Noise,Killer of Mankind

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　　Unwanted sound， or noise， such as that produced by airplanes， traffic， or industrial machinery， is considered a form of pollution.Noise pollution is at its worst in densely populated areas.It can cause hearing loss， stress， high blood pressure，sleep loss，distraction，and lost productivity.

　　Sounds are produced by objects that vibrate1 at a rate that the ear can detect2. This rate is called frequency and is measured in hertz3， or vibrations per second. Most humans can hear sounds between 20 and 20，000 hertz， while dogs can hear high-pitched4 sounds up to 50，000 hertz. While high-frequency sounds tend to be more hazardous5 and more annoying to hearing than low-frequency sounds， most noise pollution damage is related to the intensity of the sound. Measured in decibels6， noise intensity can range from zero， the quietest sound the human ear can detect， to over 160 decibels. Conversation takes place at around 40 decibels， a subway train is about 80 decibels， and a rock concert is from 80 to 100 decibels. The intensity of a nearby jet taking off is about 110 decibels. The threshold for pain， tissue damage， and potential hearing loss in humans is 120 decibels. Long-lasting， high-intensity sounds are the most damaging to hearing and produce the most stress in humans.

　　Solutions to noise pollution include adding insulation7 and sound-proofing8 to doors， walls， and ceilings； using ear protection， particularly in industrial working areas； planting vegetation to absorb and screen out9 noise pollution； and zoning10 urban areas to maintain a separation between residential areas and zones of excessive noise.

　　噪音，人類的殺手

　　人們不希望聽到的聲音，或稱噪音，比如飛機(jī)、交通車輛或工業(yè)機(jī)械產(chǎn)生的噪音，被認(rèn)為是一種污染。在人口密集的地區(qū)噪音污染的影響最糟。它可以導(dǎo)致人們失聰、精神緊張、血壓升高、睡眠減少、注意力分散以及生產(chǎn)力降低。

　　物體以人耳能感覺的速率振動(dòng)而產(chǎn)生聲音。這種速率叫做頻率，計(jì)算單位為赫茲（每秒鐘振動(dòng)頻率）。大多數(shù)人能夠感覺到20至20000赫茲的聲音，而犬類能聽到高達(dá)50000赫茲的高頻聲音。雖然高頻聲音比低頻聲音更加危險(xiǎn)且惱人，大多數(shù)的噪音污染損害卻與聲音強(qiáng)度有關(guān)。按分貝計(jì)算，噪音強(qiáng)度可以從零（人耳所能感到的最低聲音）到160分貝以上。人交談的聲音強(qiáng)度一般為40分貝，地鐵的噪音強(qiáng)度約為80分貝，搖滾音樂會(huì)聲音強(qiáng)度在80到100分貝之間。一架在附近起飛的噴氣機(jī)的聲音強(qiáng)度大約是110分貝。120分貝是人類感到痛苦、組織受損、造成潛在的聽力喪失的下限。長(zhǎng)期高強(qiáng)度的聲音對(duì)聽力損害最大，給人類帶來最緊張的情緒。

　　解決噪音污染的措施包括對(duì)門、墻和天花板進(jìn)行隔音處理，使用耳朵保護(hù)裝置（尤其是在工業(yè)生產(chǎn)區(qū)），種植植物吸收并屏蔽噪音，對(duì)城市分區(qū)使居住區(qū)與過量噪音區(qū)分開。

　　注釋：

　　1.vibrate vi.振動(dòng)，抖動(dòng)，振動(dòng)著傳播

　　2.detect vt.測(cè)出，察覺，偵查出

　　3.hertz n.（物）赫茲（頻率的單位，略作Hz）

　　4.high-pitched adj.聲調(diào)高的，失聲的

　　5.hazardous adj.有危險(xiǎn)的，有危害

　　6.decibel n.分貝（表聲音強(qiáng)度的單位）

　　7.insulation n.隔音，隔音材料

　　8.soundproofing n.隔音設(shè)備

　　9.screen vi.屏蔽～out去掉，消除

　　10.zone vt.將…分成區(qū)，指定…為區(qū)