Can a microphone be built to enhance the ability to record the voices of ghosts?
The recording of ghost voices is known as electronic voice phenomena, or EVP for short. Unexplainable voices being heard during the use of electronic devices was discovered as early as the 1930's, though it's been said that Nikola Tesla might have been the first to notice disembodied voices in 1898 being transmitted by his Colorado radio tower. This might have been the first ghost microphone to have been unwittingly invented. Later, scientists would come along who devoted their time to diligently record and document their findings about ghost voices. The first to make EVP recordings was Friedrich Juergenson.
As legend would have it, in 1959 the Swedish film producer was outdoors recording bird calls when he discovered hearing his deceased mother's voice speaking to him upon playback of the audio tape. This led to Juergenson experimenting with EVP and, over time, recording hundreds of ghost voices. He is now considered to be the “father of EVP.”
Fascinated by the work of Juergenson, Latvian psychologist Dr. Konstantin Raudive began his own EVP experiments. He would eventually record and study thousands of disembodied voices, creating a system of classification for electronic voice phenomenon in order to rate the quality and clarity of the messages.
During his experiments, he solicited help in building a microphone to enhance his EVP experiments. Using a Germanium Diode as an external microphone, he found he received greater results. More ghost voices were recorded. Incredibly, those who have experimented with the Raudive Diode claim that the device will not allow your audio recorder to record human voices, even if people are talking in the same room!
This schematic is the design used by Dr. Raudive to record ghost voices. The Raudive Diode schematic. L1 = .5mh coil, R1 = 100k resistor, D1 = 1N34A germanium diode.
A Germanium Diode picks up AM radio frequencies so, when using one to record EVP, it should be placed inside a Faraday Cage. A Faraday Cage is used to block all outside AM radio transmissions from reaching the ghost microphone.
Another method of using the Germanium Diode that's achieved success is to simply attach one to a microphone jack and plug it directly into your digital audio recorder. (If using an older, cassette tape recorder, you will need to use a connecting wire placed between the recorder and diode to keep it away from the motor noise which may cause interference. This set-up makes it easier to incorporate the Faraday Cage.)
When using a digital recorder, you may need to cover the external microphone if it does not disengage automatically. It will depend on your recorder, as the power level of the diode is quite low and may not signal the audio recorder to switch from the internal microphone to an external one. Also, because you might be unable to incorporate a Faraday Cage using this technique, you will need to be wary of radio broadcasts, limiting positive results to only credible phrased answers to questions. One word, irrelevant responses should not be considered. This will reduce the chance of AM radio snippets being mistaken for EVP in your recording.