{{ :sound:sound-banner-790x50.jpg |Sound Band Banner}} ====== UNDERSTANDING SOUND - FLIPPED CLASSROOM: ====== **{{http://en.wikipedia.org/wiki/Flipped_classroom|FLIPPED CLASSROOM}}** is a form of blended learning in which students learn content online by watching video lectures, usually at home. What used to be called 'homework' is now done in class with teachers and students collaborating, discussing and solving questions. In a 'flipped' project, teacher interaction with students is more personalised. The emphasis is on guidance and mutual discovery rather than lecturing. More information and resources are available for teachers in the WPS Teacher WIKI. The starting point for this particular 'flipped' activity is an on-line science QUIZ: IT IS IMPORTANT THAT STUDENTS & TEACHERS FIRST COMPLETE **[[http://goo.gl/forms/2UHbVI5GhL|THE SOUND QUIZ]]** BEFORE VIEWING THE STUDENT WIKI (THIS PAGE!), THE FLIP CONTENT OR THE TEACHER WIKI CONTENT. === Links To Answers & Supplementary Learning Materials: === * When the QUIZ has been completed, students are sent results by email. * In the email, there is a link for more information, activities and experiments to help the student understand more about each question and the answer. * Students are encouraged to investigate, ask questions and design their own experiments. * Each QUIZ question/answer section has links to student resources, which are mostly limited to a simple presentation style, whilst attempting to remain remaining scientifically correct. * The [[http://www.physicsclassroom.com/class/sound|Physics Classroom]] provides an excellent 'one-stop-shop' for more detailed information about the physics of sound. ---- ======= WHAT IS SOUND: ====== {{ youtube>INqfM1kdfUc?640x360 |Vibrating Strings From Inside Guitar}} ** Video 1. How are sounds created and what do sound waves look like?** * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/INqfM1kdfUc|Vibrating Strings From Inside Guitar]] * [[http://www.physicsclassroom.com/class/sound/Lesson-5/Guitar-Strings|Click here for a more detailed explanation about the physics of guitar strings]] * A simple audio interactive to have fun with! [[http://dinahmoelabs.com/plink|Plink - Play some sounds - On-line jamming]] * Simple on-line sequencer http://www.onlinesequencer.net/ * Sing into your computer's microphone. The UJAM Studio will analyze your recording and create a matching playback. http://www.ujam.com/ujamstudio ---- {{ youtube>u1ZB_rGFyeU?640x360 |Fun with physics and music}} ** Video 2. Fun with physics and music** * IF UNABLE TO ACCESS YOUTUBE VIDEO TRY VIEWPURE:[[http://viewpure.com/u1ZB_rGFyeU|Fun with physics and music]] * Visit [[https://www.youtube.com/watch?v=WCwzaTPARtU|this link to see how the video was made]] ---- ++++ CLICK HERE IF YOU CANNOT VIEW YOUTUBE VIDEO(S) ABOVE:| {{:learn:sound:waves:iphone-4-inside-a-guitar.mp4?640x360|Vibrating Strings From Inside Guitar}} {{:learn:sound:i-wont-let-you-down.mp4?640x360|How physics, music & art can work together}} **Videos: Only view these videos if youtube videos (above) are not available** ---- ++++ ++++ CLICK HERE TO SEE HOW SOUND WAVES WORK:| **Sound Waves In Scientific Language: ** The following animation (Fig 1.) shows the difference between the oscillatory motion of individual particles and the propagation of the wave through the medium (gas, liquid or solid). Notice how the particles move backward and forward around a fixed point: The 'wave' effect travels (note the black arrow), but not the particles themselves (note the red dots and arrows). The animation also identifies the regions of compression and rarefaction. {{:learn:sound:waves:longitudinal-wave-02.gif|Longitudinal Waves (sound) - particle movement & wave propagation}} **Fig 1. Longitudinal Waves (sound) - particle movement & wave propagation** More scientific explanation of sound waves is available at [[http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-is-a-Pressure-Wave|The Physics Classroom]] ---- === How Do Heat & Sound Interact === Why is sound absorption in water less than in air? According to my text, for a 1 kHz signal in water the loss by medium absorption is about 0.008 dB/100 m. In air, the loss is much greater: about 1.2 dB/100 m. Imagine that we could take a very fast picture of certain properties of a sound wave during transmission. The pressure varies from a little above atmospheric, to a little below and back again as we progress along the wave. Now the high pressure regions will be a little hotter than the low pressure regions. The distance between two such regions is half a wavelength: 170 mm for a wave at 1 kHz in air. A small amount of heat will pass from hot to cold by conduction. Only a very small amount, because, after half a cycle (0.5 milliseconds for our example), the temperature gradient has reversed. Although it is small, this non-adiabatic (non-heat conserving) process is responsible for the loss of energy of sound in a gas. What happens when we change the frequency? The heat has less distance to travel (shorter half wavelength), but less time to do so (shorter half period). These two effects do not cancel out because the time taken for diffusion (of heat or chemical components) is proportional to the square of the distance. So high frequency sounds lose more energy due to this mechanism than do low. This, incidentally, is one of the reasons why we can tell if a known sound is distant: it has lost more high frequency energy, and this contributes to the 'muffled' sound. (Another contributing effect is that the relative phase of different components is changed.) So, let's now dive into the main question. Three different parameters make the loss less in water. First, sounds travels several times faster in water than in air. (Although the density of water is higher by a factor of about 800, the elastic modulus is higher by a factor of about 14,000.) So, for a given frequency, the wavelength is longer and the heat has further to travel. Second, the water does not conduct heat so rapidly as does air. (This may seem odd if you've recently dived into cold water, but the effect in that case is largely due to water requiring more heat for the same temperature change. Not counting the fact that you probably wear more clothes when out of the water.) Third, the temperature of water rises less under a given imposed pressure than does that of air. All three effects go in the same direction, and their cumulative effect is substantial, as your text's values suggest. Source - http://newt.phys.unsw.edu.au/jw/musFAQ.html#absorption ++++ === MORE FLIPSTER RESOURCES - ONLY IF YOU HAVE COMPLETED THE QUIZ: === The content of both the [[learn:forces:discover:home|DISCOVER]] and [[learn:forces:projects:home|PROJECTS]] sections are for students who have already completed the [[http://goo.gl/forms/2UHbVI5GhL|QUIZ]] and the [[:learn:sound:quiz:home|feedback supplied for each question]]. ---- === SCIENTIFIC EXPLANATIONS - ONLY IF YOU HAVE COMPLETED THE QUIZ: === **[[:learn:sound:quiz:home|CLICK HERE TO VIEW SCIENTIFIC EXPLANATIONS FOR QUESTIONS FROM THE ON_LINE QUIZ:]]** ----