every one would need to have the same speakers, same amp, same EQ levels set to get some form of a bench mark and have an understanding of microphone used, ive sent my mate recordings of various things before done with a mic and he always tells me they sound crap laptop speakers
which is ofcourse what hes using to listen to the audio with.
but yeah just too hard, if you were gonna do it, youd want a spectrum spectrum analyzer and take a reading at set frequencies and various volume levels least you would have a visual interpretation, sadly those little amp ICs are hardly worth the time though.
EDIT: and youd need a sound proof room