The impact of different decibels of ambient noise on attention

Ambient noise is often perceived as a distractor; however, some individuals may benefit from certain levels of ambient noise to enhance cognitive performance. Despite this, the optimal range of ambient noise for improving attention remains unclear. To disclose this relationship, thirty-eight healthy college students were recruited to perform a 6 ⋅ 6 Schulte grid test under varying ambient noise levels. All participants performed the tasks under three noise conditions presented in a fixed order of increasing intensity (20-40 dB, 40-60 dB, and 60-80 dB). Functional near-infrared spectroscopy (fNIRS) was employed to measure dynamic changes in hemoglobin levels, while facial expressions and physiological signs were also assessed. The findings demonstrated that 40-60 dB group exhibited strongest visual brain functional connectivity. Among the three groups, the 40-60 dB group exhibited the highest values for anger expression, surprise expression, and heart rate (HR) (all p < 0.0001). Additionally, this group showed significantly higher heart rate variability (SDNN) compared to the 60-80 dB group (p < 0.05). The region of interest (ROI) pars triangularis Broca's area left~ pars triangularis Broca's area right revealed a significant difference (P = 0.004). Furthermore, the pairwise post hoc tests revealed the significant differences between the 20-40 dB group and 60-80 dB group (P = 0.007), as well as between the 40-60 dB group and 60-80 dB group (P = 0.017). In conclusion, moderate noise (40-60 dB) appears to induce an optimal level of arousal. In contrast, high-intensity noise (60-80 dB) likely prompts functional reorganization between the bilateral triangular parts of Broca's area to support cognitive control and interference suppression.The moderate intensity of noise may arouse the attention.