A further study of a mathematical model for a screen in open-plan offices

In order to obtain a good acoustical environment in open-plan offices, the acoustic performance of a single screen needs to be well estimated. Based on the sound pressure or the sound energy summation, the models proposed by previous investigators provided the predictions of the speech intelligibility index (SII) at the receivers behind a single screen in the open-plan offices. In the development of these models, the expression describing the diffracted field of a screen was an empirical formula and the sound diffraction is assumed to be appeared in the shadow region of the screen. In the present study, the MacDonald analytical formula is applied to describe the diffracted field of a screen, and both the diffractions in the visible region and in the shadow region are considered in the proposed model though it seems that the diffraction in the visible region is small compared with that in the shadow region. The comparison of the predicted and experimental results of the Wang and Bradley and the predicted results of the improved model shows that the improved model can provide a more accurate prediction, and further calculations indicate that the improvement is mostly due to the application of the MacDonald analytical diffraction formula.