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A new research shows human activity is changing the sound of the Earth's oceans and seas. Scientists say the sound changes of our oceans, seas, and other waterways affect many marine (海洋的) animals - from very small shrimps to huge whales.

Sound travels very far underwater, Francis Juanes, an ecologist at the University of Victoria in Canada, told the Associated Press. For fish, he explained, sound is probably a better way to sense their environment than light. Sounds help fish and other marine animals survive and communicate with each other. Sounds also help some ocean animals find food and avoid their hunters.

However, increased noise from humans is making it harder for these animals to hear each other. The noise is coming from shipping traffic, underwater exploration, and other noisy human activities. For many marine animals, their attempts to communicate are being masked by sounds that humans have produced. Experts explain that masking happens when one or more noises in the water block sound important to a marine animal's living. The overall number of marine animals has gone down by about half since 1970. Some studies show the stress from human noise might also affect the immune system as well as reproductive health or behavior. Imagine having to raise your kids in a place that's noisy all the time," said Joe Roman, a marine ecologist at the University of Vermont.

"When people think of problems facing the ocean, we often think of climate change, plastics, and overfishing. But noise pollution is another thing we need to be monitoring. Sound pollution may be easier to deal with than other ocean problems," Scientist Juanes says. "If we make something for the ocean, think about how to make it quieter."