United Kingdom, May 2 -- Scientists in Canada claim to have discovered the reason why so many older buildings are believed to be haunted.

A new study by boffins at MacEwan University in Edmonton, Alberta looking into the effects of infrasound - sound waves with frequencies below 20 Hz which are unable to be heard by the human ear but can often be felt as physical vibrations - and concluded it can lead to increased irritability and higher cortisol levels even when participants in the study were not aware of it.

Professor Rodney Schmaltz, senior author of the study published in Frontiers in Behavioral Neuroscience, explained: "Infrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial mac...