[Abstract] A review of literature describing the effects of very low-frequeney sound on humans revealed a controversy between authors claiming that infrasound is very harmful to humans and those claiming that infrasound cannot engender any subjective or objective symptoms. This report shows that these discrepancies may be explained by individual variability in response to low-frequency sound.
An experiment was performed to determine whether some individuals are uniquely sensitive to infrasound. Three acoustic conditions were employed. These consisted of a control (amplifier hum) condition and two 8 Hz infrasound conditions: a high distortion signal and a low distortion signal. Subjects were grouped by their subjective responses.
No control subjects exposed to amplifier hum reported any adverse responses. The distribution of symptoms (headache and fatigue vs dizziness and nausea) between the high and low distortion groups was significantly different. In persons reporting symptoms, the higher level of harmonics was primarily associated with headache and fatigue, while reduction of harmonics primarily resulted in dizziness and nausea.
Subjects reporting dizziness and nausea were subjected to up to four additional sessions – two control, one low distortion, and one with only some harmonics without infrasound. These sessions showed that these symptoms were replicable and related only to the infrasound.
Multivariate and univariate analyses showed that the subjects reporting adverse symptoms can be distinguished from the other groups on the basis of heart rate, respiratory rate, systolic and diastolic blood pressure changes, gaze nystagmus, time estimation and mood scales but not EEG, p1ethysmography, TTS, a short-term memory task, Eysenek Personality Inventory, Cornell Medical Index or age.
The adverse responses of some individuals closely resemble motion sickness. Individua1 differences in the reaction to infrasound may then be explained by variability of inner-ear structure or central adaptive mechanisms.
D. S. Nussbaum and S. Reinis
Department of Psychology, University of Waterloo
Institute for Aerospace Studies, University of Toronto
UTIAS Report No. 282, January 1985
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