A Study on the Acoustic Simulation for the Components of an Intake System

摘要

The reduction of intake noise is a very important factor in controlling the interior noise levels of vehicles, particularly at low and major engine operating speeds. A vehicle intake system generally consists of air cleaner box, hose, duct, and filter element. Also, resonators and porous duct are included, being used to reduce intake noise. For more accurate estimation of the transmission loss (TL), it seems important to develop a CAE model that accurately describes this system. In this paper, simple methods, which can consider the effects of filter element and vibro-acoustic coupling, are suggested which could remarkably improve estimation accuracy of the TL. The filter element is assumed as equivalent semi-rigid porous materials characterized by the flow resistivity defined by the pressure drop, velocity, and thickness. Then, the transfer admittance matrices, the relation between the sound velocities on both sides of the filter element with the corresponding sound pressure, can be obtained. The effect of filter element can be considered in CAE model when this relation is used as a boundary condition. A correction factor is proposed to include other absorption effects such as the vibro-acoustic coupling effect, etc. Additionally, the effect of a porous duct can be considered in CAE model by using the acoustic wall impedance of porous duct as a boundary condition. Comparing the predicted data and the measured, it can be seen that great improvement is achieved in the prediction accuracy of the TL.