# Courtyard Sound Field Characteristics by Bell Sounds in Han Chinese Buddhist Temples
## 3 Results and Discussion
### The Position and Height of the Bell Tower  
The history of bell towers in Buddhist temples dates back to the [PERSON] dynasty (AD 618-907). Figure 1 illustrates a general change in the trend of bell tower positioning. Under the Song dynasty (AD 960-1279), the bell tower was placed in a corner of the first courtyard; under the Qing dynasty, it was placed at a fixed position opposite the drum tower. The bell and drum towers sit on either side of the central axis in the first courtyard [3]. In this study, Buddhist temple sound fields with different bell tower positions that corresponded to either the Qing or the Song dynasty were simulated, with a 3 m courtyard wall height, and the results were compared to cases where the bell tower was placed in the centre of the first courtyard (results presented in Figure 9a,b). There was no significant difference between the three bell-tower position conditions in the SPL(A) of the first courtyard. There was also no significant difference between the two bell-tower position conditions of the Qing and Song dynasties  
Figure 8: Diagram of sound rays. Figure 7: Diagrams of the effects of courtyard partition walls on courtyard sound fields. (**a**) Variation in SPL(A). (**b**) Variation in RT. (**c**) Variation in C\({}_{80}\). (**d**) Variation in (1–IACC\({}_{\text{E3}}\)). regarding the SPL(A) of the second through fourth courtyards; nevertheless, the SPL(A) values for both were higher--by about 2.0 dBA, 5.1 dBA, and 4.8 dBA and 4.1 dBA, 6.0 dBA, and 6.3 dBA, respectively--than those of their counterparts when the central bell tower was positioned in the first courtyard. Meanwhile, the standard deviation of SPL(A) in the second and third courtyards was higher by about 1 to 2 dBA for the Qing dynasty temple layout than for the other two layouts, whereas there was no significant difference between the three conditions in the SPL(A) of the fourth courtyard. The results indicate that different positions of the bell tower had no significant or regular effects on RT or the standard deviation of RT. Figure 9c shows that a modification in bell tower position did not cause significant changes in C\({}_{80}\) in the first courtyard, but C\({}_{80}\) in the second through fourth courtyards, which featured Qing and Song dynasty bell tower layouts, was higher than their counterparts with a central bell tower layout. For the second through fourth courtyards, which featured the Qing dynasty layout, there were increases in C\({}_{80}\) values of 2.9 dB, 5.1 dB, and 2.0 dB, respectively. For the second through fourth courtyards that featured the Song dynasty layout, C\({}_{80}\) values increased by 6.8, 2.4, and 3.9 dB, respectively. As  
Figure 9: Diagrams of the effects of bell tower position on courtyard sound fields. (**a**) Variation in SPL(A). (**b**) Variation in the standard deviation of SPL(A). (**c**) Variation in C\({}_{80}\). (**d**) Variation in (1–IACC\({}_{\text{E3}}\)). shown in Figure 9d, the (1-IACC\({}_{\rm E3}\)) values of the first through fourth courtyards, which featured the Qing dynasty layout, were higher by 0.079, 0.071, 0.12, and 0.13, respectively, when compared to their counterparts with the Song dynasty layout. Differences were above the JND (i.e., 0.075) except for the second courtyard. These results show that in addition to affecting courtyard landscape, the bell tower's position also affects the SPL(A), C\({}_{80}\), and (1-IACC\({}_{\rm E3}\)) values of each courtyard, except for the first courtyard. Bell tower layout had small effects on the RT and RT standard deviation in the courtyards. In large Han Chinese Buddhist temples, the bell is placed on a two-storey bell tower that hangs about 6 m above the ground. Simulation results indicate that with a 3 m courtyard wall height, an increasing bell tower height (i.e., raising the position of the sound source) would lead to a smaller average SPL(A).