This is a mystery.
Ever since 12.04 I noticed that the volume control got a little too loud in some area and too soft in another. I got used to it, making sure not to use the keyboard control and instead used only the mouse control. For my usual music needs, I learned to leave the volume at around 75% of its bar space.
Today I decided I needed a RAM upgrade. Bought chip, installed, tested it with memtest. All seems fine. But now , pulseaudio is much, much louder o_O. I have to move the bar to around 40% if I don't want it to explode my ears.
I am baffled, does anyone have a rational explanation for this?