Some scientists say that animals in the ocean are increasingly threatened by noise pollution caused by human beings. The noise that affects sea creatures comes from a number of human activities. It is caused mainly by industrial underwater explosions, ocean drilling, and ship engines. Such noises are added to natural sounds. These sounds include the breaking of ice fields, underwater earthquakes, and sounds made by animals themselves. Decibels(分贝) measured in water are different from those measured on land. A noise of 120 decibels on land causes pain to human ears. In water, a decible level of 195 would have the same effect. Some scientists have suggested setting a noise limit of 120 decibles in oceans. They have observed that noises above that level can frighten and confuse whales. A team of American and Canadian scientists discovered that loud noises could seriously injure some animals. The research team found that powerful underwater explosions were causing whales in the area to lose their hearing, which seriously affected the whales’ ability to exchange information and find their way. Some of the whales even died. The explosions had caused their ears to bleed and become infected(感染的). Many researches whose work depends on ocean sounds disagree with a limit of 120 decibels. They say such a limit would mean an end to important industrial and scientific research. Scientists do not know how many and what kinds of noises are harmful to ocean animals. However, many scientists suspect that noise is a greater danger than they previously believed. They want to prevent noises from harming creatures in the ocean. 小题1:The second paragraph mainly tells us that the noises on land and in water .
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