E.V.P.s are Electronic Voice Phenomena. The theory behind this is that spirits exist on a different plane and can interfere and communicate through electronic media at different frequencies. By listening to frequencies either higher or lower than normal speech, you may be able to pick up on ghostly communication. There are a lot of varying theories and people have been able to secure possible EVPs in lower, higher, or even the same frequencies as voice.

One cheap way to try and catch EVPs that may have come in on different frequencies is to get a tape recorder that will record and play back at various speeds It can also help you in listening to the audio afterwards in case you think there is something on the tape. According to theories, if the speech comes in faster or slower than the normal human speech that was around you when the audio was recorded, it could be an E.V.P. However many supposed EVPs have been captured in normal time and at normal voice frequency.

The average range for the human voice is 600 Hz - 4KHz. There are some good programs to analyze sound. A potential EVP can be very faint or garbled and you might need to boost it up. One such program which is complete free to use is Audacity. This is a very powerful little program. Below are some images that will show you what techniques Audacity can help you with as far as isolating EVPs. There are other more advanced programs as well like Sound Forge but they are commercially based.