I lived next door to a medium. There was a very thin wall that separated us. A group met there and they "contacted the dead" on a frequent basis. It was very loud and I overhead the whole thing on many occasions. The noise was coming from the mouths of the people present, not from any other source.
She told me there were many spirits present in her home and there would be some in mine as well. She said not to be afraid but if they gave me any trouble, to let her know.
I never had any supernatural experiences or heard any noises which I couldn't explain. I'm a skeptic and am convinced there's nothing in it.