Modeling the Sound Source of an Intake and Predicting the Intake Sound Pressure Level for a Motorcycle

In order to accurately estimate the intake sound pressure level, it is important to improve the accuracy of the air cleaner simulation model and precisely estimate the sound source of the intake. It has been confirmed that the modeling accuracy of an air cleaner can be improved by considering the vibro-acoustic coupling. Meanwhile, the sound source of the intake depends not only on the engine specifications, but on the intake system and even the exhaust system design. In this reported example, since it is difficult to estimate the sound source of the intake only by calculation, due to the aforementioned reasons, actual measurements were carried out to define the sound source. The method is such that the sound source is modeled by acoustic impedance and volume velocity in the engine, and the acoustic impedance is measured using an impedance tube. Then, the sound pressure at the intake opening is measured. Then, the volume velocity is calculated backwards using the results of measurement and the intake system unit model. This method allows defining the sound source by experiments. In addition to that, estimation of sound pressure level at the intake opening has become possible by using measured acoustic impedance and volume velocity, which are determined by experiments, as the boundary conditions of the air cleaner model.