The ocean isn't a quiet place as you imagine.Most of the noise is caused by sea animals themselves.Most of them use sound to find what they eat，whom they play with，or which general position they move towards.But the noise from human activities is increasingly troubling the lives of ocean animals.According to scientists，loud noise may cause more whales and other sea animals to take the ground（擱淺）.Researchers recorded only five of these events in the first half of the 20th century.But from 1950 to 2004，they recorded more than 1，200 times.These were perhaps because of the use of sonar（聲吶） under water since 1950.
    Another main reason of loud underwater noise is pile driving（打樁）.Piles are driven deep into the floor of the ocean.Driving in a single pile can take several hours and as many as 5，000 hits.This process creates a lot of noise.
    To control that noise，some companies are making use of tiny bubbles（氣泡）.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 is placed in a ring around a pile.Air is then let out through closely spaced openings on the tube.When the bubbles rise，they act as a wall and take in some of the noise.Some more of the sound reflects（反射） back and becomes stuck inside the wall.Such bubble walls are really helpful.Scientists found that these walls can reduce noise by 30 decibels（分貝）.A German company even says that its Big Bubble Wall can cut down the noise of pile driving by up to 95 percent.What exciting news it is!Such small changes in human activities can help make life better for animals in the oceans.


Tiny Bubbles Offer Big HelpThe source of sea noise From sea animals：It's （1）

necessary

necessary

in the ocean.
    From human activities：The events of sea animals taking the ground are（2）

increasing

increasing

because of the use of sonar.
    The control of sea noise
    Loud noise may（3）

cause

cause

problems for sea animals.
    （4）

Methods

Methods

：Use a tube to act as a bubble wall.The noise of pile driving could be（5）

taken in

taken in

or reflected back in this way.
    Purpose：To make life better for sea animals around the world.