HiFiiPod » MP3 vs AAC vs OGG

An interesting article/test comparing the audio quality of MP3, AAC and OGG VORBIS. As I expected, the MP3 frequency response curve tails off pretty significantly over 10KHz, and OGG provides a relatively flat curve all the way up. Interestingly, OGG also sacrifices some linearity, which comprises natural reproduction of the music.

The biggest surprise is that AAC, which is a compressed (lossy) format that Apple recommends, seems to provide the best response curve across the spectrum. Looks like I'll be using AAC for most of my rips!

If you're interested in the frequency response curve for lossless (WAV/AIF) files, it's here. As you might suspect, it's completely flat throughout the spectrum, but of course it also requires a tremendous amount of space to store (like 10x more than compressed formats).

The HiFiiPod site also has some very interesting tests of the various iPod models; it seems that the audio circuitry compares favorably with low- to medium-end audiophile gear, which is pretty impressive for a unit that costs $400 at the top end.