{"id":9644,"date":"2018-02-13T12:08:44","date_gmt":"2018-02-13T06:38:44","guid":{"rendered":"http:\/\/mycbseguide.com\/blog\/?p=9644"},"modified":"2018-03-19T11:43:25","modified_gmt":"2018-03-19T06:13:25","slug":"sound-class-9-notes-science","status":"publish","type":"post","link":"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/","title":{"rendered":"Sound class 9 Notes Science"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_76 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 eztoc-toggle-hide-by-default' ><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/#CBSE_Guide_Sound_class_9_Notes\" >CBSE Guide Sound class 9 Notes<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/#9_Science_notes_Chapter_12_Sound\" >9 Science notes Chapter 12 Sound<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/#Download_Revision_Notes_as_PDF\" >Download Revision Notes as PDF<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/#Sound_class_9_Notes\" >Sound class 9 Notes<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/#CBSE_Class-9_Revision_Notes_and_Key_Points\" >CBSE Class-9 Revision Notes and Key Points<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<p>CBSE class 9 Science Chapter 12 Sound notes in PDF are available for free download in myCBSEguide mobile app. The best app for CBSE students now provides Sound class 9 Notes latest chapter wise notes for quick preparation of CBSE exams and school based annual examinations. Class 9 Science notes on Chapter 12 Sound are also available for download in CBSE Guide website.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"CBSE_Guide_Sound_class_9_Notes\"><\/span>CBSE Guide Sound class 9 Notes<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>CBSE guide notes are the comprehensive notes which covers the latest syllabus of CBSE and NCERT. It includes all the topics given in NCERT class 9 Science text book. Users can download CBSE guide quick revision notes from myCBSEguide mobile app and my CBSE guide website.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"9_Science_notes_Chapter_12_Sound\"><\/span>9 Science notes Chapter 12 Sound<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Download CBSE class 9th revision notes for Chapter 12 Sound in PDF format for free. Download revision notes for Sound class 9 Notes and score high in exams. These are the Sound class 9 Notes prepared by team of expert teachers. The revision notes help you revise the whole chapter in minutes. Revising notes in exam days is on of the best tips recommended by teachers during exam days.<\/p>\n<h1 style=\"text-align: center\"><span class=\"ez-toc-section\" id=\"Download_Revision_Notes_as_PDF\"><\/span><strong><a href=\"https:\/\/mycbseguide.com\/downloads\/cbse-class-09-science\/1218\/cbse-revision-notes\/7\/\">Download Revision Notes as PDF<\/a><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n<p style=\"text-align: center\"><strong>CBSE Class 9 Science<br \/>\nRevision Notes<br \/>\nCHAPTER \u2013\u00a012<br \/>\nSound<\/strong><\/p>\n<p><strong>1. <u>Production of Sound\u00a0<\/u><\/strong>Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an object.<br \/>\nVibrating objects are the source of all sounds Irregular, chaotic vibrations produce noise Regular, controlled vibration can produce music. All sound is a combination of pure frequencies. A stretched rubber band when plucked vibrates and produces sound.<\/p>\n<p><strong>2. <u>Propagation of Sound<\/u>\u00a0<\/strong>When an object vibrates, the particles around the medium vibrate. The particle in contact with the vibrating object is first displaced from its equilibrium position.<br \/>\nThe disturbance produced by the vibrating body travels through the medium but the particles do not move forward themselves.<br \/>\nA wave is a disturbance which moves through a medium by the vibration of the particles of the medium. So sound is considered as a wave. Sound waves Require medium for transmission.<\/p>\n<p><u><strong>Sound waves are called mechanical waves<\/strong><\/u>\u00a0When a vibrating object moves forward, it pushes and compresses the air in front of it forming a region of high pressure called compression (C). When the vibrating object moves backward, it forms a region of low pressure called rarefaction(R).