The Infrasonic Impact: Exploring the cognitive impact of frequencies below the hearing threshold during short term exposure

Infrasonic sound or sound below the generally accepted audible threshold is a persistent part of most modern environments and human beings have a near-constant exposure to it as it exists both naturally and from mechanical sources. While infrasonic sound frequencies are below the hearing threshold (20 to 20,000 Hz), studies show that they are still perceived by the human auditory system. Despite this evidence, studies determining the potential impact of infrasonic sound or the perception of the existence of infrasonic sound on cognition are scarce due to the challenges surrounding the delivery of infrasonic frequencies in a controlled environment such as replicating a non-audible sound, delivering this to participants and avoiding other overlap with other frequencies. There is rigorous discussion around what impact the placebo effect may have on infrasonic sound, with schools of thought vacillating between the placebo effect having no impact at all and it being the sole cause of any reported symptoms including changes to concentration abilities and diminished memory in subjects. As there remains no conclusive explanation for the relation between priming in the form of created expectation and the actual effect of infrasound, this leads to the question of whether infrasound may be able to affect cognitive functioning in any way. Determining the affect, and then studying the applications or mitigations needed to achieve a beneficial outcome to improve cognition by enhancing or inhibiting infrasonic sound are the focal point of this study. This project explores the influence of infrasound on cognition by testing reaction time to stimuli and working memory in the presence and absence of exposure to infrasonic frequencies, using an advanced technical setup alongside tools like the Simon test and the n-back test. This approach creates a system to deliver infrasonic sound discreetly (without participant knowledge in all instance, unless briefed) and study the impact on short-term exposure patterns. In contrast, most research to date has investigated the possible effects that long-term exposure to infrasound (spanning months to years) may have on sleep 4 patterns and biological functions, with mixed findings. A number of studies have attempted to detect any correlation or investigate the relationship between reported symptoms (irritability, trouble with concentration/attention, dizziness, anxiousness, extreme fatigue and other self reported health concerns) in those exposed to constant infrasound generated by wind turbines, with some arguing a relationship between this exposure and perceived negative effects (the validity of which remains uncertain) and others unable to find evidence of a clear link between sound and symptomatology. While exposure to infrasonic frequencies is a temperamental process due to the complexity of the technical set up needed and variation in exposure and delivery (and the reported effects are being debated), functional magnetic resonance imaging (fMRI) studies have been able to map the neural changes based on cerebral blood flow. Certain fMRI studies make note of brain stimulation on exposure to infrasonic sound, and are consistent with a potential effect on cognitive performance. This project aims to explore whether exposure to infrasonic sound can influence cognitive function using measures of accuracy, and reaction times as outcome measures in tests of reaction times and working memory intended to determine whether this could enhance or inhibit cognitive functioning. While long-term exposure could have a number of variables that may not be noticed, short term exposure limits any potential long lasting negative effects and allows us to take a closer look at immediate impact. This project additionally intends to further explore the impact of positive and negative expectation on individuals exposed to infrasound, by creating positive/negative impressions prior to exposure using media created for the purpose of creating expectation. The concepts of placebo and nocebo, or the impact of positive and negative expectation, are argued to be contributory to the real and imagined impacts of infrasonic sound. If infrasonic sound has a genuine impact on human cognitive performance, then the level to which this can be exploited or inhibited may have a proportional relationship with individual expectation of impact. 5 This research intends to further provide insight into the impact of infrasound on cognitive functioning and the relationship that awareness of infrasound (in the form of expectation) has on this outcome. The outcome of this study showed that accuracy when conducting cognitive tasks is not affected by the presence of infrasonic frequencies in a significant way. However, there was an observed negative impact on simple reaction times (time taken between the observation of a stimulus and the response to the stimulus as set out by the task) in the presence of infrasonic frequencies. This suggests an impact on cognition due to the presence of infrasonic frequencies in an environment requiring computer-based information processing tasks. This outcome has practical implications for drug free methodology for cognitive enhancement, potentially creating a context within which we can purposefully prevent deterioration of memory recall and reaction time using the controlled absence of infrasonic sound.