I'm shielding the pickup cavity of a guitar to minimize interference. I'm doing this with copper tape that has conductive adhesive, and I'm connecting this tape to ground.
Without getting into too much detail, let's say there's a small spot I miss or purposely leave uncovered because it's difficult to reach, so that the Faraday cage is not completely "sealed" all the way around. Would this drastically reduce the effectiveness of the cage, or would it simply reduce it proportionally to the size of the hole?
I ask because I'm fine if it's just slightly less effective, but if it ruins the whole thing, then I'll put in the extra effort.
It's fairly common to make Faraday cages out of mesh rather than sheet copper, so you can imagine that a single small round hole is not going to degrade the effectiveness enormously. But the holes in the mesh must be much smaller than the wavelength you're trying to screen.
In particular, it's the largest dimension of the hole, not its area, that matters. A 1-mm round hole will allow much less leakage than a seam 10 mm long but only 1 um wide.