Sound insulation means reflecting and absorbing sound from the material to prevent the incident sound from passing through. Methods such as sound pressure level difference, transmittance, and sound transmission loss are used to display sound insulation, and in general, transmission loss for each frequency band is mainly used. In this study, the CAE technique was used to predict the negative transmission loss for the wall made up of various structures. Through this, it was possible to identify the frequency characteristics of the sound source and present the structure of the wall that could effectively reduce the sound in the frequency band of interest.