Ryujin
Legend
EVP is one of many things that "paranormal investigators" will truck out, with absolutely no factual basis to support it. When you get to the point of amplifying background noise to that extent, you're almost certainly going to pick up stray signals from other sources. Radios are just tuned amplifiers. Recording devices have amplifiers. The loudest electronic "noise" that you'll find is terrestrial broadcast signals. I'm guessing that no paranormal investigator has ever built a crystal radio or, if they have, they're conveniently forgetting the principles involved when they "receive" EVP.When I got to hang out with the ghost hunting group at my museum, we went room-to-room where we'd all sit down and someone would ask questions to any spirits that might be listening while using a recording device. Later on, we all listened to these recordings and in the background hisses and static some of them insisted their heard something. That's when I learned about electronic voice phenomenon, where folks interpret noises in recordings as voices from beyond the other dominion. A few of them insisted they heard something whereas I heard nothing but background noise.
EDIT - Then there are the "magnetic field detectors", when there's nothing even anecdotal to suggest that ghosts have an effect on magnetic fields. It's a "They MUST!" sort of assumption.
Another Edit - Regarding the creating of accidental crystal radios, pretty much everyone has heard the story of someone who could receive radio transmissions via their fillings. Lucille Ball helped root out a Japanese spy, during WWII, by hearing a secret radio broadcast via her fillings.

Crazy story with Lucille Ball discovering a Japanese spy communications morse code in her mouth
Crazy story in 1974 interview with Lucille Ball talks about discovering a Japanese spy communications out side of L.A in her case morse code, was can be pick...

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