著火了，唱歌吧！

Ｂｙ?。粒欤椋螅铮睢。樱睿洌澹?/p>

現(xiàn)代科技研究表明，歌聲在未來(lái)或許不僅可用來(lái)欣賞和娛樂(lè)，還可以用來(lái)滅火！

For over 150 years, scientists have known that fires can be extinguished1) with sound waves, but they still don't know how.

"I throw more power into my voice, and now the flame is extinguished," wrote Irish scientist John Tyndall about his experiments with sound and fire in 1857. After countless public demonstrations and a handful of lab tests, researchers are still struggling to determine exactly how sound snuffs2) flames.

Sound travels in waves, which are simply variations of pressure in a medium—whether solid, liquid or gas. The energy from vibrating3) objects moves from particle to particle in the air in a repeating pattern of high- and low-pressure zones that we perceive as sound. According to the ideal gas law, temperature, pressure and volume4) are related; therefore, a decrease in pressure can lead to a corresponding decrease in temperature, which may explain how sound can extinguish a flame.

In 2004, Dmitry Plaks, now a student at the Georgia Institute of Technology, and his classmates at the University of West Georgia tested whether sound waves could extinguish fires in hopes of using sound to extinguish flames in a spacecraft. They placed a candle in a large topless chamber with three bass5) speakers attached to the walls. The candle was lit and the Canadian rock band Nickelback6)'s "How You Remind Me" was pumped through the speakers. Within roughly 10 seconds, once the song hit a low note, the flame was out.

Physicist James Espinosa, a former advisor to the student team, notes that the candle wasn't running out of oxygen to fuel the flame because the chamber was large and open to the air. He also doesn't believe that wind—which would actually displace the warm air around the candle with cooler air—had put out the fire. There is another indication that the fire hadn't been extinguished by wind: frequency7). The students tested a range of frequencies and found that the effective range was between 40 and 50 hertz, within the range of human hearing.

Plaks speculates8) that the pressure drop created by the sound wave was what extinguished the flame. Gary Ruff, project manager for fire suppression technologies at NASA's Glenn Research Center, agrees: if the difference between the high-pressure peak and low-pressure trough9) in the sound wave was large enough, the flame would go out.

Such acoustic10) fire suppression might prove useful in space, Espinosa suggests. But Ruff and NASA disagree with him: Making the sound waves to extinguish a fire would require electricity, and astronauts would also have to be able to see the flames in order to direct sound waves at them.

Nevertheless, this summer Espinosa will try to extinguish a larger flame with a smaller speaker system. He plans to create an electric arc11), like that used for welding12). This spark creates a shock wave13) that can be focused with an acoustic horn14) so that an array15) of such waves can be aimed at the fire.

Such a system might prove useful here for putting out fires in locations whose contents could be damaged by water, such as museums that house valuable artwork or centers with data servers or other electrical equipment. "Sound is being used to cut pieces of metal, to destroy kidney stones," Espinosa adds. "It can do more than people give it credit for16)," including, apparently, firefighting.

一百五十多年以來(lái)，科學(xué)家們?cè)缫阎揽梢杂寐暡▉?lái)滅火，但他們還是沒(méi)找出滅火的方法。

“我提高了嗓音，接著火焰被熄滅了?！边@是1857年愛(ài)爾蘭科學(xué)家約翰·廷德耳寫(xiě)下的一段實(shí)驗(yàn)記錄，實(shí)驗(yàn)研究的是聲音與火的關(guān)系。經(jīng)過(guò)無(wú)數(shù)次公開(kāi)演示及一系列實(shí)驗(yàn)測(cè)試，研究人員仍在努力探究聲音能滅火的確切原因。

聲音以波的形式傳播，聲波其實(shí)就是介質(zhì)中的壓力變化——不管介質(zhì)是固態(tài)、液態(tài)還是氣態(tài)。振動(dòng)的物體發(fā)出的能量在空氣中的粒子間傳遞，形成一系列連續(xù)的高壓帶和低壓帶——這就產(chǎn)生了我們聽(tīng)到的聲音。根據(jù)理想氣體定律，溫度、壓力和體積三者相關(guān)；因此，氣壓的降低可以引起溫度的相應(yīng)降低，這或許可以解釋聲音為什么能滅火。

德米特里·普拉克斯現(xiàn)在是佐治亞理工學(xué)院的學(xué)生。早在2004年，他和西佐治亞大學(xué)的同學(xué)就曾做過(guò)一個(gè)實(shí)驗(yàn)，研究聲波能否滅火，以期能用聲音來(lái)?yè)錅绾教祜w機(jī)內(nèi)的火焰。他們把一支蠟燭放入一個(gè)無(wú)蓋的大燃燒室，并在燃燒室的內(nèi)壁上安裝了三個(gè)低音喇叭。蠟燭點(diǎn)燃后，那些超低音喇叭就開(kāi)始播放加拿大搖滾樂(lè)隊(duì)“五分錢(qián)樂(lè)隊(duì)”的歌曲《你如何提醒我》。結(jié)果，大概在10秒內(nèi)，歌曲只要唱到一個(gè)低音處，蠟燭就會(huì)熄滅。

