How Sound Works

You hear sound every day. More than likely you are hearing something right now. But how does it work? The study of sound is a fascinating science. This instructable is designed to give you a basic understanding of how sound works.  This instructable is more of a how it works as opposed to a how to.  Once you understand how it works, it is much easier to learn the how to.

Please note that I am constructing this from a sound engineer's point of view.  Most of the content is theory, so please keep that in mind when you read this.

Also, this is my first instructable, so please don't be too harsh.  :)

Sound travels in waves.  Almost all sounds can be created from, or reduced to a sine wave.  You can see a very deep sine wave in the picture.

Sound is the movement of air.  When you hear something, parts of your ear are vibrating.  When you speak, your voice causes air to move, which causes parts in your ear and other people's ears to vibrate.  Most microphones work in a similar way to the human ear.  When sound travels across the diaphragm, it causes it to vibrate, and then convert into electricity (signal).  A speaker works in the opposite way.  When a speaker receives signal (electricity), it causes parts of the speaker to move back and forth which causes air to move.  This way, it allows you to hear the sound.

When you hear something, you have to remember that volume has very little to do with how loud a sound is.  It is all about pressure (SPL).  The greater the pressure, the more the parts in your ear move, and the louder the sound is heard.  This is why having your music too loud is bad for your ears.  Your ear is like anything else in this world, it has limits.  When you have a lot of movement in your ear, your ear tries to adjust, so that it doesn't totally destroy your ear.  It adjusts by limiting the movement/sensitivity within your ear.  Once your ear adjusts, it is very hard to undo.  Your ear adjusts in many other ways too.  If you are straining to hear a specific frequency, your mind will adjust what frequencies it wants to hear so that it encompasses what you are trying to hear.  You do not have any more or less hearing, but a different frequency range.  In this way, you are not straining your ear, but it can make it harder to hear/understand frequencies that you were able to hear/understand with no problem before.  When sound travels, the pressure decreases.  The inverse square law states that in normal conditions, as you double your distance from the source, the sound is reduced by 6 dba (4x).

Reverberation is what happens when sound bounces off something flat and hard.  Many people mistake reverberation for echo.  Reverberation is what happens when you shout and you hear Hello o o o o o o o o o etc.  Echo is when you shout and you hear Hello Hello Hello Hello Hello etc.  Many times you have problems with too much reverberation when you are in a gymnasium.  Acoustical treatments can be used to reduce reverberation.  Some times you may want to use a little reverberation to make something sound big and "booming".  In this case, you can use digital effects to add just the right amount of reverberation.

So I hope that you now have a little bit of understanding of how sound works.  If you liked this instructable and would like me to post some more in-depth instructables about sound, please comment or let me know.  Thanks!

Please note that I do claim copyright to the information. I did not use any specific sources when compiling this information, all of this is from my personal experience.

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© 2011