In order to perform acoustic analysis with sufficient accuracy, the method of treating sound absorption characteristics is important. Modeling theories using flow resistance or complex density / complex sound velocity are generally used in the modeling methods of porous materials. However, since it is difficult to find out necessary material characteristic for prediction of the sound absorption characteristic, acoustic characteristics of sound absorption material may be unable to be predicted. In this research, an easy modeling method of sound absorption material will be proposed for analyzing the 3-dimensional acoustic field that has a sound absorption material. Therefore, an experiment was conducted on the sound tube that has a sound absorption material. The validity of a simple modeling method of sound absorption material is verified by comparison of the experimental result and the calculated result. And the simple modeling method will be applied to automatic water supply equipment. An optimal arrangement of the sound insulation / absorption material was calculated by the numerical analysis. Consequently, the noise could be reduced by 4dB(A). In addition, structural acoustic coupled analysis is due to be performed to the noise reduction in consideration of the sound absorption characteristic of material of automatic water supply equipment.