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The noise killing system is not yet popular mainly because
A．it is still being tried out
B．drivers still have their doubts
C．it increases the cost of car production
D．carmakers are not sure if it is necessary
答案
更多“The noise killing system is not yet popular mainly becauseA．it is still being tried outB．d”相关的问题
第1题
Besides its main use the noise killing system can______.
A．make a car lighter
B．make a car quieter
C．reduce the cost of a silencer
D．improve the performance of a silencer
第2题
Besides its main use the noise killing system can
A．make a car lighter
B．make a car quieter
C．reduce the cost of a silencer
D．improve the performance of a silencer
第4题
The noise killing system is not yet popular mainly because______.
A．it is still being tried out
B．drivers still have their doubts
C．it increases the cost of car production
D．carmakers are not sure if it is necessary
第5题
Besides its main use the noise killing system can -'
[ A] make a car lighter
[B] make a car quieter
[ C] reduce the cost of a silencer
F D ] improve the performance of a silencer
第7题
The noise killing system is not yet popular mainly because --'
[ A]it is still being tried out
[ B]drivers still have their doubts
[C] it increases the cost of car production
[ D] carmakers are not sure if it is necessary
第8题
Which of the following gives a general idea of how the noise killing system works？
A．By producing pressure waves going in the opposite direction.
B．By mixing high frequency sound waves with low frequency sound waves.
C．By mixing new sound waves with the noise and sending them out together.
D．By making copies of the unwanted sound waves and letting them out a little later.
第9题
D
To fight a noise by making more noise sounds strange, but that ' s exactly what motor engi-
neers are doing in Germany and some other countries.
Carmaker ' s research and development laboratories have already proved that mixing more noise
with the help of loudspeakers can reduce the unwanted noise. Physicists have known about the tech-
nique for a long time. Sound is made up of pressure waves in the air. If two sound waves' of the
same frequency(频率） mix so that the highest point of one wave happens at the same time as 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(周期) ,we can kill the unwanted noise. Using this
technique many carmakers are racing to develop noise killing systems(系统) borh inside and outside
the cars.
Another good thing about the use of noise killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor bum less fuel and work better. Sorpe engineers believe that the noise killing system will be used in most cars within a few
years. But the carmakers haven' t decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.
69. Which of the following gives a general idea of how the noise killing system works？
[ A]By producing pressure waves going in the opposite direction.
[ B ] By mixing high frequency sound waves with .low frequency sound waves.
[C]By mixing new sound waves with the noise and sending them out together.
[D]By making copies of the unwanted sound waves and letting them out a little later.
第10题
根据下列材料请回答 73～75 题：
第 73 题 Which of the following gives a general idea of how the noise killing system Works？
