Before voting, can we compile a list of things to listen for?
Extracting previously helpful comments from this thread . . .
"I focus entirely on transients. Drums, cymbals, surface noise. I don't know if that's just because I'm very sensitive to the sounds of transients in hi-fi reproduction in general, or because transients are the most complex waveforms, or because the design of the codecs did not place much emphasis on dynamics . . .
Same poster also said: "It seems a number voted based on computer speakers or cheap headphones. Those votes are useless--they poison the pool."
"I prefered the Menu 1 because I had the feeling that the instruments were more spread out, especially the trombones and tuba . . . This gave also the effect of orchestral fullness.
Also I found Menu 2 very compact less "airy" going in the direction of congested. I had the feeling the instruments were crunched in the centre.
Saying this the image of some instruments (flute oboe and clarinet) were more consistent and "real" with Menu 2."
"With MP3s, AACs etc it is the file size that is being compressed, not the dynamic range. The loud bits are just as loud, the quiet bits just as quiet, the thing that is missing is certain detail that has been thrown away in order to make a smaller file . . . lossy compression loses low-level detail . . . to my ears it mainly screws up reverb / depth / space and becomes confused when the going gets tough, i.e. it becomes harder to identify instruments or recording acoustic in busy or noisy passages.
The Jimmy Smith. I really struggled with this one to be honest. I felt there was a little more acoustic space around the applause, the cymbals just a little better defined, a little more sense of things occurring in a plausible acoustic, but it was the best preserved of the tracks I listened to by far, and based upon this track alone I'm not sure I'd have committed and may well have hit the 'don't know' option.
The Jane Monheit. The vocal reverb gave a coherent sense of three dimensional space on the wav and sounded flatter, crunched, and more like a tacky FX unit on the AAC. The piano also sounded more real / better recorded / and in a more believable acoustic space on the wav. I was certain of my choice by now and I'd have happily committed to option 2 without listening to anything else.
RATM. Lossy compression is always pretty crap with heavily distorted guitars, it just loses that 'thing' that makes a well mic'd overdriven Marshall stack sound so much better than a 50 quid distortion pedal. It's also a lot easier to hear the vocal quality and kit metalwork. This was the easiest IMO, the wav just sounds a lot better, cleaner, better separated, more real, the AAC kind of blurs it altogether into one homogenised sound.
Reverb, acoustic space, the 'air' around instruments, all the ultra-low level 'round-earth' stuff as it is this which tends to be mangled or missing in action once the file has been compressed. Concentrate on the vocal reverb on the Jane Monheit track, all the info needed to make a choice is in that acoustic space, then listen to the guitars, vocal and drum kit metalwork on the RATM track, listen to how separated the instruments are, try and figure out how many guitar tracks there are, listen to how the voice fairs when the guitars are really loud, what happens to the cymbals at this point.
That's it! No magic, no golden ears! Just zone in on what the technology buggers up and you'll spot it assuming the replay equipment is up to it."