Pictured above: a visual example of the difference between sampling at a high rate and a low rate forcing your brain to fill in the blanks. Photo of Radiohead at Coachella by Joe Puglisi.
MP3 formatting has changed the way we listen to music, allowing for consumers to hold massive libraries of content without the hassle of a physical collection, or excessive digital storage. Compact Disc audio and MP3s are both digital audio– instead of creating sound waves with physical technology– like the grooves of a vinyl record– digital audio recreates sound waves with samples, a numerical value assigned to each frequency in the spectrum of what you’re hearing. Many people realize that there is a difference in quality, but don’t necessarily know why. The MP3 isn’t a replacement for CD quality, and here’s why:
1. Size Matters
CD audio is uncompressed. What that means is the average CD can hold 80 minutes of music, or about 700MB of sample data, and the typical track winds up being around 30-40 MB in size, which was certainly unrealistic for early portable devices with limited memory. The MP3 encoding reduces this file size to about 3-4MB per song, a much more manageable size for a digital library. But this reduction comes at a cost. There is even a difference between a 2MB song and a 4MB, even if it’s the same song, and the size differential seems negligible. Even when you “rip” a CD into iTunes or a similar program, depending on your settings, it converts the CD-quality files into a smaller format.
2. Quality vs. Quantity
While there are standardized formats (Amazon’s MP3 store, iTunes AAC files), the prominence of MP3 technology has led to a myriad of different file types, shapes, sizes, samples rates, and qualities. Simply obtaining a song in the MP3 format does not guarantee the compression or the clarity of the audio. Also, when an album is recorded, it goes through a final process called “mastering.” If this is done with the intention of having the best quality audio, even more might be lost in the compression process. Some artists have opted to master their albums with the intention of turning them into MP3s, in which case the CD “quality” audio may not sound all that spectacular.
The average ear can still discern a decent quality file from one that has been poorly created, and if the numbers mumbo-jumbo doesn’t suit you, there are a few tricks to telling how much has been removed from the samples in your file.
Things to listen for when judging the quality of your audio:
1. Listen to the cymbal decay. When the drummer hits a crash cymbal, does it sound clean and even, or does it get a bit glitchy and sound almost computerized? Any suspect distortion is probably an indication of poor quality.
2. Can you clearly hear the separation between the guitar, bass, and vocals? Or is it all a bit muddled, like you’re looking through frosted glass?