声现象讲义.doc

专业好文档环球雅思学科教师辅导教案 组长审核： 学员编号： 年级：初二 课时数：3课时 学员姓名： 辅导科目：物理 学科教师：杨冬梅授课主题声现象教学目的1、知道声音产生和传播条件。2、了解声音的特征。3、了解现代技术中与声有关的应用。4、知道防治噪声的途径 。教学重点 区分声音的特性；声速的应用，噪声的控制授课日期及时段教学内容 1、运动物体在_通过的路程（也就是路程与时间的比值）叫做速度。2、1m/s=_=_km/h 1km/h=_=_m/s 36km/h= m/s 24m/min= m/s3、火车的速度是72km/h，汽车的速度是30m/s，是火车快还是汽车快？4、物体沿_，速度（快慢）_的运动。叫做匀速直线运动。 物体运动_或_时刻改变的运动。叫做变速直线运动。在变速运动中，用_除以_，得出的速度叫平均速度。平均速度公式 5、李华同学在百米赛跑时，前50m用了5s,后50m用了4s,李华前50m、后50m及全程的平均速度各是多少？想一想：我们都知道蝙蝠眼睛是看不清东西的，但是他能够在黑夜中自由飞翔，准确定位周围的事物，比我们“看”的都清楚，知道是为什么吗？知识点一、声音的产生与传播1.声音是由发声体 振动 产生的，一切发声的的物体都在 振动。2.声音的传播靠介质 ，真空不能传声，3.声音在固体中传播速度最快，在液体中较快，在气体中较慢。4声音以声波形式传播，在空气中的传播速度是340米/秒（15）。5.回声现象(1)回声是声音在传播过程中碰到障碍物而被反射回来的现象，人耳要区分开回声和原声，回声到达人耳的时间比原声晚0.1秒以上（障碍无与发声体相距大于17米）(2)利用回声测量距离：s=vt2例1、一切正在发声的物体都在_，通常称为声源，由声源发出的声音是通过_传播到人耳的。_中声音是不能传播的。例2、气体、液体、固体都能_声音。传播最快的是_。例3、为了听到回声，反射声波的障碍物至少应该离开我们多远？猎人在射击后6秒钟听到射击的回声，障碍物离猎人有多远？（空气中的声速是340米/秒)【解】设障碍物离我们s，人要听到回声，声音应传播的路程为2s，听到回声需要的时间至少要多于t1=0.1秒。利用s=vt得s=3400.12=17m s1 =34062=1020m知识点二、声音的特性音调：声音的高低，跟发声体的频率有关系。频率越大，音调越高；频率越小，音调越低。 物体在一秒内振动的次数叫做频率。 人耳的听觉范围是20hz到20000hz。小于20hz的叫次声波，大于20000hz的叫超声波 响度：声音的大小。跟发声体的振幅有关，声源与听者之间的距离有关系。 音色：不同的发声体音色是不同的。例1、声音的三个特征是：_ 响度 音色 音调例2、 频率是描述物体振动_的物理量，它等于每秒内物体振动的_ ，它的单位为_ 快慢；次数；赫兹例3、 敲鼓时，用力越大，鼓面振动的幅度越大，则鼓声（）音调越高 b.音色越好 c.响度越大 d.越低沉 c响度越大例4、 一曲梁祝哀婉动听，用小提琴或钢琴演奏能呈现不同的特点，你能区分出是钢琴还是小提琴，主要是依据声音的（）音调 b.响度 c.音色 d.节奏解：因为不同乐器的发声结构不同，所以会发出不同音色的声音，所以我们可以通过音色辨别是何种乐器；故选c知识点三、声音的利用人耳听不到的声音：人耳的听觉范围是20hz到20000hz。小于20hz的叫次声波，大于20000hz的叫超声波1、超声波的特点：（1）方向性好 （2）穿透能力强 （3）易于获得集中的能量2、超声波的应用：（1）声呐-发出超声波-回声-探测海底形状、测定潜艇鱼群位置等。（定向性好，水中传播距离远） （2） b超（超声波能成像） （3）超声波清洗器3、次声波的特点：（1）传得很远； （2）很容易绕过阻碍物； （3）而且无孔不入。