Bottlenose dolphins simplify and raise the pitch of their whistles to be heard above underwater shipping noise. Christopher Intagliata reports.

宽吻海豚简化并提高口哨的音调，以便在水下航运噪音的影响下互相交流。Christopher Intagliata报道。

撰文播音：克里斯托弗·因塔利亚塔（Christopher Intagliata）

翻译：张朵儿

审校：郭晓

The oceans are getting louder. And coastal areas are some of the noisiest, as in this underwater recording, captured 17 miles off the coast of Ocean City, Maryland.

海洋正变得越来越嘈杂。而海滨地区是最嘈杂的地方，正如在距离马里兰州海洋城海岸17英里处录制的这段水下录音一样。<一段马里兰海域船只的噪声>

The noise could be a problem for marine mammals, which, like us, use sound to communicate. "Just like if we're in a noisy bar, we have to shout to each other, they might have to do that too." Helen Bailey is a marine biologist at the University of Maryland Center for Environmental Science.

噪声可能会给海洋哺乳动物造成不少困扰，而海洋哺乳动物和我们人类一样也利用声音交流。“就像是我们在一个嘈杂的酒吧里，我们必须互相喊叫，它们可能也必须这样做。” 马里兰大学环境科学中心的海洋生物学家海伦 贝利（Helen Bailey）如是说。

She and her colleagues recorded two months of underwater sounds, in that same area off the coast of Maryland. They used automated software to fish out 200 bottlenose dolphin whistles from the noise, and visually compared the spectrograms. Here's a normal whistle.

她和她的同事在马里兰州海岸外的同一地方录制了两个月的水下声音。他们使用自动化软件从噪音中捕获到200只宽吻海豚的哨声，并将其可视化为频谱图进行比较。这是正常的哨声。<一段口哨声>

But what they found was that dolphins dumbed down the complexity of their whistles and raised their pitch, when they were competing with shipping noise. Which apparently helps, but could also hurt, their ability to communicate.

但他们发现，当海豚在船只噪音中互相交流时，它们简化了哨声的复杂性并提高了它们的音调。<第二段哨声>这显然有帮助，但也可能伤害它们的沟通能力。

"By using simpler calls, yes, there is a risk they're not communicating as much information as they would if it was quieter. Also for younger dolphins they actually learn these sounds from hearing other dolphins. So they're hearing this much simpler language."

“使用简化的叫声会带来传递的信息下降的风险。而对于年幼的海豚来说，它们是从其他海豚那儿学习这些声音。所以它们听到的就会是这种大大简化的语言。”

The results—and a few of those spectrograms—are in the journal Biology Letters. [Leila Fouda et al., Dolphins simplify their vocal calls in response to increased ambient noise]

 结果连同部分光谱图发表在《生物学快报》上。

The survey site is the proposed future home of a wind farm - which could mean lots of noise as the huge towers are installed. Until then, it's the chronic roar of ships and boats that Bailey wants people to ponder. "I think people think about boats in terms of the emissions, just like with cars. And I think what we need to think about is sound is also an emission." 

调查地点是未来风力发电场的选址，这就意味着巨型风塔搭建好后会产生很多噪音。到那时，这种噪音相当于船只发出长期的噪声，贝利希望人们能仔细思考这个问题。“我认为人们会考虑船只的废气排放问题，就像汽车尾气问题一样。但是我们必须意识到，声音也是一种排放。”