托福阅读材料(331)：噪音对我们的影响

　　托福阅读背景知识/材料之噪音对我们的影响，更多托福阅读背景材料/知识尽在新东方在线托福考试频道！

　　I'm grad to see so many of you here. We'vebecome really alarmed over the health center by thenumber of students we are seeing， who areexperiencing hearing loss. First， I want to go oversome basic about hearing. Then we can take a look atour school environment and see if we can figure out some ways to protect hearing. Theleading cause of preventable hearing loss is excessive noise. Too much moderate noise for along time or some types of intense noise for even a short time can damage hearing. Loudnessis measured in units called decibels. One decibel is the lowest sound that the average personcan here. Sounds up to 80 decibels generally aren't harmful. That's noise like traffic on a busystreet. But anything louder than 80 decibels， especially with continuous exposure， mayeventually hurt your hearing. Once you are up to around 140 decibels， that's like a jet planetaking off， then you might even feel pain in your ears. And pains are sure sign that yourhearing's at risk. Even one exposure to a really loud noise at close range can cause hearingloss. So what you need to do is limit your exposure to harmful levels. If you pass along thishandout， we can take a look at the decibel level of some common campus sounds. Notice howloud those horns are that people take to football games. They are really dangerous if blownright behind you. Now， let's try to generate a list of damaging noises.