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

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. The authors would like to thank Intelligent Hearing Systems Corporation, and particularly Rafael Delgado, for his continued support and willingness to assist throughout the development of this study.

The authors also express their sincere gratitude to all participants, who generously dedicated their time to take part in this research. The authors declare that financial support was received for the research and/or publication of this article. This work was supported by the National Fund for Scientific and Technological Development (Fondo Nacional de Desarrollo Científico y Tecnológico, FONDECYT), grant number FONDECYT 11241179.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Escuela de Fonoaudiología, Facultad de Ciencias de la Rehabilitación y Calidad de Vida, Universidad San Sebastián, Santiago, Chile Anthony Marcotti & Alejandro Ianiszewski Instituto de Salud Pública, Facultad de Medicina, Universidad Andrés Bello, Santiago, Chile Departamento de Fonoaudiología, Escuela de Ciencias de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile Research and Development Department, Intelligent Hearing Systems, Miami, FL, USA Escuela de Psicología, Facultad de Ciencias Sociales, Pontificia Universidad Católica de Chile, Santiago, Chile Centro Interdisciplinario de Neurociencia, Pontificia Universidad Católica de Chile, Santiago, Chile Correspondence to Anthony Marcotti or Alejandro Ianiszewski. All the authors declare no competing interests.