Also a few year ago on the Astral Pulse there was "spirit voice" stuff being taped using a mic close to white noise, or something.

http://www.crystalinks.com/evp.html

Anyway, with my research about spirits (neg or not) and their connection with EM fields I realized how that Electric Voice phenomena probably works.

http://www.howstuffworks.com/cassette.htm

Recordings using ferrous oxide magnetic tape are basically picking up sound (or "background" noise, i.e. Em fields) through a mic, turning it to EM fields/pulses, which then effect the ferrous metal tapes.