What is Sound?(Sound Explained) – Sound Speed & Pressure Waves & Frequency

What is Sound?(Sound Explained) – Sound Speed & Pressure Waves & Frequency


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!

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About the Author: Oren Garnes

6 Comments

  1. Estes 6 minutinhos passaram a voar, valeu a pena a espera! 😀

    A forma como combinas o humor com a transmissão de conhecimento é brilhante!

  2. Interesting. @2:41 you almost 'got it' and then went right back to being dead wrong again. The balls on the pool table do collide and they do transfer something to the next ball in the line. But, they don't generate anything like a wave structure.

    Sound also does not generate a wave structure (alternating compressions and rarefactions as shown here – http://resource.isvr.soton.ac.uk/spcg/tutorial/tutorial/Tutorial_files/longipatm.gif).

    In spite of all the science classes that tell you that it works that way (and as you say it works), it doesn't. So, how does it work?

    A simplified answer is needed here since you also learned pretty much everything about how air and sound work wrong.

    If the cure stick that hits the first ball is riding on an oscillating platform, each time it hits the ball it's most likely in a different position. Because of that, the timing of when that ball is hit changes.

    With sound in air, there are about 70 trillion air particles striking each square inch. If that inch is moving, as the air particles strike it, they pick up a time/position offset. An extremely tiny offset. Basically the time difference of when one particle strikes the inch and the next one does. Those offsets are extremely durable and persistent.

    When those offsets reach an eardrum, if the movement of the inch was toward the eardrum at the time the offset was impressed on the particles, they will arrive earlier than they normally would. If the inch was moving away from the eardrum at that time, the offset particles will arrive later.

    When they arrive earlier, they add to the ones that are there with no offset and add force to the eardrum and it flexes away from the source inch. When they arrive later, they subtract from the number striking the eardrum with less force than the ones with no offset and the eardrum flexes toward the source inch.

    But, the eardrum can't flex by itself. There must be a force differential across it. That differential is applied by air particles on the back side of the eardrum (via the oral/nasal cavities and Eustachian tubes to the ears. BTW: that's why things sound odd or dead when you have a cold and the Eustachian tubes are swollen and blocked (and why it's painful to change altitude when the force differential across the eardrum cannot equalize).

    There are filter effects to the cavities which is why, when people first hear their voice as recorded it sounds different to them than when they are speaking.

    So, in synopsis, the position of the source surface (like a speaker cone) gets transferred to the eardrum via collisions of the air particles conveying the early/late offsets. Because it takes time for the collision chain the reach the eardrum, there is a propagation delay of the sound which is the speed of sound. Even in your animation of the pool table you can see how that works.

    You got the propagation method right but completely missed the sound part of it.

    See. I told you that you just don't have enough background info to 'get it' and that;'s due to the years you spent learning it wrong. And, most of you who may read this will reject it on the basis that it's not how you learned it so it must be wrong.

    It's not my place to tell you how to do your science so you're welcome to have any truth you want.

    salaphysics
    070619

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