When audio is captured from its source, it is then modified and transformed into a notably different file of a certain format. The modification also allows for easy distribution of the audio file electronically. Audio files come in various formats; each one being different from the other in terms of how the audio source is modified.
Modifying the original audio source essentially means sampling the audio voltage at regular intervals and storing the sampled value in digital format with a certain resolution. The sampling rate, the resolution used and the number of channels (ex. in stereo, there are 2 channels) are the distinguishing parameters of different digital audio file format.
Audio formats are grouped in three major categories:
a. slightly compressed file format, ex. WAV, AU, AIFF
b. lossless compression format, ex. lossless WMA, Apple lossless, WavPack, FLAC, Monkey’s Audio, TTA
c. lossy compression format, ex. MP3, OGG (Vorbis), AAC, lossy WMA
Most of the examples given above are the names and, at the same time, the file extensions of the different audio formats. Some of the formats are described in brief below.
WAV – This is one of the most popular file formats of audio data. WAV files are just slightly compressed thus it gives the best audio quality and large file size. WAV files’ size makes it unsuitable for sharing over the internet. Its slight compression also makes it compatible with Mac OS and Windows. With the WAV format’s flexibility in storing any sampling rate or bitrate combination, it becomes the preferred format in storing an original recording.
AIFF - The "Audio Interchange File Format" was developed by Apple for storage of sound in the data fork of Macintosh files. It has been adopted as a standard audio format by the OMFI (Open Media Format Interchange) group for cross-platform media exchange, which includes Silicon Graphics, Avid Technology and others.
Mac-based professional digital audio recording systems and multimedia applications such as Macromedia Director, Adobe Premiere and Movie Player allow importing and exporting of AIFF files. Using this format, audio can be stored as mono or stereo, 16-bit or 8-bit, and at a wide range of sample rates.
MP3 – Yet another popular and most widely used audio file format, MP3 paved the way for easy and effortless music file sharing over the internet. MP3 stands for Mpeg-1 Layer 3 or Mpeg Audio Layer 3. As per the categories above, MP3 is one kind of lossy compression. With the MP3 compression, a user can reduce a regular music CD into a tenth of its original size. The sound quality is also changed with the compression, yet the difference is sometimes not too audible. Audio streaming is also possible with MP3 which means that a user need not complete the download of the file just to be able to listen to a few parts of the music.
WMA – Windows Media Audio, or WMA, is Microsoft’s counterpart for MP3. Windows Media Audio is integrated with Windows Media Player which is also installed with a new Windows installation. Microsoft claims WMA to offer CD-quality audio at only a fraction of its size. WMA also do not allow further distribution of copyright-protected songs which made it the more preferred format over MP3 of music corporations. WMA is also known in the World Wide Web for its streaming capabilities.
AAC – Advanced Audio Coding was supposed to be the successor of MP3. It was created by the same people who made MP3 as the answer to the limitation of the latter format in lower sample rates. However, it did not meet its goal as loss of quality is still noticeable even at 96kbps with the aac format. Also, there is almost no software that supported this file type.
OGG Vorbis – OGG is another audio file format yet it is an open source project which makes it free of patent. Its development started in 1993 and still continues. With every new development, the quality of sound OGG offers gets better. New versions are also backwards compatible. This file type offers encoding at different sample rates, as well as multi-channel compression.
Real Audio – This format has the file extension .ra and is common to radio stations being aired over the internet. Real Audio is generally a streaming audio format hence the small file size. However, if a real audio file is played over a slow internet connection (ex. dialup connection), there is a great loss in the compression and the sound quality is not that good.
MIDI – This file format is not like the other formats mentioned. Midi is not a compressed audio, instead, it is the medium that lets computers and musical instruments communicate. Midi files come with file extension .mid and are just small files, around 30 to 60 kb for each song. You can download thousands of free midi files in the free midi file section on our site.
RMF – The company Beatnik developed the RMF (Rich Music Format) as part of its strategy to create a cross-platform audio standard for the web. RMF files can contain MIDI as well as other audio information, such as sampled sounds. To play an RMF file, you need the Beatnik Plug-In