The whole question hinges on our (human) perception of what is happening around us which is often proved to be fallible. People mistake planets and bright stars for UFOs and recall how they were chased by them down the highway. Don’t rule out the power of suggestion. I’ve seen people terrify each other pushing a glass around in a Ouija session.
Sound frequencies also have their part to play in our perception of what supernatural things may be around us. I recommend Vic Tandy’s exploration of the 19hz wave and resolution of his ‘haunting’ here.
https://www.theguardian.com/science/2003/oct/16/science.farout
Which contains this excellent nugget…
So it becomes a distinct possibility that audio frequencies can disorient and promote a fear response in humans.
Then we have to contend with the effect of electromagnetic energy on the mind. In terms of the Supernatural we have…
https://science.howstuffworks.com/science-vs-myth/afterlife/ghost3.htm
Going really far out there, we enter the almost Sci Fi Bio world of fungi.
Entrenched deeply under our feet and decorating the surface of our world and even entering our homes, we’re not really sure about fungi or the effect their spores can have on us.
https://www.scientificamerican.com/article/strange-but-true-largest-organism-is-fungus/
Scientists are currently looking into fungal intelligence and feats of memory and adaptation.
https://psyche.co/ideas/the-fungal-mind-on-the-evidence-for-mushroom-intelligence
I know this come across as weird but what if spores can do more? We’ve seen the affected ants that climb a stalk as high as they can, clamp their mandibles and wait until the spore becomes fungus and literally blows its brains out.
Then there’s bacterial effect on the brain. Toxoplasma Gondii for instance. Blame the cat for that.
Before we start looking at shifting the goalposts to look at alternative supernatural explanations for ghosts, we should explore all of the natural possibilities as, in the long run, this would give us a greater insight into this mad ball we’re all riding around on instead of just sitting in the dark and scaring the shit out of ourselves.