How Sound Works




About: I am an AV and IT guy... I have been involved with sound and lighting since I was 7 yrs old. I currently do Information Technology work for a living, and professional sound as a side job. Although I do bot...

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.  :)

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Step 1: What Sound Is/air Movement

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.

Step 2: Volume Vs. Pressure

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).

Step 3: Reverberation Vs. Echo

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.

Step 4: Conclusion

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.

You may quote parts of this information for educational purposes. Under no circumstances will you sell this information.

I do not own the copyright to any of the images, however, as far as I have been able to find, I have the right to use them in this instructable. If there is any question about whether or not I have the right to use these images, please contact me. I have no intention of stealing anyone's intellectual property.

Use of this information implies that you agree to these copyright terms.

© 2011

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    20 Discussions


    6 months ago on Step 4

    Awesome. Simple and short. Can you do a more complex one on how sound merges with other sounds and how it works via radio waves?


    Tip 1 year ago on Step 4

    This intractable on sound is lovely. I'm very very glad you posted it. I'm eager to see your next post on other sound related topics! Thanks.


    5 years ago on Introduction

    Thank you for your basic intro on sound. I have to teach sound to my 6th graders, and I have been looking for a fun way to introduce it. Do you have any suggestions? I have seen an Instructable for a "space phone," but the instructions refer to needing a diaphragm, but it is not included in the list of supplies. Would you be able to illuminate me?

    1 reply

    7 years ago on Step 4

    Your instructable is very interesting. Could you please write another one, or at least explain in short about how sound interacts with or in liquids, like for example water, because i am very much interested about this, of course if you have any experience in this area. I like the way you have posted this instructable, in simple words, so that anyone could understand..

    Thanks in advance

    2 replies

    Reply 7 years ago on Step 4

    I'm glad you enjoyed it! That is a very interesting idea for a topic... Most of the information in here is written from what I have figured out on my own, not just rephrasing what someone has taught me. I don't have a lot of experience with it interacting with bodies of water per say, but how it interacts with humidity has been an interest of mine for awhile. I will play around with that idea and see what I can come up with. It might take awhile to make an instructable on that, since I am currently very busy with one of my companies. I will be sure to let you know once I have something together. :)


    7 years ago on Step 4

    I had a read through, thanks for the links. I'm sorry to see the hecklers took the time to add posts! This is all very helpful!

    I might not have understood what I was asking with disruption. If you had the ability to condense 10 years of experience on the topic into an instructable it would be great to see o_O

    Any tips on how to reverse phase sound when it hits a surface? Something along the lines of 'the principles of egg crate foam'? Not sure if what I'm asking is paragraph or a dissertation ;)

    3 replies

    Reply 7 years ago on Step 4

    No, hitting a surface is more of disruption. ;)

    Basically, depending on the texture of a surface, the sound will react differently when it hits it. Generally, the smoother the surface, the more the sound will "slap" it, which causes it to vibrate that surface which is why you can hear things through walls, but it sounds muffled. It also reverberates back towards the source of the sound at a slightly reduced pressure. The more pitted a surface is, the more the sound is broken up and absorbed.

    That's the concept in a brief nutshell... I am thinking about how to write my next 'ible... I'll be sure to let you know when it's done. It may take awhile! ;)

    Thanks for the encouragement!


    Reply 7 years ago on Step 4

    This is all good stuff!

    Thanks for the follow ups, I look forward to the next instalment.


    7 years ago on Step 4

    Thanks for the post!

    For someone like me (no real understanding of the principles of sound) this is a good overview. Just when I started to get into it, it stops. If you did have any more information like this it would be appreciated.

    (In particular, cancelling sound waves, dissipation, disruption etc. ;)

    Again, thanks!

    1 reply

    Reply 7 years ago on Step 4

    I'm glad you enjoyed it! I have written 7 instructables on sound so far, but some of them have been written more as an introduction to professional audio equipment rather than the physics behind sound.

    There are two that I think you might be interested in the first one:
    This deals with dissipation.
    The second one is:
    This is the basics of phasing. What you put as canceling sound waves is basically a reversed phase. When you have two sound waves hit each other, if one is the inversed phase of the other and each has the same pressure and volume, then they will cancel each other out. This is how noise canceling earphones work.

    Disruption is not something that is easy for me to cover online... It took me over 10 years to be able to visualize how sound interacts with a room. I can post the basics, maybe I can do a video, but I will start thinking about how I could make an instructable on that. If you want, I can PM you a link if/when I make an instructable on that.

    Thanks again for letting me know you liked this... I really appreciate out! :)


    8 years ago on Introduction

    On the bottom of this page:

    It says: "© Copyright 2011iPad Wallpaper all rights reserved - Design by Thomas Beal"

    1 reply

    Reply 8 years ago on Introduction

    No problem! I really enjoy sound, so I figured that it was about time I actually published something on the internet. :)


    Reply 8 years ago on Introduction

    Half of the work isn't your's, though. These pictures are made by other people and have not been properly accredited.


    Reply 8 years ago on Introduction

    I'm sorry I didn't see this comment sooner... for some reason it didn't show up on my comments alert!

    My copyright step specifically states that I do not claim copyright to the images, but as far as I can find I have the right to use them. The copyright that you are referencing actually applies to the web site, not the image.  I do not claim that I made the image, however, all the images that I download, I download from stock image sites that I pay for.  That is why I say that if there is any question about whether or not I have the right to use the images to please contact me.  Again, I see not copyright on the image... although I do see a company name on it, but I see nothing about not having the right to use the images.