Influence of Infrasound on the Alpha Rhythm of EEG Signal

The alpha waves were first registered and named by Berger in 1929. They are oscillations in the frequency range 8-12 Hz, originating from the occipital lobe during wakeful relaxation with closed eyes. The alpha blockage is the result of desynchronisation of the bioelectric activity of the brain induced by sensory stimulation. When the subject's eyes are closed, the alpha rhythm is generated. As soon as the eyes are open, alpha disappears. This is called alpha block and may be elicited also by any form of sensory stimulation. This replacement of the alpha rhythm is also called desynchronization because it represents a change of the synchronized activity of neural elements. This state is also called arousal or alerting response. Infrasounds are acoustic waves of frequency below 20 Hz. They are not directly perceived by humans because the natural frequency of vibrations of the part of the basilar membrane distant from the round window is about 20 Hz. The hearing organ, therefore, is well adapted to receive waves with frequency in excess of 20 Hz. The purpose of the experiment was to determine the effects of infrasound waves on variations in the alpha waves. Tests were done on a group of 32 participants. The experiment showed that infrasounds of frequency f = 7 Hz and acoustic pressure level SPL = 120 dB (HP) cause a statistically significant reduction of the alpha rhythm power