【英语时差8,16】无声杀手

 You've seen them in spy movies.   The evil assassin is about to kill the helpless victim, but he's worried that someone might hear the shot. What's an evil assassin to do? In Hollywood, the answer is simple: He deftly¹ attaches a silencer to his gun, fires a soundless shot, then escapes into the night. Do silencers really work this way?

Actually, real silencers are likely to be bulkier and noisier than the ones in a Hollywood stockroom. Many are actually larger than the guns they are designed to work with, and no silencer can remove ALL sound of a shot.

Most of a gunshot's noise comes from hot gasses bursting out of the gun behind the bullet. The more suddenly these gasses emerge, the sharper and louder the sound will be. A silencer works by slowing and cooling this burst of gas, trapping it in a spiral of steel wool and forcing it to exit the gun more gradually. As they emerge, these slower moving gasses make less sound than the concentrated burst of a normal gunshot.

You can feel the difference yourself by making the sounds "Bam!" and "Phoof!" The sharp burst of air following the "B" sound of "Bam!" will make a sharper, more percussive² noise than the more gradual escape of "Phoof!" It's the same difference as letting the air out of a balloon slowly instead of popping it.

Both gun silencers and car mufflers work the same way---they were invented by the same person, Hiram Maxim³, in the early twentieth century. Maxim didn't care much about gun-toting assassins or spy movie screenwriters. He was ecologically minded. What was his main, ecological⁴ concern? Noise pollution!  

1 deftly   

adv.灵巧地，熟练地，敏捷地

参考例句：

• He deftly folded the typed sheets and replaced them in the envelope. 他灵巧地将打有字的纸折好重新放回信封。 来自《简明英汉词典》
• At last he had a clew to her interest, and followed it deftly. 这一下终于让他发现了她的兴趣所在，于是他熟练地继续谈这个话题。 来自英汉文学 - 嘉莉妹妹

2 percussive   

adj.敲击的

参考例句：

• When it is dragged over pliant areas, an additional percussive tap could indicate this collision. 当它被拖到受范区域时，一个附加的敲击声提示这种碰触。 来自About Face 3交互设计精髓
• Pneumatic DTH (Down-The-Hole) hammer is one of main pneumatic percussive-rotary drilling equipments. 风动冲击器是气动冲击回转钻进的主要设备之一。 来自互联网

3 maxim   

n.格言，箴言

参考例句：

• Please lay the maxim to your heart.请把此格言记在心里。
• "Waste not,want not" is her favourite maxim.“不浪费则不匮乏”是她喜爱的格言。

4 ecological   

adj.生态的，生态学的

参考例句：

• The region has been declared an ecological disaster zone.这个地区已经宣布为生态灾难区。
• Each animal has its ecological niche.每种动物都有自己的生态位.