托福学习 托福听力材料大集合四

托福学习之托福听力材料七：噪音影响

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.

托福学习之托福听力材料八：天文

In ancient times,many people believed the earth was a flat disc.Well over 2,000 years ago; the ancient Greek philosophers were able to put forward two good arguments proving that it was not.Direct observations of heavenly bodies were the basis of both these arguments.First,the Greeks knew that during eclipses of the moon the earth was between the sun and the moon,and they saw that during these eclipses,the earth's shadow on the moon was always round,they realized that this could be true only if the earth was spherical,It the earth was a flat disc,then its shadow during eclipses would not be a prefect circle; it would be stretched out into a long ellipse.The second argument was based on what the Greeks saw during their travels.They noticed that the North Star,or Polaris,appeared lower in the sky when they traveled south,in the more northerly regions,the North Star appeared to them to be much higher in the sky.By the way,it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth,a figure recorded in ancient documents says 400.000 stadium,that's the plural of the world stadium.Today,it's not known exactly what length one stadium represents,but let's say it was about 200 meters,the length of many athletic stadiums.This would make the Greek's estimate about twice the figure accepted today,a very good estimate for those writing so long before even the first telescope was invented.