ABSTRACT 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 INTRODUCTION A vehicle intake system supplies a fresh air to the engine. In addition to this main function, the reduction of intake noise is a very important factor in controlling the interior noise levels of vehicles, particularly at low and major engine operatingspeeds, because the intake noise is one of the four main noise sources of a vehicle. It generally consists of air cleaner box including the air filter element, hose, duct, and resonators as shown in Figure 1. An intake noise can be classified according to the cause as 1) shell radiation noise, 2) flow induced noise, and 3) orifice noise. The noise control elements as like Helmholtz resonators, side-branch resonators, and etc. have usually been used for controlling the intake orifice noise, which originates from the intake system resonances. A porous duct ( Figure 2), called by various names such as ‘porous woven hose’, ‘porous pipe’, ‘porous hose’, and ‘acoustic duct’, has also been used in many internal combustion engines for reducing the intake noise [ 1]. It is considered as a very promising and good silencing component. In addition, the flexibility of the porous duct is very advantageous from the viewpoint of system layout, installation, and vibration isolation. BEM (Boundary Element Method) or FEM (Finite Element Method) tools have been generally used to predict the acoustical performance of an intake system. This CAE analysis can predict the weak frequency range, acoustical effect of resonators, and effective position of resonators. For more accurate estimation of the acoustic performance of an engine intake system, 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 ( Figure 3) and vibro-acoustic coupling, are suggested. Additionally, the effect of a porous duct can be considered by using the acoustic wall impedance of porous duct as boundary condition in a CAE model. A Study on the Acoustic Simulation for the Components of an Intake System2011-01-1520 Published 05/17/2011 ChulMin Park, Jihoon Jeong, Gihwan Kim, Dohyun Kim, Sang-il Lee and Hyunku Lee Hyundai Motor Company Copyright © 2011 SAE International doi:10.4271/2011-01-1520Downloaded from SAE International by University of Minnesota, Tuesday, July 31, 2018Figure 1. Consist of an intake system. Figure 2. Noise control element: porous duct. Figure 3. Air cleaner box and air filter element.