An audio file is a file format for storing digital audio data on a computer system. Any digital information with speech or music stored on and played through a computer is known as an audio file or sound file. Audio is sound within the acoustic range available to humans. An audio frequency (AF) is an electrical alternating current within the 20 to 20,000 hertz (cycles per second) range that can be used to produce acoustic sound.One of the most common types of audio file formats used today is the MP3.