This is Scientific American — 60-Second Science. I'm Christopher Intagliata.
Light doesn't travel well underwater. So dolphins and other toothed whales navigate like bats, using echolocating clicks.
"They're like lasers of sound they produce out of their forehead, and they bounce them off things the same way bats do, to interpret their environment."
Kait Frasier is an oceanographer at the Scripps Institution of Oceanography. And her studies of underwater clicks include tossing computers, worth $100,000 dollars each, over the side of a ship, into the Gulf of Mexico.
"It just feels so wrong. But a year later you go back, you send out this little ping signal, it goes, doo doo doo doo doo, and that goes out to the instrument and it drops its weights and floats to the surface. And it's this magical moment, like 'My gosh, I never thought we'd get that back.'"
The waterproof computers have underwater microphones attached. So when they float back up, they're loaded with a symphony of underwater sounds. Including more than 50 million clicks. And by the way that sample was slowed down by half, and lowered an octave.
Frasier used to comb through that audio, staring at the signals, trying to differentiate one from the other. "Yeah, more than I would like to spend my time sifting through."
So she set machine learning algorithms at the data instead... which sifted out seven distinct clicking patterns. And the algorithms were able to identify one species—called Risso's dolphin—by sound alone. The results are in the journal PLOS Computational Biology.
Traditional marine mammal surveys scan surface waters from a boat, and extrapolate from there. But this tech might offer an alternative. "Instead of going out on a boat you put this instrument out, and it does this passive acoustic listening for a year, or many years in a row, and you can use that to get better time series of these animals over a long period of time."
If it can figure out how to tease out more individual species types, this survey method might really click.
Thanks for listening for Scientific American — 60-Second Science Science. I'm Christopher Intagliata.
光在水中会衰减 。所以海豚和其他齿鲸类动物在水中用回声定位，就像蝙蝠一样 。
斯克里普斯海洋研究所的海洋学家的凯特·弗莱泽说道 。为了研究水下定位，她将几台电脑从船上投进墨西哥湾，每台电脑价值10万美元 。
“感觉不太好 。可是一年以后你再回来时，你发出这种小的砰砰信号，信号嘟嘟嘟地响，传到电脑之后，电脑就会浮出水面 。这是神奇的时刻，你会感叹“我的天哪，我从未想过还能把电脑找回来 。”
这些防水电脑装有水下麦克风 。电脑浮出水面时，里面装满了水下的各种声音 。其中有超过5000万个“滴答声” 。顺便说一下，采集到的声音样本经过了处理——速度减半，音调也降低了一个八度 。
弗莱泽以前梳理过这些音频，她盯着那些信号，试图将它们区别开来 。“是的，我很乐意花时间来仔细检查这些音频 。”
所以，弗莱泽用机器学习算法来处理这些数据，筛选出7种不同的“滴答声” 。这一算法仅凭声音就能识别出灰海豚这一物种 。这项研究结果发表在《公共科学图书馆·计算生物学》期刊上 。
传统的海洋哺乳动物调查是在船上对水面进行扫描，然后进行推断 。但是，这项技术可能提供了一种新的选择 。“不用乘船出海，你只要将这个机器放入水中，它会在一年或连续多年的时间里收集水下的声音，长期来说，在动物研究方面你就可以获得更好的时间序列 。”
谢谢大家收听科学美国人——60秒科学 。我是克里斯托弗·因塔利亚塔 。
1. comb through 在(信息)中仔细搜寻；
例句：Eight policemen then spent two years combing through the evidence.
2. differentiate from 区分；区别；辨别；
例句：At this age your baby cannot differentiate one person from another.
3. sift through 细查；详审；
例句：We sift through the information carefully to find a clue that will help us.
4. tease out 套取，套出，巧妙获得(信息或答案)；
例句：They try to tease out the answers without appearing to ask.