Physiological and psychological effects of infrasound on humans

Sixteen subjects were exposed for three hours to inaudible infrasound, audible infrasound, traffic noise and a quiet control condition, while they performed various psychological tasks. Some cardiovascular and hearing parameters were recorded and after the experiments the subjects answered a questionnaire concerning their experiences during the noise exposure. The most conspicuous effect of infrasound was a high rating of annoyance and a feeling of pressure on the ear at less than 20 dB above the threshold of hearing. No influence on the cardiovascular system was seen and the performance only deteriorated in one of nine tasks. Infrasound below the threshold had no effect. It is concluded that a better knowledge of the hearing at low frequencies is required, the most urgent being an extension downward in frequency of existing curves of equal loudness and equal annoyance. </jats:p