Prediction of Reverberation Time in Office Spaces by Investigation of the Scattering Factor in Odeon

Abstract: Accurate estimations of the reverberation time of furnished office spacesis essential as an acoustic consultant. A time efficient way to predict thefurniture’s effect is to investigate it by software modelling. The room acousticsoftware Odeon is suitable for doing this. In today’s geometrical room acousticmodellers (such as Odeon) a parameter called the scattering factor was usedwhich was of large importance in this thesis. This thesis set out to investigatehow well Odeon predicts the reverberation time in smaller and larger officespaces given that the correct scattering factor for each type of furniturecould be established. The method for the investigation was to perform fieldmeasurements in two office spaces of different sizes and geometry. Thenuse different setups of furniture to examine the furniture’s effect on thereverberation time connected to their sound scattering properties. The modelwas designed with 2D objects in SketchUp and exported to Odeon. A referencevalue for a pair of measurement setups was obtained by using the ratio of thetotal reverberation time (octave bands 125 Hz to 4 kHz) of the rooms. Thisratio was used as a target in Odeon for the same simulated pair of room setups.The scattering factor was adjusted in increments of the specific furniture usedin the setup until an optimized fit was reached. These steps were carried outfor each combination of setups. Afterwards the simulations were comparedto the measured and calculated reverberation times using Sabine’s formulaand Arau-Puchades formula. It was possible to establish specific scatteringfactors for the furniture types within Odeon although their accuracy was hardto determine. The resulting reverberation times from the Odeon simulationsof the large and small spaces were not closer to the measured reverberationtime than the calculated ones to any distinct degree. It’s worth noting that allof these calculations are dependant on ideally diffuse circumstances which theactual rooms rarely are. This is why they tend to underestimate the room’sreverberation time. The main goal of this thesis is to an extent fulfilled,although maybe not with as great future utility as hoped. The scattering factorscorrespond to each other independently of what room was being modelled. Inan isolated framework of Odeon, the attained scattering factors may be of use,especially if the measured room can be assumed ideally diffuse.