Environmental noise exposure partially accounts for the association between socioeconomic status and neural encoding of speech

Abstract

Socioeconomic status (SES) has been associated with variability in neural speech encoding as indexed by the frequency-following response (FFR), yet the mechanisms underlying this association remain poorly understood. Environmental noise exposure represents a plausible pathway, given its socioeconomic patterning and established effects on neurophysiology. This cross-sectional study examined whether environmental noise exposure mediates the association between SES and neural speech encoding. Forty-seven young adults with normal hearing underwent FFR recordings to a speech syllable presented in quiet and noise. SES was operationalized using a composite index derived from maternal education, household income, and school type. Environmental noise exposure was estimated using modeled noise maps and quantified across cumulative lifetime and age-specific developmental windows. Multilevel mediation analyses estimated total, direct, and indirect effects of SES on FFR timing, magnitude, and fidelity. Higher SES was associated with lower cumulative lifetime noise exposure. Cumulative lifetime noise exposure partially mediated SES-related differences in onset and transition timing and stimulus–response correlation, whereas no mediation was observed for age-specific windows or frequency-specific magnitude measures. These findings suggest that chronic environmental noise constitutes one pathway through which socioeconomic conditions shape auditory neural function, with effects reflecting long-term accumulation. Persistent direct SES effects indicate additional contributing pathways.