Mental and spiritual energy, intuitively speaking, are like a magnetic field, a radio wave; when it touches you, it often manifests as hallucinations but never interferes with the real world.
Everyone grew up influenced by materialistic ideology, and they were unlikely to easily believe in ghosts and spirits, but they had indeed just heard a series of noises that could not possibly be made by human effort, which deeply furrowed Kevin's brow... If he had heard it alone, it might have been a hallucination, but the fact that all three of them heard it suggested that something unusual might really exist.
Bai Zhexian said, "What's the matter, are you scared?"
"Ha, I'm not scared by just a little noise." Although Kevin was indeed startled by the darkness earlier, it stemmed from a fear of the unknown; after all, he had experience in tough situations, and besides, he had two strong partners by his side.