TriField Natural EMF (electromagnetic field) Meters measure changes in natural electromagnetic fields and filter out all man-made electromagnetic fields (anything with an AC current). During investigations, meters are placed in various locations in each room in an attempt to substantiate the theory that when a spirit is present, it changes the Natural EMF of the area. It is hoped that the presence of a “ghost” will be detected when it passes by one of these meters. In past investigations, the TriField Meters have recorded fluctuations in natural EMF when Sturges and other investigators have asked deceased members of the Tredwell family or servants to stand next to or place their hands over the meters. EMFs have indicated changes when investigator Dan Sturges asked any presence in the room to stand beside the meter.
Digital Audio Recorders (basically, high-end digital tape recorders) capture EVP (Electronic Voice Phenomena: words, phrases, music or any other relevant sounds that are not heard at the time of the recording but are heard during the playback of the recording. Any voice or relevant noise that is heard during an investigation and is picked up by recording media is called Direct Voice Phenomena.