I just tried this test out of curiosity.
I can tell differences between all four files but it gets complicated to assign some of the bitrates and file formats because some of the differences I hear are actually a bit confusing and make me wonder if all the tracks were taken from different sources or if they're all from the same source and downconverted from there...
The only posts, of this thread, I've read so far are the first one and the last one.
I haven't read the answers disclosure yet, will do only after posting this.
My system: PC - foobar2000 - Yulong D100 - German Maestro GMP 400 (modified)
Ranking the files by sound quality:
Sample_1 > Sample_3 > Sample_4 > Sample_2
This is what my ears tell me, however it gets difficult to assign the 128Kpbs mp3 and HE-AAC file formats...
Anyway here go my guesses:
Sample_1 is Flac. I'm pretty sure of this one as it sounds cleaner, more articulate, better imaging, more saturated tonal colors, smoother and more extended treble without any harshness or congestion, more transparent.
Sample_2 is 64 Kpbs HE-AAC. This one sounds definitelly the worse, and it sounds very different from the Sample_3 and 4 which makes me think that it might have been taken from a different source or that it was encoded with a different method and this is the reason why I think that it is in HE-AAC and not 128Kpbs mp3. (I have no reference and don't know how a HE-AAC file compares with a mp3 for sound quality)
Sample_3 is 256Kpbs mp3. This one and Sample_4 sound very alike in the way that both seem to have a very slightly prominent and muffled low frequncies performance which makes me think they're both mp3s, this one sounds better than Sample_4 but not as good as Sample_1.
Sample_4 is 128Kpbs mp3. Most prominent low frequencies, muffled and second worst performance at frequency extremes after Sample_2, kinda forward sounding . Just like Sample_3 this one sounds warmer than Sample_1 and 2.
So let's see if I got it right.
EDIT: LOL, you guys might not believe it but I didn't really read the last post completelly (i didn't mention it) so my guess for the HE-AAC was right HaHa!
EDIT2: Well seems like I failed the Flac and 256Kpbs, lol... it makes sense though... Flac always preserves low frequency better than mp3 so the slightly muffled impression I got from Sample_3 is from the song itself. Sample_1 always sounded clearer and crisper probably because of the more recessed bass... not sure why the 256Kpbs sounds less warm than Flac and 128Kpbs, though... are these songs from the same source? Strange that nobody could tell HE-AAC... it was pretty clear to me...
Edited by kkl10 - 7/1/12 at 3:08pm