The most common compressed audio formats use ``psychoacoustic models'' to discard audio data that cannot be heard or that is typically ignored by the human ear. By eliminating this data, a file can be reduced in size while minimizing the effect on the sound. These formats that selectively discard data are known as lossy formats, and they can produce files that are anywhere from one-fourth to one-thirtieth the size of the original uncompressed audio, with a corresponding degradation in fidelity.