2005 Volume 3 Issue 1 Pages 29-40
This paper describes a model to predict the acoustic absorption of Enhanced Porosity Concrete (EPC). The acoustic absorption coefficient was determined experimentally using an impedance tube, while an electro-acoustic analogy was implemented to develop the predictive model, considering the pore structure of EPC as a series of resistors and inductors. The physical features of the pore network were experimentally characterized using image analysis and a pore volume characterization technique. A parameter termed “structure factor” was introduced to account for the increased density of air that is not displaced by the acoustic wave pressure. The maximum acoustic absorption coefficient was found to decrease linearly with an increase in the structure factor. The development of this model and its correlation with physical measurements enable the prediction of acoustic absorption in EPC based on the geometric features of the pore structure. This model enabled a parametric study to be conducted to ascertain the effects of pore size, aperture size, porosity, and specimen thickness on acoustic absorption. An optimal pore to aperture diameter ratio was observed to exist, that maximizes acoustic absorption. The parametric study is believed to be able to aid in the design of EPC for acoustic absorption by better understanding the type of pore features that should be targeted for best performance.