Musicians in the orchestra pit in opera houses are exposed to relatively high sound pressure levels during the rehearsals and the performance. As a consequence, the communication between the diverse musicians is disturbed and potentially the hearing ability is endangered. In order to improve the situation for the musicians in-situ measurements of the room acoustic properties are performed (e.g. reverberation time T, clarity C 80 , strength G etc.) in order to provide evaluation data. On the other hand, acoustic simulations of the entire opera house or parts of it are performed by both the Finite Element Method (FEM) for low frequencies and the ray tracing approach for middle and high frequencies.The results are compared to the experimental data. Subsequently, optimization measures, like additional absorbers or diffusers, can be investigated in detail by the simulations. The most promising will eventually be chosen for realization and be measured in-situ.