Noise exposure exceeded safe limits during neonatal care and road transport but was reduced by active noise cancelling

Abstract

Aim: Noise levels above 45 dB in a neonatal intensive care unit (NICU) and 60 dB during neonatal transport are recognised hazards, but protective equipment is not standard. We measured noise levels in both settings, with and without noise protection.

Methods: Peak sound and equivalent continuous sound levels were measured in a NICU and during road transport, at a mannequin's ear and inside and outside the incubator. Recordings were made without protective earwear, with noise protecting earmuffs and with active noise cancelling headphones.

Results: In the NICU, the peak levels at the ear, and inside and outside the incubator, were 61, 68 and 76 dB. The equivalent continuous sound levels were 45, 54 and 59 dB. During road transport, the respective levels were 70, 77 and 83 dB and 54, 62 and 68 dB. In the NICU, 80% of environmental peak noise reached the ear and this was reduced to 78% with earmuffs and 75% with active noise cancelling. The respective figures during transport were 87% without protection and 72% with active noise cancelling, with an unexpected increase for ear muffs.

Conclusion: Noise levels exceeded safe limits in the NICU and during transport, but active noise cancelling reduced exposure.

Keywords: active noise cancelling; neonatal intensive care unit; neonatal transport; noise exposure; noise reduction.