<br \/>\n<img decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_01.png\" \/><\/p>\n<p>A vibrating object producing a series of compressions (C) and rarefaction (R)<\/p>\n<p>In these waves the particles move back and forth parallel to the direction of propagation of the disturbance. <strong>Such waves are called longitudinal waves. <\/strong><\/p>\n<p><strong>There is another kind of waves called transverse waves<\/strong>. In these waves the particles oscillate up and down perpendicular to the propagation of the direction of disturbance.<\/p>\n<p>Sound propagates in a medium as a series of compressions (C) and rare factions (R).<\/p>\n<p>Compressions are the regions of high pressure and density where the particles are crowded andare represented by the upper portion of the curve called crest.<\/p>\n<p>Rarefactions are the regions of low pressure and density where the particles are spread out and are represented by the lower portion of the curve called trough<\/p>\n<p><strong>Characteristics of a sound wave<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_02.png\" width=\"431\" height=\"198\" \/><\/p>\n<p><strong><u>Frequency of sound wave<\/u><\/strong><\/p>\n<p>The number of oscillations per unit time is called the frequency of the sound wave. It is represented by the symbol v<span dir=\"RTL\">\u00a0 <\/span>(Greek letter nu). Its SI unit is hertz (Hz)<\/p>\n<p><strong>Time period of sound wave:<\/strong><\/p>\n<p>The time taken by wave to complete one oscillation is called time-period.<\/p>\n<p>Frequency and time are represented as follows :-<\/p>\n<p>V for one oscillation<\/p>\n<p><span class=\"cke_widget_wrapper cke_widget_inline cke_widget_selected\"><span class=\"math-tex cke_widget_element\"><img decoding=\"async\" src=\"https:\/\/elpiscart.com\/cgi-bin\/mathtex.cgi?T = \\frac{1}{V}\\;\\;\\;\\;or\\;\\;\\;V = \\frac{1}{T}\" \/><\/span><\/span><\/p>\n<p><strong>Amplitude of sound wave <\/strong><\/p>\n<p>The amplitude of sound wave is the height of the crest or tough.<\/p>\n<p>It is represented by the letter A.<\/p>\n<p>The SI unit is the same as that of density or pressure.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_03.jpg\" \/><\/p>\n<p>The wavelength is the distance between the &#8220;crests&#8221; of two waves that are next to each other.<\/p>\n<p>The amplitude is how high the crests are.<\/p>\n<p><strong>Pitch and loudness of sound <\/strong><\/p>\n<p>The pitch of sound (shrillness or flatness) depends on the frequency of vibration.<\/p>\n<p>If the frequency is high, the sound has high pitch and if the frequency is low, the sound has low pitch<\/p>\n<p><strong>Speed of sound <\/strong><\/p>\n<p>The speed of sound is more in solids, less in liquids and least in gases.<\/p>\n<p>The speed of sound also depends on the temperature of the medium. If the temperature of the medium is more, the speed of sound is more<\/p>\n<p><strong>3. Reflection of Sound <\/strong><\/p>\n<p>Sound gets reflected at the surface of a solid or liquid and follows the laws of reflection.<\/p>\n<ol>\n<li>The angle of incidence is equal to the angle of reflection.<\/li>\n<li>The incident ray, the reflected ray and normal at the point of incidence all lie in the same plane.<\/li>\n<\/ol>\n<p><img decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_04.png\" \/><\/p>\n<p><strong>4. Echo <\/strong><\/p>\n<p>If we shout or clap near a reflecting surface like tall building or a mountain, we hear the same sound again. This sound which we hear is called echo. It is caused due to the reflection of sound. To hear an echo clearly, the time interval between the original sound and the echo must be at least 0.1 s.<\/p>\n<p>Since the speed of sound in air is 344 m\/s, the distance travelled by sound in 0.I s = 344<\/p>\n<p><span class=\"cke_widget_wrapper cke_widget_inline cke_widget_selected\"><span class=\"math-tex cke_widget_element\"><img decoding=\"async\" src=\"https:\/\/elpiscart.com\/cgi-bin\/mathtex.cgi?{\\text{m}}\/{\\text{s x }}0.{\\text{1 s }} = \\;{\\text{34}}.{\\text{4 m}}\" \/><\/span><\/span>. So to hear an echo clearly, the minimum distance of the reflecting surface should be half this distance that is 17.2 m.