次声波的作用：（1）科学家通过研究和监测，将它作为预报地震、台风的依据和监测核爆炸的手段。 （2）次声波武器4、 声音可以传递信息：叩诊，根据声音判断病情 在铁轨上面听，知道车离的多远! 敲敲西瓜，就可以知道熟或不熟。 超声波探测海底深度、利用超声波探测鱼群、b超5、声音可以传递能量：超声波粉碎结石 利用超声波清洗牙齿 爆竹声震耳发痛例1、关于超声波和次声波，下列说法正确的是（ ）ba超声波就是速度超过340m/s的声音b超声波在水中的速度比在空气中大c次声波就是没有传播介质使人听不到的声音d超声波可以透过一定厚度的真空向前传播例2、关于超声波的说法中正确的是（ ）aa超声波能获得较集中的能量，可以进行超声清洗 b超声波的穿能力比较好，可以穿透任何物体c超声波能够成像，人耳能直接听到超声波 d超声波缺乏方向性，且不稳定例3、蝙蝠可以靠超声波发现昆虫，这说明声可以传递_信息_ ，人们利用这个原理发明了_声呐_装置例4、如图所示，在鼓的一侧放一支点燃的蜡烛，敲击另一侧鼓面，会发现烛焰摇曳甚至熄灭，这说明声能够传递_能量 知识点四、噪声的危害和控制噪音：从物理学角度看：发声体无规则振动产生 从环境保护的角度看：干扰人们正常生活、学习、工作的声音危害：生理和心理都造成危害噪声的防治： 引起听觉的阶段：声源的振动产生声音空气等介质的传播耳朵鼓膜的振动。 控制噪声的方法：在声源处防止噪声产生阻断噪声的传播防止噪声进入耳朵。 在声源处消声 在传播过程中隔声 在人耳处消声例1、交通噪声是城市的主要来源之一，如图6所示，甲、乙两图分别表示在_和_控制了噪声 例2、减弱噪声的途径有三条，北京市区内禁止汽车鸣笛和燃放烟花爆竹，这是在_ 减弱噪声；在公路和住宅区内设置屏障墙和种草、植树，这是在_减弱噪声；“掩耳盗铃”，这是在_减弱噪声例3、以下措施不能达到减弱噪声目的的是 ( )a摩托车上安装消声 b.街头设置噪声监测仪c机场工作人员佩戴有耳罩的头盔d高架道路两侧建起透明板墙 1、用竖直悬吊的泡沫塑料球接触发声的音叉时，泡沫塑料球被弹起，这个现象说明 _。发声的物体在振动例题2：如图所示把正在发声的闹钟放在玻璃罩内，闹钟和罩的底座之间垫上柔软的泡沫塑料，逐渐抽出罩内的空气，闹钟的声音会逐渐变小，直至听不到声音。这个实验说明了( )a声音是由物体振动产生的 b声音必须通过介质才能传播c声波在玻璃罩中发生了反射 d声波在传播过程中能量逐渐减少空气被抽出后，没有了传播的介质，所以才会听不见声音，选b2、旅游者进入两侧是峭壁的山谷，大喊一声后经2秒听到一侧峭壁反射回的声音；又经1秒听到另一侧峭壁反射的回声。求两峭壁间的距离约多远？（声速约344米/秒）【分析】两峭壁间的距离为旅游者到两侧峭壁间的距离之和。【已知】 v=344米/秒 t1=2秒 t2=1秒【求】s3、打靶时，靶与射击者之间距离为300米。射击后经过1.4秒开枪者听到击靶的声音，声速为340米/秒。求枪弹的平均飞行速度。【分析】从射击到听到击靶声的t=1.4秒，等于子弹飞行时间和声音从靶传回所用时间之和。【已知】 v1=340m/s t=1.4s s300 m【求】v24、关于声现象，下列说法中正确的是（）a声音在各种介质中的传播速度一样大b“闻其声而知其人”主要是根据声音的响度来判断的c用超声波可击碎人体内“结石”，说明声波能传递能量d市区内“禁鸣喇叭”，采用的是在声音传播过程中减弱噪声1.黄河大合唱歌词中的“风在吼、马在叫、黄河在咆哮”，这里的“吼”、“叫”“咆哮”说明固体、液体、气体都可作为_。2.敲打桌子，听到声音，却看不见桌子的振动，你能想出什么办法来证明桌子的振动？3.“风声、雨声、读书声，声声入耳”中声源分别是：_ 。 4.