The sound level in the neonatal intensive care unit (NICU) may induce adverse effects for neonates, their family, and the staff. This study evaluated the sound level in a NICU before and after the implementation of an educational program.A baseline audit determined the most exposed area of the NICU and the most exposed periods over 24 h. Then an educational program started, including sound level measurement methods, side effects for neonates, results from the baseline audit, and new visual monitoring equipment (SoundEar®). Sound levels were measured before, 1, 2, and 3 months after starting the educational program and the use of SoundEar®. The NICU staff was blind to the periods of sound level measurements.The base noise level was high, especially near the central part of the NICU and during transmission time (mean Leq: 60.6±3.6dB(A); sound peaks: 94.8±6.8dB(A)). A decrease in the sound level (P<0.001) was found 1 and 2, but not 3 months after starting the educational program. It remained high compared to the guidelines.Human activity was responsible for most of the sound level. An educational program was effective in reducing the sound level, but did not reach the guideline's target. The continuous use of sound-monitoring equipment after starting the project reduced the sound level for 2 months, but no longer. Therefore, a continuous educational program about the sound level in the NICU including feedback monitoring every 2-3 months should be encouraged.