The ocean is not a quiet place. This is partly caused by sea animals. They use sound to find what they eat, whom they play with, or which place they move towards. But the noise from human activities is increasingly troubling the lives of ocean animals.
According to scientists, loud noise may increase mass strandings (大规模搁浅) of sea animals. Researchers recorded only five of these events in the first half of the 20th century. From 1950 to 2004, they recorded more than 1,200 mass strandings. These were perhaps because of the use of sonar (声呐) underwater. Another main reason of loud underwater noise is pile driving (打桩). Piles are supports for bridges, oil and gas-producing areas. They're driven deep into the floor of the ocean. Driving a single pile can take several hours and result in as many as 5,000 hits. This process creates a lot of noise.
To restrain that noise, some companies are making use of tiny bubbles (气泡). A single bubble is easily broken. However, the bubble wall can make pile driving quieter. The bubble wall is usually created in this way: A tube (管子) is placed in a ring around a pile. Air is then let out through closely spaced openings in the tube. When the bubbles rise, they act as a wall and take in some of the noise. Some more of the sound reflects back and becomes stuck inside the wall. Such bubble walls are really helpful.
Other changes to pile driving can help as well. For example, people can take breaks while pile driving and let animals travel through.
Our noise in the ocean is causing big problems. But small changes in our behaviors can make a big difference in animals' lives in the world's oceans.
B . 
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D . 
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