Electronic voice phenomena (EVP) were investigated by him and a German parapsychologist Hans Bender. Following the publication of Raudive's book on his research (Breakthrough: An Amazing Experiment in Electronic Communication with the Dead, 1971) these phenomena are now often referred to as "Raudive Voices".

In 1964, Raudive read Friedrich Jürgenson’s book, Voices from Space, and was so impressed by it that he arranged to meet Jürgenson in 1965. He then worked with Jürgenson to make some EVP recordings, but their first efforts bore little fruit, although they believed that they could hear very weak, muddled voices. According to Raudive, however, one night, as he listened to one recording, he clearly heard a number of voices. When he played the tape over and over, he came to understand all of them, some of which were in German, some in Latvian, some in French. The last voice on the tape, a woman’s voice, said "Va dormir, Margarete" ("Go to sleep, Margaret"). Raudive later wrote (in Breakthrough):

These words made a deep impression on me, as Margarete Petrautzki had died recently, and her illness and death had greatly affected me.