the early xing mp3 codec famously cut everything off above 18khz, but that was out of spec. :) instead perceptual audio compression typically filters out frequ

the early xing mp3 codec famously cut everything off above 18khz, but that was out of spec. :) instead perceptual audio compression typically filters out frequencies that neighbor other frequencies with lots of power. deleting these neighbors is called perceptual masking and to the best of my knowledge, we do not actually know if it works the same way in animal auditory systems.