how little noise from the outside world actually reaches you when your head's underwater. We've been talking about how sea animals find their way underwater how they navigate, and this brings up an interesting puzzle and one I'm sure you'll all enjoy I mean everybody loves dolphins, right?And dolphins well, they actually produce two types of sounds, um, one being the vocalizations you're probably all familiar with, which they emit through their blowholes.But the one we're concerned with today is the rapid clicks that they use for echolocation, so they can sense what is around them these sounds, it's been found, are produced in the air-filled nasal sacs of the dolphin.And the puzzle is: How do the click sounds get transmitted into water? It's not as easy as it might seem.You see, the denser the medium, the faster sound travels.So.sound travels faster through water than it does through air.So what happens when a sound wave um, okay, you've got a sound wave traveling merrily along through one medium, when suddenly it hits a different medium. NARRATOR:Listen to part of a lecture in a marine biology class.
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