In order to play digital audio files you need to have a player program installed on your computer. Most people think of iTunes as the player of digital audio files. However, QuickTime on the Mac, and Windows Media Player on the PC are also available to play most audio files. There are lots of other player programs for PCs, Macs, and even Linux computers, but a good one that works on all three platforms is VLC. Remember, VLC is not just for video. The reason that I distinguish between iTunes and other players is that sometimes you want to play an audio file quickly. iTunes is a music (and video, and podcasts, and audiobooks, etc.) manager program, and it does take a few seconds for it to start up. VLC on the other hand is a small program and will start playing your audio almost immediately.
You can permanently change the default player for your audio files, but a quick way to play an audio file in a different player is to right click on it and choose “Open With…” and choose from a list (this works on both Macs and PCs).
VLC will play a variety of formats, but here are the ones worth mentioning. The standard audio file format for the PC is the WAV file. There are different quality settings of wav files, from CD quality stereo, down to telephone quality in mono, and many combinations in between. The equivalent sound file on the Macintosh is AIF/AIFF and it has similar quality settings to the wave files. They are both examples of what is known as uncompressed audio. The method by which the files are encoded is called PCM, or Pulse-Code Modulation.
A widely popular format for several years has been the MP3 format. Originally this format was conceived to be audio and video, however, the video portion was dumped and the MPEG-1 Layer 3 audio format was born. These files are popular because they are compressed (smaller) in comparison to wave files, but the sound quality can be virtually indistinguishable. This makes them good for transferring over the internet because of their relatively small size.
Apple’s format for compressed audio is Advanced Audio Coding or AAC. Apple is backing this MP3 successor that is part of the MPEG-4 specification. If you download music from Apple’s iTunes store, it is in the AAC format. Another type of compressed audio comes from Microsoft. The Windows Media Audio (WMA) format is another direct competitor to MP3. iPods can play AAC and MP3 files, while other MP3 players can play WMA and MP3 files. At this point, MP3 seems to be the universal format that is playable virtually anywhere.
There are many more formats, but I’ll mention just two more that come from the open source community (as in completely free to use and encode with). FLAC is the Free Lossless Audio Codec and as it’s name implies it’s free and even though the file is compressed, the sound quality is true to the original. The other is Vorbis which along with the open source video codec, Theora, is gaining in popularity.