Masking
The impact of environmental noise is a serious concern to scientists because the presence of excessive noise in an animal’s environment can threaten its survival. Animals regularly produce andreceive sounds in their daily lives for a variety of purposes, such as communication of the search for food. When environmental sounds are louder than sounds that the animal uses, the result is known as masking. Masking is a covering over of one sound with another sound. Scientists believe that masking impedes animals’ ability to transmit or receive biologically important signals that are essential for survival.
听力材料：
A good example of this is shown in a scientific study involving whales, orca Whales, which happened to be one of the largest whales species. Now, orcas have a very sharp sense of hearing that is absolutely vital to their existence. In fact, they make special sounds and listen to the sounds, echoes to help them determine the location, shape, and size of objects in their appetite, like food. In other words, an orca whale uses an ecosystem to gather Information about its immediate surroundings. It makes a series of clicking sounds, and the echoes from these clicking sounds helplead the whale to the location of its next meal.
Now, in their research, scientists studied noises in an orca whale habitat of the west coast of Canada. The scientists focused on noise from boats using the same waterway as the whales. These researchers wanted to learn about possible changes in the whale's behavior when the noise level from the boats increased.
In the end, an increase in the level of environmental noise from the boats is believed to have blocked the transmission distance of the whales clicking sounds. Scientists noticed that the size of the area in which the whale searched for food became smaller by up to 20 %. It appears that the whales ecosystems were not able to function fully. Basically, the whales couldn't gather as much Information about possible sources of food in their surroundings.
Question：
Explain the concept of masking and how it affects orca whales.