<\/p>\n<p><strong>Reverberation <\/strong><\/p>\n<p>Echoes may be heard more than once due to repeated or multiple reflections of sound from several reflecting surfaces. This causes persistence of sound called reverberation.<\/p>\n<p>In big halls or auditoriums to reduce reverberation, the roofs and walls are covered by sound absorbing materials like compressed fibre boards, rough plaster or draperies.<\/p>\n<p><strong>5. Uses of Multiple Reflection Of Sound <\/strong><\/p>\n<p>i) Megaphones, horns, musical instruments like trumpets, etc. are deigned to send sound by multiple reflection in a particular direction without spreading in all directions.<\/p>\n<p>ii) Doctors listen to sounds from the human body through a stethoscope. The sound of heartbeat reaches the doctor\u2019s ears by multiple reflection.<\/p>\n<p>iii) Generally the ceilings of cinema halls and auditoriums are curved so that sound after multiple reflection reaches all parts of the hall. Sometimes a curved sound board is placed behind the stage so that sound after multiple reflection spreads evenly across the hall.<\/p>\n<p><strong>6. Range of Hearing <\/strong><\/p>\n<p>Human beings can hear sound frequencies between 20 Hz and 2000 Hz., called as audible range of sound.<\/p>\n<p>Sound whose frequency is less than 20 Hz is called infrasonic sound<\/p>\n<p>Sound whose frequency is more than 2000 Hz is called ultrasonic sound<\/p>\n<p><strong>7. Uses of ultrasonic sound <\/strong><\/p>\n<p>Ultrasonic sound is used to clean objects like electronic Components, used to detect cracks in metal blocks, used in ultra sound scanners for getting images of internal organs of the human body used to break small stones formed in the kidneys into fine grains.<\/p>\n<p><strong>8. Sonar <\/strong><\/p>\n<p>It is a device which uses ultrasonic waves to measure distance, direction and speed of underwater objects. The distance of the object can be calculated by knowing the speed of sound in water and the time taken between the transmission and reception of ultrasound<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_05.jpg\" \/><\/p>\n<p><strong>9.Structure of the human ear<\/strong><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/media-mycbseguide.s3.amazonaws.com\/images\/static\/revise\/09\/science\/09_sc_ch12_06.jpg\" \/><\/p>\n<p>The sound waves passes through the ear canal to a thin membrane called eardrum. The eardrum vibrates. The vibrations are amplified by the three bones of the middle ear calledhammer, anvil and stirrup. Middle ear then transmits the sound waves to the inner ear. The brain then interprets the signals as sound.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Sound_class_9_Notes\"><\/span>Sound class 9 Notes<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ul>\n<li>CBSE Revision notes (PDF Download) Free<\/li>\n<li>CBSE Revision notes for Class 9 Science PDF<\/li>\n<li>CBSE Revision notes Class 9 Science \u2013 CBSE<\/li>\n<li>CBSE Revisions notes and Key Points Class 9 Science<\/li>\n<li>Summary of the NCERT books all chapters in Science class 9<\/li>\n<li>Short notes for CBSE class 9th Science<\/li>\n<li>Key notes and chapter summary of Science class 9<\/li>\n<li>Quick revision notes for CBSE exams<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"CBSE_Class-9_Revision_Notes_and_Key_Points\"><\/span><strong>CBSE Class-9 Revision Notes and Key Points<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Sound class 9 Notes. CBSE quick revision note for Class-9 Science, Chemistry, Maths, Biology and other subject are very helpful to revise the whole syllabus during exam days. The revision notes covers all important formulas and concepts given in the chapter. Even if you wish to have an overview of a chapter, quick revision notes are here to do if for you. These notes will certainly save your time during stressful exam days.