题目

帮忙翻译下BBC文章
Since 1999, researchers with the Elephant Listening Project have used an acoustic monitoring system to record elephant sounds in the African rainforest.
They’ve learnt that elephants use infrasonic calls - calls too low in frequency to be heard by the human ear - for long-distance communication. Infrasound can travel farther than higher pitched sound. Elephant families separated by several kilometers use them to keep track of each other. Male elephants find fertile females by using these low frequency sounds.
Elephant populations in Africa are decreasing due to encroaching human civilization. But, even as we humans have become stewards to the elephants, it’s hard to know exactly how many elephants are left. Elephants in the dense forests of Africa are difficult to count. Sightings are rare. The Elephant Listening Project can use the elephant’s calls to determine the size and health of the herds. At least one such study was used to locate hotspots of elephant activity.
And it’s not just the elephants' sounds that get monitored. The recorders also pick up human sounds - gunshots, chainsaws and vehicle noise - which help to identify potential threats to forest elephant populations.
And for today that’s our show. We do hope you come to our website to let us know what you think at earthsky.org. We’re Block and Byrd for Earth and Sky.

提问时间：2020-10-08

答案

从1999年,大象监听工程的研究员已经使用音频监听系统来记录非洲热带雨林里大象的声音.
他们已经知道大象的声音是次声的-次声的频率很低不能被人耳所听见-用于远距离通信.次声比更高的噪声传播的远.大象们相隔好几公里,用次声来互相联系.公象通过用这种低频率的声音来寻找多产的母象.
非洲大象的数量正在增长由于渐渐渗入的人类文明.但是,正当我们人类成为大象的服务员时,又很难准确的知道有多少大象还存活着.在非洲密集森林里的大象是难以计算的.能够亲眼看见是很稀罕的.大象监听工程能用大象发出来的声音来判断象群的大小和健康状况.至少,这种研究能用于找到大象活动的热点地区.
不仅仅是大象的声音得到监控.那个录音器也录了人的声音-枪声,锯东西的声音和车辆噪声-这些有助于发现对森林里大象的数量的潜在威胁.
这就是我们今天所展示的.我们希望你访问我们的网站earthsky.org让我们知道你怎么想的.
我们是 Block and Byrd ,为了每一寸土地每一片天空