Why Hearing Today May Be Gone Tomorrow 今日听力尚好

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1、WhyHearingTodayMayBeGoneTomorrow今日听力尚好，明日何故耳聋ByAndrewDerringtonThehumanearisanincrediblepieceofengineeringandexquisitelysensitive.Calculationsshowthatthequietestsoundwecanhearvibratestheeardrumbylessthanthediameterofahydrogenatom.[2]Beforethosevibrationsareanaly

2、sedbythebraintheypassthroughseveralstagesofmechanicalandneuralprocessingthatselectthesoundswewanttohear,adjusttheirlevelforcomfortandintelligibility,andturndownthevolumeofdistractingsounds.[3]Butfor8.5mpeopleintheUKsomethinggoeswrongwithoneofthestages.Differentp

3、artsoftheprocessingchainarevulnerableatdifferentages.Someofthecausesareavoidableandmanyaretreatable.Treatmentsforproblemsthatoccurearlyintheprocessingchainaremorestraightforwardandmoreeffective.[4]Theeasiestproblemtotreatistheonethatoccursearliestinthechain.Obst

4、ructionoftheearcanalbywaxcausesarelativelymildhearingloss.Thelossisnegligibleunlessthecanaliscompletelyblocked,whichisrare,andiseasilyrestoredbycleaningoutthewax.[5]Thingsgetmorecomplicatedbehindtheeardrum,intheairfilledmiddle-earcavity.[6]Middle-earproblemsarec

5、ommon,treatableandthesubjectofintensedebateaboutwhoshouldbetreatedandhow.Anythingthatimpairstransmissionacrossthemiddleear--evenifitisonlythepressurechangesinanaircraftcabin,orblockageoftheeustachiantubebyacold--causeshearing人的耳朵构造精巧，反应敏捷，是个不可思议的器官。多次计算表明，我们所能听到

6、的最微弱的声响，给耳鼓带来的振幅还抵不过一个氢原子的直径。[2]在大脑对那些振动进行分析之前，它们要通过好几道机械程序和神经程序——包括选取我们想要听的声音，把它们调到舒适清晰的程度，还要把令人分神的声音压低。[3]但在英国，有850万人在某道听觉程序中存在着障碍。年龄不同，在听觉处理上各有不同的薄弱环节。引起听觉障碍的原因有些是可以避免的，很多则可以医治。对早期出现于听觉处理环节的问题，医治起来更为直接有效。[4]最早出现于听觉环节的问题处理起来最容易。耳垢堵塞耳道会引起轻度的听力下降。若非完全堵塞耳道(这是极为罕见

7、的)，这类失听不足为虑，只需清除耳垢就能轻易地恢复听力。[5]在鼓膜背后、充满空气的中耳室内所发生的问题就复杂得多了。[6]中耳的问题较普遍，可以治疗，并且是有关谁该治、怎样治的激烈争论的主题。任何损害中耳传导的东西——哪怕只是飞机机舱气压的变化，或感冒引起的耳咽管堵塞——都会引起听力下降。 loss.[7]Atthecentreofthedebateovertreatmentisthecommonchildhoodconditionknowninthemedicalprofessionasotitismediawit

8、heffusionorOME.[8]Thisisusuallycausedbyaninfectionofthemiddleear,oftenintheafter-mathofacold,inwhichthemiddleearcavityfillsupwithaliquideffusion.Theeffusioncanbethick