An audio file format is a file format for storing digital data on a computer system or digital media. This data can be stored uncompressed to preserve the fidelity or compressed to reduce the file size. Over the years, there have been many file types introduced in the digital recording world, but only a handful have actually caught on and remained in popular usage. Every once in a while a new format shows up that catches on, the AAC format used by Apple’s Itunes store being the most recent, but the history of digital recording and distribution is full of format that never made the cut. Some of the most common file formats used in audio sounds includes WAV, AIFF, MP3 and AAC. This paper presents some of the salient differences that exist in audio sounds that are in MP3 format file format and WAV file formats. To accomplish this, the paper presents the unique characteristic of each file and the differentiating characteristics of each type of format based on a recording experiment that I undertook prior to writing this paper.
Wave form audio file format is a digital audio standard that windows Operating Systems can recognize and manipulate. This file format was conceived by Microsoft and supports a number of compressed and uncompressed audio formats (Richmond, 2010, p. 139).WAV files are playable on windows and Macintosh computers but because of their large size seldom uploaded to the internet. Waveform Audio File format is uncompressed and provides the highest quality digital representation of sound. It is the most popular uncompressed audio format presently. It is a frequently used format in audio signal-processing tools such as MATLAB (Cai, 2014, p. 80).
MP3 is a compressed audio file format that is very popular in the consumer market. These files are used for audio file sharing over the internet and in MP3 players and also video games (Viers, 2011, p. 138). The MP3’s compression ratio allows for files to be tenth of the size while maintaining a reasonable level of quality. MP3 is the file format that powered the popularity of digital music. MPEG 1, Layer 3, shortened to MP3, is simply a standard set of mathematical algorithms used for compressing sound files into an attractive format for downloading or streaming across the internet. When the MP3 algorithms are run through a set of musical data, such as a digitally encoded recording, it eliminates virtually all of the 0s and 1s the human ear cannot reasonably discern, leaving only those 0s and 1s that are recognizable (Kohn & Kohn, 2010, p. 726). Because about 90 percent of the data in a typical digitally encoded musical recording are not essential to the reasonable listening experience, that 90 percent can be removed, leaving a greatly compressed file having only a slight reduction in sound quality. Though an audiophile or sound engineer could determine the difference between the original WAV file containing all the data of a recording and the compressed MP3 version of the recording, the latter, although degraded, still provides a quite acceptable listening experience for the average person. The MP3 format offers quite a lot of different compression and quality settings, so that a listener can fine tune the format to get better quality, sacrificing hard drive space as the quality is dialed-up.
Method and Results
To conduct the experimentation on the two formats of the audio files, that is , MP3 and WAV, the program that was employed is audacity, however, other programs such as Wavosaur, Linux MultiMedia Studio, Traverso DAW, and Ardour could have served the same purpose.
An audio recording of my voice was made as expected it was stored in a WAV file format. Thereafter, a compression of the raw WAV file was conducted to transform it into an MP3 file format and was fed back into the program together with the original WAV file format. Various sound characteristics such as pitch, wave shape, phase, frequency and amplitude were used as the basis for comparison.
Screenshot of the frequency chart before compression:
Screenshot of the frequency chart after compression:
Comments on uncompressed vs. compressed audio file:
While listeningtto the two different file formats, to the human ear the qualities of the sound are similar and indistinguishable. However, according to Kohn and Kohn(2010, p. 726), sound engineer or listening through an audiophile can determine the difference between the original WAV file containing all the data of a recording and the compressed MP3 version of the recording. The latter, although degraded, still provides a quite acceptable listening experience for the average person.
Discussion and conclusion
The inability of the human ear to discern the differences in sound quality of the two file formats is attributable to the lossy method that is used to compress the audio files. The lossy method removes non-audible frequencies and by removing less important signals. By removing non-audible frequencies, the compression removes what a normal human being ear cannot hear, although this assumption is subject to argument (Bove & Rhodes, 2005, p. 234).
Recorded Audio File Spectrum Graph before Compression
Recorded Audio File Spectrum Graph after Compression
Analysing of the spectrum graph obtained from the Recorded Audio File before and after Compression, certain characteristics of the two file formats can be identified in terms of frequencies, wave shape and phase.
This assessment of the two graph observed the following unique features: first, the two files differ in terms of their frequencies. The original WAV file that is in its raw uncompressed format demonstrates a spectrum graph that boosts of well-defined and distinct frequencies; this is as opposed to the spectrum graph of the MP3 file format. Secondly, the uncompressed WAV file demonstrates a more pronounced frequency changes as exhibited by the broad span of frequencies that ranges from 0Hz to 20,000Hz. This is remarkably large comparable with the frequency exhibited by the compressed MP3 file whose range of frequency is 0Hz to 11,000Hz. Thirdly and lastly, it can be observed from both the spectrum graphs that the compressed MP3 file is simply a mirror copy of the uncompressed file, only that it has a limited frequency range.
Discussion and Conclusion
The two files can be considered to be mirror copies of each other only that the compressed MP3 file has a shorter frequency range, while its curves are more evened out and pronounced. These differences can be attributed to the encoding of the MP3 file which compresses the original WAV file to a format that is smaller. The reduction in the frequency range is attributed to the encoding process which removes audio frequencies which the human ear cannot discern. The smoothening of the MP3 spectrum graph in comparison to the WAV file can also be attributed to the encoding process that uses the Lossy method which removes non-audible frequencies and by removing less important signals removes unnecessary sounds which according to Bove & Rhodes(2005, p. 234) makes up to 90 percent of a WAV file.
Line graph for the audio file before compression (Wav)
Line graph for the audio file after compression (mp3):
The following could be observed from the line graph of the two files. First, the amplitude of the uncompressed raw WAV file is higher reaching 25,000 as opposed to the amplitude of the compressed MP3 file which is relatively reduced by almost a half to 12,000. Secondly, from the line graphs it can be observed that the frequencies of both files, the WAV file and MP3 file, remain unchanged. Lastly, it can also be observed that the gradients for both files are similar, and are infact mirror images of each other.
With regards to the line graph observations, and as expected, the frequencies of sounds usually remain unchanged after encoding.
In summary, it can be concluded that as opposed to an uncompressed raw WAV file which are large and require bigger storage space, compressed MP3 file formats are smaller and lighter in terms of the space they take. As a result MP3 file format are considered more durable. Apart from the reduced sized, the other advantage of MP3 is that it is almost universally recognized. Just about any media player or portable audio player can recognize and play an MP3 file. This makes the file format popular among users.
From the experiment it was noticeable that indeed MP3 file formats present a myriad of advantages that are over and above a WAV file. An MP3 file is leaner and produces a sound that is of good quality despite the reduced file size. MP3 files are also recognizable and can be played by just about any media player or portable audio player. It is thus the best recommendable file format to keep audio files.
Bove, T., & Rhodes, C. (2005). iPod & iTunes For Dummies. New York: John Wiley & Sons.
Cai, Y. (2014). Ambient Diagnostics. CRC Press.
Francis, G. (2009). Home Recording for Beginners. New York: Cengage Learning.
Kohn, B., & Kohn, A. (2010). Kohn on Music Licensing. Aspen Publishers.
Mitra, U. (2004). Introduction to Multimedia Systems. Academic Press.
Richmond, C. F. (2010). Audio, Video, and Media in the Ministry. Thomas Nelson Inc.
Viers, R. (2011). Sound Effects Bible. Michael Wiese Productions.
Williams, R. C. (2004). WindowsXP Digital Music For Dummies. New York: John Wiley & Sons.
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