An Overview of MEMS Microphones for Accurate Sound Pressure Level Measurements in the Context of Urban Noise Monitoring

This systematic review examines the evidence supporting accurate sound pressure level measurements with micro-electro-mechanical systems (MEMS) microphones for environmental noise monitoring, with emphasis on urban applications. A structured search and screening process identified 45 studies, classified into microphone calibration, sensor development and evaluation, and application-oriented research. Bibliometric analysis revealed geographical and project concentrations and increasing adoption of digital microphones. An evidence-based grading framework assessed mechanical implementation, acoustic characterization, cost reporting, and deployment maturity. The findings reveal substantial heterogeneity in calibration practices, uncertainty reporting, and environmental validation. Among the 10 application reports, seven provided minimal information on long-term acoustic stability, and none offered comprehensive environmental characterization. Documented Class~1 type approval of a commercial MEMS instrument demonstrates the feasibility of conformity for a specified configuration, whereas most prototype studies report only partial performance evaluations. A complementary framework links physical error mechanisms across the complete measurement chain to their consequences, mitigation strategies, and remaining research needs. The central gap is the transition from agreement under controlled conditions to traceable, uncertainty-qualified field measurements. Priorities include reproducible calibration of complete sensor nodes, interlaboratory comparisons, quantified environmental and ageing assessments, and scalable network quality assurance.