They go all over the world to find ghosts.
All ghosts understand and speak English.
the brain is a series of electronic impulses, meaning is not only conveyed through sound but also through image and intent. Which are universal brain impulses.
a ghost is electromagnetic in nature, likely able to detect intent and mental images.
As such it should at least partially understand what you are saying, at least meaning.
However if it speaks back, chances are the english minded investigators may be interpriting a vague sound as english when it isn't.
check out the GHI forum, especially those episodes like that, had plenty of people from those location inform them it sounded like something else in their own language.
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