AVFan,

There are a couple reasons that you may see increased dB readings over your calibration. First off is that if calibration used a slow response (i.e. RMS or 'average') then that will show up a bit lower volume than fast response (i.e. peak). With sine waves RMS levels tend to be around 70% of peak levels.

This can be exacerbated by how CD's are mastered. Their average to peak values are reduced via limiting and compression. While the peak values should not get any higher, the average values do which makes them sound louder and puts more sound energy into the room.

For your second concern, slight volume changes are one of many clues the brain uses to figure out where sound is coming from. While a typical person may not usually be able to hear a 1dB change in volume from a single source they still will be able to interpret this change (and smaller) in the situation you tried.

When we discussed many people not discerning a 1dB change, you would have to change the level of all speakers that amount, or the inputs, to test that. The problem with testing that is that one becomes more sensitive when they are doing the adjustments, and they can lead themselves to believe they are hearing what they aren't. Basically when you adjust the levels you become more aware of it and it makes the test not as accurate. In some cases since you know you are adjusting things you will fool yourself into hearing a change that is imperceptible. To properly test this you would need someone else making changes where you couldn't see them.