Codecs are nowhere near this sophisticated. Using the noisy restaurant example, the rela- tive signal levels of the hustle and bustle of the restaurant may even exceed the level of the conversation upon which we’re eavesdropping. But we can still actively decipher the information that is coming in, and pick out the conversation. Codecs cannot do this. They can divide the audible frequency range into different slices, but cannot distinguish between things that fall into the same frequency range.