# Courtyard Sound Field Characteristics by Bell Sounds in Han Chinese Buddhist Temples
## 2 Research Methods
### Acoustic Parameter Settings of Simulation Software  
First, there is a lack of references for the simulation of a courtyard sound field in Han Chinese Buddhist temple for this paper. Moreover, it is prohibited to fully and systematically measure the sound field in a Buddhist temple, as it is a sacred religious space in China. Therefore, in order to ensure the accuracy of the simulated temple sound fields in this research, courtyard sound field measurements were taken at Shenyang Imperial Palace, which has a similar architectural form to traditional Buddhist temples and uses comparable materials; notably, however, there are no Buddhist bell towers and drum towers in the courtyard of Shenyang Imperial Palace. Next, the sound absorption and scattering coefficients of traditional Chinese building materials were determined in the sound field simulation software by comparing simulated and measured data. Those coefficients will be used in the following simulation of a Buddhist courtyard sound field. Shenyang Imperial Palace was built in 1625; in addition to being a World Heritage site, it is also the largest ancient architectural complex in northeast China, with an area exceeding 60,000 m\({}^{2}\). Currently, all buildings and courtyards are well preserved, and various facilities have been restored to their original Qing dynasty (AD 1636-1912) forms. In this study, three traditional palace courtyards were selected, namely Qingning Palace, with a single courtyard (planar dimensions 69 m x 68 m and 2.5 m-high courtyard walls), East Palace, with three courtyards (planar dimensions 105 m x 25 m and 2.7 m-high courtyard walls), and West Palace, with multiple courtyards (planar dimensions 115 m x 21 m and 3.8 m-high courtyard walls). Three courtyards in Shenyang Imperial Palace were selected for measurement and their sound fields were simulated; furthermore, results were cross-verified to ensure the accuracy and universality of the simulation. Figure 3a shows the layout of the West Palace. The measurement process basically followed the international standard ISO 3382-1 [43]. (Note that ISO 3382 is usually used for enclosed performance spaces, such as concert halls. The courtyards in Chinese Buddhist temples in this paper are semi-closed spaces, and some have certain performance functions. However, because of the lack of measurement specifications for these kinds of semi-closed spaces, this study refers to some measurement methods and parameters of ISO 3382). During field measurement, a dodecahedron speaker was used as the sound source and placed at an appropriate location in each courtyard. After the speaker produced pink noise at 100 dB or higher, onsite RT and SPL measurements were taken for each courtyard. Figure 4 shows average values for the measured EDT of each courtyard \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & **G** & **RT** & **EDT** & **C\({}_{\text{80}}\)** & **IACC\({}_{\text{E3}}\)** \\  & **(0.5–1 kHz)** & **(0.5–1 kHz)** & **(0.5–1 kHz)** & **(0.5–1 kHz)** & **(0.5–2 kHz)** \\ \hline JND & 1 dB & 5\% & 5\% & 1 dB & 0.075 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: JND for objective parameters. in Shenyang Imperial Palace. Next, SketchUp software was employed to create a courtyard model of Shenyang Imperial Palace, which was imported into Odeon to simulate the sound field. Figure 3b shows the simulated sound field model of West Palace. Acoustic parameters of courtyard material mainly included absorption and scattering coefficients. The absorption coefficient of a particular material was selected from the software's built-in material parameter library; alternatively, values of similar materials were referred to in acoustic reference books [37; 38]. The scattering coefficient of a particular material was first set by considering both the outer surface condition of the material and the simplification degree of the acoustic model; the coefficient was repeatedly adjusted according to the difference between the sound field's simulated and measured results.