The Effects of Infrasound on Rhesus Monkey Performance of a Continuous Compensatory Tracking Task

Abstract

Background: Potential bio-behavioral effects of infrasonic energy (<20 Hz) have generally been considered to be due to extra-aural (non-hearing) mechanisms. Since systems that deliver acoustic energy, including infrasound, are being considered for use as non-lethal weapons, it is important to elucidate the possible aural and extra-aural effects of such energy. Methods: Subjects (5 adult male rhesus monkeys) engaged in a continuous compensatory tracking task. The effect of short-term exposure to high-intensity infrasound (160 dB), using a custom-made system, on tracking task performance was measured. The effects of the infrasound exposure on auditory measures (otoacoustic emissions and auditory brainstem evoked potentials) were also examined. Results: Tracking behavior of the subjects was substantially disrupted by exposure to 10-Hz infrasound at 160 dB. There was no evidence of any post-exposure alterations in tympanometry, distortion product otoacoustic emissions, or in auditory brainstem evoked potentials. Conclusions: Although the present experiments showed significant effects on performance, further experiments using larger working volumes would have to be undertaken to address the potential uses of such a device.