Prediction of Flanking Noise Transmission in Lightweight Building Constructions: A Theoretical and Experimental Evaluation of the Application of EN12354-1
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The standard, EN12354-1 describes a simplified statistical energy analysis (SEA) model to predict the apparent sound reduction index between two rooms inclusive of the contributions of the flanking paths. There is interest worldwide in applying the EN12354 model to lightweight building elements. However, lightweight elements typically do not meet the requirements of an SEA subsystem and therefore applying the EN12354 model to these elements may result in inaccurate predictions.
The purpose of this investigation was to systematically evaluate the application of the EN12354 model to lightweight building constructions. The evaluation included the determination of the probability density functions and the propagated uncertainty of the calculations. Knowledge of the probability density functions resulted in alternative calculations of the structure-borne sound transmitted through the constructions. The uncertainty analysis revealed that the uncertainty of the predictions is directly affected by the variance of the vibratory field measured on the elements. The vibratory fields of lightweight elements typically show large variances and therefore the propagated uncertainty of the EN12354 predictions for these elements can be significant.
The investigation included measurements both in the laboratory and in the field. The results of the laboratory measurements were compared to both predictions using the EN12354 methods and ESEA models which included higher order flanking paths and non-resonant transmission paths. The field measurements included in this investigation were unique because the flanking intensity sound reduction indices of the elements in the source room were measured. The measurements allowed for the EN12354 predictions for each flanking element to be assessed instead of just the apparent sound reduction index between the rooms.
The study resulted in proposed correction factors for when reciprocity does not hold and proposed changes to ISO10848 to improve the accuracy of the predictions when the EN12354 method was applied to lightweight building elements. However, neither the proposed correction factors nor the proposed changed to ISO10848-1 could correct for the potentially large differences between the predicted and the measured results.
Based on the findings of this study, the use of the EN12354 model for the calculation of the apparent sound reduction index of lightweight elements is not endorsed. Lightweight constructions may not be categorized as ideal SEA subsystems due to the lack of diffuseness of the vibratory field. Furthermore, in order for EN12354 to be applied to lightweight constructions, a reliable method of calculating the resonant component of the sound reduction index of double-leaf elements is required. Therefore, statistical methods including the EN12354 method may be unsuitable for use for the prediction of flanking noise for lightweight building constructions.