第12课 (282字 2分钟)

Passage Twelve

（K4 level）

1.The idea of fighting a noise by making more noise sounds strange , but that's exactly what motor engineers are doing in Germany and some other countries.

2.Carmakers’research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise.

3.Physicists have known about the technique for a long time.

4.Sound is made up of pressure waves in the air.

5.If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound.

6.Therefore , by producing a perfect copy of the noise and delaying it by half a wave cycle , we can kill the unwanted noise.

7.Using this technique many car-makers are racing to develop noise-killing systems both inside and outside the cars.

8.Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor burn less oil and work better.

9.Some engineers believe that the noise-killing system will be used in most cars in 2005.

10.But the carmakers haven’t decided if they will put it into production because it would add several hundred dollars to the cost of their cars.

生词表（New Words）

1. idea 想法                           fighting 对抗                  noise 噪音

strange 奇怪                       motor 汽车                      engineers 工程师 

2. carmakers 汽车制造商      research 研究              development 开发
laboratories 实验室           loudspeakers 扬声器    unwanted 不需要的 

3. physicists 物理学家          pressure 压力                  waves 波

frequency 频率                  mix 混合 

4. sound 声音                         made up 组成                 pressure waves 压力波
air 空气 

5. highest 最高                       lowest 最低                     result 结果

sound 声音 

6.producing 产生                   perfect 完美                    copy 复制

delaying 延迟                    cycle 周期                       kill 消除

unwanted 不需要的 

1. technique 技术                  racing 竞相                     develop 开发

systems 系统                     inside 内部                      outside 外部 

2. silencer 消音器                 reduce 减轻                    weight 重量

burn 燃烧                           oil 油                               work 工作

better 更好 

3. engineers 工程师               believe 相信                    noise-killing 噪音消除

system 系统                       cars 汽车 

4. production 生产          cost 成本                         several 几百

dollars 美元

1. 用噪音对抗噪音的想法听起来很奇怪，但这正是德国和一些其他国家的汽车工程师正在做的事情。

2. 汽车制造商的研究和开发实验室已经证明，通过扬声器混入更多的噪音可以减少不需要的噪音。

3. 物理学家很早就知道这种技术。

4. 声音是由空气中的压力波组成的。

5. 如果两个相同频率的声波混合，使得一个波的最高点与另一个波的最低点同时出现，结果就是没有声音。

6. 因此，通过产生噪音的完美复制品，并将其延迟半个波周期，就可以消除不需要的噪音。

7. 利用这种技术，许多汽车制造商正在竞相开发车内和车外的噪音消除系统。

8. 噪音消除系统的另一个好处是，它可以省去消音器的需要，这不仅减轻了汽车的重量，还使发动机燃烧更少的油并且工作得更好。

9. 一些工程师相信，到2005年噪音消除系统将被应用在大多数汽车上。

10. 但汽车制造商尚未决定是否投入生产，因为这将增加几百美元的成本。