Use of sound-absorbing panel to reduce noisy incubator reverberating effects

OBJECTIVES: To assess the amplification and distortion of noise in incubators by measuring noise levels from various sources under various conditions. STUDY DESIGN: We recorded sound pressure levels (SPL) of background noise, baby crying, alarms and porthole closing with the incubator hood open or closed. Then we tried to reduce the sound level in the incubator by applying a sound absorbing panel to the ceiling of the hood. RESULTS: The sound sources analysed produced very high SPL. In free field baby crying and porthole noise were, respectively, 81-83 dB and 70-71 dB, closing the hood they raised to 84-87 and 73-74 dB: this means that the noise perceived by a baby in the incubator had twice the SPL of the same noise emitted in a free field; alarm noise was 56-57 dB inside incubators. Sound emitted inside the hood was also distorted, i.e. it had different features from the same source in a free field. The insulating panel prevented amplification and distortion due to the hood and reduced the SPL of alarms. Only background noise did not decrease with the panel. Sound absorbing panel reduced baby's crying, porthole noise and alarm noise SPL to 82-85, 70-71 and 50-51 dB, respectively. CONCLUSIONS: Incubators are reverberating environments, which amplify the baby's cry and other noises produced inside the hood. The frequency components of noises are altered by the hood. The sound absorbing panel reduced this phenomenon.