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How does all that music fit on an iPod?
1500 CDs would make a stack taller than most houses, but we can now carry round all of that music in something the size of a pack of cards. How does it all fit in?
First of all you have to turn the original music wave into a series of numbers. You do this by sampling or measuring the wave at different times. Music on a CD is sampled at about 44,000 times a second. The result is a digital recording that can be stored as just numbers. Mp3 is a type of compression that squashes up this data. A four minute song on a CD uses about 40MB of space, but with mp3 compression it gets down to about 4MB.
Music is a mixture of sounds at different frequencies and volumes. Mp3 files get rid of the sounds that your ears are not so good at detecting. If there is a loud sound in one split second of the track then some of the other sounds can be thrown away and you won’t notice they have gone. By doing this you can get rid a lot of the information, but of course you are also losing some element of the music.
Most people think that the small loss in quality is worth it for the convenience of carrying all those tunes around with you!
For more information see:
http://electronics.howstuffworks.com/mp3-player1.htm
