The correlation between brain response and subjective annoyance under natural sound masking of road traffic noise

Urban road traffic noise is a growing environmental concern, and noise masking offers an alternative solution. However, the underlying neural mechanisms of natural sound masking of noise remain unclear. Here, the brain's physiological responses to natural sound masking (birdsong and water sound) were explored using functional near-infrared spectroscopy. The functional connectivity between brain regions was analyzed by graph-theoretical network analysis, and the subjective annoyance was correlated with brain activation and graph-theoretical network parameters. Results revealed that masking conditions significantly reduced annoyance compared to the road traffic noise condition. Birdsong and water sound masking increased activation in the right superior temporal gyrus and right middle temporal gyrus, which is positively correlated with the annoyance reduction percentage. Birdsong masking globally decreased the connections between brain regions and neighboring regions at the group level, which is negatively correlated with the annoyance reduction percentage. These findings demonstrate that natural sound masking can modulate brain network topology and functional connectivity, offering insights into effective noise-masking strategies.