After decades of development room acoustical computer models have matured. Hybrid methods combine the best features from image source models and ray tracing methods and have led to significantly reduced calculation times. Due to the wave nature of sound it has been necessary to simulate scattering effects in the models. Today’s room acoustical computer models have several advantages compared to scale models. They have become reliable and efficient design tools for the acoustic consultants, and the results of a simulation can be presented not only for the eyes but also for the ears with new techniques for auralisation.