1995年高考英语全国卷 - 阅读理解C

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.
通过制造更多的噪音来对抗噪音的想法听起来很奇怪，但这正是德国和其他一些国家的电机工程师正在做的事情。

Carmakers' research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise.
汽车制造商的研发实验室已经证明，在扬声器的帮助下混合更多的噪音可以减少不必要的噪音。

Physicists have known about the technique for a long time. Sound is make up of pressure waves in the air. 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. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle, we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars. 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 bum less oil and work better.
物理学家早就知道这项技术。声音是由空气中的压力波组成，如果两个频率相同的声波混合，使得一个波的波峰与另一个波的波谷同时出现，就会消除声音。因此，完美复制一份噪音，并将其延迟半个波的周期, 我们就可以消除不必要的噪音。使用这项技术，许多汽车制造商正在竞相开发车内和车外的消声系统。使用消声系统的另一个好处是，不再需要消声器，这不仅减轻了汽车的重量，而且使发动机燃烧更少的油，运转得更好。
　　
Some engineers believe that the noise-killing system will be used in most cars in 1996. 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.
一些工程师认为，这种消声系统将在1996年用于大多数汽车。但汽车制造商尚未决定是否将其投入生产，因为这将使汽车成本增加数百美元。