Static in earphones when scrolling with mouse
The "static" is noise coupled into the headphone driver circuit via its power supply. An action such as scrolling a window on a display causes a large burst of memory activity (a "block move" of the pixels involved, plus drawing the new material that is revealed), and if the decoupling is inadequate, this causes rapid sags in the voltages of the power supplies involved in this activity. If those same voltages are used to drive the headphone, or if there is sufficient coupling between voltages, and the headphone driver has poor power supply rejection, you'll hear this noise in the headphones.