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EVP stands for Electronic Voice Phenomenon; voices caught on recording devices such as tape recorders. Thomas Edison first introduced this concept to the world during the latter part of his life. He became obsessed with the afterlife and began trying to prove that we do go on when our bodies die. In the few weeks prior to his death, he kept himself locked in a room with a modified version of the phonograph he invented earlier in his life. He would turn this machine on, and while alone, begin asking questions. It would record his questions as well as the pauses in between. When playing the recording back on a regular phonograph, he was amazed to find other voices providing answers. Since no one else was in the room during the experiment, he deducted \par that these were “spirit voices” . The recording device he used is currently on display at the Smithsonian Institute. Using the same concept, we place tape recorders, DAT (Digital Audio Tape) recorders, etc., in “active” areas and find strange voices recorded. Often times, people talking about us and questioning what we are doing with all this strange equipment.
EVP has always been and still remains one of the more controversial methods of trying to provide evidence of the paranormal. The basic principle behind EVP collection is the use of an audio recording device in an attempt to catch voices and/or sounds of an unexplained nature. Before we begin to analyze sounds we need to gain a greater understanding of how they operate and the physics behind their creation.
Sounds are changes in pressure in an elastic medium such as the atmosphere that can be detected by the human auditory system. This pressure change is called a sound wave. The human auditory system can only interpret these changes in pressure or sound waves if they are cycling in the range of 20 to 20,000Hz. Anything below the 20Hz level is called infrasonic and anything above 20,000Hz is called ultrasonic. The human ear cannot perceive sound waves in the infrasonic or ultrasonic sound range. A sound wave will also loose intensity the farther away from the source of the atmospheric disturbance it travels. A sound wave can also travel through solid objects such as walls. This makes it difficult to determine the originating source of the sound wave.
Frequency is the measure of the rate at which electromagnetic waves are generated. Frequency is measured in cycles per second, called hertz (Hz) after the German scientist who first discovered radio waves. (1 Hz equals one cycle per second.) The field around power lines, for example, is predominantly 60 Hz. Radio wave frequencies range from 300 Hz to billions of hertz. Electromagnetic waves with similar frequencies can be grouped together. These groupings form the electromagnetic spectrum with low-frequency waves (sometimes called ELF for “extremely low frequencies”) at one end and high-frequency waves at the other. Radio waves, microwaves, and infrared light can be found at the lower end of the spectrum. Ultraviolet light, X-rays, and gamma rays occupy the upper end. Visible light, including sunlight, occupies the middle region. Microwaves are used in the transmission of telephone and telegraph messages, communications between earth and orbiting satellites, and in relaying certain television broadcast signals.
Based on what we know in regards to the physics of sound, most people will accept that the human voice is generally incapable of speaking below the 280 Hz mark. Extremely low frequencies (30 to 300 Hz) are the range most EVP is captured, and according to the laws of physics, impossible for the human voice to cycle at. When you capture a potential EVP you must first analyze the voices through spectral analysis to prove it is in fact in the ELF range of the sound spectrum. Once you validate the voices in question are in the ELF range, you have a legitimate EVP. These anomalies seem to be limited to locations with purported activity thusly linking them with ghostly phenomena.
There are a number of computer software programs on the market that will detect and log the spectral range of a recorded or live sound wave. The most widely used is a program called Cool Edit. When looking for software to analyze your EVP you want to make sure it has a built in Spectrogram. The Spectrogram is the portion of the sound program that will show you the spectral range or Hz level the sound cycles at. Most of these spectrogram programs will give a visual representation of the spectral graph chart along with the Hz level of each spectral region.
When importing a sound from an external recording device, you want to pick up an adapter from Radio Shack or any other electronics store of your choice. This adapter will plug into the headphone or audio output portion of your recording device and plug into the MIC or audio input of your sound card. Once you have your recording device connected to your computer you want to launch the spectrogram portion of your software and press play on the recording device you are using. This will immediately begin to read the Hz level of the sounds you have recorded. When you reach the portion of your recording with the suspected EVP you can view the spectrogram and validate its Hz level. Some of these programs will save the files to your hard drive in electronic format. If your software has the capability, it is easy to isolate and convert that portion to MP3 or WAV format for posting to your website. This is how we capture, analyze, and validate these anomalous voices that defy rational, logical, and physical explanation.