Music… …a magnificent composition of sounds… …that touches our souls! Well… We know about things that can make sounds… Like the strings on a guitar. Thunders. Pooping a balloon Or even… (Fart Sound) Who did that? Oh sorry…That was me! Who are you ? I am Wikipedia Man! The superhero that helps students do their homework! And i’m here to help you understand sound ! Cool! So what is sound ? Sound is a vibration… …that propagates as a typically audible mechanical wave of pressure and displacement! In a medium… Such as air or water! Well…That doesn’t really help very much… Is just a definition using terms i don’t really understand! Sorry, can’t go any deeper… I only have the power of approximated knowledge in a vast range of areas. My duty is to spread a medium level of information through the world! WIKIMAN AWAY! Oh! I can’t fly… Can you point the door? So sound is a vibration Hello? (Angry Korean) Hi there ! Who are you ? I’m you! Five years from now! A smarter version of you… …sent from the future… …to teach you what sound is! What? What’s happening in my room today? Do i need to hire a secretary? Wait a minute… You come from the future? So… Do we have a girlfriend now? I’m not here for that! I’m here to explain you what sound is! And sound… Is a vibration! (Already heard that!!) Well… Is a vibration because is caused by vibrating objects! Sound is also a wave! (Sea sound) Not that kind! Is a wave because basically … Is a medium like air … Continuously changing in pressure! To better understand this , let’s watch this simple example! Imagine a pool table, with 5 balls in a straight line! If you push the first ball… …it will push the second, and so on until the last one hits the wall! With air something similar happens… The air molecules are pushed… And bump into each other… Until they reach our hears! But with a small difference … Air is a compressible gas! What means … It has elastic properties! Is like the balls had invisible springs between them! And when you pushed, they push the next one! But return to their place! Sound is like that! Air is pushed at a certain rhythm! Until it reaches our hears! The pressure variation i talked about earlier… Is due to the air motion! There’s places where the molecules are closer together! And where they are further apart! Inside this megaphone, something is pushing the air! And in our hears an organ is being pushed by the air! Converting this vibration… Into electrical signals… Sent to our brain! And this is how we perceive sound ! Now you’re probably thinking… Wait a second!! If i move my arm like this… I’m moving air I’m pushing it! And i can’t hear nothing! Why is that ? Well… It’s because a very important property of sound! Frequency Frequency is measured in HERTZ What means cycles per second Humans can only hear sounds between 20 and 20.000 Hertz For example… If the minion moves his arms one time per second… His frequency is 1 Hertz And because is below 20 Hz, we can’t hear it! Now If he increases his frequency to 50 Hz… He reaches the hummingbird frequency! We can hear it… And he will probably start flying! What about the speed of sound ? You must have heard about it! Like when jets break the sound barrier! The speed of sound In dry air Is about.. What means the pressure waves or sound… Travel 343 meters or 328 yards… In 1 second But what about in the water? Does the sound travel at the same speed ? Actually sound travels 4.3 times faster in liquids! That’s because liquids are incompressible ! When a molecule of water is pushed… Almost immediately pushes the next one! What if i told you, you can break a glass with your own voice ? (Mom i broke it!!) Mom:you did not! Well, you can, but don’t do it… Is dangerous! You can also visualize sound… And levitate small objects with it! As you can see, sound is a wonderful thing! And has a lot of potential! My name is Joel… And i love science! Thanks for watching … And remember… Don’t judge people on their music taste!