## 1 Introduction
For seats close to the walls, the initial delay increased from 9 to 37 ms. Using the scale-model method, [PERSON] and [PERSON] [11] carried out a comparative study before and after adding diffusers to nearby side walls of the Gold Sea Art Gallery multifunctional hall; the diffusers reduced the initial delay, the energy intensity of first-order reflected sound, the sound pressure level, \(RT\), and early decay time (\(EDT\)). Based on a scale model, [PERSON] [12] used reflecting materials to block the diffusers on nearby side walls, finding that the diffusers served to reduce the standard errors of interaural cross-correlation coefficient (\(IACC\)) and early decay time (\(EDT\)). All of the aforementioned studies examined a single space and made no comparisons between multiple spaces. In an article on scattering, [PERSON] [13] argued that, in a room with specular reflection, sound decay would not be linear and the slope of time-decaying sound energy would be lower than predicted by [PERSON]. In a room with high diffusivity, however, the slope of time-decaying sound energy would present more linear characteristics. In a space with uniform acoustic absorption, the proportion of three dimensions would affect the decay of sound energy; specifically, the effect of surface scattering on the decay of sound energy would vary in accordance with the relative proportions of three dimensions. The diffusion effect of the sound field would be affected by spatial shape, as well as the shape of the diffuser. [PERSON] et al. [14] added diffusers to same-area surfaces in three spaces (the first rectangular, the second sectorial, and the third elliptical); the calculation results confirmed the above arguments. [PERSON] [15] investigated the relationship between diffused reflection and \(T_{30}\) in a sound ray tracing model; they found that when wall surfaces were tilted, linear decay was caused by a low scattering coefficient. However, tilted wall surfaces alone do not diffuse indoor sound fields. [PERSON]'s [10] findings show that the impact on sound fields varies in accordance with the position and quantity of diffusers. [PERSON] [16] conducted a comparative study before and after increasing the diffusion of the concert hall's side wall using the scale model test method and found that when the side wall increases sound diffusion, the room's \(T_{30}\) decreases. Using a 1/50 scale model, [PERSON] et al. [17] found that, in both shoebox-shaped and sectorial performance spaces, the \(RT\) decreased as the diffusivity increased. These studies show that spatial shape and surface scattering coefficients work together to affect acoustic parameters. However, none of these studies investigated the relationship between spatial shape and surface scattering, or between spatial volume and surface scattering. It can be seen from the above research that the influence of surface scattering change on the \(RT\) is different in different shapes of space. It can be concluded that different spatial forms can \"diffuse\" the energy of sound field to a certain extent, and the diffusion of sound field is affected by both spatial forms and surface scattering. Both the scale model test and computer simulation can be used to study scattering. Using the scale model method, although the results can be close to real situations, the number of cases that can be studied is limited due to the modelling complexity. All of the studies mentioned above pertained to a single space, in which there were scattering sources or not; none compared multiple spaces of different shapes. Currently, no existing study on surface scattering has investigated the sensitivity of \(RT\) to surface scattering in differently shaped spaces and the extent to which \(RT\) varies in accordance with spatial volume. The present study thus aims to investigate the impact of scattering on \(RT\) in differently shaped spaces. Under the conditions of a constant absorption coefficient, \(RT\) is also affected by spatial volume.