Science and sound are irrevocably tied together (mathemathics as well, but anywho). Why does your voice sound so different when you hear it recorded versus when you normally talk? I'm not normally a math or science gal, but this stuff is fascinating.
All sound is energy that is caused by a vibration; sound waves. Sound waves that are more mathmatically perfect make sounds that are more pleasing to the ear (such as an instrument, bell tone, etc), and ones that aren't we would classify more as "noise". There is more to the mathmatics of it, but I won't go into that here.
My amazing, fantastic MSPaint skills aside, above is a rudimentary representation of "music" versus "noise". The first group of sound waves would be something considered noisy; a jackhammer, a loud truck, etc. The waves are inconsistent and are not symmetrical at all. The bottom group of waves would be a sustained tone of an instrument or a human voice, or even an electronic sound. You can see these waves are much more uniform (disregarding the aforementioned MSPaint skills).
When those sound waves (vibrations) are heard by us, it becomes sound. Or does it? It goes back to the saying of "If a tree falls in the woods, and no one is around to hear it, does it make a sound?" Many people would argue something isn't a sound unless it's heard by someone or something. I'll let you toil under that philosophical question.
When we hear vibrations, whether or not something sounds high or low is measured by the sound wave's hertz. Here is a quick chart to give you an idea:
Humans can generally hear anything starting at 20 Hertz (or hz) and going as high as 20,000. Someone with better than average hearing could hear more. The frequency or hertz of sound refers to its pitch; or how high or low it sounds. The lower the hz, the lower the sound. Think of a dog whistle; the frequency of the dog whistle is so high human ears can't hear it, but dogs can!
Volume is separate, and measured in decibels. Most of us know that if we listen to a sound at too high of a decibel level, we can cause hearing damage.
So to review, how loud something is refers to its decibel. If we want to translate that into its sound wave, we look at volume as amplitude. How high or low pitched something sounds is measured by hertz. When looking at a sound wave, we refer to that as its frequency.
Phew, that was a lot of information! Now onto something I had always wondered:
Why does my voice sound so different when I hear a recording, versus when I hear myself speaking?
I've always wondered this! The answer is just as scientific as everything above. The folks at SciShow have made a great video about this.
Well, that does it for Part I of the Science of Sound! Stay tuned for Part II!
-DMM