Exposure to Infrasound — Perception and Changes in Wakefulness

Abstract

The present paper is a description of some laboratory experiments carried out in order to investigate the perception and changes in wakefulness occurring during exposure to infrasound. Perception of infrasound is based on hearing and vibrations in different parts of the body. Threshold of audibility was found to be approximately 110 dB(lin) at 4 Hz and 90 dB(lin) at 20 Hz. Sensations through vibrations were found to occur at about 20 dB above the hearing threshold levels. As far as vibrotactile sensation is concerned no difference was found to exist between deaf and hearing subjects. Hearing sensations could not be registered for neurosensory deafness. 10 deaf and 10 hearing subjects were exposed for 20 minutes at 6 Hz, 115 dB(lin). Reduced wakefulness was noticed among the hearing subjects but not among the deaf subjects. According to these results, changes in wakefulness of infrasound is based on cochlear stimulation. It is suggested that a reduction in wakefulness that is attributable to infrasound occurs at pressure levels close to the auditory threshold.