It might be that new "feature" implemented in F11 called "flat
In an attempt to copy Windows, for only God knows why, the PA folks made
your apps change the system volume. This, coupled with a bug in
gstreamer adjusting at logarithmic amounts instead of linear, it makes
volume management a pain. The fix?
Uncomment "flat-volumes = yes" and change it to "no" and save. Log
wait 30 seconds for pulse to die (another great "feature") and log in.
Volume level changes are now normal again! Coupled with the latest PA
update yesterday, F11 now sounds like F10. Ah...
Have a good one.