Noise exposure, circadian misalignment, and fatigue in maritime operations: A case study on a Ro-Pax vessel

Abstract

[Abstract] Fatigue represents a critical human-reliability concern in maritime operations and can undermine the safety performance of ship systems. This exploratory case study examines associations between onboard noise exposure, work–rest patterns, circadian typology, and seafarer fatigue aboard a Spanish-flagged Ro-Pax vessel. Objective noise measurements were collected following IMO guidelines, and crew fatigue and mental workload were assessed using the NASA-TLX, SOFI-SM, and rMEQ instruments (n = 22, representing 95.6% of the crew). Engine-room noise exceeded 96 dB(A), and cabin noise, while compliant with IMO limits, surpassed World Health Organization recommendations for undisturbed sleep. Higher role-based noise exposure was associated with higher levels of occupational fatigue, particularly in dimensions related to physical fatigue and physical discomfort, while no significant association was observed with perceived mental workload. Fatigue levels varied descriptively across occupational roles and circadian profiles, with higher fatigue observed in duty schedules misaligned with individual circadian preferences. The findings indicate that compliance with existing noise regulations does not necessarily ensure conditions conducive to adequate recovery or sustained human reliability. While causal relationships cannot be inferred, the study provides context-specific evidence supporting the integration of noise management, circadian-aware scheduling, and improved accommodation insulation into maritime safety and reliability frameworks.