Variations of NICU sound by location and time of day

The primary aim of this study was to identify time periods of sound levels >45 decibels (dB) in a large Level III NICU. The second aim was to determine whether there were differences in decibel levels across the five bays of the NICU, the four quadrants within each bay, and two 12-hour shifts.

A repeated measures design was used. Bay, quadrant, and shift were randomly selected for sampling. Staff and visitors were blinded to the location of the sound meter, which was placed in one of five identical wooden boxes and was preset to record for 12 hours.

Sound levels were recorded every 60 seconds over 40 12-hour periods, 20 during the day shift and 20 during the night shift. Total hours measured were 480. Data were collected every other day during a three-month period. Covariates of staffing, infant census, infant acuity, and medical equipment were collected.

The main outcome variable was sound levels in decibels, with units of measurement of energy equivalent sound level (Leq), peak instantaneous sound pressure level, and maximum sound pressure level during each interval for a total of 480 hours.

All sound levels were >45 dB, with average readings ranging from 49.5 to 89.5 dB. The middle bay had the highest levels, with an Leq of 85.74 dB. Quadrants at the back of a bay were louder than quadrants at the front of a bay. The day shift had higher decibel levels than the night shift. Covariates did not differ across bays or shifts.