Ear acoustic authentication, a type of biometric authentication, uses the acoustic characteristics of the ear canal as a feature. Because ear acoustic authentication acquires features using earphones, the process of authentication is easy, and the method has attracted much attention recently. However, the mechanism of the acoustic characteristics of the ear canal has not been sufficiently studied. In this study, we verified two methods, the image matching method and Slicing method. In conclusion, Slicing method was found to outperform the image matching method, based on the results of this study.