John’s Entertainment Technology Blog has an interesting series of postings related infra-sound (sounds lower in frequency you can hear):
Gravesend Inn-frasound: Subsonic Show Business article says that 19Hz standing air wave may under certain conditions create sensory phenomena suggestive of a ghost.
Gravesend Inn-frasound: The Experiment tells about a psychological experiment made on the effects of infra-sounds.
Gravesend Inn-frasound: Creating and Measuring Infrasound tells the technology challenges met in creating the needed 19 Hz infra-sound. The article tells why the idea of playing infrasound out of the computer failed and why they went to the idea of using an external function generator.
Gravesend Inn-frasound Experiment: Using Show Control Technologies in Psychological Research article tells details of the show control system used to run the experiment.
Gravesend Inn-frasound: Science! article tells if there was statistically signficant difference in response between the group that was exposed to infrasound and the group that was not.