Effects of infrasound on cognitive performance.

The cognitive performance of 40 subjects was measured during exposure to infrasound and noise in three experiments. In the first experiment, 12 subjects were exposed for 15 min to each of four experimental conditions while performing a Serial Search Task. The conditions were: 65 dB ambient noise (AN), a low-frequency background noise (BN) at 110 dB, a 7-Hz tone at 125 dB + AN, and the 125 dB tone + BN. The second experiment was the same as the first except a Complex Counting Task was used and the exposure duration was increased from 15 min to 30 min. In the third experiment, the Complex Counting Task was used and the subjects were exposed for 15 min to each of the following four conditions: BN, 125 dB at 7 Hz plus BN, 132 dB at 7 Hz plus BN, and 142 dB at 7 Hz plus BN. No decrements in performance were obtained in any of the three experiments, and there were no subjective reports of dizziness or disorientation as suggested in some of the previous literature. The authors conclude that adverse effects of infrasound have been exaggerated and the current levels of infrasound components as produced by modern jet aircraft are not considered in themselves a practical problem.