A flashlight. A kitchen knife. A digital recorder. A cell phone… As his hand closed over this last item, the vaguest outlines of a plan began to come together.
“As best I can tell, the high-frequency sound waves stimulated— in today’s terms— serotonin receptors in the frontal cortex of the brain. Perhaps they acted on the raphe nuclei, as well.”
“What phenomenon was that?” “Unusual sensory manifestations. Odd, unpredictable behavior. Even, in extreme cases, what a psychologist would term ‘dissociation.’ ” “That sounds like a form of schizophrenia,” Logan said.
This haunting had been a discovery by researchers at Coventry University: that extremely low-frequency sound, in the vicinity of 19 hertz, caused feelings of disquiet and dread. A side effect of this infrasound was a peculiar ocular vibration that triggered visions of a shadowy, ghostly apparition.