Mechanisms and Control of Infrastructure-Related Interior Noise in Suburban Railways: A Zhejiang Case Study

Excessive interior noise in tunnel segments of a 120 km/h suburban railway prompted a combined field-measurement and modelling investigation. Interior and exterior noise tests of the train of the infrastructure were conducted both in tunnels and on open-track sections. The dominant sound sources were identified and their spectral characteristics analyzed. A Statistical Energy Analysis (SEA) model was developed to evaluate noise-control strategies targeting vehicle interior components. The results show that, in the high-speed suburban railway, tunnel reverberation selectively amplifies acoustic energy in the 200–1000 Hz band, making this range the principal contributor to excessive interior noise. Sound source identification reveals that, in tunnels, the passenger side door is the primary transmission path, followed by the floor. A sensitivity analysis with ±3 dB variations in the sound insulation of the side door and floor indicates that a 1 dB improvement in side-door sound insulation reduces interior noise by approximately 0.3 dB(A), compared with 0.1 dB(A) for the floor. These findings suggest that prioritizing side-door sound insulation enhancement, together with vibration-mitigation measures in the bogie region, constitutes an effective strategy for controlling interior noise under tunnel operating conditions.