This paper reviews the sounds of bells cast during the Shilla Dynasty. One unique characteristic of Korean bells is that they create beats. The beats of various ancient bells are summarized and analyzed with regard to mass, and other geometrical dimensions. Other interesting and unique features of the old Korean bells are that they have sound pipes on top and hollows below the bells. The types of pipes and hollows are also studied and reported. In fact, the pipe is a high-pass filter so that it dissipates high-frequency sound as fast as it can, and the hollow is a resonator that can somehow sustain a beating sound. Bells cast during the Shilla and Korea Dynasty and their sound characteristics are investigated and summarized.