Uncertainty of input data for room acoustic simulations

Although many room acoustic simulation models have been well established, simulation results will never be accurate with inaccurate and uncertain input data. This study addresses inappropriateness and uncertainty of input data for room acoustic simulations. Firstly, the random incidence absorption and scattering coefficients are insufficient when simulating highly non-diffuse rooms. More detailed information, such as the phase and angle dependence, can greatly improve the simulation results of pressure-based geometrical and wave-based models at frequencies well below the Schroeder frequency. Phase-included input data are proven to produce perceptually noticeable changes in the objective parameters, such as the sound pressure level, and loudness-based reverberation time. Surfaces should not be assumed to be locally reacting, particularly for multi-layered absorbers having air cavities. Secondly, the current measurement techniques produce uncertain input data. For example, Sabine absorption coefficients according to ISO 354 measured in reverberation chambers have a poor reproducibility. The same happens for sound scattering and transmission, which depend greatly on the test chamber. This study summarizes potential advanced absorption measurement techniques that can improve the quality of input data for room acoustic simulations. Lastly, plenty of uncertain input data are copied from unreliable sources. Software developers and users should be careful when spreading such uncertain input data. More careful citations and references to detailed information about the measurement condition may prevent from spreading uncertain room acoustic input data.