There are a handful of audio file types you should be familiar with if you are planning to copy music off the Internet or even copy a CD. If you aren't sure what file types you are working with, you can distinguish any file type on your computer by the extension in the file name. The extension is the set of letters that follows the dot, as is in: seashore.wav.
Waveform Audio (.wav)
Waveform Audio (.wav) is a common file format. Created by Microsoft and IBM, WAV was one of the first audio file types developed for the PC. WAV files are defined as lossless, meaning that files are large and complete; nothing has been lost. Professionally recorded CDs are also a lossless audio source.
In contrast, the three audio formats listed below are lossy-redundant and non-auditory data is removed to allow for more compact storage; in essence, some data has been lost. This process of removing data to shrink the file size is called compression.
The three file formats below must begin with a lossless format-such as a store-bought CD or a computer WAV file-then compress it. Most lossy formats boast little or no detectable change in sound quality. But because each compressing format selects the deleteable data differently, converting one compressed file into another lossy format will sometimes result in lower quality audio. Again, always start with a CD or WAV file, then compress.
MPEG-1 Audio Layer 3 (.mp3)
MPEG-1 Audio Layer 3 (.mp3) is a common, compressed WAV file. MPEG-1 files are about one-twelfth the size of WAV files. This is why MP3 players can accommodate hundreds of songs on a tiny chunk of storage space.
Windows Media Audio (.wma)
Windows Media Audio (.wma) was developed to compete with the MP3 format for Windows Media Player. Microsoft claims that the WMA files are compressed three times more than MP3s yet retain their original sound quality.
Ogg Vorbis (.ogg)
Ogg Vorbis (.ogg) is another compressed source code similar to MP3, but like WMA, more compressed. Ogg Vorbis is also open source (free to all, unlicensed, no strings attached). While MP3 compresses data at a constant bit rate, Ogg uses a variable bit rate. To illustrate-if you are copying chunks of silence into MP3 format, the compression bit rate stays the same as if you were compressing the sound of an entire orchestra. But if you are copying chunks of silence into Ogg, your compression rate will drop to nothing. The rate varies with the need.
Musical Instrument Digital Interface (.midi)
Musical Instrument Digital Interface (.midi) is commonly used for computer keyboards and other computer-based musical tools. MIDI files contain musical notes, rhythm notation and other information often needed by a composer.
Audio Interchange File (.aif, .aifc or .aiff.)
Audio Interchange File (.aif, .aifc or .aiff.) was developed for the Macintosh computer to store audio files.
Sun Audio (.au)
Sun Audio (.au) or Audio/Basic was developed by Sun Microsystems for use on UNIX systems.
Emblaze Audio (.ea)
Emblaze Audio (.ea) was created by Geo and offers compression similar to MP3 formats, but its purpose is to be played with a JAVA applet-a miniature Internet program. Online greeting cards often use JAVA applet programs for motion and .ea sound files to play music.