Reverberation time measurements of a neonatal incubator

Abstract

New-borns are exposed to high noise levels inside infant incubators. Some authors suggest that these noise levels are amplified by the reverberant nature of the materials that compose incubators. In this paper, the impulse response and the reverberation time of an incubator with standard dimensions were calculated. Two incubator configurations were evaluated, with and without mattress, under two measurements methods, impulsive, and interrupted noise method. The incubator was considered as a linear time-invariant system, and therefore the impulse response was easily obtained for each configuration and measurement method. Consequently, the impulse response for each of the six-octave bands was obtained to get the reverberation time in each band. Results show reverberation times (T30) with mattress of 0.6 s (average of all 1/8 octave band frequencies), measured in a room with controlled acoustic conditions (reverberation time of the room below 0.15 s). The longest sound persistence was obtained at low frequencies, with a reverberation time of 1.47 s in the configuration with mattress, and of 1.87 s in the one without mattress. Even if the average reverberation time is relatively reasonable for a standard room, it may be considered long and uncomfortable for such a small space. It is essential to highlight that, due to the low acoustic isolation of the incubator dome, there is a considerable influence of the reverberation time of the room in which the incubator is located.