Audio is a technical term, and the term audio has been used to describe generally sound-related equipment and its role in the audio range. All sounds that humans can hear are called audio, and it may include noise and so on. After the sound is recorded, whether it is speaking, singing, or musical instruments can be processed by digital music software, or it can be made into a CD. At this time, all the sounds have not changed, because the CD is originally a type of audio file. Audio is just sound stored in the computer. If there is a computer plus a corresponding audio card—that is, a sound card we often say, we can record all the sounds, and the acoustic characteristics of the sounds such as the sound level can be stored in the form of a computer hard disk file.