Towards the acoustical characterisation of an Intensive Care Unit

Intensive Care Units (ICUs) can be immensely noisy places, where high noise levels may have deleterious effects on patients, visitors and staff alike. Many studies have identified sound levels exceeding World Health Organisation's recommendations, although very few measured for more than 24h or concurrently in multiple locations, as normally done in outdoor studies. In order to assess the feasibility of installing a continuous monitoring system in the indoor environment of an 18 bedded general intensive care, a MEMS-based microphone was used to monitor the noise levels for 7days. Results showed minimal variation between night and day, but changes in sound level could be correlated with regularly occurring activities. The impact of microphone-holding structure on the measurements and the possibility of inferring patient and visitor's exposure from a fixed measurement position are also discussed. Laboratory analysis, confirmed by in situ testing, identified ideal microphone positioning, and led to a correction of about 1dB for the sound pressure level measured at the microphone to obtain the level experienced by the patient.