Researchers say infrasound -- low-frequency vibrations from things like pipes, HVAC systems, and traffic that humans can't consciously hear -- may help explain why some old buildings feel unsettling or "haunted ." Rodney Schmaltz, senior author and professor at MacEwan, says: "Consider visiting a supposedly haunted building. Your mood shifts, you feel agitated, but you can't see or hear anything unusual. In an old building, there is a good chance that infrasound is present, particularly in basements where aging pipes and ventilation systems produce low-frequency vibrations. If you were told the building was haunted, you might attribute that agitation to something supernatural. In reality, you may simply have been exposed to infrasound." ScienceBlog.com reports: Infrasound sits below roughly 20 Hz, the lower limit of what the human ear can ordinarily detect.…