It is necessary to rethink the need for acoustical parameters instead of sticking to the well-established parameters meant for concert halls. Also, parameters that use the balance between early and late reflections are problematic when late reflections are more or less absent. The lack of late reflections means that the decay curve is often far from a straight line, and the reverberation parameters turn out to be unreliable. However, these parameters have been derived with closed spaces in mind, and it is not obvious that the same parameters are meaningful in an open-air theatre. * Corresponding author: acoustics of performance spaces are usually characterized by the reverberation time and a handful of other acoustical parameters defined in ISO 3382-1. Odeon A/S, DTU Science Park, Kongens Lyngby 2800, Denmark
