Yeah this has come up a few times in our local group here in Durham. We do a lot of EVP sessions and the static burst thing is real, we've caught it on multiple recorders at the same time which rules out a dodgy mic or interference from one device.
My theory, and its probably nothing groundbreaking, is that whatever is drawing energy to manifest is also messing with the electromagnetic field around the equipment. Same reason you get battery drain I reckon.
The interesting bit for me is the gap between the burst and the actual voice. Ours tends to be about 2-3 seconds. Anyone else timing that gap? Would be good to know if its consistent across different locations or if it changes depending on the strength of the contact.
Not an expert by any means but I've been logging this stuff for about two years now and the pattern is pretty hard to ignore. Would love to hear if anyone's cross-referenced it with any temperature drops at the same moment.