Konsole - silence in session 'Default'
Solution 1:
You must have inadvertently pressed Shift+Ctrl+I. Press it again to switch it off. I had something similar, but with "Activity in Monitored Session", which pops up whenever you press a key. It can be toggled with Shift+Ctrl+A. Alternetively, you can use the View menu entry in Konsole. See the page Konsole Command Reference for more details.