敲鼓时，撒在鼓面上的纸屑会跳动，且鼓声越响跳动越高；将发声的音叉接触水面，能溅起水花，且音叉声音越响溅起水花越大；扬声器发声时纸盆会振动，且声音响振动越大。根据上述现象可归纳出： _ _ 。a把弦拉得紧些 b把弦放松些 c增加发声部分的长度 d用更大的力拉琴5电影泰坦尼克号描述的是1912年一艘名叫“泰坦尼克号” 的大游轮，因为跟冰山相撞而沉没的悲剧为了避免悲剧的重演，科学家发明了一种利用声音传播规律制成的探测装置，把这种探测装置安装在船上，利用它能较早地发现冰山或暗礁的存在（1）这种装置的名称叫_ ，为使它发出的声音有更好的回收效果，最好用 _声波(2)这种装置 _（能/不能）用来进行月球等太空的探测，因为_ 6.下列四个句子：(1)这首歌调太高，我唱不上去； (2)引吭高歌； (3)她是唱高音的；(4)请勿高声喧哗。其中“高”字指音调的是( )a(1)(2)b(2)(4)c(1)(3)d(3)(4)7.我们生活在声音的世界里，声音无处不在。下列声音工厂车间机器的轰鸣声，剧场里京剧表演的演奏声，清晨公园里小鸟的鸣叫声，装修房子的电钻声，婚庆时的爆竹声，山涧小溪潺潺的流水声。其中属于噪声的是 （ ）a b. c. d.8.:以下措施不能达到减弱噪声目的的是 ( )a摩托车上安装消声 b.街头设置噪声监测仪c机场工作人员佩戴有耳罩的头盔d高架道路两侧建起透明板墙9.如图所示，将一把钢尺紧紧按在桌面上，一端伸出桌面适当的长度，拨动钢尺，就可听到钢尺振动发出的声音。逐渐增加钢尺伸出桌面的长度，钢尺振动发出声音的音调会逐渐变_。当钢尺伸出桌面超过一定长度时，虽然用同样的力拨动钢尺，却听不到声音，这是由于_101738年，法国有几位科学家为了探测声音的速度，曾把两门大炮架在相距27km的两个山头上，甲山头放炮时，乙山头上的人便测量从看见炮的火光到听见炮声所经历的时间；再由乙山头放炮，甲山头的人测量炮声所经历的时间这样计算出来的声音在空气中的速度是337m/s。你能设计一个测量声音在铁管中的速度的方案吗？（将所选句子前的序号填上即可）你需要的器材是 _。 你的方案是_ 。你的计算方法是_。可选句子如下：a请一个同学用铁锤敲击铁管的一端； b选择一根铁管，并测出它的长度l；c铁管 d在停止敲击的时候开始计时，到听到声音的时候停止计时，记下时间为t ；e用耳朵在另一端听两次声音的时间间隔t； f卷尺 j钢尺 k秒表lvl/t mv = v0l/(l- v0t)， v0是当时声音在空气中的速度.winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. theyve been great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceless asset going into saturday.the kiwis are a lot less experienced but winning a dramatic match like their semi-final against england will do wonders for their confidence.they defeated australia in the four nations final in 2010 and the last world cup, and know they can rise to the big occasion.winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they will not make the same mistake against the kiwis in m