Accuracy of computer simulation software using hybrid models for microscale urban environments

To investigate environmental acoustics in large urban areas, macroscale simulation software uses calculation methods based on simplified algorithm models. However, in order to examine microscale acoustics environments such as a street or a square, those simplified algorithms may not be enough. The technological advances of the last decades in acoustic simulation software based on hybrid calculation methods, such as raytracing and image source, now allows new experimentations in urban environments. Several researches have shown the reliability of results of hybrid models when compared to in-situ measurements in closed spaces. Hybrid calculation models may also be used to simulate small open urban environments, however there are few studies showing the reliability of the results. This research aimed to investigate the accuracy of hybrid computer calculation models in microscale urban spaces. An open space with an “L” shaped edification was selected in order to provide proper reflections for the study. Acoustics measurements in situ were done using the method of impulse response. Computer models were also created using software Odeon v.13. Accuracy was evaluated comparatively using JND values of acoustics parameters as reference. Analyzed parameters were T30, EDT and SPL. Energy-Time curves and Impulse Responses were also compared. It was found that parameters have a good agreement between simulated and measured results, especially in mid-high frequencies. There is also a position dependent variation in T30 due to the detachment of the building and approximation to the free field. Results showed that hybrid models based software can be successfully used in the acoustic characterization of microscale urban environments.