i'm a computer enthusiast, but total science noob. lately i've been reading about EM shielding of computer cases.
a perfectly sealed metal box would provide the best shielding, but the majority of consumer PC cases are not like that and most have holes for fans. is it correct that a mesh covering these holes does provide some shielding, but depending on the layout and dimensions of said mesh it will let certain waves go through completely? also, say i have a hole in my computer case and there's some device sensible to EM radiation in my room, does it matter which way the hole is facing in regards to the device or will the waves bounce around the room anyway?