（ 听力SectionC ）The people who lived in Rome two thousand years ago were already complaining about the noise in their city. They couldn’t sleep, they said, with all that traffic in the streets. For them, noise was a distce. For us i t has become a real er . We know that the sounds of an city are loud enough to cause serious damage to the inhabitants’ ( 居民 ) hearing in the United States, one out of twenty has suffered some hearing loss . And all over the world the situation is all the time, since noise increases with the population. I t has also increased enormously in the twentieth century with the development of machines . We live in an environment surrounded by loud planes, trucks, motorcycles, buses, electric tools, radios, e tc . That roar s day and night up to 90 or 100 decibels ( 分贝 ). Unfortunately, the human ear does not judge clearly of a noise . A sound ten decibels louder than another one is felt as twice as loud, when in fact it is ten times louder. Since we cannot measure the increase or decrease of noi s e, we never know to what er .