Tutorial 2: WAV or MP3?

For the past 20 years or so, music enthusiasts have chosen compact discs (CDs) as the primary medium for listening to recorded music.  Before CDs, audiophiles listened to everything from cassettes to vinyl records (even 8-track cassettes for a limited time).  Today, however, music is available via digital download from websites such as iTunes, Amazon, and Napster to name just a few.  With the advent of digital recording and the public’s desire for immediate accessibility, audio formats (such as MP3) are allowing companies to distribute compressed music files, resulting in a sub-par offering for the consumer.


Defining the Formats

Wave Audio File Format or WAV is a format standard developed by Microsoft and IBM for storing audio on personal computers.  WAV is the primary format used by Windows-based PCs for “raw and typically uncompressed audio."¹  Although capable of storing compressed audio, most WAV files contain uncompressed audio in the form of linear pulse code modulation (LPCM), which is the standard audio file format of compact discs.  In addition, LPCM contains “two channels of 44,100 samples per second, 16 bits per sample.”¹  Due to LPCM’s storage of all uncompressed samples of an audio track, professional users and audiophiles tend to utilize the WAV format to obtain the best audio quality.  However, attaining optimum audio fidelity also means accepting disproportionately large file sizes, making the WAV file format unpopular among most of today’s consumers concerned with digital storage.

 

Observing the properties of the WAV file “iii” on my computer’s internal hard disk drive, you can see the file size is very large at 39.2 MB.

By comparison, MPEG-1 or MPEG-2 Audio Layer 3 (MP3) is a patented digital audio encoding format designed to reduce the amount of data necessary to represent an uncompressed audio recording, while simultaneously remaining faithful to the original recording.²  Referred to as a codec, MP3 condenses analog information to a digital medium resulting in a “lossy” form of compression, as some frequencies are lost during the encoding process. Furthermore, these lost frequencies will not return if the user reconverts the file to its original format.³

In a method known as perceptual coding, MP3 formatting uses psychoacoustic models to discard or reduce elements of an audio recording deemed inaudible to humans by compressing certain elements within the audio, then efficiently recording the remaining information.²  For example, digital content on a typical music CD requires nearly 10 megabytes (MB) per minute of audio.  As a song is “ripped” from a CD, mp3 formatting condenses the same minute of audio to approximately 1 megabyte, resulting in a 90% reduction of the original file size.³  Additionally, users may construct MP3 files at different bit rates, or specifically “kilobits used per second of audio.”²  For instance, an MP3 file created at 192,000 bits per second (192 kbps) results in a file size 7.35 times smaller than the original audio source.²

 
After compressing the original "iii" WAV file to an MP3 file format at 320 kbps, the properties reveal a 77% decrease in file size to 8.89 MB.

Compression = Loss of Audio Quality

Unfortunately, the consumer must accept a trade-off between storage capacity and sound quality when determining which type of audio file format to use.  Although audio in MP3 format may sound similar to the human ear, remember that greater compression of the original audio file will result in lost sonic details within the music.  In fact, even the slightest compression will usually discard extremely high and low frequencies within the audio file.  Regardless of whether these lost frequencies are inaudible or not, they provide depth by strengthening the harmonic texture of the music.³  Thus, compressing an audio file inevitably diminishes “the differences between loud and soft passages, [thereby] decreasing dramatic impact.”³  In extreme circumstances, users incorporating a very low bit rate (i.e. 64 kbps or lower) to increase storage capacity may encounter “compression artifacts” (sounds unheard in the original recording) becoming audible in the file.²  However, creating MP3 files larger than 192 kbps will maintain most of the original WAV file’s sonic information.  In fact, at these bit rates, “acoustic instruments tend to keep their natural warmth, and electric instruments sound fuller while retaining their punch.”³  Furthermore, the listener’s environment, attention, training, as well as their choice in audio equipment will influence their perceived quality of an audio file.²

The Recording Lounge provides a terrific example of how two identical pieces of music, in both WAV and MP3 formats, compare in terms of audio quality.


It’s Your Choice: Fidelity or Utility

When selecting which audio file format to use for your music, the choice is clear.  Choose the WAV format if you wish to hear your music in its most pristine, unaltered brilliance or if you want archive quality music in your digital storage medium.  However, if you are on the go and simply need some music to “fill the air,” then load up your favorite digital player with music in MP3 format.  Whatever audio file format you choose, enjoy the music that moves you.

Works Cited

Embedded Links (in order of appearance):

Apple:  http://www.apple.com/itunes/

Amazon:  http://www.amazon.com/MP3-Music-Download/b?ie=UTF8&node=163856011

Napster:  http://www.napster.com/index.html?darwin_ttl=1298190962&darwin=s1210J&regflow_id=s1210J&naps_app_id=0

example:  http://www.youtube.com/watch?v=u5gdwpPrv_8

Citations:

¹http://en.wikipedia.org/wiki/WAV
²http://en.wikipedia.org/wiki/MP3
³http://www.crutchfield.com/S-kVofihAUYMV/learn/learningcenter/home/mp3.html

^*All screen shots are original work.