Wednesday, January 21, 2009

EVP: Infrasound, Ultrasound or Something Else?

by: Brian Miller

Over the years there has been a lot of debate regarding the nature of Electronic Voice Phenomena or EVP. One prevailing idea is that EVP is composed of either ultrasonic or infrasonic sound waves, and that is the reason why investigators are unable to hear EVP at the time of capture. Although this is an elegant idea, it is unlikely because it defies the basic understandings of acoustic energy.

Sound is very simply a physical vibration (acoustic energy) transmitted by either a gas, liquid or solid. Sound is characterized by the properties of sound waves, which are defined by frequency, wavelength, period, amplitude and speed. Although the human ear is capable of detecting sound between 20Hz and 20,000Hz, the ear is most sensitive to sound waves that register between 1000Hz and 3,500Hz. Most human speech occupies a range between 200Hz and 8000Hz. So if EVP is truly "speech" as we currently understand it, isn't it logical to assume that EVP should occur only in that narrow frequency range?