​Silence of the Night Owls|无声飞行的夜间猫头鹰

by Bruce Bagnell

A bird that moves silently through the air has sent engineers back to the drawing board.

无声穿越黑夜的鸟给工程师带来了灵感。

What horror movie would be complete without a night scene using an owl or two hooting in the woods? NASA flight engineers are especially interested in these night owls, for they may hold the secret _(1)_ silent aircraft.

Ornithologists, or bird experts, have long known about the great difference _(2)_ day-flying and night-flying owls. Like all other birds, day-flying owls create sound as they fly, while their _(3)_ cousins do not. A close examination of the latter explains why. Their primary feathers are jagged, much like the teeth of a comb. Their trailing feathers on the back ends of the wings, _(4)_, are fringed, much like the ends of a scarf. Furthermore, the rest of the wings and the legs of the owl are _(5)_ in soft, small feathers. The fringe on owls' trailing feathers helps reduce noise, and the soft, small feathers actually _(6)_ sound. The combined effects of the feathers make for silent flights.

As everyone knows, aircraft _(7)_ are extremely noisy. Most airports around the world have strict noise pollution standards, which means that during a 24-hour period, only a certain amount of _(8)_ noise can be produced. If aircraft can be _(9)_ to be soundless or nearly silent, airports may be open for business 24 hours a day. The number of take-offs and landings could _(10)_, which would be good for business and more convenient for travelers. Flight engineers from commercial airlines to NASA are excited about the possibility of designing the first silent aircraft as they continue their studies of the world's only silent flying bird.

(A) designed    (B) to  (C) covered (D) increase    (E) in flight

(F) in contrast (G) absorb  (H) nocturnal   (I) measurable  (J) between

　如果没有一两只猫头鹰在树林间叫的夜间画面，有哪部恐怖片称得上完整？美国航天总署的飞航工程师对这些夜晚活动的猫头鹰特别感兴趣，因为牠们身上可能藏有静音飞行器的秘密。

　　鸟类学家从以前就知道白天飞行和夜间飞行的猫头鹰有很大不同。像其他所有鸟类一样，白天飞行的猫头鹰飞行时会制造声响，但牠们的夜行表亲则不然。一项针对后者所做的详细调查说明了原因。牠们的主要羽毛呈锯齿状，就像梳子的齿。相对地，在翅膀后端的尾部羽毛则成须状，就像围巾的末端。此外，猫头鹰翅膀的其他部分和脚上都覆盖着细软微小的羽毛。猫头鹰尾部羽毛上的须须有助于减少声响，而那些细软微小的羽毛实际上可以吸收声音。这些羽毛结合起来的效果造就了无声飞行。

　　大家都知道，飞机在飞行时会产生极大的噪音。世界上大部分的机场都有严格的噪音污染标准，也就是在 24 小时内，飞机只能产生定量的可测噪音。如果飞机能设计成无声或接近无声，机场就可以每天 24 小时都开放营业。飞机的起降次数增加，对公司营运有好处，对旅客也比较方便。不论是商业性质的航空公司或国家航天总署的飞航工程师，在他们持续研究这种世上唯一无声飞行的鸟类之际，对于可能设计出首架静音飞行器都感到非常兴奋。

标准答案:   1. (B)  2. (J)  3. (H)  4. (F)  5. (C)
   6. (G)  7. (E)  8. (I)  9. (A)  10. (D)

For Your Information

大多数猫头鹰是夜行性动物，在夜晚活动时，除了无声飞行可让牠们成功地抓到猎物，其他特性像是极佳的听觉和视觉也让牠们可自在悠游于夜间。

与体型类似的哺乳类相较之下，猫头鹰的眼睛要大得多，在暗光之下也仍然十分敏锐；牠们的两眼几乎位于同一平面，像人一样可以用双眼视觉定位。不过牠们的眼睛本身并不太能随意转动，视野比人类的要来得窄。为了弥补这样的缺失，猫头鹰的颈部非常灵活，可以做 270 度的转动。

牠们还有极佳的听觉。像是领角鸮头上两个尖尖像耳朵的突起，那其实不是耳朵而只是羽毛，但也具有耳朵集音的功效，称为『角羽』；而猫头鹰的耳洞两边不对称，它们的大小、形状及水平位置也都不尽相同，这让牠们可以利用声波到达两耳时间的差距，对猎物的所在位置做更精确的判断。