Method: In a prospective study, the sound levels were measured for 3 weeks in a 4 person intensive care room of a class 3 intensive care. Subsequently a visual noise warning system was fixed to the wall on a highly visible place. Thereafter the sound levels were again measured for 4 weeks. The sound level measurements were done using a BG-5 class 2 sound level meter, which recorded the sound level every minute. This meter was fixed to the roof in the middle of the room. The visual noise warning system looked like a traffic light and displayed an amber light at 45 to 55 dB and a red light above 55 dB.
The perception of the nurses of unnecessary noise factors was investigated using the Topf’s Disturbance of Hospital noise scale. (Topf, 2000) It exists of a list of 29 items each describing a particular sound. The respondent has to indicate using a 5 point Likert scale to what degree a particular sound disturbed him or her during work. The questionnaire was translated to Dutch.
Results: The mean sound level before the introduction of the traffic light was 54.6 dB, after the introduction it was reduced to 53.9 dB (ttest, p <0.001). The Topf’s Disturbance of Hospital noise scale had an internal consistency (Cronbach’s alpha) of 0.883. All 120 intensive care nurses were approached to complete the questionnaire, 83% of the questionnaires were returned. The 4 most disturbing noises beside alarm signals were all noises which are dependent upon the behaviour of the persons present: loud conversations in the corridors at night, mobile phone usage, conversations among nurses in the rooms and slamming of doors. The 5 least disturbing noises were all noises which are not dependent upon the behaviour of persons present: traffic noise, flushing of toilets, washing of hands, sounds created by cutlery or serving trays, airconditioning or heating.
Conclusion: In this study, the influence of a visual noise warning system was limited. Noise which was generated unnecessarily disturbed the nurses most. Therefore a visual noise warning system seems to contribute to noise reduction but additional interventions are necessary to effectuate a change in behaviour towards noise. The nurses are well aware of which behaviours need to change.