This post is cool, we have I think got right to the heart of Hi-Fi and in doing so revealed a little about human nature. If I can voice an opinion on the comments made about listening and hearing of effects and possibly the double blind thing. I feel that, from my own experiences in life, not just music, or playing an instrument, that we are to all intense and purposes 'perfect' at whatever we do relating to the world around us. To say we could not hear something because the change is too small is applying the human understanding of a machine or device to the mind/body which I think is incorrect. I think the human is capable of detecting any change no matter how small as it operates on an analogue principal. I learnt to play the violin as a child using my subconcious (part of the suzuki method in which music to be learnt is played to you during sleep) and the music comes to your consciousness when you start to play the piece. Anyhow I have digressed, it is known to me that when I concentrate on something I am actually just limiting how I look at something with my mind and can absorb/notice/understand things which are much more subtle when I 'turn off' my conscious focus and let my mind do what it does without me controlling it. I hope you can understand what I am saying. I have experienced this in martial arts as well as playing the violin and listening to music. I could propose that the act of forcing yourself to listen in fact stops you from 'hearing' everything and this would make me say that double blind tests are not really reliable when used with something like music which is in fact an emotional thing in truth. If you read the page at   http://brain.web-us.com/thescience.htm#Various Uses Of Audio With Embedded Binaural Beats   then you will see that we do not know the limits of human 'hearing' at all. Cheers Ben.