Turn Down the Volume: A Study of Excessive Sound Levels in the Neonatal Intensive Care Unit

Background: World Health Organization (WHO) guidelines recommend that environmental sound levels in the Neonatal Intensive Care Unit (NICU) should be an hourly average level (LAeq) <45 dB and maximum level (LAmax) <65 dB. While studies have shown that ambient sound in NICUs often exceed these levels, information is lacking regarding sound exposure at the bedside. Our purpose in this study was to determine sound levels of common medical interventions in the NICU and inside the bedsides of neonates under varying conditions and to determine the association, if any, between NICU design, ventilator, incubator and shift of day and sound levels at the bedside. Methods: This observational study was conducted in 2 parts. In Part A, sound levels were measured during the following interventions: a) turning on the incubator and ventilator b) monitor alarms c) suction of mouth and gastric secretions and d) closing the port holes of the incubator. In Part B, sound levels were measured every 2 seconds for 24 hours in 42 neonates in 7 groups with and without incubator and ventilator, in a single room or multi-pod NICU, categorized as three 8-hour shifts (morning-M, evening-E and night-N). LAeq and LAmax were measured using the Cirrus Optimus sound meter and were A-frequency weighted to the perceived loudness. Data were processed using the Noise Tools Q4 software. Statistical analysis (SPSS Inc., Chicago, IL) included ANOVA and linear regression. Results: Baseline sound inside the incubator was 48 dB, with the center of the incubator producing 3-dB less noise than the side walls. The highest noise was generated by slamming the porthole door and by turning on the suction machine, both at 81dB. All interventions produced noise levels that were higher than recommended (Table 1). In Part B, LAeq ranged from 55-65 dB in different scenarios and shifts and were always above the recommended levels. LAmax levels reached as high as 95 dB, with a minimum of 79 dB. There were significant differences between the 7 groups in LAmax in the M and E shifts, and over 24 hours (Table 2). There was significant variation in LAeq [M 59.9 (2.9); E 59.9 (4.6) N 57.5 (4.5), p=0.011] and LAmax [M 88.7 (6.1) E 88.9 (4.8) N 84.7 (7.3), p=0.003] between shifts, with the lowest levels at night. On linear regression, with ventilator, incubator and NICU design as covariates, LAeq was significantly lower in a single room NICU [B 2.60 (SE 1.06), p=0.018]. Conclusions: In this observational study, we found that most interventions in the NICU generate higher than recommended sound levels. A single room design NICU is associated with reduced sound exposure to the neonate. This may have important benefits to the neonate in quality of sleep, hearing and neurodevelopment.