<\/p>\n<ul>\n<li><a href=\"http:\/\/mycbseguide.com\/downloads\/cbse-class-09-mathematics\/1234\/cbse-revision-notes\/7\/\">Revision Notes for class-09 Mathematics<\/a><\/li>\n<li><a href=\"http:\/\/mycbseguide.com\/downloads\/cbse-class-09-science\/1218\/cbse-revision-notes\/7\/\">Revision Notes for class-09 Science<\/a><\/li>\n<li><a href=\"http:\/\/mycbseguide.com\/downloads\/cbse-class-09-social-science\/1895\/cbse-revision-notes\/7\/\">Revision Notes for class-09 Social Science<\/a><\/li>\n<li><a href=\"http:\/\/mycbseguide.com\/downloads\/cbse-class-09-english-communicative\/1900\/cbse-revision-notes\/7\/\">Revision Notes for class-09 English Communicative<\/a><\/li>\n<\/ul>\n<p>To download Sound class 9 Notes, sample paper for class 9 Mathematics, Social Science, Science, English Communicative; do check myCBSEguide app or website. myCBSEguide provides sample papers with solution, test papers for chapter-wise practice, NCERT solutions, NCERT Exemplar solutions, quick revision notes for ready reference, CBSE guess papers and CBSE important question papers. Sample Paper all are made available through\u00a0<a href=\"https:\/\/play.google.com\/store\/apps\/details?id=in.techchefs.MyCBSEGuide&amp;referrer=utm_source%3Dmycbse_bottom%26utm_medium%3Dtext%26utm_campaign%3Dmycbseads\"><strong>the best app for CBSE students<\/strong><\/a>\u00a0and myCBSEguide website.<\/p>\n<ul>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/matter-surrounding-class-9-notes-science\/\">Matter in Our Surrounding class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/matter-around-us-pure-class-9-notes-science\/\">Is Matter around Us Pure class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/atoms-molecules-class-9-notes-science\/\">Atoms and Molecules class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/structure-atoms-class-9-notes-science\/\">Structure of the Atoms class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/fundamental-unit-life-class-9-notes-science\/\">The Fundamental Unit of Life class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/tissues-class-9-notes-science\/\">Tissues class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/diversity-living-organisms-class-9-notes-science\/\">Diversity in Living Organisms class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/motion-class-9-notes-science\/\">Motion class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/forces-laws-motion-class-9-notes-science\/\">Forces and Laws of Motion class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/gravitation-class-9-notes-science\/\">Gravitation class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/work-energy-class-9-notes-science\/\">Work and Energy class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/\">Sound class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/fall-ill-class-9-notes-science\/\">Why Do We Fall ill class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/natural-resources-class-9-notes-science\/\">Natural Resources class 9 Notes Science<\/a><\/li>\n<li class=\"entry-title\"><a href=\"https:\/\/mycbseguide.com\/blog\/improvement-food-resources-class-9-notes-science\/\">Improvement in Food Resources class 9 Notes Science<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>CBSE class 9 Science Chapter 12 Sound notes in PDF are available for free download in myCBSEguide mobile app. The best app for CBSE students now provides Sound class 9 Notes latest chapter wise notes for quick preparation of CBSE exams and school based annual examinations. Class 9 Science notes on Chapter 12 Sound are &#8230; <a title=\"Sound class 9 Notes Science\" class=\"read-more\" href=\"https:\/\/mycbseguide.com\/blog\/sound-class-9-notes-science\/\" aria-label=\"More on Sound class 9 Notes Science\">Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":9574,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[45,456],"tags":[457,150,426,240,674],"class_list":["post-9644","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse-class-09","category-revision-notes","tag-cbse-notes","tag-cbse-notes-and-key-points","tag-quick-revision","tag-quick-revision-notes","tag-sound"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Sound class 9 Notes Science | myCBSEguide<\/title>\n<meta name=\"description\" content=\"Sound class 9 Notes Social Science chapter 12 in PDF format for free download. 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