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.

Excel Project

Excel is an extremely powerful software application!  In fact, after using the program to complete the Excel Project, I have a newfound admiration for its capabilities.  To analyze large arrays of data in a matter of seconds still boggles my mind!  Although I have worked with Excel in my career, I have only utilized some of the many functions within the program.  However, after working on this particular project, I have a greater understanding for the relevance of Excel’s capabilities in the business world.

The project required me to analyze heart rate data collected from 500 different individuals’ 20-minute exercise sessions.  Initially, I had to rename the worksheet and format row headings/data within the array.  However, the first challenge in the project was to “freeze” rows 1 and 2, which allowed for continuous display while I analyzed the remaining rows of data.  To perform the “freeze,” I simply highlighted row 3 (the row below the two rows I wanted to remain visible), then I “froze” rows 1 and 2 by selecting the Freeze Panes icon in the Windows group of the View tab.  This simple, yet effective, method allowed me to know exactly where I was in the document, regardless of whether I was viewing row 8 or row 492 of the data array.  Furthermore, I had to create additional columns and formulas to obtain the following requested information:

• Maximum Heart Rate (MaxHR)
• Highest Heart Rate Achieved (TgtHR)
• Target Heart Rate Achieved (TgtAchieved)
• Percent Increase in Heart Rate (PctIncreaseHR)

Fortunately, creating the formulas to achieve the desired results was easier than I had expected, because of my previous experience working with Excel.

Finally, I had to create two pivot tables in new worksheets within the Excel Project workbook.  The first pivot table (TgtAchieved) provided the amount of subjects that reached their target heart rate during the 20-minute exercise sessions.  To create this first pivot table, I selected the Gender field for my rows, the TgtAchieved field for my columns, and the TgtHR field for my values.  Then, I chose to summarize the values by count rather than the default setting of sum.  In the second pivot table (AvgIncrease), I had to determine which demographic groups received the most benefit from the exercise program.  To create this second pivot table, I selected the Subject Age field for my rows, the Gender field for my columns, and the PctIncreaseHR field for my values.  With this pivot table, however, I chose to summarize the values by average rather than by count.  Additionally, I grouped the ages by decade (i.e. 20-29, 30-39, and 40-49 years) and deleted the grand totals for both the Age and Gender fields.

From the raw data in the Exercise Study, the AvgIncrease pivot table above displays the average percent increase in heart rate for all subjects.

The Excel Project was a tremendous opportunity for me to hone my Excel knowledge and skills.  I look forward to working with other software programs throughout this semester as I aim to enhance my proficiency in business software applications.

Works Cited

*Screen shot displayed is original work.