This might be interesting if anyone can bother giving it a try -
I've made a 256kbs mp3 about one minute long. It starts with the R-44 string quartet fragment. Then comes some digital silence. Then comes some 'studio silence' getting louder through to the end. I'd be interested to know at what point (seconds) you are sure you can hear the studio silence.
So the way to do it is to first listen (maybe a few times) just to the short music part, and set the playback volume at a normal, realistic level. Then play through past the end of the music at that level, and note the time that you are sure you hear the noise. Ideally, report whether you first hear background sound, hum, or preamp hiss.
After people have had a chance to try it I'll reveal how much amplification was added to the noise at which point, though you could work that out with a DAW anyway. That might give some interesting evidence about practical signal vs noise audibility and what effective margin the R-44 has.
Obviously, don't watch any meters or spectral displays as your eyes will guide your ears, and don't turn up the level beyond normal.
The file is at
http://www.fileden.com/files/2007/9/22/1451533/R-44%20graduated%20noise.mp3