I think i know what your saying, although the room that the speakers where in had stairs to a second floor and another room attached to it and also a hall i think that this was probably part of it too since most of the walls where concrete. I would still like to see an experiment done like this...
I think i understand it better now.
I found a definition of amplitude of sound waves and all it is is the "maximum change in position of the particles that make up the medium"so it is really just the amount the air molecules in the case are compressed.
So i think the answer would be that neither...
Ok so I was sitting out back one day listening to some music with some friends around.
We had some music playing on a stereo inside the house and we were out the back with the glass door open about 10 cm's.
I thought I noticed that some sounds with different frequencies seemed louder then...