If EVPs are real, it is defying physics. A sound would have to be created from nothing and travel through the air loud enough to be recorded by a digital or analog device.
I asked MB how a sound could be generated from a ghost. His response is below:
MB: “Sound is also a form of energy – Sound needs a medium to travel through. If a ghost makes noise, it means that it has enough energy to form a sound wave which interacts with the molecules in the air to make a noise. What would generate it? No clue – same unknown thing as why ghosts would show in a form of light. We simply don’t know anything about it.”
What are your theories on how sound forms from nothing?
UnScene: Paranormal Investigation 