Sound PDF

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- ire Iii -J.J" ) '""' \_) Sound ~ r ning Objectlves At the nd of this............11$ w;u be able to oodecstand How I s ~ ""lht OhoractecLstocs of "bcat,ons Mus,ca[ ,nst,uments. The concept ol _,nd pradqq,j Iii,.....,.._ S-.. needs a med,um to, pcopagat,on The wo,k,ng of human,., JIMo.~ ~,.......... :Qe':i"' ~ w ·. ~-iv -- · §S,.... "! t~ o l. Qlstingu,sh belween aud,ble and ,naud,ble sound. Technolog,cal L-.~·· ~-.._.,it; ·.r-:r Oistingu,sh belween no,se and mus,c The hannful It «t!t. ' ec~..areno1sy ~ g ea r - favou rite ·'but sou nd 'h llp you ids... :fUnd birds, irking 1itoes, !!'5i Some common musical instruments ♦ SOUND  und helps us to communicate with one [!] SO can you recognize your friends by Just · 13.1 HOW IS SOUND PRODUCED? ~ 10 their voices? Yes, you can because [!],. ~ g nd has a different character r.., 1L.'. P Put your finger tips in front of your throat sou w'".. will address several questions In the ,,.~~tll" What do you feel? Again touch It when you speak 'xt of sound in this chapter. How 1s sound What do you feel now? Your finger tips feel some nteJ t(l? How does sound travel from one place v1brat1ons while you speak. ~ther? Why does one sound differ from the So, vibrating obiects make sound. Every type !!ff' of sound Is produced by something in a state of v1brat1on Let us perform these act1v1ties krMr, 13.1 ac~ available at home) Hang It with the help way that It does not touch any wall. Now beating shallow pan Now touch the pan ? You feel the Vibrations Id 1t tightly with your hands immediately ~ ·ou observe that as your hands come in in the pan stop and no sound Is produced. uctng sound What do you feel? You feel A CTIVITY 13.2 "'a ruccer cane 0 D" once "'cax ana band from the middle the pencil box with the or feel' You observe the sound heard A v1bra t1on 1s a rapid to and fro or back and forth as oscillatory motion ,ound tor experi ments and waves lnpples] on the surface of SOUND ♦ B-35  SCIENCE BITS! SCIENCE BITS! l-lidr, and seek Is a game in which one player lul"ing -· -.---.- cce blindfolded and has to catch the remaining players of metal It has two arms rn the Sound of feet or voice of remaining players help Li-shaped section are calil?ci prongs blind-folded player to catch them and a handle called stem. Tuning fork Is used to produce a certain fixed frequency sound...... ACTMTY 13.3 Aim : The vibrating tuning fork produces wavc,c; rn Willer Requirements : A metal d,st>, water, tu'l\Ing fork and rubber pad Procedure : Take a metal dish and pour water m rt Now take a tuning fork and struck its one prol'lg on rubb~!" pi)d What do you observe' Do you hear any sound' You observe that prongs are bratmg II you hold this Vibrating tun'ng 'ork near the any ear You hear a sound. so tuning fork produces sound Now touch the vibruttng pron g w. th the surface of water m a metal dish What do you see? Waves are produced on the surface of water In all the act1v1t1es described above, you notice that SCIENCE BITS ! a vibrat ing obJect produces sound In some cases, Longitudinal and Transverse waves the vibrations are easily v1s1ble to us but in some When v1brat1on 1s produced, sound cases they can only be felt and not seen However, we can feel them propagates m the forms of waves w~.:::n ~ types Longitudinal or transverse waves. 13.2 CHARACTERISTICS OF ~J~ ~ If the d1rect1on of the vtbrat10n of Lie - VIBRATIONS IOSCJLLATIONS) g.;:w "UE3 the medium rs the same as the d:.-e Amplitude, frequency and the time period the sound wave Is travelling, the Wd are the three important characteristics of the longitudinal wave. vibrations.. Example Sound waves in air travel as (1) Anlpl..1111, ~ JlJt...mex;mum displacemen t waves · o/~ -~ -~. - , its mean pos1t1on When the Vibration of the particles al.... -..~. & Its SI units rs rs perpend icular to the d,reel' :011 c waves, the wave Is called transverse waves in water are the example of trans,erse IG3 I a Its SI unrt 1s hertz (Hz) rn honollf d German phys1c1st Hemrich R Hert: u, v1bra tmg body makes 60 vibratc~.s elf seco nd its frequency 1s 60 Hz. (3) Time Period : The time taken hi r of vibrations of vibra ting body to comp,ete o?e ~ e second 1s called ,s called the time period of Vlbra SI unit 1s second(s) B-36 ♦ SOUND  between lirno Period tlr\d fro frequency rs represen t ed by. ~llt:!nc-y by T, then frequenc-y h. ) ts re~t and time [T) as , V:::: _ ed to time T o r, T :::: -1 V 11 3 MUSICAL INSTRUMENTS ~I:!) Sound ,s produced not only by "'b"'toons gs but also by "1bn,toons in '" tcheo ~ brane, as Well as by v1bn,t,ons 1n a1c columns. instruments such s m OJ ra lcymbats1, - :001 ~ (mud-pots), the ghatam Od lhe kartat uce sound by simply beaten or stnick Gliatarn...__ These instruments are commonly used m different parts of India. Some of these are very simple and can make at home. Let us perform these act1V1t1es. ACTtVrty 13.4 or an ea rthen pot, membrane en block lbndgel, string and ll and t o ,t attached a spltt I an open in g cut m the coconut the bamboo cane Now stretch coconut shell, over the bndge, to use :h one finger , the pit ch can be with the help of tuning peg SCIENCE BITS! Ii:!! So, Ektara means one string instrument. E.ktara also called the SOUND ♦ B -37  - 1~ ACTMTY 13.5 Aim : TO make Jaltarang at home Re · quirements : 6-8 tumblers. water and a pencil. Procedure : Take 6-8 tumblers and fill them with water up to different levels as shown in the figure Now take a pencil and strike the tumblers gently all of them in succession You will hear pleasant sounds. Ad;ust the amount of water in tumblers so that you can get th e notes sa. re, ga, ma. pa, dha. n,, sa from them. Play simple tunes on your Jal Tarang When you str ke the membrane of a mndangam. (3) Percussion Instruments : They ~ the sound that you hear 1s not only that of stretched skrn whose vibrations P"-:," the membrane but of the whole body of the sound. The pitch or frequency of v · instru ment. Similarly, when you pluck the string can be increased by stretching t".e of an instrument. like the violin, the sound that more. Drum, tabla, mndangam, ett we hear 1s not only that of the string. The whole percussion instruments. ii instrument is forced to vibrate. and rt 1s the sound of the vibration of the instrument that we hear According to sound of the vibrations they are classified into three types : (1J Wind Instrument : The instrument where vibrations in air columns produce sound. The frequency is changed by changing the length of the vibrating air column. For example, shehnai. flute, clarinet, etc. ✓- ~ Tabla ~ Identity the v·brating parts of the van musical instruments given n the It:: and fill them 1n the table Table 13.1 : Musical in~truments and their v1br