People exposed to infrasound may not consciously hear it, but they can show higher cortisol levels and increased irritability, which may help explain reports of “haunted” locations. Infrasound refers to sound at very low frequencies, below 20 Hertz (Hz), a range that people usually cannot hear. It can be produced by natural events such as [...]from SciTechDaily https://ift.tt/RCuQbDt
