263 Underwater Listening Devices
263 水下监听系统
It is hard to track the blue whale, the ocean’s largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior.
海洋中最庞大的生物蓝鲸现已很难找到，由于商业捕杀蓝鲸几乎被杀尽了，现在它已经被列为濒危物种。将无线设备绑到蓝鲸身上非常困难，而视觉观察又太不可靠，无法对其行为进行真正的观察研究。
So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy’s formerly top-secret system of underwater listening devices spanning the oceans.
因此今年早些时候．生物学家对能获得海军的帮助感到非常高兴。他们现在能对一只特定的蓝鲸进行长达43天的跟踪，并记录它发出的声音。由于海军以前的绝密系统——水下监听系统．这一切都成为可能。
Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies.
追踪蓝鲸只不过是冷战结束后，向广大科学家开放的令人激动的新世界的一个例子，因为海军部队开始把先前为了跟踪潜在敌舰，花几十年时间建立起来的全球海底监听系统部分解密，并开始同他人分享。
Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption for the first time and that they plan similar studies.
地球科学家最近在记者招待会上称，他们已经开始运用这个系统对深海火山活动进行严密的监控，而且正在计划进行类似的研究。
Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures.
其他科学家也都提出建议，利用这套系统跟踪洋流，探测海洋和全球气温变化。
The speed of sound in water is roughly one mile a second - slower than through land but faster than through air. What is most important, different layers of ocean water can act as channels for sounds, focusing them in the same way a stethoscope does when it carries faint noises from a patient’s chest to a doctor’s ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles.
声音在水中的传播速度大约是1英里/秒，比在陆地中的传播速度慢，却比在空气中的传播速度快。最重要的是，海水的不同层面都能作为声音传播的渠道，它们汇聚声音的方式就像听诊器一样，把病人胸部的微弱声音放大后，清晰地传到医生的耳朵里，这种汇聚技术是大海中即使相对微弱的声音，尤其是低频的声音，也可以传到千里之外的主要原因。