Except for being potential topics on a skeptic blog, there would seem to be no connection between ghosts and psychic animals.

But they may have a common explanation through infrasound. These are extreme bass sounds under 20 Hertz, which is too low to be heard by humans, unless at a decibel level much higher than infrasound usually reaches.

Humans make infrasound with large music pipes, detonations, rocket launches, and sonic booms. It is also produced during large releases of energy, such as in extreme weather, earthquakes, meteor explosions, and turbulent mountain air.

Though inaudible, the sound can cause strange and uneasy feelings. These feelings are sometimes akin to seasickness, except the sufferer can never get off the ship. They stay queasy as long as the infrasound continues to pump. It can also cause unease, fear, dread, and sadness, as well as well as unpleasant physiological effects such as nausea, disorientation, and loss of equilibrium. The French movie “Irréversible” included infrasound in its opening scenes to produce these sensations in audience members. It was also tried on a suspecting crowd. During a controlled experiment in a British concert hall, scientists were able to instill morbid feelings in volunteers via infrasound. These feelings included melancholy, chills, and anxiety.

Nazi engineers recognized the phenomenon and tried unsuccessfully to build an infrasound weapon. It would have been quite the tussle if both they and Stalin’s mad scientists had succeeded, and auditory bombers had squared off against ape-men.

Infrasound may explain alleged paranormal activity since it cannot be seen, heard, or felt, yet overtakes people with feelings of fear, dread, and sadness.

Infrasound can also be used to monitor for earthquakes and volcanoes, and some animals can hear and communicate at this frequency. This may explain why they sometimes flee before natural disasters, and the ability is sometimes credited as being animal intuition by the New Age camp. Less frequently, creationists will claim it is God telling the rabbits and moose to commence their scurrying.

Besides poltergeists and animal mysticism, some have tried to connect spiritual experiences at church to long pipe organs that can produce infrasound. I find this unlikely. For one, these uplifting experiences are reported in all churches, the vast majority of which don’t have this musical capability. Also, the feelings reported are the opposite of dread and fear.

The strongest piece of evidence for infrasound’s impact was provided by Vic Tandy, a part-time law lecturer at Coventry University in England. Tandy had a pair of unsettling experiences at the school. First, he felt the unease associated with infrasound while also seeing a gray blob come at him out of the corner of his eye. Another time, his fencing foil was moved by strong vibrations. It is unclear why a law lecturer was armed with a fencing foil, but I’m guessing it was in case the gray blob came back.

Frightened, but determined to find a scientific explanation, Tandy used instruments to measure sound waves and see what he could detect. As a control, he did this during the daytime with others in the room, and checked to see if the dread returned and the foil vibrated. In both cases, they did. Tandy eventually deduced that infrasound was coming from a ventilator in the air conditioner. When the air conditioner was turned off, the vibration and sinking feeling both stopped. This finding suggests that infrasound is a possible explanation for some instances of Sick Building Syndrome.

And it likely goes a long ways toward explaining many paranormal experiences. Ghosts don’t haunt newly-opened malls or condos, but prefer mountain castles, and there is a connection beyond ghost hunters expecting to find them there. Mountaintop castles are regularly bombarded with strong gusts of wind, which can make their way through tunnels and winding staircases and manifest as infrasound. This can be interpreted as paranormal, especially when combined with the post hoc reasoning of attributing any bumping sounds and beeping electronic gadgets to a ghostly presence.