Inspired by the work of Jürgenson, the next big name in the field of paranormal research was Konstantin Raudive, a Latvian parapsychologist, writer, and student of the famous Swiss psychiatrist, Carl Jung.

Raudive got in contact with Jürgenson after reading his book and initially worked with him to capture EVPs in 1965. In one of these early experiments, Raudive heard multiple voices in a recording, with voices speaking in German, Latvian, and French. One of the voices said "va dormir, Margarete," which translates as "go to sleep, Margaret."

In his 1968 book on EVPs, 'Unhörbares Wird Hörbar' (translated into English as "what is inaudible becomes audible", but published in 1971 as 'Breakthrough: An Amazing Experiment in Electronic Communication with the Dead,') Raudive wrote, "These words made a deep impression on me, as Margarete Petrautzki had died recently, and her illness and death had greatly affected me."

Raudive also recorded the voice of a...