托福听力材料(45)：噪音影响

　　托福听力背景知识/材料在复习的过程中经常会遇到，新东方在线托福考试频道为同学们带来了托福听力背景知识/材料是和噪音影响相关的内容，一起来学习下吧！

　　I'm grad to see so many of you here. We've become really alarmed over the health center by the number of students we are seeing, who are experiencing hearing loss. First, I want to go over some basic about hearing. Then we can take a look at our school environment and see if we can figure out some ways to protect hearing. The leading cause of preventable hearing loss is excessive noise. Too much moderate noise for a long time or some types of intense noise for even a short time can damage hearing. Loudness is measured in units called decibels. One decibel is the lowest sound that the average person can here. Sounds up to 80 decibels generally aren't harmful. That's noise like traffic on a busy street. But anything louder than 80 decibels, especially with continuous exposure, may eventually hurt your hearing. Once you are up to around 140 decibels, that's like a jet plane taking off, then you might even feel pain in your ears. And pains are sure sign that your hearing's at risk. Even one exposure to a really loud noise at close range can cause hearing loss. So what you need to do is limit your exposure to harmful levels. If you pass along this handout, we can take a look at the decibel level of some common campus sounds. Notice how loud those horns are that people take to football games. They are really dangerous if blown right behind you. Now, let's try to generate a list of damaging noises.