Stop.Listen!WhatdoyouhearYoumayhearmanydifferentsounds.Someofthosesoundsmaybenouse.Noiseisaloudorunwantedsound.Noisecanbecausedbymanykindsofmachines,suchasmotorcycles,jetplanes,farmtractors（拖拉机）.rock

　　Stop.Listen!WhatdoyouhearYoumayhearmanydifferentsounds.Someofthosesoundsmaybenouse.Noiseisaloudorunwantedsound.

　　Noisecanbecausedbymanykindsofmachines,suchasmotorcycles,jetplanes,farmtractors（拖拉机）.rockmusicisalsonoise.

　　WhathappenswholivenearnoisymachinesorusethemoveraperiodoftimeDoctorshavefoundthatthesepeoplehavetroubleinsleeping.But,mostimportant,constant（不断的）loudnoisecancausealossofhearing.

　　Scientistsuseaunitofmeasurecalleddecibel（分贝）tomeasuretheloudnessofasound.Thesoundofaquierroom,forexample,measures35decibels.Talkingmeasuresbetween40and65decibels.Soundsfromtrafficandfromsomerockbandscanmeasureover120decibels.Noiseatthishighlevel（层次）causesgreathearingloss.

　　（）1.Accordingtothepassage,noiseis（）

　　A.anykindofsound

　　B.aloudorunwantedsound

　　C.allsoundsthatyoucanhear

　　D.terriblesound

　　（）2.Accordingtothepassage,loudnoisecan（）

　　A.helppeopletosleepbetter

　　B.stopmachines

　　C.causealossofhearing

　　D.killpeople