Scott Gardner a écrit :
I picked up a copy of "The Great Fantasy Adventure Album" (I
think it's put out by Telarc?), which has a LOT of very low-frequency
bass content. When I encode it to AAC, even at a relatively high
bitrate, like 192 or 224 kbps, it seems like a good portion of the low
bass content is being lost.
I know that compression algorithms like MP3 and AAC work by
removing content that the algorithm determines to be less audible than
the rest of the signal, but do they also have an arbitrary low-end
attenuation?
Usually, I can't tell the difference between a CD and a 224
kbps AAC file of the same song, but it's noticeable with this one
bass-heavy example.

Scott Gardner


You can check that in SoundForge.
You can compare the original .wav with the compressed AAC or MP3.
Starting from this point you can make the necessary adjustement in
low-pass filter (depends on your compression software). I don't know AAC.