Hi,
I'm sure AAC and other codecs have been improved considerably, although I'm skeptical that 128 kb/s would be totally "transparent," even now. It might be for lots of uncritical material.
It really depends on how you define that. It should be noted that in the 1992 tests, even the best codecs had occasional little artifacts that some listeners heard now and then, but they weren't so bad as to be rated "annoying."
For instance, if you played some Spanish orchestral music with castinets, there might be a slight timbral change to the sound of the castinets, but not enough that it would annoy you. But do we still call that transparent? In fact, without an immediate A/B comparison to the original source, you might not even detect a tonal shift. Does it matter if everything else in the music selection sounds just fine, except for a slight tonal coloration on the castinets or the triangle (those two instruments, harpsichord and sometime vocals, were the most revealing of any audible flaws in a codec).
Regards,
Alan
