Abstract
In terms of the overall diffusion sound field, the inherent diffusion state of the space and the scattering coefficient of indoor surfaces work jointly to diffuse sound energy. This study has investigated the impact of surface scattering on reverberation time in differently shaped spaces. First, 10 spaces with the same volume but different shapes were calculated using a computer simulation; Next, two typical spaces were selected to calculate 10 states, in which the volume was multiplied. The calculations results show that the impact of surface scattering on reverberation time in differently shaped spaces follows three laws: in a group of spaces with the same variation pattern, T20 varies with scattering coefficients at a similar rate. In a group of spaces with different variation patterns, there is a difference of more than 5% in the change rate of T20 with scattering coefficients; in imperfect diffusion spaces, decay curves vary in accordance with scattering coefficients. If the scattering coefficients are the same, T20 varies with spatial shapes; when the volume of rectangular spaces and trapezoidal space ranges from 3000 to 30,000 m3, the change rate of T20 is less than 5%. In the present study, spaces were classified by the position combination of shape surfaces. On this basis, we proposed and then graded the concept of “morphology diffusivity”.
Highlights
In the acoustic design of performance buildings, walls and ceilings are usually fitted with diffusion devices to diffuse indoor sound fields
When the scattering coefficient ranged between 0.3 and 0.99, the T20 change tended to be smooth, while the T20 change rate was always lower than 5%
As the scattering coefficient increased, the T20 decreased in three spaces; the T20 change range was different across the four spaces
Summary
In the acoustic design of performance buildings, walls and ceilings are usually fitted with diffusion devices to diffuse indoor sound fields. Based on a 1/10 scale model and a real performance hall, Jeon et al [9] compared two states (diffusion and reflection) of wall surfaces; they found that adding diffusers reduced the standard error of early decay time, and increased the quantity of high-frequency reflected sound peaks. Using the scale-model method, Ryu and Jeon [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). Using a 1/50 scale model, Kim 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. (3) In spaces with different volumes, the way in which RT varies with an increase in the surface scattering coefficient
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