This paper is analyzing the acoustical comfort in an evangelic church building in Trnava which is used not only for the church services but also for organ concerts. Three simulations were performed and compared by using the Odeon software. First, the current acoustical situation in the church was simulated. Second acoustical model represents the solution related to the improvements of the speech intelligibility in the church by changes on the interior surfaces. The third model has to be understood as an academic example in which a 100% of sound absorption was used for all walls behind the audience and for the ceiling to have an idea how the acoustical situation would be in an open air theatre with the ground floor shape similar to this church. Comparisons between these three different alternatives were done with a respect to Reverberation Time (T30), Sound Pressure Level (Lp), and Speech Intelligibility defined by STI values.