The economic costs of noise to society are several. Airports
are currently op- erating at less than capacity because of noise regulations,
which restrict their 62. ______. hours of
operation. For instance, at Washington’s national airport no jet traffic
is allowed from 11 p. m. to 7 a. m. Other airports restrict the use of
certain run- ways. One estimated is that noise restrictions reduce possible
airport use by 20 63. ______. percent. The
profitable cargo trade is especially affected by night restrictions.
In the case of airports, jet engines may be modifying to reduce their
noise lev- 64. ______. el, or insulation (隔音) from air
traffic noise may be provided by the purchasing 65.
______. of land around airports. It is estimated that $ 5.7 billion would be
required to equip all existing jet engines for noise control devices.
However,
66. ______. consider the current state of the art, even taking
this step will not reduce noise 67. ______. levels
at all points to acceptable values. Some combination of methods is proba- bly
necessary. If all aircraft are made quieter by existing methods,
there would be a number 68. ______. of
economic benefits. An increase in airport capacity would occur. Property
val- ues near airports might rise. Transportation costs to and from airports
could be increased since the airports now could be located closer to
population centers. 69. ______.
Much research still needs to be done on the economic aspects of noise
re- duction and noise effects. Although some of the effects of noise
pollution are known, more must be discovered about their effects on health,
productivity, prop- 70. ______. erty values and
the quality of life. Furthermore. the cost of noise pollution to the economy
as a whole needs to be investigated. The public must be alert
about the dangers and economic costs of noise poi-
71. ______. lution so that people may make intelligent choices
and exert appropriate pres- sures.