Infrasonic Threshold Levels of Physiological Effects

The investigation was conducted in order to study the correlation between physiological changes and exposure to low levels of infrasound. The exposures were made at two frequencies, 6 Hz and 16 Hz. In order to investigate the correlation with the hearing perception thresholds, the exposures were made at two different levels, 10 dB above the hearing threshold and 10 dB below the hearing threshold. At 6 Hz the level was adjusted to 95 dB(lin) and 115 dB(lin). The corresponding values at 16 Hz were 80 dB(lin) and 100 dB(lin). At levels above the hearing threshold, the exposure was correlated to a reduction in wakefulness. No clear effect was observed at pressure levels below the hearing threshold. The results of the investigation are in accordance with the theory that changes in physiological reactions will not occur at levels below the hearing perception threshold.