Likom PC monitor having hi-pitch sound

Question

my computer monitor produces a head aching, at first with hissing sound
then followed by hi-pitch sound in diff wave lengths when turned on for
about 5 mins. I already having a migrain. Please help me. I already
changed its memory into a bigger size and even reformat my computer but
to no avail. So I just turning it off whenever I hear that sound and
just be back after 10 min or so and do my comp works... and that sound
will be gone for a moment only.What could be the reason? My cousin suspected that it could be my monitor. Can it be repaired?