Abstract:

The bells cast during the Silla dynasty were hung over various types of hollows or cavities in the ground. The sound pipe, called the eumtong, which opens through the top, appears in most of the bells. Another characteristic of these bells is that they ring with a very long beating frequency, sometimes for more than 3 s. The King Songdok bell (``Emille'' bell) cast during the Silla dynasty (771 A.D.) is the most famous one among these. Its height is 3.66 m, the diameter of bell mouth is 2.23 m, and its mass is about 20 000 kg. A very extensive experiment was designed and conducted. To visualize how the bell radiates sound, a cylindrical acoustic holograph was attempted. The total measurement points for the holograph are 32x12; 32 microphones at every 30 degree. The acceleration signals were also measured extensively at many points, which were 11x12. The acoustic characteristics of the inside cavity of the bell were also analyzed. This paper explains the role of the acoustic cavity in the ground, the sound pipe, and the source of long beating. Sound visualization based on the holographic measurement will demonstrate how its sound radiates in space.