1. Tachyon Theory - Messages transmitted from the future.
At present time we do not have tachyon recivers so we
can not tune in, only pick up distorted fractions of the signals.

2. Survival Theory - A way to commuicate with spirits.
The voices of the dead can be recorded and heard when
played back.

3. PK Theory - Recorded thoughts of sleeping or awake people.

4. Residual Energy - Echoes from the past, Energy that hangs around anywhere, and does or does not need a geomagnetic
source to increase it.

5. Alien Theory - Signals from space.

6. Hoax - EVP does not exist.

7. Interference - From a nearby CB operator or cross modulation.
Static noise from power lines; lightning; arcing. All of these produce electromagnetic waves which pass through the recorder without passing through the speaker.

8. Perception - A very complex process, and when our brains
try to find patterns, they are guided in part by what we expect to hear.

9. Reverse Speech - A form of communication arising from the uncoscious mind, according to David John Oates.
The unconscious mind sends out backwards messages to the conscious mind every 10 to 15 seconds.

10. Conspiracy Theory - Secret military experiments.

11. Dimension Theory - Messages from parallel universes.

12. Over Correction - Recordings are "butchered" by enhancement software.

13. Holographic Recordings - Multidimensional holographic recordings.
A conventional holographic photograph captures an image in
apparent three dimensions.
Here we are talking about a world of multiple dimensions where
time and space have no meaning.
In this world, a holographic recording might contain all of
the information of a persons personality, allowing it to respond
to questions and otherwise interact with the living in real time.
EVP somehow tapps into the holographic imprints left behind
by spirits who have moved on to higher realms.