Dynamic EEG changes during exposure to noise at different levels of loudness and sharpness

From a psychological standpoint, noise can disturb human mental performance in the workplace. While loudness and sharpness of noise are usable factors for evaluating the subjective effects of noise exposure, there has been comparatively less focus on their influence on human reaction time and the dynamic changes in brain waves. Therefore, this study aimed to investigate the temporal changes in the theta beta ratio (TBR) and reaction time (RT) before and during exposure to different noise loudness and sharpness levels. Eight different loudness and sharpness levels of noise were generated and broadcast. Sixty-four men performed the Integrated Visual and Auditory (IVA) test both before and during exposure to the generated noise, and their brain waves were recorded simultaneously. The main step of the IVA test lasted approximately 12 min and consisted of 250 visual and 250 auditory stimuli presented randomly. The highest difference in TBR before and during exposure to various loudness levels was associated with 65 phon at 250 Hz and 75 phon at 4000 Hz, with values of 0.86 and 0.75, respectively. This difference equaled 0.69 for the 1.23 acum sharpness level at a frequency of 4000 Hz. In addition, the sharpness of 3.29 acum at a frequency of 8000 Hz led to the highest difference equaling 0.71 in TBR between before and during exposure to various sharpness levels. The most significant difference in RT was observed before and during exposure to lower loudness levels (65 and 75 phon), resulting in 405.75 and 347.5 ms, respectively. This highest difference was also observed for sharpness levels of 1.23 (391.4 ms) and 3.29 acum (427.4 ms) compared to other sharpness levels. Furthermore, attention deficit increased with longer exposure times to all noise levels. The results showed a statistically significant correlation between TBR and RT during exposure to all noises. Specifically, lower loudness at frequencies of 250 and 4000 Hz and higher sharpness at frequencies of 4000 and 8000 Hz had the most significant impact on the attention parameter. In psychoacoustics studies, it is important to consider both the frequency and duration of exposure in addition to assessing the loudness and sharpness level of noise.