The synthesis of psychoacoustically accurate room impulse responses from room characteristics such as geometry and materials is at the heart of many virtual acoustics systems. There are now a number of mature synthesis methods available, including those based on ray tracing and the image method, finite element and finite difference schemes, and modal techniques. Comparisons among these techniques are scarce, and here we compare the accuracy of impulse responses synthesized using a number of these methods to ones measured in a 20ft x40ft x20ft (6.1m x 12.2m x 6.1m) racquetball court, a shoebox-shaped space comprised of pairs of orthogonal, flat surfaces. Room responses synthesized using the image method, ray tracing, FEM, and scattering delay networks are compared with impulse response measurements made using a Bose SoundLink Revolve+ loudspeaker and balloon pop sound sources and a Core Sound TetraMic A-format microphone. Comparisons are made using the normalized echo density (NED) profiles, and frequency-dependent early decay times and T30s estimated from the impulse responses.
The timing and arrival directions of reflections were clear during the measured impulse response onset, and reasonably well predicted by the image method. The decay times and echo density profiles estimated from the measured impulse response were consistent with that predicted by the Eyring/Sabine theory. Finally, the synthesized impulse responses all captured the perceptual character of the space.