Wherein does your buzz occur?

[mopleez]

If you're like me, you acoustic players especially, are after optimal action. This usually means, "How low can you go" before getting fret buzz. My question is, when you do get fret buzz, where - string & fret - is it most likely to occur? Thanks!

[tjcurtin1]

Low E string with a capo on 4th fret, if I'm strumming hard enough, so the buzz is somewhere higher up