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something i learned in school that i thought was interesting.
mpeg layer 3
motion picture experts group
cd quality- 44.1kHz, 16 bit resolution
a 2 track, stereo interleaved file
44.1kHz (or 44100 samples per second)
1411200 (samples per bit)
itunes offers their mp3's at a rate of 128kbps.
divide the number above by 128kbps ( 128000 bits per second) and you get 11.025. so the mp3 is compressed at a ratio of about 11:1.
for every 11 bits of dynamic range, you are getting 1 bit back.
now do the opposite and divide 128000 by 1411200.
converting that into a percentage, we get about 9%. this is how much is left of the original audio at 128kbps.
of the audio signal has been removed from the original waveform.
the data is removed permanently, based on priority.
low priority to keep masked frequencies, and frequencies outside of 20Hz-20kHz (the range of human hearing).
highest priority to keep are frequencies from 1kHz- 4kHz (mid range).