AAC vs. MP3: Is there an audible difference?

With the I-Tunes Store’s recent announcement that all songs in their catalog are now 100% “I-Tunes Plus”, I was a bit skeptical as to whether this new format (known as AAC, with the .m4a extension) actually sounded any better than the MP3 format.  I decided to do my own listening test.

I decided to use a rather dynamic track by Rush called “Far Cry” as my test track.  First, I extracted the AIFF audio directly from the CD with no conversion or compression.  Then, I created MP3 versions at 192, 256, and 320-mbps. Finally, I created an AAC/M4A version at 256mbps, which is the format currently being used for I-Tunes Plus.

I listened to various sections of the song, both through my monitors and through my headphones, to listen for any noticeable difference.  The results actually surprised me.  While this is a completely subjective, non-scientific test, I thought it would be of interest to my readers.  The results:

First of all, you can definitely hear the difference between the CD audio and any of the compressed versions, so don’t believe Apple’s claim that M4A’s created at 256mbps are “virtually indistinguishable from the original recordings”.  This claim is patently false.

However, since CD tracks (aif’s) take up so much hard drive space, we have to lose something in order to make the music portable.  So, is there an audible difference between an AAC/M4A and an MP3?

Answer: YES.  I heard a distinct, significant difference in sound quality, sonic depth, and accuracy between the AAC/M4A and the MP3’s.  The MP3’s encoded at 192 and 256 really sounded inferior, with audible loss of depth and clarity.  The MP3 that came closest to the sound quality of the M4A was encoded at 320mbps, but it did not sound quite as good, and it took up more disk space (12.2 MB vs. 10.7 MB).

So, I encourage music lovers to use the AAC/m4a format when encoding music in I-Tunes, and I’m glad that the I-Tunes Store is offering this format, which is superior in quality to the MP3.

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