Efficacy of noise reduction bundle in reducing sound levels in a Level II neonatal care unit in China

BACKGROUND: Noise is a hazard for newborns. Preterm infants are more vulnerable to negative effects of noise because their auditory system is at a critical period of neurodevelopment. We conducted this study to determine whether noise exposure in our Level II unit met the American Academy of Pediatrics (AAP)-issued recommendation of less than 45 dB. We also aimed to assess the efficacy of a bundle of noise reduction methods and the role of noise supervisors in assuring the compliance of modification. METHODS: Hourly mean equivalent continuous noise level (Leq) was collected in two phases: (I) Phase 1: baseline data for 4 weeks, (II) Phase 2: study period for 13 weeks, 1 week (Stage 1) under close monitoring by the noise supervisors and 12 weeks (Stages 2, 3 and 4, lasting 4 weeks each) without supervisors. RESULTS: The baseline noise level consistently exceeded recommendations with an hourly mean incubator noise of 53.6 dB (±5.2). Our bundle resulted in a significant reduction in incubator noise levels by 9.1 dB (±0.75). The sound levels remained <45 dB most of the time except for three-time windows, correlating with morning handovers/physical assessments (7:00–9:00), procedures/discharges/phone calls (13:00–15:00), and night handovers (19:00–20:00). The change in the reduction was most significant (–4.1 dB) in Stage 1 during the day shift. A minor trend of decline in sound levels inside the incubator was observed from Stage 1 to Stage 2 (P=0.057), with a rebound occurring in Stage 3 followed by stabilization in Stage 4, suggesting the role of noise supervisors in ensuring the compliance of the modification. CONCLUSIONS: The baseline noise levels consistently exceeded recommendations, but the bundle was effective in achieving the reduction. Noise supervisors are essential to ensure the compliance of the modification. Resolution focused on the three-time windows is required in future work.