A further study of the prediction method for aerodynamic sound produced by two in-duct elements

A prediction method based on the theory of Nelson and Morfey for aerodynamic sound produced by the interaction of two in-duct elements was developed by Mak and Yang. Their predicted results were compared with the experimental results of Oldham and Ukpoho. However, there are some discrepancies between their results and those of Oldham and Ukpoho, especially, when the measured values are greater than 6 dB. In addition, some parameters such as the phase of cross-power spectral density of source volumes used in their prediction method are not obvious to be determined. In order to solve these problems, this paper is therefore an attempt to modify the prediction method of Mak and Yang by re-considering the mechanism of the sound generated by two turbulences. A modified prediction method has finally been produced and verified against the measured results of Oldham and Ukpoho.