Hi, everybody. I am a comparative（比较的） anatomist. And a comparative anatomist is someone who studies the structure of the body of lots of different animals. And my favorite animals are whales. And I like to study whales because they're so interesting. They've adapted（使适应） to a unique（唯一的） environment of living in the water.

  And what I'm going to tell you about is how whales make（使） sounds by basically（基本上） farting with their face. Now, you know that they do this farting thing with their blowhole（喷水孔）. They blow out air like that. But they also use air in lots of other ways. They use it for sound production, which is what I'm going to focus on. But I also study other things they do with air, like how they keep it out of their bloodstream（血流） so that they don't get bubbles, which is what happens to human scuba（水肺） divers when they dive（跳水） and they get decompression sickness.

  But what I'd like to do is start with the story of how these animals make these farting noises. And that story begins with understanding how hard it is to look at whales because they live underwater and they're really big. So they're hard animals to study. And just in this picture, you see that animal in the middle? That's a baby whale, and it's already the size of a bus. When you look at whales, you have to start with the top of their head because their nose is on the top of their head.

  It's kind of like a built-in snorkel. And they breathe through that because their mammals（哺乳动物） and mammals（哺乳动物） breathe air. And their nose can actually be open and closed, kind of as if you were to pitch（倾斜） it like this. So you can see it's open in the bottom frame there where the red arrows（箭） are. But not all whales have two nostrils（鼻孔）. Whales includes the groups of dolphins and porpoises（海豚）.

  And the dolphins and porpoises, the small whales, have only one nostril on the top of their head. And they open and close that nostril by taking what is essentially（ 本质上） an upper（上面的） lip, like this, and turning it back over their nose, like this. That's how they open and close their nose. So when they make sounds, what they're basically doing is a raspberry, like... which is kind of like a fart, right? Or up in New York, we call it a Bronx cheer（ 欢呼）.

  And the way they do that is by taking that big fatty（脂肪的） structure of a big fat lip, which as you can see here in this picture, which is a cut through the middle of a dolphin's head, that big fat lip is that big yellow portion（部分） there, and they roll it back and forth（向前） over the top of their nose so that they vibrate（使颤动） it, kind of like when you let the air out of a balloon（气球） and it makes（使） that weird（怪异的） vibration sound.