Reduction in aerodynamic noise emitted from a pantograph is an important subject for reducing environmental impact of high-speed trains. In the previous study, aerodynamic noise reduction method by pantograph head support covering with porous material were proposed. Furthermore, two alternative and easier applicable methods of porous material, the one is applying channels and the other is applying perforated plate, are also proposed. In this study, relation between opening ratio and aerodynamic noise reduction effect of these two methods are investigated. From a wind tunnel test result, it is clarified that setting opening ratio around 35%-45% for applying channel and around 50% for applying perforated plate can reduce aerodynamic noise to the same extent as applying porous material.