Learn in the textbookDigital Representation of Audio and File Formats
DefinitionMP3 is a lossy compression audio file format that makes audio data smaller by removing components the human ear has trouble hearing.
ExplanationLossy compression is a method in which discarded information does not come back even when the compressed data is decompressed (伸長, converted back to its original form). MP3 cuts parts that are hard to make out, such as a quiet sound right next to a loud one, and depending on the settings can shrink the data to about one tenth of the original PCM data. The more it cuts, the smaller the file, but the lower the sound quality.
AnalogyIt is like lightening a bag by taking out things you can do without when packing. What you take out cannot be recovered later.
Memory hookMP3 stands for MPEG-1 Audio Layer-3, a name taken from the audio part of MPEG, the compression standard for video and audio.