Not IT related but magnetic field related...
A band I knew back in the 80s spent a lot of time and money recording their forthcoming album in their own very well equipped studio and, when the recording was completed, took the master tapes home to keep them safe. Except... (and I'm sure you know where this is going)
One of 'em - the utter bladder head - put the tapes down on top of one of his hideously expensive and ridiculously powerful stereo speakers, had a few celebratory drinks and played a lot of music through his stereo at very high volume. For hours. No, he wasn't the drummer. Bass player and musical director of the band.
Oops.