物理學(xué)家詹姆斯·埃斯皮諾薩曾擔(dān)任過(guò)這個(gè)學(xué)生實(shí)驗(yàn)組的指導(dǎo)老師。他指出，蠟燭并不是因燃燒所需的氧氣耗盡而熄滅的，因?yàn)閷?shí)驗(yàn)所用的燃燒室很大，而且不是密閉的。他還認(rèn)為，也不是風(fēng)使火熄滅的——雖然風(fēng)確實(shí)能讓冷空氣取代蠟燭周圍的熱空氣。另有跡象表明，火并不是被風(fēng)吹滅的，那就是頻率。學(xué)生們當(dāng)時(shí)對(duì)不同波段的頻率進(jìn)行了測(cè)試，發(fā)現(xiàn)對(duì)滅火有效的頻率介于40～50赫茲之間，而這一波段在人類的聽(tīng)覺(jué)范圍之內(nèi)。

普拉克斯推斷，聲波引起的氣壓下降是讓火焰熄滅的原因。加里·拉夫是美國(guó)宇航局(下稱NASA)格倫研究中心的滅火技術(shù)項(xiàng)目負(fù)責(zé)人，他贊同普拉克斯的觀點(diǎn)：如果聲波中高壓的波峰與低壓的波谷之間的壓力差足夠大的話，火就會(huì)被熄滅。

埃斯皮諾薩認(rèn)為，這種聲學(xué)滅火法或許能在太空派上用場(chǎng)。不過(guò)拉夫和NASA并不認(rèn)同他的看法：產(chǎn)生滅火用的聲波需要用電，而且航天員還必須看得到火焰，才能將聲波瞄準(zhǔn)火焰。

不過(guò)，今年夏天，埃斯皮諾薩將嘗試使用更小的揚(yáng)聲裝置來(lái)?yè)錅绺蟮幕饎?shì)。他打算制造出類似焊接所用的電弧。電弧光會(huì)產(chǎn)生沖擊波，而這種沖擊波可以通過(guò)射聲器聚焦后對(duì)準(zhǔn)火焰?zhèn)魉汀?/p>

這種滅火系統(tǒng)也許最終會(huì)對(duì)擺放有怕水物體的場(chǎng)所的滅火工作十分有用，比如在收藏有珍貴藝術(shù)品的博物館和裝有數(shù)據(jù)服務(wù)器或其他電子設(shè)備的中心場(chǎng)所?！奥暡ㄒ驯挥脕?lái)切割金屬和粉碎腎結(jié)石，”埃斯皮諾薩補(bǔ)充說(shuō)，“它的用途遠(yuǎn)比人們認(rèn)為的要多，”顯然也包括滅火。

Vocabulary

1. extinguish [Ik5stIN^wIF] vt. 熄滅，撲滅(火等)

2. snuff [snQf] vt. 熄滅，掐滅(蠟燭等)

3. vibrate [vaI5breIt] vi. 顫動(dòng)；振動(dòng)；抖動(dòng)

4. volume [5vRlju:m; (?@) -jEm] n. 音量，聲量；響度

5. bass [beIs] adj. (樂(lè)器)低音的

6. Nickelback: 加拿大當(dāng)紅搖滾樂(lè)隊(duì)，其專輯All the Right Reasons自2005年發(fā)行以來(lái)，創(chuàng)下了在美國(guó)音樂(lè)排行榜Billboard 200中停留156周的紀(jì)錄，迄今為止總銷量接近700萬(wàn)張。最新專輯Dark Horse也憑借32.6萬(wàn)張的驕人銷量奪得了Billboard 2008年12月的亞軍。

7. frequency [5fri:kwEnsI] n. 【物】頻率，周率

8. speculate [5spekjuleIt] vt. 推測(cè)，推斷

9. trough [trC:f] n. 【物】波谷

10. acoustic [E5ku:stIk] adj. 受聲波控制的

11. electric arc: 電??；arc [B:k] n. 弧

12. welding [5weldIN] n. 焊接；焊合

13. shock wave: 沖擊波，運(yùn)動(dòng)氣體中的強(qiáng)壓縮波

14. acoustic horn: 射聲器，喇叭(筒)，傳話筒

15. array [E5reI] n. 整齊的一批；大量

16. give sb./sth. credit for: 認(rèn)為某人(物)有(某種優(yōu)點(diǎn)或能力)