Which Is the Best File Format For Your Music: AAC or MP3?

Which Encoding Format Is Best for the Average Listener?

shuffle music on iphone
image credit: Aeriform & Maria Teijeiro/Ikon Images/Getty Images

There are multiple formats digital music comes in, with two of the most popular being AAC and MP3. When you're downloading or streaming music, you usually can't choose what format you get, but if you're ripping music from CDs to digital, you can. The question is, which format should you use? I conducted a test to determine if one format out-performs the other in sound quality.

Audiophiles vs. Compressed Music

Most audiophiles—people who have superior hearing, top-notch audio equipment, and place great value on the best possible sound quality—tend to detest MP3, AAC, and other digital audio formats because they use compression to create smaller files.

The trade off for the smaller files created by compression is that some information—usually the very highest and lowest ends of the sound range—is removed. Most average listeners can't hear the loss. 

While many audiophiles have strong feelings about music compression, this article isn't really aimed at them. This article is for the average listener—someone with a standard iPhone or iPod, decent, but not very expensive speakers or headphones, and about average hearing. 

AAC vs. MP3

It's widely believed that AAC music files—the preferred audio format of iTunes and Apple Music—sounds better and takes up less space than an MP3 of the same song. I put that theory to the test to help you decide which file format to use for songs in your iTunes library and on your iPhone and iPod.

To conduct this audio file format shoot-out, I encoded two songs in different ways: as 128 Kbps AAC and MP3 files, as 192 Kbps AAC and MP3 files, and as 256 Kbps AAC and MP3 files.

The higher the Kbps number, the bigger the file, but the better the quality—at least in theory. For all files, I used the encoder built into iTunes.

If you haven't already, you may also want to read AAC vs. MP3: Which to Choose for iPhone and iTunes to get some additional useful information.

The Test Subjects

For my test, I chose two songs: the quiet, intricate "Wild Sage," by The Mountain Goats, and the loud, raucous cover of "Leaving on a Jet Plane," by Me First and the Gimme Gimmes.

"Wild Sage" is full of subtle pianos and finger-picked guitar, with high, breathy singing. I chose it because I hoped that those intricate sections would reveal a lot of detail in the various versions of the file.

"Leaving on a Jet Plane," on the other hand, is fast, loud, bass heavy, and full of complex drum sections. This song hopefully showed more dynamic range and revealed other things that the quieter "Wild Sage" won't.

I used my CD copy of both songs—presumably the highest quality available to me—as a baseline.

Here’s what I found:

256 Kbps

  • Wild Sage: Both versions of the song sound great at 256 Kbps. I can clearly hear the plucking of the guitar strings and the breathiness of the vocal with no distortions anywhere. The MP3 and AAC versions sound nearly identical. No clear winner here. The MP3 version is 1.2MB smaller, though.
  • Leaving on a Jet Plane: Same situation here. The song sounds great. The vocal is clear with subtle intonations and a general sense of brightness, but neither sounds appreciably different.

192 Kbps

  • Wild Sage: This version sounds a bit muddied compared to the 256 Kbps version. However, there's still no clear distinction between AAC and MP3. The MP3 is almost 1MB smaller.
  • Leaving on a Jet Plane: The pattern holds true. Not as good as 256 Kbps but similar between the two file formats.

128 Kbps

  • Wild Sage: Finally a difference. In this version, the AAC version is a bit clearer and brighter than the MP3, which suffers from slight muddiness and a slurring together of some sounds. The file sizes are almost exactly the same, making the AAC version the clear winner here.
  • Leaving on a Jet Plane: Here the AAC is slightly superior in drum clarity. Otherwise, the songs sound fairly similar and are exactly the same size.

Conclusion

While there are differences in the sound waves of the three files, they sound roughly equivalent.

Though there may be a bit more detail in the 256 Kbps MP3, it's difficult for my untrained ear to discern, and the files are much larger than either other version. The only place you're likely to hear a difference is in the low-end 128 Kbps encodings, but I don't recommend those anyway.

So, given these test results, it seems that the debate between AAC and MP3 may come down to a matter of taste, opinion or having better ears than I have.

File Size by Encoding Type/Rate

 MP3 - 256KAAC - 256KMP3 - 192KAAC - 192KMP3 - 128KAAC - 128K
Wild Sage7.8MB9.0MB5.8MB6.7MB3.9MB4.0MB
Leaving on a Jet Plane4.7MB5.1MB3.5MB3.8MB2.4MB2.4MB