Calculation of impulse responses and acoustic parameters in a hall by the finite-difference time-domain method

Impulse responses in a hall were calculated by the finite-difference time-domain (FDTD) method, and typical room acoustic parameters were obtained from the responses. The calculated parameters were compared with those actually measured in the hall. In the FDTD calculation, the impedance boundary condition was modeled by an equivalent mechanical system comprising masses, springs, and dampers. To calculate the impulse responses, the normal acoustic impedance of the interior finishing materials of the various surfaces in the hall were measured by applying the impedance-tube method, and the model of the room boundary condition was determined for the respective parts. A comparison between the calculated and measured values showed that the values of reverberation time RT, definition D50, clarity C80, and center time Ts were in good agreement in the middle-frequency bands. However, in low-frequency bands, large discrepancies were observed because of the difficulties in determining and modeling the boundary conditions.