Investigation of mid-frequency prediction using combined pressure acoustics and power-based methods

Simulation of sound propagation in duct networks is essential for many applications. Some applications e.g. car mufflers, need only simulation in the low frequency range where the plan wave is dominant due to application small size. In other applications e.g. HVAC systems, the size of the duct network is relatively large, hence the entire frequency range analysis is needed. The low frequency range can be analyzed using FEM or pressure two-ports method which give high accuracy. In the high frequency range, power-based method is usually used for the analysis where the source and the network are decoupled hence, the acoustics power is suitable variable for the analysis. In standards such as ASHRAE and VDI, the power-based analysis is used for the entire frequency range which is inaccurate. It is more appropriate to use pressure-based algorithm in the low frequency and power based in the high frequency. This paper investigates the relation between the low and high frequency predictions trying to develop a method to predict the mid-frequency range behavior. Different networks configurations are investigated, and different techniques of prediction are applied. The results of these techniques are compared to FEM analysis results and evaluation of each technique is presented.